Caleffi Solar Thermal Informatio
Caleffi
NorthAmerica,
America,
Inc.
Caleffi North
Inc.
th
3883
W. Milwaukee
9850 South
54 StreetRd
Milwaukee,
Wisconsin 53208
Franklin, WI 53132
T: 414.238.2360
414.421.1000 F:
T:
F:414.421.2878
414.238.2366
Dear Hydronic Professional,
Dear Hydronic Professional,
Welcome to the 6th edition of idronics, Caleffi’s semi-annual design journal
for
hydronic
Welcome
to professionals.
the 2nd edition of idronics – Caleffi’s semi-annual design journal for
A Technical Journal
from
Caleffi Hydronic Solutions
Caleffi North America, INC
3883 W. Milwaukee Rd
Milwaukee, Wisconsin 53208 USA
Tel: 414-238-2360
FAX: 414-238-2366
E-mail: [email protected]
Website: www.caleffi.us
To receive future idronics issues
FREE, register online www.caleffi.us
hydronic professionals.
The global recession has slowed nearly all industries over the past year.
However,
despite
declines was
in construction,
solar water
heater
shipmentsto over
The 1st edition
of idronics
released in January
2007
and distributed
in
the US
increased
50%
during 2008.
80,000
people
in North
America.
It focused on the topic hydraulic separation. From
the feedback received, it’s evident we attained our goal of explaining the benefits
As
andapplication
more HVAC
become
familiar with
solar water
andmore
proper
ofprofessionals
this modern design
technique
for hydronic
systems.
heating, many recognize opportunities to extend solar thermal technology
for
combined
domestic
hot
water
and
space
heating
applications.
This
is a in the
If you haven’t yet received a copy of idronics #1, you can do so by sending
trend
our reader
parent response
Caleffi SpA
identified
several years
agoat
inwww.caleffi.us.
Europe, and is The
attached
card,
or by registering
online
now
a topic will
of growing
interest
America.
For
this
reason, the
publication
be mailed
to youhere
freeinofNorth
charge.
You can
also
download
solar
“combisystems”
was file
selected
as the
topic
complete
journal as a PDF
from our
Web
site.for this edition of idronics.
Caleffi
is pleased
to provide
theair
information
this edition
to assist
thosenot a new
This second
edition
addresses
and dirt ininhydronic
systems.
Though
designing
solar
combisystems.
also stand
ready with
state-of-the-art
topic to our
industry,
the use of We
modern
high-efficiency
equipment
demands a
hardware
support installation
of sucheffects
systems.
thorough to
understanding
of the harmful
of air and dirt, as well as knowledge
on how to eliminate them. Doing so helps ensure the systems you design will
We
encourage
to sendand
us feedback
on this
edition ofservice.
idronics by
operate
at peakyou
efficiency
provide long
trouble-free
e-mailing us at [email protected]
We trust you will find this issue of idronics a useful educational tool and a handy
reference
for are
your
future hydronic
system
designs.
We alsoplease
encourage
Finally,
if you
interested
in previous
editions
of idronics,
go toyou to send
us feedback onwhere
this issue
idronics
using
the attached
reader
response
card or by
www.caleffi.us
they of
can
be freely
downloaded.
You
can also
register
e-mailing
at [email protected]
to
receive us
future
issues online.
Sincerely,
Mark Olson
General Manager,
Caleffi North America, Inc.
InDEX
3
INTRODUCTION
3
FUNDAMENTALS OF SOLAR COMBISYSTEM DESIGN
Essential Design Principles
Instantaneous Collector Efficiency
Freeze Protection
6
SPACE HEATING OPTIONS
Heated Floor Slabs
Heated Thin-Slabs
Other Site-Built Radiant Panels
Panel Radiators
Forced-Air Distribution Systems
13
ANTIFREEZE-BASED SOLAR COMBISYSTEMS
Advantages of Antifreeze-Based Systems
Disadvantage of Antifreeze-Based Systems
Heat Dump Provisions
Antifreeze-Based Combisystem Designs
Antifreeze-Based Combisystem #1
Antifreeze-Based Combisystem #2
Antifreeze-Based Combisystem #3
Antifreeze-Based Combisystem #4
Antifreeze-Based Combisystem #5
Using a Pool as a Heat Dump
23
DRAINBACK SOLAR COMBISYSTEMS
Advantages of Drainback Systems
Disadvantages of Drainback Systems
Open-Loop vs. Closed-Loop Drainback Systems
Operation of a Drainback System
Siphon Limitations
Sight Glasses
Tank Piping Connections
Drainback Combisystem #1
Drainback Combisystem #2
Drainback Combisystem #3
Drainback Combisystem #4
40
PERFORMANCE EXPECTATIONS
Estimations
f-chart Analysis
Case Studies
Collector Orientation in Combisystems
Storage Tank Size in Combisystems
44 SUMMARY
45
46
48
49
APPENDIX A:
APPENDIX B:
APPENDIX C:
APPENDIX D:
Piping Symbol Legend
Heat Exchanger Performance
Tank and Piping Volume Formulas
Unit Conversion Factors
Product Information Pages
© Copyright 2009
Caleffi North America, Inc.
Printed: Milwaukee, Wisconsin USA
solar thermal combisystems
1. INTRODUCTION
Most Americans are increasingly aware of rising energy
prices and the environmental implications associated with
continued use of conventional fuels. “Sustainable living”
is one of the most prevalent topics being discussed in a
variety of media.
This situation has created growing interest in renewable
sources, such as sun, wind and biomass materials. It is
also fostering a rapidly expanding market for equipment
that harvests this energy.
Hydronics technology is the “glue” that holds most
thermally based renewable energy systems together.
Although heat sources such as solar collectors, solid-fuel
boilers and geothermal heat pumps are indispensable
components in such systems, they are not the sole
determinants of efficiency, energy yield or financial viability.
Without proper heat conveyance, even the best renewable
energy heat source will not perform as expected. Thus,
the proper application of modern hydronics technology
is vital to the continued growth of the thermally based
renewable energy systems market.
This issue of idronics focuses on systems that use solar
energy, as well as an auxiliary energy source, to supply a
portion of the domestic hot water and space heating needs
of a building. Such configurations are commonly called
solar thermal combisystems. Several design variations will
be introduced and discussed in the context of residential
and light commercial building applications. In each case,
state-of-the-art hydronic technology such as variable flow,
manifold-based distribution, hydraulic separation, thermal
mass and precisely controlled zoning are used to enhance
the system’s energy efficiency, enabling it to deliver the
same unsurpassed comfort, reliability and long life as that
provided by a well-designed conventional hydronic system.
Both piping and control aspects of solar combisystems
are illustrated and described. In many cases, the control
techniques are similar to those used in modern “nonsolar” hydronic systems. When properly applied, these
techniques allow combisystems to smoothly transition
between use of solar and auxiliary energy so that
occupants experience no difference in comfort.
The energy savings potential of such systems will also be
discussed. The goal is for designers to develop reasonable
expectations for what typical solar thermal combisystems
can provide based on differences in climate, system size
and loads.
2. FUNDAMENTALS OF
SOLAR COMBISYSTEM DESIGN
The largest sector of the solar thermal market is domestic
water heating. This is true both in North America and
worldwide. The underlying reason is the capacity to use
solar energy on a year-round basis, and in particular, the
ability to collect solar energy when it is most abundant — in
summer. Solar thermal systems for heating domestic water
were discussed in detail in idronics #3 (January 2008).
A natural extension of a solar domestic water heating
system is adding capability to offset a portion of the
space heating load in the same building, and hence the
name “combisystem.”
Most combisystems intended for residential applications
treat domestic water heating as the primary load, and
thus take advantage of high solar energy availability in
summer. Beyond their DHW “base load,” combisystems
typically use greater collector area and larger storage
tanks to capture and contain additional energy that can
offset a portion of the building’s space heating load.
As with solar DHW systems, combisystems require a
reliable means of freeze protection, as well as an auxiliary
energy device that supplies the energy required for
uninterrupted delivery of hot water and space heating
when solar heat gains cannot cover the load.
Essential Design Principles:
The following design concepts are imperative to the
success of a solar combisystem. Each will be discussed
in the context of specific system designs described later
in this issue.
• The cooler the solar collectors can operate, the higher
their efficiency, and the greater the amount of solar
energy they harvest.
3
• In an “ideal” solar thermal system, none of the heat
produced by the auxiliary heat source would enter the
solar storage tank. This prevents the auxiliary heat source
from increasing the temperature of the storage tank above
what it would be based solely on solar energy input. Such
heating, if allowed to occur, delays the startup of the solar
collection cycle, and thus reduces the energy collected
during that cycle.
Some “single tank” combisystems discussed in this
issue do not adhere to this principle. However, they all
rely on temperature stratification to direct heat added
by the auxiliary heat source to the upper portion of the
storage tank. This minimizes heating of the lower portion
of the tank, and thus reduces interference with the solar
collection control process.
• The collector array and any piping outside of the heated
space must be protected against freezing.
• Almost every solar combisystem gathers more energy
on a sunny summer day than can be used by the load
(which is typically just domestic water heating). All solar
combisystems must have a means of dealing with this
surplus energy so it doesn’t damage the system.
Instantaneous Collector Efficiency:
The performance of any solar combisystem is implicitly
linked to the performance of its solar collector array.
The best solar combisystems are designed to enhance
collector efficiency. Doing so requires a fundamental
knowledge of what collector efficiency is and how it is
affected by operating conditions imposed by the balance
of the system.
Figure 2-1
collector efficiency=
The instantaneous thermal efficiency of a solar collector
is defined as the ratio of the heat transferred to the
fluid passing through the collector divided by the solar
radiation incident on the gross area of the collector, as
Instantaneous
collector efficiency can
shown
in figure 2-1.
be m
through the collector along with simultane
Instantaneous collector efficiency can be measured by
recording
the flow
rate through
the collector along
with
inlet and
outlet
temperature.
The
intensity
simultaneous measurement of the collector’s inlet and
collector
must
beof measured.
Formula
outlet
temperature.
The also
intensity
the solar radiation
striking
the collector must also
be measured.
Formula of the
the instantaneous
thermal
efficiency
2-1 can then be used to calculate the instantaneous
thermal efficiency of the collector.
Formula 2-1:
Formula 2-1:
ηcollector =
(8.01× c × D) × f × (Tout − Tin )
I × Agross
Where:
Where:
c = specific heat of fluid (Btu/lb/ºF)
D = density of fluid (lb/ft3)
f =cflow
rate (gallons heat
per minute)
= specific
of fluid (Btu/lb/ºF)
Tin = collector inlet temperature (ºF)
3
)
D==collector
density
fluid (lb/ft
Tout
outletof
temperature
(ºF)
I =finstantaneous
solar(gallons
radiation intensity
(Btu/hr/ft2)
= flow rate
per minute)
2
Agross = gross collector area (ft )
collector
Tin= =
8.01
a unit
conversion inlet
factor temperature (ºF)
Tout = collector outlet temperature (ºF)
The phrase instantaneous collector efficiency can vary
from
to moment depending
on the operating
I =moment
instantaneous
solar radiation
intensity
conditions. Do not assume that a given set of operating
2
gross collector
(ft )and
Agross =conditions
is “average” area
or “typical,”
couldconversion
be used to determine
8.01 = thus
a unit
factor the
collector’s efficiency over a longer period
thermal output from collector (Btu/hr)
of time.
solar radiation striking GROSS collector area (Btu/hr)
(
The word instantaneous implies that the co
Instantaneous collector efficiency is very
momentdependent
to moment
depending
on the ope
on the fluid
temperature entering
Tout
GROSS COLLECTOR AREA
Tin
4
the collector, as well as the temperature
surrounding it. It also depends on the
intensity of the solar radiation incident
upon the collector. This relationship is
shown in figure 2-2 for a typical flat plate
and evacuated tube collector.
The thermal efficiency of each collector is
plotted against the inlet fluid parameter. This
parameter combines the effects of inlet fluid
temperature, ambient air temperature and
solar radiation intensity into a single number.
Figure 2-2
1
collector thermal efficiency
(decimal %)
0.9
0.8
glazed flat plate collector
0.7
evacuated tube collector
0.6
0.5
0.4
0.3
0.2
0.1
0
0
0.1
0.2 0.3
0.4 0.5
Inlet fluid parameter
0.6
0.7 0.8 0.9
2
 Ti − Ta   º F ⋅ ft ⋅ hr 


 
Btu

 I  
1
1.1
For a given solar radiation intensity and outdoor air
temperature, any operating condition that increases
the fluid temperature entering the collector causes the
inlet fluid parameter to increase. This causes a drop in
thermal efficiency for both the flat plate and evacuated
tube collectors. Conversely, any operating condition that
lowers the inlet fluid temperature also lowers the inlet
fluid parameter and increases collector efficiency.
Designers are cautioned about assuming any given
value of the inlet fluid parameter as “representative” of
average operating conditions. Instead, the variability of
this parameter is accounted for in system simulation
software. The latter is essential in determining the net
effect of any collector in a solar combisystem.
Systems that can operate with relatively low collector
inlet temperatures generally allow flat plate collectors
to reach thermal efficiencies higher than those attained
by evacuated tube collectors. Conversely, systems that
require the collector to operate at higher temperatures are
usually better suited to evacuated tube collectors. Design
tools such as simulation software can be used to determine
which type of collector allows a given combisystem to
harvest the greatest amount of solar energy.
All solar combisystems require a means of protecting the
collectors and piping outside of the heated space from
freezing. Although there are several possible ways to
do this, two methods of freeze protection dominate the
market worldwide:
The value of the inlet fluid parameter often changes
from moment to moment depending on the operating
conditions of the system and the prevailing weather. For
example, if a cloud temporarily shadows the collectors
from direct sun, the value of the inlet fluid parameter could
easily double, which temporarily decreases efficiency.
Freeze Protection:
• Use of antifreeze fluid in the collector circuit
• Gravity drainback systems
Each of these systems has advantages and limitations, and
several options for each approach will be described.
5
3. SPACE HEATING OPTIONS:
Heated Floor Slabs:
Not every hydronic space heating distribution system is
suitable for use with a solar combisystem. Distribution
systems that operate at low water temperatures are greatly
preferred because they allow for higher solar energy yields.
Heated floor slabs with relatively close tube spacing and
low finish floor resistances are generally well suited for
use with solar combisystems. The graph in figure 3-1
shows upward heat output from a heated slab based on
tube spacing of 6 inches and 12 inches, and for finish
floor resistances ranging from 0 to 2.0 (ºF•hr•ft2/Btu).
The steeper the line, the better-suited the distribution
system is for use in a solar combisystem.
Space heating distribution systems that provide design
heating load output using supply water temperatures
no higher than 120ºF will allow the solar subsystem to
deliver relatively good performance.
Distribution systems that supply each heat emitter using
parallel piping branches rather than series configurations
are also preferred because they provide the same supply
water temperature to each heat emitter.
Examples of space heating systems that allow the solar
subsystem to provide good performance include:
• Heated floor slabs with low-resistance coverings
• Heated thin-slabs over framed floors with low-resistance
coverings
• Generously sized panel radiator systems with parallel
piping
• Forced-air systems with generously sized water-to-air
heat exchangers and carefully placed diffusers that do
not create drafts
Each of these will be discussed in more detail.
Figure 3-1
Upward heat output vs.
Driving ∆T
for 4" concrete slab
upward heat flux
(Btu/hr/ft2)
12-inch tube spacing
Rff=0
Rff=0.5
Rff=1.0
40
Rff=1.5
Rff=2.0
20
0
0 10 20 30 40 50 60 70 80 90 100
Driving ∆T (Tw-Tr) (ºF)
Average water temp. - room air temp
Rff = resistance of finish flooring (ºF/hr/ft^2/Btu)
6
For comparison, consider supplying the same 20 Btu/hr/ft2
load using a heated floor slab with 12-inch tube spacing and
a finish floor resistance of 1.0ºF•hr•ft2/Btu. The driving ∆T
must now be 42.5ºF. The average circuit water temperature
required to maintain a room temperature of 70ºF would be
70 + 42.5 = 112.5ºF, and the supply temperature likely in the
range of 120–123ºF. This higher temperature would reduce
the efficiency of the solar collectors, and decreases the total
energy collected by the system during the heating season.
Again, the net effect of such a change on a seasonal basis
would have to be assessed through computer simulation of
a given system.
Figure 3-2
6-inch tube spacing
60
For example, achieving an upward heat output of 20
Btu/hr/ft2 from a slab with no covering (e.g., Rff = 0) and
6-inch tube spacing requires the “driving ∆T” (e.g., the
difference between average water temperature in tubing
and room air temperature) to be 17.5ºF. Thus, in a room
maintained at 70ºF, the average water temperature in the
circuit needs to be 87.5ºF. The supply water temperature
to the circuit would likely be in the range of 95–98ºF.
This is a relatively low supply water temperature, and
should allow the collectors to operate at reasonably good
efficiency, especially if flat plate collectors are used.
The following guidelines are suggested in applications
where a heated floor slab will be used to deliver heat
derived from a solar collector array:
• Tube spacing within the slab should not exceed 12
inches
• Slab should have minimum of R-10 underside
insulation
• Tubing should be placed at approximately 1/2 the slab
depth below the surface, as shown in figure 3-2
• Bare, painted or stained slab surfaces are ideal because
the finish floor resistance is essentially zero
• Other floor finishes should have a Total R-value of 1.0
or less
Heated Thin-Slabs:
Another common method of installing floor heating uses
a “thin slab” (1.5-inch to 2-inch thickness) poured over a
wooden floor deck. Figure 3-3 shows an example of such
an installation, awaiting placement of the slab material.
Figure 3-3
• Tube spacing within the thin slab should not exceed 9
inches
• Slab should have minimum of R-19 underside
insulation
• Floor finishes should have a total R-value of 1.0 or
less
• Never use “lightweight” concrete for heated thin slabs
Other Site-Built Radiant Panels:
Radiant panels can be integrated into walls and ceilings
as well as floors. Several of these configurations may
be suitable for use with solar combisystems. The
key is ensuring the radiant panel can deliver design
load output while operating at a relatively low water
temperature. This helps ensure the solar collectors will
also operate at a relatively low fluid temperature and
reasonably good efficiency.
This criterion favors radiant panels that provide high
surface areas relative to the rate of heat delivery. It
also favors panels that have relatively low internal
resistance between the tubing and the surface area
releasing heat to the room.
One example is a radiant wall panel constructed as
shown in figure 3-4.
When finished, this “radiant wall” is indistinguishable
from a standard interior wall. Its low thermal mass
allows it to respond quickly to changing internal load
conditions or zone setback schedules. The rate of heat
emission to the room is approximately 0.8 Btu/hr/ft2 for
each degree Fahrenheit the average water temperature
in the tubing exceeds room air temperature. Thus, if
the wall operates with an average water temperature of
110ºF in a room with 70ºF air temperature, each square
foot of wall would release about 0.8 x (110 - 70) = 32
Btu/hr/ft2. This performance makes it well suited for use
with a solar combisystem.
Courtesy of H. Youker
Because the slab is thinner than with slab-on-grade floors,
it has slightly lower lateral heat dispersal characteristics.
This translates into a slightly higher water temperature
requirement for a given rate of heat output relative to that
required for a slab-on-grade. This difference is slight.
A 1.5-inch-thick concrete thin slab with 12-inch tube
spacing and covered with a finish flooring resistance of
0.5ºF•hr•ft2/Btu yields about 8% less heat output than
a 4-inch-thick slab with the same tube spacing and
finishing flooring. This can be easily compensated for by
using 9-inch rather than 12-inch tube spacing.
The following guidelines are suggested:
Another possibility is a radiant ceiling using the same
type of construction as the radiant wall, as shown in
figure 3-5.
As with the radiant wall system, this radiant ceiling
has low thermal mass and responds quickly to interior
temperature changes. Heated ceilings also have the
advantage of not being covered or blocked by coverings
or furniture, and thus are likely to retain good performance
over the life of the building.
For the construction shown, the rate of heat emission is
approximately 0.71 Btu/hr/ft2 for each degree Fahrenheit
7
Figure 3-4
crossection
wooden nailer (@ end of wall)
7/16" oriented strand board
3/4" foil-faced polyisocyanurate insulation
2.5" drywall screws
6"x24" aluminum heat transfer plates
1/2" PEX-AL-PEX tubing
1/2" drywall
fiberglass insulation
1/2" PEX-AL-PEX tubing (8-inch spacing)
6" x 24" aluminum heat transfer plates
3/4" foil-faced polyisocyanurate foam strips
7/16" oriented strand board
finished radiant wall
thermal image of wall in operation
Btu
= ( 0.8 ) × (Twater − Troom )
hr • ft 2
8
Figure 3-5
top side insulation
ceiling framing
tube
7/16" oriented strand board
aluminum heat transfer plate
3/4" foil-faced polyisocyanurate foam strips
1/2" drywall
finished radiant wall
thermal image of ceiling in operation
Btu
= ( 0.71) × (Twater − Troom )
hr • ft 2
the average water temperature in the tubing
exceeds room air temperature. Thus, if the ceiling
operated with an average water temperature of
110ºF in a room with 70ºF air temperature, each
square foot of wall would release about 0.71 x
(110 - 70) = 28.4 Btu/hr/ft2. This performance
makes the radiant ceiling well suited for use in a
solar combisystem.
Manufacturers provide output
ratings for their panel radiators
in either graphical or tabular
form. In many cases, “reference”
heat output ratings for a
given size panel are stated
along with corresponding
water temperature and room
air temperatures. Correction
factors are then given, which,
when multiplied by the reference
heat output, give the actual heat
output for specific water and
room air temperatures.
Figure 3-6 shows a typical
fluted water panel radiator.
Figure 3-7 gives reference heat
output ratings for this type of
panel based on an average
panel water temperature of
180ºF and room air temperature
of 68ºF. Figure 3-8 gives
correction factor to modify the
reference heat output ratings
based on different average
water temperatures and room
air temperatures. The formula
on the graph in figure 3-8 can
also be used to calculate these
correction factors.
For example: Figure 3-7
indicates that a panel with a
Figure 3-6
Panel Radiators:
Generously sized panel radiators can also provide
good performance when used as part of a solar
combisystem. Again, the suggested guideline is
to size panels so they can deliver design space
heating output using a supply water temperature
no higher than 120ºF.
Courtesy H. Youker
9
Figure 3-7
length
Heat output ratings (Btu/hr)
at reference conditions:
Average water temperature in panel = 180ºF
Room temperature = 68ºF
temperature drop across panel = 20ºF
height
1 water plate
1 water plate panel thickness
16" long
24" long
36" long
48" long
64" long
72" long
24" high
1870
2817
4222
5630
7509
8447
20" high
1607
2421
3632
4842
6455
7260
16" high
1352
2032
3046
4060
5415
6091
2 water plates
2 water plate panel thickness
16" long
24" long
36" long
48" long
64" long
72" long
24" high
3153
4750
7127
9500
12668
14254
20" high
2733
4123
6186
8245
10994
12368
16" high
2301
3455
5180
6907
9212
10363
10" high
1491
2247
3373
4498
5995
6745
3 water plates
3 water plate panel thickness
16" long
24" long
36" long
48" long
64" long
72" long
24" high
4531
6830
10247
13664
18216
20494
20" high
3934
5937
9586
11870
15829
17807
16" high
3320
4978
7469
9957
13277
14938
10" high
2191
3304
4958
6609
8811
9913
For example: Figure 3-7 indicates that a panel with a single water plate,
For example: Figure 3-7 indicates that a panel with a single water plate,
single water
plate, measuring
24high
inches
high
72 This
example
systemsBtu/hr
limiting the
measuring
24inches
and
72and
inches
long,
has a demonstrates
heat outputthat
of 8447
measuring
24inches
high
72 based
inches supply
long, has
output
8447
inches long,
has a heat
output of
8447and
Btu/hr
watera heat
temperature
to of
120ºF
to Btu/hr
retain good
based
onconditions
the reference
conditions
of 180ºF
average
water
temperature
and
on the based
reference
of 180ºF
average water
performance
of water
the solar
collectors and
often require
on the reference
conditions
of 180ºF
average
temperature
68ºFand
room
airroom
temperature.
UsingUsing
the formula
in figure
3-8,radiators
the correction
temperature
68ºF
air temperature.
substantially
larger panel
compared to systems
68ºF room air temperature. Using the formula in figure 3-8, the correction
the formula
in figure
the correction
factor
with temperature
an with conventional
heat sources
that often supply much
factor
with3-8,
an average
panel
water
of 110ºF
and room
with temperature
an averageofpanel
temperature
110ºF and room
averagefactor
panel water
110ºF water
and room
higher waterof
temperatures.
temperature
of 68ºF is:
temperature
of 68ºF is: of 68ºF is:
temperature
When panel radiators are used in a solar combisystem,
1.33
they should be piped in parallel. Ideally, each panel
CF = 0.001882 (110 − 68 )1.33 = 0.271
CF = 0.001882 (110 − 68 ) = 0.271
radiator is served by its own supply and return piping. A
manifold-based distribution system, as shown in figure
The estimated
heat
output
at
the
lower
water
temperature
usestemperature
small diameter PEX
or PEX-AL-PEX tubing to
The estimated heat output at the lower3-9,
water
is thus:
watereach
temperature
thus:
is thus: The estimated heat output at the lowersupply
radiator. Tubeissizes
in such systems varies
from 3/8-inch to 5/8-inch depend on flow rate and head
Output = ( 0.271) × 8447 = 2289Btu / hr
loss allowances. This type of distribution system is well
Output = ( 0.271) × 8447 = 2289Btu / hr
suited for solar combisystems and is shown in several
subsequent schematics.
10
This example demonstrates that systems limiting the supply water temperature
This example demonstrates that systems limiting the supply water temperature
to 120ºF to retain good performance of the solar collectors often require
to 120ºF to retain good performance of the solar collectors often require
substantially larger panel radiators compared to systems with conventional heat
substantially larger panel radiators compared to systems with conventional heat
sources that often supply much higher water temperatures.
sources that often supply much higher water temperatures.
Forced-Air Distribution Systems:
Figure 3-8
1
Although most solar combisystems use hydronics
technology, it is possible to use a forced-air system to
deliver both the solar-derived heat and any necessary
auxiliary heat to the building. This is usually done using a
hot water coil mounted in the plenum of the air handling
device (furnace, heat pump indoor unit, etc.), as shown
in figure 3-10.
1.33
CF = 0.001882 ( ∆T )
0.8
0.7
reference condition
Correction factor (CF)
0.9
0.6
0.5
0.4
0.3
The coil is mounted on the discharge plenum to avoid
heating the components inside the air handler. Although
this may not be an issue with devices such as furnaces,
it could void warranties on other types of air handlers
containing refrigeration components.
0.2
0.1
∆T=112 ºF
0
0
20
40
60
80
100
120
∆T (ave water temp - room air temp) (ºF)
Reference condition:
Ave water temperature in panel = 180ºF
Room air temperature = 68ºF
The check valve installed in the pipe supplying the
plenum coil prevents reverse heat migration from the
furnace to the solar storage tank when the latter is too
cool for use.
An air temperature sensor is located in the discharge
plenum, downstream of the coil. This is used in
Figure 3-9
panel radiator
TRV
TRV
thermostatic
radiator valves
(TRV) on each
radiator
TRV
TRV
TRV
TRV
small diameter (3/8", 1/2", 5/8") PEX or PEX-AL-PEX
manifold station
11
Figure 3-10
supply air temperature sensor
mixing valve
check valve
supply air
to/from
solar storage
tank
duct coil
(in plenum)
blower
burners off
when heated
water is supplied
from solar subsystem
filter
return air
furnace
Figure 3-11
combination with a mixing device to regulate the temperature
of the supply air stream. Such regulation prevents very hot
water in the solar storage tank from creating a burst of very
warm air to the heated space.
The size of the plenum coil should allow relatively low water
temperatures in the solar storage tank to meet the heating load.
Coils with multiple tubing rows and large aluminum fins improve
heat transfer at low water temperatures, and as such are preferred.
Coil manufacturers can size coils for the required rates of heat
transfer at specified entering water and air temperatures.
This type of system may not always create supply air
temperatures as high as those created by a furnace, especially
if the water temperature supplied to the coil is regulated by
outdoor reset control. The registers and diffusers used for
such a system should be carefully sized and placed to avoid
creating drafts within the heated space. Ideally, supply air
from the diffusers should be mixed with room air above the
occupied zone. Vertical air velocities into the occupied zones
should be minimized to avoid drafts.
Fin-tube baseboards, although commonly used in conventional
hydronic systems, generally do not provide good performance
12
in solar combisystems. Most systems using fin-tube
baseboard are designed around relatively high water
temperatures (180ºF or higher). While it is possible to
lower the supply water temperature by adding fin-tube
baseboard to the system, lowering it from 180ºF to 120ºF
typically requires about 3.5 times as much fin-tube length
for the same heat output. Few rooms can physically
accommodate this, and few occupants would accept the
associated aesthetics.
Another advantage of antifreeze-based systems is that
tubing to and from the collector array can be installed in
any orientation. This allows flexible stainless steel or other
types of coiled metal tubing to be installed in spaces where
it would be difficult or impossible to install rigid tubing, or
to maintain a minimum slope on that tubing.
Some radiant floor panels require water temperatures
well above 120ºF at design load conditions. Such panels
will not allow a solar thermal subsystem to perform as
well as the previously discussed radiant panels. Careful
analysis using solar simulation software can quantify the
differences in expected solar subsystem performance.
One disadvantage of antifreeze-based systems is that a
heat exchanger is required between the antifreeze solution
in the collector circuit and the water in the remainder of
the system. Any heat exchanger imposes a performance
penalty on the system because it forces the collector
circuit to operate at a temperature higher than that of the
water near the bottom of the storage tank. The magnitude
of this temperature difference depends on the sizing of
the heat exchanger. The greater the internal surface of the
heat exchanger is relative to the rate of heat transfer, the
less the performance penalty. The performance of heat
exchangers and the penalty factor they impose on solar
combisystems are discussed in Appendix B.
Cast iron radiators sized for steam heating but converted
for use with higher temperature water are also unlikely to
be suitable. The possible exception would be a building
that has undergone extensive weatherization since the
steam radiators were installed. In some cases, the
significant reduction in heating load relative to the surface
area of the original radiators might allow operation
at water temperatures within the range that can be
consistently supplied by solar collectors. In such cases,
the original radiator system should also be internally
cleaned and flushed to remove any accumulated residue
associated with steam heating.
4. ANTIFREEZE-BASED SOLAR COMBISYSTEMS
The use of antifreeze fluids to protect solar collectors and
exposed piping against freezing is very similar to its use
in other hydronic systems. The piping circuits containing
the antifreeze solution are closed loops. When the system
is commissioned, these loops are purged of air and
slightly pressurized. In a closed, fluid-filled piping circuit,
the weight of the upward flowing fluid is exactly balanced
by that of the downward flowing fluid.
Advantages of
Antifreeze-Based Systems:
In a properly purged closed piping circuit, the circulator
is only responsible for overcoming the head loss due to
friction between the piping components and the fluid. It is
not responsible for “lifting” fluid into unfilled piping. That
task is handled by a separate filling/purging pump. Thus,
the circulator in a closed, fluid-filled piping loop can be
relatively small. In residential combisystems, the collector
loop circulator might only require 25 watts or less of
electrical input energy. This keeps the operating cost of
the solar collection subsystem low.
Disadvantage of
Antifreeze-Based Systems:
Another disadvantage of antifreeze-based systems is
that glycol-based antifreeze will chemically degrade
and become acidic over time. In such a state, the
fluid can cause internal corrosion of both piping and
collectors, eventually leading to failure. This degradation
is accelerated at higher temperatures. It is not good for
glycol-based fluids to be maintained at high temperatures
over long periods of time. This can happen in solar
combisystems that generate far more heat in summer
than is required by the load. It also implies that annual
testing of the pH and reserve alkalinity of glycol-based
antifreeze solutions is imperative.
Heat Dump Provisions:
The potential for thermal degradation of glycol-based
antifreeze solutions justifies the need for a “heat dump”
provision on antifreeze-based solar combisystems.
The heat dump provides a way for the system to shed
excess heat when the solar storage tank has reached
a user-set upper temperature limit and there is no
immediate need for further heat in the system. Heat
dumps can take the form of:
• Additional storage tanks.
• Passive or fan-forced convectors through which the
hot antifreeze solution is diverted when necessary. These
convectors are typically located outside the building and
dissipate heat directly to outdoor air.
13
• Heat exchangers that dissipate surplus heat to high
thermal capacity loads, such as swimming pools, spas
or buried earth loops. The latter is well-suited for
geothermal heat pump systems in climates with relatively
small cooling loads.
• Nocturnal cooling — the antifreeze solution is circulated
between the tank heat exchanger and the collector array
at night to dissipate heat back to the atmosphere. In
some systems, the check valve in the collector loop can
be manually opened to allow nocturnal cooling without
operation of the circulator. Note: Nocturnal cooling can
only be used with flat plate collectors.
Heat dumps (other than nocturnal cooling) are usually
brought online using an electrically operated diverting
valve. In its unpowered state, this valve allows the
antifreeze solution to flow between the collector array
and the normal load — such as a heat exchanger in the
solar storage tank.
When the solar tank reaches a user-specified temperature
limit, the solar system controller powers up the diverting
valve. The heated antifreeze solution returning from the
collector array is then routed to the heat dump. If, during
the heat dump mode, the solar storage tank temperature
drops, the solar system controller discontinues the heat
dump mode and redirects the heated antifreeze to the
normal load.
Power outages are one of the chief causes of collector
stagnation. For a heat dump to be effective during such
times, it must be able to operate in the absence of utilitysupplied power. DC circulators operated from batteries
are one possibility. Passive heat dissipation devices that
operate based on buoyancy-driven flow are another.
Heat dump subsystems should be sized to dissipate
the entire heat gain of the collector array during a warm
and sunny summer day and with no load assumed on
the system. This is based on the premise that two or
more such days could occur in sequence, and that
the first could bring the solar storage tank to its upper
temperature limit. The absence of load during this
scenario is based on the occupants being away from
the building.
Antifreeze-Based Combisystem Designs:
Solar combisystems can be designed many ways
depending on project requirements and constraints.
For example, a narrow doorway might require that a
system needing several hundred gallons of storage is
designed around multiple smaller tanks rather than a
14
single large tank. A ground-mounted collector array
may not provide the elevation change required for a
drainback system, and thus the only choice would
be an antifreeze-based system. The size of the space
heating load and the type of auxiliary heat used will
certainly influence overall system design. In short,
there is no “universal” design concept for a solar
combisystem that suits all situations.
The remainder of this section discusses several
“templates” for solar combisystems that can work for
many residential or light commercial applications. All
these systems use antifreeze-based closed collector
circuits. Section 5 will present several additional templates
for drainback combisystems.
Antifreeze-Based Combisystem #1:
The first design presented is a natural extension of a solar
domestic water heating system. It adds an auxiliary storage
tank to accept heat from the collector array whenever
it’s available, and the domestic hot water storage tank
has reached a user-set maximum temperature. A piping
schematic for the system is shown in figure 4-1.
A standard solar circulation station like that used in a
solar DHW system controls flow through the collector
array. Whenever the temperature sensor (S2) on the
domestic water tank is below a user-selectable maximum
setting, flow returning from the collectors is routed to
the left, through the internal heat exchanger in the DHW
storage tank. It then passes into the “B” port of the
3-way diverter valve (D1), out through the “AB” port and
back to the supply side of the solar circulation station.
The diverter valve is not energized in this mode. There is
no flow through the coil in the auxiliary storage tank. A
spring-loaded check valve helps prevent heat migration
into the auxiliary storage tank during this mode.
If the solar controller detects that temperature sensor
(S2) has reached the maximum temperature setting,
it applies line voltage to the diverter valve (D1). Hot
antifreeze solution returning from the collectors is now
routed through the coil of the auxiliary storage tank.
As heat is diverted to the auxiliary storage tank, the solar
controller continues to monitor the temperature of the
DHW tank sensor (S2). If its temperature drops a preset
amount, the diverter valve (D1) reverses position to route
the antifreeze solution returning from the collectors
through the coil in the DHW tank. The solar controller
always treats the DHW storage tank as the “priority” load,
directing heat to it whenever its temperature is under a
user-specified maximum value.
Figure 4-1
air vent
w/ shut off
valve
or
ar
ra
y
collector sensor (S1)
so
la
r
co
lle
ct
outdoor
temperature
sensor
outdoor
temperature
sensor
room
T thermostat
(C2)
low temperature
radiant panel circuits
(P3)
outdoor
reset
controller
cold water
DHW
P&T
solar
circulation
station
(C3)
relay R1
A
(P1)
(D2)
electric
element
AB
B
(P2)
tank
sensor
(S2)
AB
VENT
B
A
(D1)
diverter
valve
DHW storage tank
aux.
sensor
(S3)
Aux. storage tank
Figure 4-2
boiler supplies heat when
temperature is climbing. Solar storage supplies heat when temperature is dropping
Supply water temperature (ºF)
solar tank supplies heat
130
120
110
5ºF
differential
(shown)
calculated target temperature
100
contacts on reset controller
open to allow solar tank
to serve as heat source
90
80
boiler supplies heat
contacts on reset controller
close to enable boiler
as heat source
70
70 60 50 40 30 20 10
0
-10 -20
Outdoor temperature (ºF)
15
Figure 4-3
L1
N
120 VAC
solar
controller
P1
sensors
collector
circulator
diverter
valve (D1)
(120 VAC
actuator)
M
P2
heat
source
circulator
R1
P3
distribution
system
circulator
transformer
120/24 VAC
24 VAC
room
thermostat
sensors
3-way
mixing
valve
controller
(C2)
R
C
sensors
R
C
D2
M
outdoor reset
controller (C3)
24 VAC 3-way
diverter valve
w/ end switch
D2
(T T)
terminals
on boiler
R1 (relay coil)
16
The temperature the auxiliary storage tank reaches depends
on the load and solar availability. During a sustained sunny
period, it is possible for the auxiliary tank to reach a
temperature well above that needed by the space heating
distribution system.
In this system, a call for space heating comes from a
thermostat, which switches 24 VAC power to the 3-way
motorized mixing valve, allowing it to begin operation. 24
VAC power also powers up the coil of relay (R1), which
switches line voltage to operate circulators (P2) and (P3). 24
VAC power also energizes the outdoor reset controller (C3),
which calculates the required supply water temperature for
the space heating based on its settings and the outdoor
temperature. An example of the logic used by the outdoor
reset controller is shown in figure 4-2.
The sloping gray line represents the “target” temperature,
which is the ideal supply water temperature (read from the
vertical axis) for a corresponding outdoor temperature (read
from the horizontal axis). The slope of the gray line can be
adjusted by changing the settings on the controller. The
dashed blue line below the gray line indicates the temperature
at the supply sensor at which the output contacts on the
outdoor reset controller close. The dashed red line above the
gray line indicates the temperature at the supply sensor where
these contacts open.
If, for example, the outdoor temperature is 30ºF, the calculated
target temperature shown in figure 4-2 is 92.5ºF. The lower
dashed line indicates the output contacts close if the temperature
at the supply sensor is 90ºF or less. The upper dashed line
indicates these contacts open if the temperature at the supply
sensor is 95ºF or more.
The controller’s supply sensor measures the temperature near
the top of the auxiliary storage tank. Thus, with these settings,
if the outdoor temperature is 30ºF, and the temperature
near the top of the auxiliary storage tank is 90ºF or less, the
controller determines that the auxiliary storage tank is too cool
to supply the space heating distribution system. It closes its
output contacts to power on the diverter valve (D2), allowing
it to change position so flow passes through the boiler. When
the diverter valve completes its rotation, an end switch in its
actuator closes to fire the boiler.
When there is a call for space heating, and the temperature at
the top of the auxiliary tank is 95ºF or higher, the outdoor reset
controller allows the auxiliary storage tank to serve as the heat
source for the distribution system.
If the storage tank is serving as the heat source, it continues to
do so until the tank sensor temperature drops to 90ºF, at which
point the system automatically switches to the boiler as the
heat source. If the boiler is serving as the heat source,
it continues to do so until the tank temperature climbs
above 95ºF, at which point the auxiliary tank becomes
the heat source.
Keep in mind that these temperatures change based on
the current outdoor temperature. The slope of the reset
line and the differential of the outdoor reset controller
can also be adjusted to suit the type of heat emitters
and auxiliary heat source used in the system.
This simple logic for switching between heat sources allows
the solar storage tank to be utilized to the lowest possible
temperature that can still satisfy the space heating load.
This improves collector efficiency, and increases total solar
energy collection over the heating season.
A wiring schematic for this system using the control
method described above is shown in figure 4-3.
Antifreeze-Based Combisystem #2:
Some combisystems are designed around a single
storage tank. The energy in this tank supplies both
domestic hot water and space heating. One example of
such a system is shown in figure 4-4.
Solar energy is added to this tank through the lower
heat exchanger coil. In smaller combisystems, a solar
circulation station (as shown) could likely handle flow
through the collector array.
The storage tank contains potable water. The upper
heat exchanger coil is used to extract heat from this
water for use by the space heating system. It is also
used to add heat produced by the boiler to the water
at the top of the tank. The latter mode ensures that
domestic hot water is always available at a suitable
supply temperature regardless of solar energy input.
Figure 4-4
y
air vent
w/ shut off
valve
mod/con boiler
CW
DHW
anti-scald
tempering valve
P&T
P3
A
AB
check
valve
outdoor
temperature
sensor
3-way
motorized
mixing
valve
(C2)
B
end switch leads from actuators
space-heating circuits
(highly zoned)
pressureregulated
circulator
3-way diverter valve (D1)
end switch leads
so
la
r
co
lle
ct
or
ar
ra
relay
(P2)
closely spaced tees
(P1)
thermostat
(1 per zone)
relay (R1)
solar
circulation
station
heat source
circulator
manifold valve actuator
make-up water
solar storage tank
(dual coil)
17
Figure 4-5
L1
N
120 VAC
solar
controller
Temperature stratification helps keep this heat at the top of the tank.
The bottom of the tank remains as cool as possible to maximize
collector efficiency. The spring-loaded check valve at the upper outlet
of the tank reduces heat migration through the attached piping. Its
function is especially important in warm weather when no space
heating is required.
A wiring diagram for this system is shown in figure 4-5.
P3
sensors
collector
circulator
diverter
valve (D1)
(120 VAC
actuator)
M
R1
(T T)
terminals
on boiler
R1
heat
source
circulator
R1
distribution
system
circulator
P1
P2
transformer
120/24 VAC
24 VAC
thermostat
M
thermostat
M
thermostat
M
sensors
3-way
mixing
valve
controller
(C2)
R
A call for heating is initiated by any zone thermostat, which powers up
one of the manifold valve actuators. When the associated manifold valve
is fully open, an end switch within the actuator closes. This provides 24
VAC power to operate the 3-way motorized mixing valve (C2), which
then regulates supply temperature to the distribution system based on
outdoor temperature. Relay (R1) is also energized to turn on the heat
source circulator (P1), and the distribution circulator (P2).
If the boiler is NOT operating, there is no power to the 3-way diverter
valve (D1). Flow passes from the tank’s upper coil into the “AB” port of
the diverter valve, and then out through the valve’s “B” port. It moves
on through the air separator to a pair of closely spaced tees. The
latter provide hydraulic separation between circulators (P1) and (P2).
Hot water passes from the side port of the upper tee to the hot port
of the motorized mixing valve as required to achieve the necessary
supply temperature. The distribution system could supply any of
the lower temperature heat emitters discussed earlier, and it could
be extensively zoned. In the latter case, a variable-speed pressureregulated circulator (P2) provides differential pressure control in
response to operation of the zone valves. A normally closed contact
on relay (R1) is now open to prevent line voltage from energizing the
diverter valve (D1).
When the temperature in the upper portion of the storage tank drops
to a lower limit, (based on the system’s ability to supply adequate
domestic hot water), the diverter valve (D1) is powered on by the solar
controller. Flow now passes from this valve’s “AB” port out through its
“A” port and onward through the boiler. When the diverter valve (D1)
reaches the end of its travel, an end switch within the valve’s actuator
closes to fire the boiler.
C
R1 (relay coil)
18
In this system, the solar controller determines when the top of the tank
requires heating, and if so, turns on the boiler, the heat source circulator
(P1) and powers up the 3-way diverter valve (D1) so flow passes through
the boiler and eventually the upper tank coil. In systems where the solar
controller does not provide this logic, it can be created using standard
hydronic control hardware as described for the previous system.
If the space heating distribution system is also operating while the boiler
is firing, some of the boiler’s heat output is used for space heating. Any
remaining heat output is transferred to the upper portion of the storage
tank by the upper heat exchanger coil. If the space heating distribution
system is not operating, line voltage from the solar controller passes
through the normally closed relay contact (R1) to operate the heat
source circulator (P1).
This configuration allows the thermal mass of the water in
the upper portion of the tank to buffer the space heating
load, and thus helps prevent boiler short cycling. This
is especially beneficial when the distribution system is
extensively zoned.
Antifreeze-Based Combisystem #3:
The functionality of antifreeze-based system #2 can also
be achieved using slightly different hardware. Figure 4-6
shows a very similar solar subsystem to that used in
figure 4-4. The difference is an external stainless steel
brazed plate heat exchanger rather than an upper coil in
the storage tank.
Domestic hot water from the storage tank flows through
the external heat exchanger based on the operation of a
small bronze or stainless steel circulator (P3). This pump
can be configured for either constant-speed or variablespeed operation. Figure 4-6 shows two different piping
arrangements based on how circulator (P3) is controlled.
If the speed of circulator (P3) is varied (as shown in the
upper portion of figure 4-6), it can meter domestic hot water
through the external heat exchanger such that the water
temperature supplied to the space heating distribution
system also varies. The higher the speed of circulator (P3),
the faster heat transfers across the heat exchanger and the
warmer the distribution system becomes.
air vent
w/ shut off
valve
ra
y
Figure 4-6
mod/con boiler
so
la
r
co
lle
ct
or
ar
relay
CW
anti-scald
tempering valve
end switch leads from actuators
DHW
P&T
A
check
valve
pressureregulated
circulator
B
3-way diverter valve
AB
(P2)
(P3)
(P1)
solar
circulation
station
heat source
circulator
zoned space heating circuits
thermostat
relay
manifold valve actuator
make-up water
Bronze or stainless steel circulator. Speed varied to maintain suitable temperature
to the distribution system.
piping using variable speed circulator (P3)
solar storage tank
A
check
valve
AB
3-way
motorized
mixing
valve
B
3-way diverter valve
fixed
speed
circulator
heat source
circulator
zoned space heating circuits
(P2)
(P3)
(P1)
end switch leads from actuators
pressureregulated
circulator
thermostat
relay
manifold valve actuator
make-up water
piping using 3-way motorized mixing valve
19
The speed of circulator (P3) could be varied based
on maintaining a fixed supply temperature to the
distribution system. It could also be varied based on
outdoor reset logic.
If circulator (P3) is operated in an on/off manner, a mixing
valve is required in the distribution system. Circulator (P3)
would turn on whenever the boiler is operating as well as
when there is a call for space heating.
The ability to control the speed of circulator (P3) also
prevents what could be very hot water in the solar storage
tank from flowing directly to a low-temperature distribution.
As such, it eliminates the need for a motorized mixing
valve in most applications. However, if the distribution
system operates at very low water temperatures relative
to the minimum temperature maintained in the top of
the storage tank (for delivery of domestic hot water),
the space heating distribution circulator (P2) should be
temporarily turned off while the boiler is heating the top
of the storage tank. Circulator (P3) should also operate
at full speed during this mode to maximize heat transfer
across the heat exchanger. When the top of the storage
tank has reached the preset water temperature, variablespeed operation of circulator (P3) can resume.
One advantage of either of these approaches is that the
external heat exchanger is serviceable or replaceable if
ever necessary. Another advantage is that the thermal
mass of the water in the storage tank will buffer a highly
zoned space heating distribution system, and thus
reduce the potential for boiler short cycling.
Figure 4-7
Antifreeze-Based Combisystem #4:
There are many homes and commercial buildings with
forced-air distribution systems for heating. It is possible
to build a solar combisystem using hydronic hardware
to collect and convey solar energy, and then pass this
energy to a forced-air distribution system. One approach
is shown in figure 4-7.
so
la
r
co
lle
ct
or
ar
ra
y
air vent
w/ shut off
valve
diverter
valve
(modulating)
water heater
temperature
controller
motorized mixing valve
w/ controller
anti-scald
tempering
valve
hot water
check
valve
cold water
P&T
(P1)
water-to-air
heat exchanger coil
solar
circulation
station
blower
VENT
solar storage tank
(dual coil)
20
The solar collection subsystem is essentially the same as
in previous systems.
The storage tank contains domestic water and absorbs
solar-derived heat through the lower coil.
If the domestic water leaving the tank needs a further
temperature boost, it is routed through the modulating
instantaneous water heater via a 3-way diverter valve,
which is operated by a setpoint temperature controller.
If this controller determines that domestic water leaving
the tank does not need further heating, the diverter
valve routes flow directly to the hot port of an anti-scald
tempering valve. This configuration eliminates the heat
loss associated with passing heated water through the
unfired water heater.
Any instantaneous water heater used in this type
of system must modulate its firing rate to adjust for
preheated incoming water. Verify that any instantaneous
water heater being considered for such an application is
warranted for use with solar combisystems that supply
preheated domestic water.
Upon a call for space heating, a controller determines if
the temperature at the top of the storage tank is sufficient
to supply the water-to-air heat exchanger coil mounted
in the supply plenum of the forced-air distribution
system. This decision can be based on outdoor reset
control. However, designers are cautioned that lowtemperature supply air must be carefully introduced into
heated spaces to avoid drafts. This may require a lower
temperature limit on the reset controller.
A motorized mixing valve monitors the temperature
of the supply air downstream of the plenum coil.
The mixing valve adjusts itself as required to prevent
potentially high-temperature water in the storage tank
from creating overly hot supply air to the building.
If the tank’s temperature is too low to properly supply
the plenum coil, the furnace’s burner (or the compressor
in a forced-air heat pump system), would operate as
normal. The space heating circulator (P1) would be
off. A check valve in this circulator, or mounted as a
separate component, prevents heat in the plenum from
migrating backward into the hydronic system.
Antifreeze-Based Combisystem #5:
Another possible system configuration uses a storage
tank with an integral gas-fired heat source, as shown
in figure 4-8. This eliminates the boiler as a separate
component. It also eliminates the diverter valve and the
piping associated with connecting the boiler and diverter
valve to the system.
As with the other antifreeze-based systems, solar energy
is added to the storage tank through the lower heat
exchanger coil.
The modulating/condensing burner and heat exchanger
assembly operate as necessary to maintain the top of
the storage tank at an adequate temperature to supply
domestic hot water whenever required (not necessarily
24/7). At other times, such as night setback periods,
the temperature at the top of the storage tank may be
allowed to drop based on outdoor reset control logic.
The position of the burner/heat exchanger assembly
within the tank encourages temperature stratification
and minimizes heating of the lower portion of the tank to
minimize losses in collector efficiency.
The water in the storage tank is not potable water.
It’s the same water that circulates through the panel
radiators during space heating. This allows the tank to be
constructed of standard steel (rather than stainless steel
or standard steel with glass lining to hold potable water).
Domestic water is instantaneously heated as it is drawn
through the system. A flow switch closes it contacts
whenever cold domestic water is drawn into the external
brazed plated heat exchanger. These contacts turn on a
small circulator (P1), which creates flow through the tank
side of this heat exchanger.
Brazed plate heat exchangers have very small volume
and low thermal mass relative to their heat transfer
surface area. They can begin heating potable water in
one or two seconds after flow is initiated. An anti-scald
mixing valve protects against high water temperatures
being sent to the fixtures. As soon as hot water flow
stops, so does circulator (P1).
Very little domestic hot water is held in the heat
exchanger. This reduces the potential for legionella. The
heat exchanger can also be removed and serviced if ever
necessary.
The heated water at the top of the tank provides thermal
mass for a stable supply of heat to the heat exchanger.
21
Figure 4-8
panel radiator
TRV
thermostatic radiator valves
on each panel radiator
TRV
TRV
ay
air vent
w/ shut off
valve
TRV
lle
ct
or
ar
r
TRV
so
la
r
co
TRV
anti-scald tempering valve
stainless steel heat exchanger
3-way motorized mixing valve
outdoor
temperature
sensor
flow
switch
manifold distribution
system using PEX or
PEX-AL-PEX tubing
(P2)
(P1)
integral
mod/con
burner / heat
exchanger
pressure-regulated
circulator
check
valve
solar
circulation
station
VENT
storage tank
As the tank’s temperature begins to drop, the burner fires
to maintain a suitable temperature at the top of the tank
for sustained domestic hot water delivery.
The thermal mass at the top of the tank also stabilizes a highly
zoned space heating distribution system. In figure 4-8, this
distribution system consists of a manifold station supplying
individually controlled panel radiators. Each radiator has
its own thermostatic valve to control heat output. This
allows for room-by-room zone control. A variable-speed,
pressure-regulated circulator (P2) automatically varies its
speed in response to radiator valve modulation.
This system would treat domestic water as its priority
load, routing solar-derived heat to the tank whenever
possible. The space heating portion of the system would
operate as described for antifreeze-based system #2.
Using a Pool as a Heat Dump:
If the temperature at the top of the storage tank
reached a user-selected maximum limit, the heat dump
subsystem would come into operation. In this system,
the following sequence takes place: 1) The diverter
valve routes the hot antifreeze solution returning from
the collectors to the pool heat exchanger. 2) The flow
switch detects this flow and turns on the pool filter
pump (if it is not already operating). 3) Heat is now
transferred to the pool.
The system shown in figure 4-9 is an extension of antifreezebased system #2, and includes a provision to dump excess
heat from the storage tank to a swimming pool.
Since the space heating portion of this system is unlikely to
operate during warm weather, a significant percentage of
the collected solar energy will likely be routed to the pool.
The extremely large thermal mass represented by the
pool can accept a significant amount of heat while only
raising a few degrees Fahrenheit in temperature.
For outdoor pools not used in winter, designers must
provide a means of disabling the pool heating mode, and
direct any excess energy to an alternative heat dump.
22
Figure 4-9
ar
ra
y
air vent
w/ shut off
valve
anti-scald
tempering valve
CW
DHW
end switch leads from actuators
3-way
motorized
mixing
valve
A
AB
check
valve
space-heating circuits
(highly zoned)
pressureregulated
circulator
B
3-way diverter valve
(P2)
closely spaced tees
flow
switch
pool heat
exchanger
outdoor
temperature
sensor
end switch leads
solar
circulation
station
mod/con boiler
so
la
r
co
lle
ct
or
relay
(P1)
heat source
circulator
spring loaded
check valve
thermostat
relay
manifold valve actuator
make-up water
AB
bypass valve
(normally closed)
A
B
solar storage tank
(dual coil)
sensor
S3
filter
pool
pool pump
5. DRAINBACK SOLAR COMBISYSTEMS
Drainback systems are the most common alternative to
antifreeze-based solar thermal systems. There are many
ways to configure drainback combisystems, depending
on the heating distribution system used, the percentage
of the load to be supplied by solar energy and the type of
auxiliary heat source used.
Whenever they are not operating, drainback systems
allow water from the collector array and piping outside
heated space to drain back to a tank located within
heated space. This action requires only gravity and
properly sloping piping components. It does not rely on
devices such as solenoid valves or vacuum breakers, and
as such is highly reliable.
This section discusses several systems that show a wide
variety of concepts. The systems are assumed to be for
residential applications. However, most can bescaled up
for commercial installations.
Advantages of Drainback Systems:
Perhaps the most apparent advantage of a drainback
system is the elimination of antifreeze fluids. This, in turn,
implies several other benefits, including:
• Antifreeze solutions require a heat exchanger between
the collector subsystem and the water in the remainder
of the system. Beside the fact that heat exchangers can
add significant cost to the system, they also induce a
performance penalty. All heat exchangers require a
temperature differential to drive heat from their “hot”
side to their “cool” side. In solar collection subsystems,
the temperature differential shows up as an increase
in collector inlet temperature relative to the water
temperature near the bottom of the storage tank. This
decreases collector efficiency. The magnitude of this
performance penalty depends on the size of the heat
exchanger. Larger, more expensive heat exchangers
reduce the penalty, but never completely eliminate it.
Appendix B gives information for estimating the thermal
performance penalty associated with a heat exchanger
between the collector array and storage tank.
• Eliminating antifreeze also eliminates the annual fluid
testing, and thus reduces system owning cost.
• The collectors in a drainback combisystem do not
contain fluid when they stagnate. A power outage,
control failure or other condition that stops the collector
loop circulator results in the water draining back from
the collectors and exposed piping. This minimizes
internal stresses on the collector relative to systems in
23
which the fluid remains in the collector or flashes to vapor
during stagnation.
• Because the collectors in a drainback system “dry
stagnate,” there is no need for a heat dump provision.
This is especially relevant to combisystems, which often
have larger collector arrays compared to DHW-only
systems, and thus have increased potential for warm
weather stagnation due to the storage tank reaching a
maximum temperature setting.
• Many drainback systems eliminate the need for an
expansion tank in the system. The air volume that
accommodates drainback water, if properly sized, can
serve as the expansion tank for the system.
Figure 5-1
roof penetration
Disadvantages of Drainback Systems:
• All piping to and from the collector array, and in some
cases the collectors themselves, must be sloped to
ensure proper drainage. A minimum pitch of 1/4-inch
vertical drop per foot of horizontal run is recommended.
The absorber plates used in some collectors ensure
that they will drain completely. Other collector designs
may require that the entire collector array be sloped to
ensure complete drainage (see figure 5-1). Verify that
any collectors being considered for a drainback system
are approved and warranted for this application.
It’s also possible to slope half the collectors in one direction
and half in the other as shown in figure 5-2. In this case,
the supply piping penetrates the
roof at the midpoint between the
two banks of collectors. Return
piping penetrates the roof at
the upper outside corners of
"downslope
each bank and is joined together
dead end"
under the roof deck.
roof penetration
cap
Designers should also ensure
that any “downslope dead ends”
(see figure 5-1) are detailed so
that water will not puddle across
the diameter of the piping. In
general, such dead ends should
be kept as short as possible.
harp style collectors are sloped minimum of 1/4" per ft.
roof penetration
roof penetration
vertical serpentine style collectors are mounted level,
but connecting piping is slope minimum of 1/4" per ft.
24
There can be no low points in any
piping connecting the collector
array with the storage tank. Any
low points can interfere with
air reentering the collectors,
or create a “trap” that could
eventually freeze and burst the
pipe.
Collectors with an integral sensor
well are preferred for drainback
applications. This detail allows
the sensor to closely track
absorber plate temperature
without relying on convection
of fluid within the collector.
Strapping a sensor to outlet
piping, as is commonly done
with systems using antifreeze
solutions, will delay the control
response. Figure 5-3 shows an
example of an absorber plate
with integrated sensor well.
Open-Loop vs. ClosedLoop Drainback Systems:
Figure 5-2
As is true with hydronic heating,
drainback systems can be designed
as either “open-loop” or “closed-loop”
systems, as shown in figure 5-4.
Open-loop drainback systems use
a non-pressurized storage tank. The
air above the water is always at
atmospheric pressure.
roof penetrations
copper caps
minimum of 1/4" per foot slope
minimum of 1/4" per foot slope
photo courtesy of Radiant Engineering
Figure 5-3
Non-pressure rated tanks are usually
less expensive per gallon of storage
than pressure-rated tanks. They can
often be assembled on site. Some
use an insulated structural “shell” to
support a flexible EPDM rubber liner
that contains the water. Others are
constructed of molded polypropylene.
All piping connections to such tanks
usually penetrate the tank wall above
the water line to minimize any chance
of leakage.
copper caps
Because the water in an open-loop
system is in direct contact with the
atmosphere, it will always contain
dissolved oxygen molecules. All
piping components must therefore
be suitable for contact with this
“oxygenated” water. Circulators
must be of stainless steel, bronze
or polymer construction. All piping,
fittings and valves must also be
corrosion-resistant. Copper piping
along with copper or brass fittings
and valves are common. Stainless
steel
and
high-temperature
composite or polymer materials are
also a possibility, provided they are
rated to withstand the potentially
high temperatures within the solar
collector circuit.
Open-loop systems will experience
some water loss due to evaporation.
The water level in the tank should
be checked monthly using the sight
glass or dip stick. Water can be
easily added to the system through
the hose bib valve at the bottom of
the collector supply piping.
25
sight
glass
All solar circuit piping sloped
minimum 1/4" per ft.
Some water will
evaporate from
tank over time
tank open to atmosphere
All solar circuit piping
sloped minimum
1/4" per ft.
lift head
lift head
Figure 5-4
air pressure control valve
pressure gauge
air
equilization
tube
sight
glass
pressurized air
atmospheric pressure
static
water
level
pressure
relief
valve
static
water
level
liner
(P3b)
(P3a)
circulators
must be rated
for "open"
systems
tank
temperature
sensor
(in well)
"open loop"
drainback system
Most of the drainback combisystems to be presented in
this section are closed-loop systems. The water and air
they contain is, for all practical purposes, sealed into
the system. Like other closed-loop hydronic systems,
they can use cast iron circulators and contain steel
components. The dissolved oxygen in the initial water
and air volume will react with any ferrous metal in the
system, forming a very light and essentially insignificant
oxide film. At that point, the water is neutralized and
will not continue to oxidize metals.
Closed-loop systems can also experience very minor
water losses over a period of time due to weepage at
valve packing or circulator flange gaskets. Some of the
dissolved air in the cold water used to fill the system will
26
"closed loop"
drainback system
also be removed and vented over time. These effects
will cause a minor drop in the system’s static water
level over time. Small amounts of water can be manually
added to the system through the lower hose bib valve to
correct for these losses.
An automatic make-up water assembly should NEVER
be connected to this type of system. Doing so, especially
in systems with high-performance air separating/venting
devices, will eventually replace the air in the system with
water. Over time this will eliminate the necessary air
space for proper drainage and could eventually lead to
freezing of water-filled piping or collectors exposed to
outdoor temperatures.
Operation of a Drainback System:
Figure 5-5
40
1
head added (feet)
35
The solar heat collection cycle in a drainback system is controlled
the same way as that in an antifreeze-based system. When the
collector sensor reaches a temperature a few degrees above
that of the tank sensor, the circulator(s) are turned on.
two circulators in series
30
25
A drainback system might contain two circulators in series, or a
single “high head” circulator. In either case, the circulator(s) push
water up through the piping and collector array. Air is pushed
ahead of this water and eventually back to the space at the top
of the storage tank. The water level within the tank drops slightly
during this process. There is no need of either a high-point air
vent (as required in an antifreeze-based system) or a vacuum
breaker at the top of the collector circuit.
20
15
10
5
single circulator
0
0
2
4
6
8
10
12
14
16
head added / lost (feet)
flow rate (gpm)
system curve
as water reaches top
of collector loop
40
t4
2
35
t3
30
OP4
25
t2
20
lift head
15
t1
10
5
t0
0
0
2
4
6
8
10
12
14
this flow rate must produce a
flow velocity of at least 2 ft/sec
in the return pipe from the collectors
t4 t5 t6 t7 t8
3
head added / loss (feet)
35
30
OP4
25
20
15
10
off
OP8
5
0
0
2
4
6
8
10
12
14
16
flow rate (gpm)
stable flow rate with
one circulator off
system curve after siphon is established
Once the siphon is established, it is usually possible to turn
off the upper of two series-connected circulators, or reduce
the speed of a single high-head circulator, and still maintain
adequate flow through the collector array.
The sequence of operation of a “dual-pumped” drainback
system using two series-connected fixed-speed circulators is
depicted in figure 5-5.
16
flow rate (gpm)
40
With proper pipe sizing, the flow velocity in the piping returning
from the collector array allows air bubbles to be entrained with
the water and returned to the top of the storage tank. As this
occurs, a siphon is formed within the return piping. This siphon
eventually cancels out most of the initial “lift head” associated
with filling the collector array.
The upper graph shows the effective pump curve of two identical
fixed-speed circulators connected in series. It is constructed by
doubling the head of the single circulator at each flow rate.
Both circulators are turned on each time the solar energy
collection process begins. During the first few seconds of
operation, water is lifted upward through the collector supply
piping. This causes the system curve to migrate upward along
the graph as depicted by the light blue dashed lines labeled t1,
t2 and t3 in the upper graph. Notice that these curves steepen as
they rise. This is due to the frictional resistance of water flowing
through more piping and the collector array as flow approaches
the top of the collector circuit.
The dark blue system curve labeled t4 represents the situation
as water “rounds the turn” at the top of the collector circuit.
The intersection of this system curve and the pump curve
for two circulators in series establishes the instantaneous
operating point marked as OP4. The flow rate associated with
this operating point can be read from the horizontal axis directly
below this point. For the example shown in figure 5-5, this flow
rate is about 5.7 gallons per minute.
27
To establish a siphon, the flow rate at operating point
OP4 must produce a corresponding flow velocity within
the return piping of 2 feet per second or higher. The flow
rates necessary for a flow velocity of 2 feet per second in
type M copper tubing are shown in figure 5-6.
Water at a flow velocity of 2 feet per second or higher
can entrain air bubbles and drag them along. This action
eventually rids the return piping of air, displacing it back
to the top of the storage tank. At that point, a siphon is
established in the return line. Think of the water going down
the return pipe as helping “pull” water up the supply pipe.
The formation of a siphon causes the system curve to shift
downward, as depicted by the light blue curves t4, t5, t6,
t7, and finally the dark blue curve t8. In a typical residential
drainback system, this sequence may take 30 seconds to
perhaps 3 minutes. Depending on the details at the top
A similar solar collection cycle process occurs in
systems that use a single speed-controlled high-head
circulator. The circulator starts at full speed to quickly
push water up through the collector array and establish
the siphon. After some period of time, the circulator
reduces its speed (based on user programmed settings).
The intersection of the circulator’s reduced speed pump
curve and the system curves after the siphon has
formed determines the stabilized flow rate through the
collector array for the remainder of the cycle.
Siphon Limitations:
Once a siphon is established within a drainback system,
it’s important to maintain it until no further solar energy
collection is possible.
Figure 5-6
Tubing
Flow rate to establish
2 ft/sec flow velocity
1/2" type M copper
1.6 gpm
3/4" type M copper
3.2 gpm
1" type M copper
5.5 gpm
1.25" type M copper
8.2 gpm
1.5" type M copper
11.4 gpm
2" type M copper
19.8 gpm
2.5" type M copper
30.5 gpm
3" type M copper
43.6 gpm
of the storage tank, the system’s pressure and the height
of the collector array, much of the initial “lift head” is now
recovered by the downward “pull” of the siphon.
When the upstream circulator is turned off, the operating
point shifts to a final position marked as OP8. This point
determines the flow rate the collector array operates at
during the remainder of the solar collection cycle. Notice
that the flow rate at the stable operating point OP8 is
higher than the flow rate through the collectors when the
water first passes over the top of the collector circuit with
both circulators operating. For the example given, it is
about 7.2 gallons per minute.
The solid red pump curve in graph 3 is shifted slightly below
the pump curve for the single circulator. It represents the
“net” effect of the lower circulator pumping through the
volute of the upstream circulator, which is now off.
Modern controllers, which vary collector
circulator speed in response to the difference
between the collector temperature and
storage tank temperature, have a minimum
speed function intended to maintain the
siphon under reduced speed operation.
If the siphon does break, the collector
temperature would rise rapidly (because
there is(because
no flow through
Theflow
controller
rapidly
there it).
is no
through it).
would detect this, and increase circulator
and
increase circulator speed to reestablish th
speed to reestablish the siphon.
addition to
to adequate
adequate flow
InInaddition
flow velocity
velocityinin the co
the
collector
retun
piping,
siphon
stability
stability depends on a relationship
between th
depends on a relationship between the
corresponding
vapor pressure, and the vertica
water’s temperature, its corresponding vapor
collector
circuit
thedistance
water between
level in the stor
pressure, and the and
vertical
the top of the collector circuit and the water
in the storageestimate
tank.
Alevel
conservative
for the maximum siph
found with formula 5-1:
A conservative estimate for the maximum siphon height
that can exist can be made using formula 5-1:
Formula 5-1
Formula 5-1
 144 
H max = 
 ( Pa + Ptop − Pv )
 D 
Where:
Where:
Hmax = maximum siphon height
D = density of water at maximum anticipated temperature
Hmax = maximum siphon height
(lb/ft3)
pressureof
(psia)
Pa = atmospheric
D = density
water at maximum anticipated
Ptop = extraPpressurization
(above
atmospheric) at the top
a = atmospheric pressure (psia)
of the collector
circuit (psi)
pressurization
(above
atmospheric
top = extra
Pv = vaporPpressure
of water
at maximum
anticipated
temperaturecircuit
(psia) (psi)
Pv = vapor pressure of water at maximum anti
28
The vapor pressure and density of water need
calculated using the following formulas:
Where:
Hmax = maximum siphon height
D = density of water at maximum anticipated temperature (lb/ft3)
Pa = atmospheric pressure (psia)
Ptop = extra pressurization (above atmospheric) at the top of the collector
circuit (psi)
Pv = vapor
pressure
of water
at maximum
For
The
vapor
pressure
and
density anticipated
of water temperature
needed for(psia)
example: Determine the maximum siphon height
based
for water at 200ºF in a system at sea level (where
formula
5-1
can
be
calculated
using
the
following
The vapor pressure and density of water needed for formula 5-1 can be
Pa
=
14.7
psia), and
where
the
pressure
at the
top
of the
formulas:
For
example:
Determine
the
maximum
siphon
height
based
for water at 20
calculated using the following formulas:
where the pressure at
in a system
atissea
level
(where
Patmospheric
a = 14.7 psia), and
collector
circuit
10
psi
above
pressure.
For example: Determine the maximum siphon height based for water at 200ºF
Pv = 0.771 − 0.0326 × T + ( 5.75 ×10 −4 ) × T 2 − ( 3.9 ×10 −6 ) × T 3 + (1.59 ×10 −8 ) × T 4
D = 62.56 + ( 3.413 ×10
−4
) T − (6.255 ×10 ) T
−5
2
top at
ofsea
thelevel
collector
is 10 psi above atmospheric pressure.
in a system
(where Pcircuit
a = 14.7 psia), and where the pressure at the
top of the collector circuit is 10 psi above atmospheric pressure.
Solution: The density and vapor pressure of water at
Solution: The density and vapor pressure of water at 200ºF is:
200ºF is:
Solution:
The density and vapor pressure of water at 200ºF is:
D = 62.56 + ( 3.413 ×10 −4 ) 200 − ( 6.255 ×10 −5 ) 200 2 = 60.1lb / ft 3
D = 62.56 + ( 3.413 ×10 −4 ) 200 − ( 6.255 ×10 −5 ) 200 2 = 60.1lb / ft 3
Where:
Where:
(
)
(
)
(
−4 −6
23
−6
−4
2
4 3
Pv = 0.771P−v 0.0326
× 200
+ ( 5.75 ×10
− (×10
3.9 ×10
× 200
1.59×10
×10 −8
= 11.49
psia×10 −8
= 0.771
− 0.0326
× 200
5.75
×)200
−+ (3.9
200
+ 1.59
) ×+ 200
) ××200
Pv ==vapor
pressure
of water
(psia) (psia)
vapor
pressure
of water
P
v
D = density of water (lb/ft3) 3
D
= density of water (lb/ft )
T = temperature of water (ºF)
T = temperature of water (ºF)
) × 200
4
=
The
siphon height
is then
calculated:
Themaximum
maximum
siphon
height
is then
calculated:
The maximum siphon height is then calculated:
 144 
 144 
H max = 
+10 ) = 31.7 ft
 ( Pa −Pv + Ptop ) = 
 (14.7 −11.49
 144

144
 D 
 60.1 
H max = 
 ( Pa − Pv + Ptop ) = 
 (14.7 −11.49 +10 ) = 31.7 ft
 D 
 60.1 
Figure 5-7
If the system were installed with a greater vertical drop from the top of the
collector circuit to the water level in the storage tank, the water in the return
If theflash
system
were installed
with
a greater
vertical drop from the
piping
vapor (e.g.,
boil) and with
break the
If thewould
systemto were
installed
a siphon.
greater vertical drop
top of the
collector circuit to the water level in the storage tank, the water in the retu
from
the top
ofheight
thedecreases
collector
circuit
the
water
level in
The
maximum
siphon
increasing
water
temperature,
piping
would
flash
to
vaporwith
(e.g.,
boil) to
and
break
the siphon.
All exposed piping
sloped minimum
1/4" per ft.
lift head
because
as temperature
the water
to itspiping
vapor flash
the storage
tank,increases,
the water
incomes
the closer
return
would
point.
sight
glass
static water
level
insulated
drainback
tank
air space for drainback and expansion
maximum
siphon
height
increasing water temperature,
flash The
to vapor
(e.g.,
boil)
and decreases
break thewith
siphon.
because
as height
temperature
increases,
the water
comes
closer
The maximum
siphon
can be increased
by raising
the pressure
within
a to its vapor flas
point.
closed-loop
drainback system.
pressure
helps “suppress”
from
The maximum
siphonIncreased
height
decreases
with water
increasing
boiling. This is a significant advantage of a closed-loop pressurized drainback
waterThe
temperature,
because
asbetemperature
increases,
system
relative
to an open-loop
pressurization
is possible.
maximum
siphonsystem
heightwhere
can no
increased by
raising the pressure within
the water
comes
closersystem.
to its vapor
flash
point.helps “suppress” water f
Increased
pressure
closed-loop
drainback
This analysis does not include the effect of frictional pressure drop in the return
boiling.
This effect
is a significant
of device
a closed-loop
pressurized
drainba
piping, or
the potential
of adding a advantage
flow-restricting
near the end
of
system
to pressure
anheight
open-loop
system
where
pressurization
The
maximum
siphon
can
beandincreased
by raising is possible
the
return
piping relative
to increases
in that
pipe
thus
helpno
suppress
vapor flash.
the pressure within a closed-loop drainback system.
This analysis does not include the effect of frictional pressure drop in the r
pressure
“suppress”
water
boiling.
IfIncreased
the height of the
building ishelps
such that
the collector circuit
mustfrom
be taller
than
piping,
or the potential
effect of adding
a flow-restricting
device near the e
the
maximum
siphon height,advantage
a separate drainback
tank may be located
high in
This
is
a
significant
of
a
closed-loop
pressurized
the to
return
piping
to increases
the building
limit the
lift head,
as shown inpressure
figure 5-7.in that pipe and thus help suppress
drainback
system relative to an open-loop system where
vapor flash.
[insert
figure 5-7]
no pressurization
is possible.
If the height of the building is such that the collector circuit must be taller
maximum
siphon
height,
a separate
may be located high
This the
analysis
does
not
include
the drainback
effect oftank
frictional
the building to limit the lift head, as shown in figure 5-7.
pressure
drop in the return piping, or the potential effect
of adding
a flow-restricting device near the end of the
[insert figure 5-7]
return piping to increases pressure in that pipe and thus
help suppress vapor flash.
PRV
If the height of the building is such that the collector
circuit must be taller than the maximum siphon height,
a separate drainback tank may be located high in the
building to limit the lift head, as shown in figure 5-7.
The lift head is now from the static water level in the
elevated drainback tank to the top of the collector circuit.
The vertical height of the piping circuit below this water
level does not affect lift head.
2 circulators
in series
or
1 high head
circulator
Sight Glasses:
storage tank
All drainback systems require a means of verifying the
proper water level in the drainback reservoir. This is true
when the top of the storage tank serves as the drainback
reservoir or if a separate drainback tank is used.
29
Figure 5-8
In some systems, particularly openloop systems using translucent
polymer storage tanks, it may be
possible to see the water level as a
shadow line on the tank wall or by
looking into the tank through a small
opening at the top. A “dip stick”
is another possibility for checking
water level in such systems.
In a closed-loop pressurized system, a “sight glass” is the common
solution for checking water level
(see figure 5-8). The sight glass
can be mounted within the upgoing
collector supply piping, directly to
the storage tank, or to two other
piping locations on the same side
of the collector circuit — one above
and one below the static water
level. In all cases, the water in the
system seeks a single level when
the collector circulators are off. It is
advisable to place the sight glass
where it can be easily accessed.
Image courtesy of Hot Water
Some sight glasses are made of
Products, Inc.
temperature resistant glass, others
may use temperature resistant translucent polymers. It is
even possible to use a piece of translucent PEX tubing
as a sight “glass” provided it is operated within its rated
temperature/pressure range.
It is suggested that the sight glass tube be a minimum of
12 inches long and centered on the desired static water
level in the tank. Longer sight glasses will obviously
allow more variations in water level to be detected. Sight
glasses should also be serviceable. The transparent or
translucent tube itself may accumulate a film over time
and require removal for cleaning or replacement. Install
isolating ball valves to ensure such service is possible
without need of draining the storage tank.
Tank Piping Connections:
There are several ways to detail the piping at the top and
bottom of a drainback tank. As previously mentioned, most
open-loop drainback systems bring all piping connections
through the top or high side wall of the tank, and above the
static water level. This reduces the possibility of leakage as
gaskets at such connecting points age.
In open-loop systems, an inverted U-tube is used to draw
water from the lower portion of the tank to the collector
circulator(s) (see figure 5-4). The top of this U-tube should
30
be kept as close to the top of the tank as possible. It
should also use generously sized piping to minimize
frictional head loss. The inverted U-tube is “primed”
with water by closing an isolation flange on the collector
circulator and adding water at a high flow rate through
the hose bib valve below the collector circulator. The
objective is to displace air within the upper portion of
the U-tube. Once this is accomplished, the water will
remain in place when the circulators are off. A valve
can be added to the top of the U-tube to minimize
the amount of air needing to be displaced at priming;
however, be sure this valve is tightly sealed at all other
times to maintain the priming water in place. Do not
place a float-type air vent or vacuum breaker at the top
of the inverted U-tube. Since this portion of the piping
is under negative pressure relative to the atmosphere,
either of these devices will allow air into the system.
There are also numerous variations in how the return piping
from the collector array attaches to the tank. It is crucial
that all such connections allow air to flow backward into
the return piping at the onset of the drainback process.
It is also preferable that the water enters the storage
tank horizontally. This minimizes disruption of the vertical
temperature stratification within the tank.
If the return piping enters the drainback tank above the
operating water level, there will be a slight “water fall”
sound created by the water falling from the end of the
pipe to the water level in the tank. Although a matter
of opinion, a drop of perhaps a few inches within a
well insulated tank, located in a mechanical room
away from primary living space, should not create
objectionable sounds.
If the return pipe enters the tank below the operating
water level, a separate air equalization tube must be used
as shown in some schematics within this section. Some
of the flow returning from the collectors may pass into
this tube as the system operates. However, momentum
will carry most of the flow past the tee where the air
equalization tube connects to the collector return piping,
and thus most of the water will enter below the water
level in the tank.
Drainback Combisystem #1:
The first complete drainback combisystem we’ll discuss
is shown in figure 5-9. This system may look familiar to
those who have read section 4. It uses the same boiler,
near-boiler piping and distribution system concept
as shown with antifreeze-based system #2. The only
difference is that a drainback solar subsystem is now
in place.
Figure 5-9
lift head
All solar circuit piping
sloped minimum 1/4"
per ft.
relay
air pressure control valve
cold water
PRV
outdoor
temperature
sensor
recirculation
end switch leads from actuators
3-way
motorized
mixing
valve
hot water
sight
glass
space-heating circuits
(highly zoned)
pressureregulated
circulator
air space
A
static
water
level
AB
check
valve
time
delay
relay
B
3-way diverter valve
end switch leads
air return
tube
(P2)
closely spaced tees
(P1)
(P3b)
heat source
circulator
thermostat
relay
manifold valve actuator
DHW coil
(P3a)
differential
temperature
controller
storage / drainback tank
This is a slightly pressurized closed-loop drainback
system. The same water that flows through the collector
array can also flow through the space heating distribution
system, as well as through the boiler when necessary.
No heat exchangers are required between these parts
of the system.
The suspended coil near the top of the tank is for heating
domestic hot water. It is constructed of either stainless
steel or copper, and in some tanks, can be removed
through a large flanged opening at the top of the tank.
The boiler operates as necessary to maintain a suitable
minimum temperature at the top of the storage tank.
This ensures that domestic hot water is always available
upon demand. Temperature stratification within the tank
minimizes heat migration to the lower portion of the tank.
The solar system controller used in this system provides
two outputs. One operates the collector circulator(s). The
other is used to operate the boiler and 3-way diverter
valve as necessary to maintain a suitable minimum
temperature at the top of the storage tank.
If two series-connected circulators are used for the
collector circuit, a separate time delay relay can be
used to turn the upper circulator off once the siphon is
established in the return piping.
Whenever the solar system controller determines the
top of the tank requires heating, it fires the boiler and
powers on the 3-way diverter valve so flow passes from
the valve’s “AB” port through its “A” port, and on through
the boiler. The same signal also turns on the heat source
circulator (P1).
A call for space heating comes from any zone thermostat,
which powers up a manifold valve actuator. When the
actuator reaches the end of its travel, an internal end
switch closes to send 24 VAC power to the mixing valve
controller. This 24 VAC signal also powers the coil of a
relay (R1), which applies 120 VAC to operate circulator
31
(P1) and (P2). The mixing valve controller operates
on outdoor reset logic to maintain the ideal supply
temperature to the distribution manifold.
If the boiler is operating during the call for space heating,
some of its heat output will be extracted at the closely
spaced tees that provide hydraulic separation between
circulators (P1) and (P2). The remainder of its output will be
absorbed into the water at the top of the storage tank.
If the boiler is not operating during the call for heat (which
is the expected situation after a significant period of solar
energy collection), the 3-way diverter valve routes flow
through its “B” port, bypassing the boiler. Heated water
is supplied directly from the storage tank to the closely
spaced tees. The motorized mixing valve draws in the hot
water it needs to control the supply temperature to the
space heating distribution system.
Notice that there is no automatic make-up water
assembly used on this system. Likewise, there is
no separate expansion tank. Minor water losses
over time can be monitored at the sight glass, and
“made up” by manually adding water through a lowpoint hose bib valve. The air reservoir at the top of
the storage tank, if properly sized, can serve as the
system’s expansion tank.
This system uses the thermal mass at the top of the
storage tank to “buffer” the space heating distribution
system. This is especially desirable if the distribution
system is highly zoned.
Drainback Combisystem #2:
Another combination of subassemblies has been used to
build the combisystem shown in figure 5-10.
Figure 5-10
lift head
All solar circuit piping
sloped minimum 1/4"
per ft.
boiler
circulator (P3)
conventional boiler
(requires protection
from flue gas
condensation)
anti-condensation mixing valve
room
thermostat
air return
tube
PRV
outdoor
temperature
sensor
sight
glass
air space
static
water
level
diverter valve
time
delay
relay
B
AB
heat source
circulator (P1)
(P3b)
outdoor
temperature
sensor
DHW coil
anti-scald
tempering
valve
differential
temperature
controller
storage / drainback tank
hot
cold
(P3a)
32
HyroLink
A
outdoor
reset
controller (C1)
other
heating
load
zone
relays
(P3)
stor.
3-way
distribution
motorized
circulator
(P2)
mixing valve
(reset control)
The solar collection process operates the same way as in
drainback combisystem #1. However, in this system, the
differential temperature controller only handles the solar
collection function. Other control devices manage the
heat source selection, distribution of heat and domestic
water heating. Many of these other controls are common
to other types of hydronic systems.
This system uses two tanks: solar storage and a
conventional indirect water heater. No auxiliary heat from
the boiler is ever sent to the solar storage tank. This
allows that tank to remain as cool as possible, and thus
maximizes solar collector efficiency.
Heat in the solar storage tank is transferred to cold
domestic water through the suspended coil heat
exchanger. This allows the solar storage tank to provide
some domestic water preheating even when it is relatively
cool. However, during or after a period of solar energy
collection, this coil may provide the full temperature rise
required. If not, supplemental heat is supplied by the
boiler through the HydroLink and then through the heat
exchanger of the indirect water heater.
For the system shown, a call for spacing heating comes
from the room thermostat, which supplies 24 VAC power
to the 3-way motorized mixing valve, as well as the
outdoor reset controller (C1). The mixing valve begins
regulating the supply temperature to the distribution
system based on its settings.
The outdoor reset controller (C1) compares the
temperature at the top of the storage tank to a calculated
“ideal” supply water temperature for the space heating
subsystem.
An example of the outdoor reset control function is shown
in figure 5-11. The “target” temperature is represented by
the solid gray sloping line on this graph, and is a function
of outdoor temperature and the current controller settings.
The blue dashed line below the target temperature line
indicates the temperature at which the contacts on the
outdoor reset controller close. The red dashed line above
the target temperature line indicates the temperature
where these contacts open.
For example, if the outdoor temperature is 30ºF, the
calculated target temperature shown in figure 5-1 is
92.5ºF. The lower dashed line indicates that the contacts
close if the temperature at the tank top sensor is 90ºF or
less. The upper dashed line indicates that the contacts
open if that temperature is 95ºF or more.
With these settings, if the outdoor temperature equals
30ºF and the temperature at the top of the solar storage
tank is 90ºF or less, the controller determines that the
solar storage tank is too cool to supply the heating
distribution system. It then closes its contacts to power
on the diverter valve, allowing it to change position and
route flow through the boiler. When the diverter valve has
completed its movement, an end switch within the valve’s
Figure 5-11
boiler supplies heat when
temperature is climbing. Solar storage supplies heat when temperature is dropping
Supply water temperature (ºF)
solar tank supplies heat
130
120
110
5ºF
differential
(shown)
calculated target temperature
100
contacts on reset controller
open to allow solar tank
to serve as heat source
90
80
boiler supplies heat
contacts on reset controller
close to enable boiler
as heat source
70
70 60 50 40 30 20 10
0
-10 -20
Outdoor temperature (ºF)
33
Figure 5-12
L1
N
R2
P3
R2
DHW
tank
P1
R1
heat
source
actuator closes to operate the boiler and the boiler circulator.
Hot water is then supplied to space heating through the
HydroLink, and eventually the 3-way mixing valve.
If the temperature at the top of the auxiliary tank is 95ºF
or higher, the outdoor reset controller (C1) allows the solar
storage tank to serve as the heat source for the distribution
system.
If the solar storage tank is serving as the heat source, it
continues to do so until the tank sensor temperature drops
to 90ºF, at which point the system automatically switches to
the boiler as the heat source.
R1
P2
distribution
system
transformer
120/24 VAC
24 VAC
room
thermostat
sensors
3-way
mixing
valve
controller
sensors
outdoor
reset
controller
(C1)
R
R
C
R1
C
M
If the boiler is serving as the heat source, it continues to
do so until the tank temperature climbs above 95ºF (from
additional solar gain). At this point, the solar storage tank
again becomes the heat source.
Keep in mind that these temperatures change based on the
current outdoor temperature. The slope of the reset line, as
well as the differential of the outdoor reset controller, can be
adjusted to suit the type of heat emitters and auxiliary heat
source used in the system. This simple method of switching
between heat sources allows the solar storage to be utilized
to the lowest possible temperature compatible with the heat
emitters. This improves collector efficiency and increases
the total solar energy gathered over the heating season.
A conventional boiler is shown in this system. As in other
hydronic systems serving low-temperature distribution
systems, such boilers require protection against sustained
flue gas condensation. This is accomplished using a
thermostatic mixing valve to monitor the inlet temperature
to the boiler and boost it when necessary by blending in hot
water from the supply side of the boiler.
A partial wiring schematic showing how the system operates
(other than solar energy collection function) is shown in
figure 5-12.
Drainback Combisystem #3:
24 VAC 3-way
diverter valve
w/ end switch
Boiler circulator powered
through C1, C2 terminal on
boiler limit controller
DHW tank
thermostat
34
(T T)
terminals
on boiler limit
controller
R2
R2
Both of the previous drainback designs use a suspended
coil heat exchanger in the solar storage tank for domestic
water preheating. While certainly plausible, this approach
limits potential tank suppliers, especially if the size of the
tank or its internal heat exchanger is “non-standard.”
The serviceability of an internal heat exchanger over the
life of the system is also a consideration. Some tanks allow
the internal heat exchanger to be lifted out through a large
flange at the top of the tank if ever necessary. Others do
not allow any access to the internal heat exchanger. The
Figure 5-13
lift head
panel radiator
air return
tube
PRV
stainless steel
brazed plate
heat exchanger
sight
glass
air space
static
water
level
check
valve
TRV
TRV
mod/con boiler
thermostatic radiator valves
on each panel radiator
TRV
to / from
other
panel radiators
outdoor
temperature
sensor
A
AB
B
(P3)
HyroLink
(P3b)
flow switch
(P2)
pressure-regulated
circulator
heat source
circulator
(P3a)
other heating loads
cold
hot
(P1)
manifold distribution
system using PEX or
PEX-AL-PEX tubing
storage / drainback tank
latter present few options if a leak, corrosion or scaling
ever develop to the point where the coil can no longer
function.
The approach used in figure 5-13 eliminates the need for
this internal heat exchanger.
Solar collection is handled by a closed-loop, slightly
pressurized drainback subsystem. The storage tank is a
simple, carbon steel vessel with no internal components
or special detailing.
The boiler operates as necessary to maintain the top of
the storage tank at a suitable minimum temperature for
domestic hot water delivery. When a hot water fixture
opens, a flow switch detects the flow of cold domestic
water and turns on the small circulators (P3). This moves
heated water from the top of the storage tank through
one side of a stainless steel brazed plate heat exchanger.
Cold domestic water flows through the other side of this
heat exchanger.
Because the plate heat exchanger has very little water
content relative to its plate area, it warms and transfers
heat within a second or two after the flow of hot
water begins. Thus, domestic hot water is produced
“instantaneously” upon demand. The thermal mass of hot
water in the storage tank allows for stable DHW delivery.
This approach also minimizes the quantity of domestic
hot water held in the system at any time reducing the
potential for legionella.
Space heating is provided from a manifold station
serving panel radiators (sized for operation at low supply
water temperature). Each panel radiator is controlled by
its own thermostatic radiator valve. A variable-speed
pressure-regulated circulator (P2) modulates its speed
as necessary to maintain a constant differential pressure
across the manifolds as zone circuits open and close.
A HydroLink serves to hydraulically isolate the space
heating distribution system and two other potential
heating zones (served from the bottom connections of
the HydroLink) from the heat source circulator (P1).
This system provides the benefits of a single storage
tank, elimination of heat exchangers between the solar
subsystem and space heating circuits, buffering for a
highly zoned distribution system, instantaneous domestic
water heating and an easily serviced external heat
exchanger for domestic water heating.
Figure 5-14 shows the original system schematic at the
top, and its operating mode while supplying domestic hot
35
Figure 5-14
lift head
panel radiator
air return
tube
PRV
stainless steel
brazed plate
heat exchanger
sight
glass
air space
static
water
level
check
valve
TRV
TRV
mod/con boiler
thermostatic radiator valves
on each panel radiator
TRV
to / from
other
panel radiators
outdoor
temperature
sensor
A
AB
B
(P3)
HyroLink
(P3b)
flow switch
(P2)
pressure-regulated
circulator
heat source
circulator
(P3a)
other heating loads
cold
hot
(P1)
manifold distribution
system using PEX or
PEX-AL-PEX tubing
lift head
storage / drainback tank
air return
tube
PRV
stainless steel
brazed plate
heat exchanger
sight
glass
air space
static
water
level
check
valve
A
AB
B
(P3)
(P3b)
hot
(P3a)
cold
flow switch
Domestic hot water supplied by solar from storage tank
storage / drainback tank
36
Figure 5-15
lift head
panel radiator
TRV
thermostatic radiator valves
on each panel radiator
air return
tube
TRV
TRV
PRV
sight
glass
air space
static
water
level
check
valve
AB
to / from
other
panel radiators
outdoor
temperature
sensor
A
B
(P3)
(P2)
HyroLink
(P3b)
pressure-regulated
circulator
heat source
circulator
(P1)
other heating loads
manifold distribution
system using PEX or
PEX-AL-PEX tubing
(P3a)
Space heating supplied by solar from storage)
storage / drainback tank
panel radiator
PRV
air space
TRV
TRV
mod/con boiler
thermostatic radiator valves
on each panel radiator
TRV
check
valve
outdoor
temperature
sensor
A
AB
to / from
other
panel radiators
B
(P3)
HyroLink
(P3b)
(P2)
pressure-regulated
circulator
heat source
circulator
(P1)
other heating loads
manifold distribution
system using PEX or
PEX-AL-PEX tubing
(P3a)
Space heating supplied by boiler (storage tank serves as buffer)
storage / drainback tank
37
water from solar storage tank. Inactive components in the
lower schematic are shown in gray.
The upper schematic in 5-15 shows the system supplying
space heating from the solar storage tank. The lower
schematic shows the system supplying space heating
from using the boiler as the heat source and the storage
tank as a buffer. Inactive components are shown in gray.
connections are usually made above the water level to
minimize any potential leakage with age. An example of
a large (550-gallon) unpressurized storage tank (partially
assembled) is shown in figure 5-17.
Figure 5-17
Drainback Combisystem #4:
Some solar combisystems may include auxiliary heat
sources that also require a storage tank. One example
is a system using a wood-fired boiler. In these cases, it’s
often possible to combine the storage requirements into
a single tank, as shown in figure 5-16.
This system is built around an unpressurized storage tank.
Such tanks typically have an insulated structural shell
supporting a flexible waterproof liner. They are vented to
the atmosphere and thus not capable of operating under
pressure. The air space above the water is sufficient to
accommodate thermal expansion of the water. All piping
Image courtesy of American Solartechnics
Figure 5-16
r
la
so
lle
co
or
ct
All solar circuit piping
sloped minimum 1/4" per ft.
y
ra
ar
(modulating)
water heater
outdoor
temperature
sensor
3-way
motorized
mixing
valve
temperature
controller
PRV
hot
relay
anti-scald
tempering
valve
cold
(P1)
closely
spaced
tees
end switch leads from actuators
space-heating circuits
(highly zoned)
pressureregulated
circulator
(P2)
thermostat
vent
wood-fired boiler
unpressurized buffer tank w/ suspended copper coils
anti-condensation mixing valve
make-up water
38
sensor in closed copper tube
copper coil heat exchangers
sight
glass
(P3)
end switch leads
lift head
diverter
valve
make-up water
time delay relay
solar loop circulators
must be rated for
"open" systems
hose bib valve
(for draining collector loop
& adding water to tank)
manifold valve actuator
All hydronic subsystems connected to this tank are
pressurized. They include the boiler circuit, domestic
water preheating subsystem and the space heating
distribution system. These subsystems absorb or
dissipate heat to the water in the tank through large,
coiled, copper heat exchangers, such as the one shown
in figure 5-18.
Figure 5-18
Energy for space heating is also extracted from the tank
through a third suspended coil. This coil and the remaining
space heating piping constitute another closed-loop
pressurized subsystem, and thus require a pressure relief
valve and expansion tank.
Heat from the collector array is added to the tank through
the drainback subsystem. The tank water passes directly
through the collector circuit. No heat exchangers are
required. The absence of a heat exchanger improves the
efficiency of the collectors.
Because this is an open-loop drainback system, the
circulators must be bronze, stainless steel or a hightemperature polymer to avoid corrosion. A “dual-pumped”
circulator is shown with a time delay relay used to turn off
the upper circulator when the siphon is established in the
collector return piping.
Image courtesy of American Solartechnics
An elbow located just below the operating water level
deflects flow returning from the collectors so it enters the
tank horizontally rather than vertically. This helps preserve
temperature stratification within the tank. A tee is installed
a few inches above the water level to allow air to reenter
the return piping fro drainback.
This heat exchanger consists of four parallel “windings”
of copper tube manifolded together at each end. This
configuration produces far less pressure drop than would
a single tube coil of the same total length.
The water level in the tank is indicated by a sight glass
installed at a suitable height. Water can be added to the
tank through the hose bib valve at the bottom of the
collector loop.
The wood-fired boiler heats the tank through a copper
coil heat exchanger suspended from the top or side of
the tank. This coil and remaining boiler piping constitute
a closed hydronic circuit, and therefore require a
pressure relief valve and expansion tank. Depending on
local codes, the boiler circuit may also require safety
devices such as a low-water cut off or manual reset high
limit. A 3-way thermostatic mixing valve is used to boost
boiler inlet temperature to prevent flue gas condensation
within the boiler. This is essential for minimizing creosote
formation within the boiler and its venting system.
An “inverted-U” piping configuration is used to supply
the collector circulators. This eliminates the need for
piping to penetrate the tank below the water level. This
piping should be kept as short and low to the tank top
as possible. The collector loop circulators should be
mounted as low as possible to maintain some slight
positive pressure at their inlet. The inverted U is primed
by closing an isolation valve on the solar loop circulators
and adding water to the tank at a high flow rate through
the hose bib valve. Once filled, the inverted U should
remain full of water.
Domestic water is preheated through another suspended
copper coil in the tank. A controller measures the
temperature of the water leaving this coil. If it’s hot
enough to supply the fixtures, the diverter valve
directs it to the anti-scald tempering valve. As in
other combisystems, this valve prevents excessively
hot water from flowing directly to the fixtures. If the
water needs further heating, the diverter valve directs
it through the modulating instantaneous water heater.
After this, it again passes through the anti-scald mixing
valve before going to the fixtures.
The combination of a solar collector array and wood-fired
boiler is synergistic. The boiler will likely be used more
during cold and cloudy winter weather. The solar array
will produce greater outputs in spring and fall, and may
even eliminate the need to operate the wood-fired boiler
for domestic water heating during warm weather.
39
6. PERFORMANCE ESTIMATION:
The performance of any solar energy system obviously
depends on weather. As such, it cannot be precisely
predicted from one day to the next. In the case of
a solar combisystem, performance also depends on
both the space heating and domestic hot water loads
of the building it serves. Both loads are highly variable
depending on personal preferences, energy saving efforts
and habits of the building occupants. Compounding this
situation are issues such as collector shading at specific
times or the possibility of snow on the collectors — even
when the sun is out.
Because of the highly variable nature of the source
as well as the demand for energy, the performance
of solar thermal systems is often estimated through
computer simulation. In some cases, these simulations
take place on an hour-by-hour basis, or possibly even
on a 15-minute basis. Because there are 8760 hours in a
year, these calculations are laborious and only capable of
being done using a computer.
Expectations:
Many people with little more than a philosophical interest
in solar heating tend to overestimate the performance
of solar energy systems. Upon seeing a typical threeto eight-collector array on a roof, a common question
to the building’s owner might be: “Can those heat your
entire house?” Implicit in this question is optimism that
solar collectors might eliminate the need for heat from
conventional fuels, such as oil, gas or electricity. Although
a lofty goal, this is almost never the case.
Constructing a very large solar thermal system that
could approach the ideal of 100% solar heating would
be very expensive, and unable to pay for itself in savings
over the useful life of the system. Such a system would
also generate much more heat than could be used
during warmer weather. In short, such a system would
be far from economically justifiable. Without economic
justification, such systems would have very limited
acceptance and contribute very little to widespread use
of renewable energy.
The most economical solar combisystems always use a
combination of solar and auxiliary energy.
Increasing the size of the solar portion of a combisystem
(e.g., more collector area and a larger storage tank)
demonstrates the law of diminishing returns. Each time
the collector area is increased by a fixed amount, say by
adding 100 square feet of collector area to the array, the
40
resulting savings will be less than that associated with
adding the previous 100 square feet. The total savings
goes up, but at a constantly diminishing rate.
From an economic standpoint, the goal is to find the
best combination of solar-derived and auxiliary heat that
produces the lowest life-cycle cost for a given project.
This requires knowledge of or accurate estimates for
many factors, such as the cost of various-size systems,
the thermal performance of the same, the cost of auxiliary
heating and its likely rate of inflation several years into
the future, the expected cost of system maintenance
and insurance, and how the system’s economics are
influenced by current incentives, such as tax credits and
subsidized loans. Having detailed and reliable information
on all these considerations during the design process
is virtually impossible. The best that can be done is to
make estimates, then use a software tool to gauge the
sensitivity of the design to variations in these estimates.
f-chart Analysis:
One established method of predicting the monthly
and annual performance of solar combisystems was
developed at the University of Wisconsin, Madison during
the mid-1970s. It is called f-chart. The letter f stands for
fraction—specifically, the fraction of the combined space
heating and domestic hot water load that is supplied by
solar energy.
f-chart was originally developed as a simplified method
for predicting the performance of solar thermal systems
for residential-scale applications at a time when the
computational performance needed for hour-by-hour
simulations was only available on mainframe computers,
and thus unavailable to most individuals. f-chart is based
on empirical correlations of the results of thousands of
hour-by-hour simulations done with a specialized solar
simulation program called TRNSYS. In its initial form,
the f-chart methodology could be completed using a
scientific calculator. Although this is still possible, the
methodology has been translated to software and is now
available from at least two sources.
Like other solar design tools, f-chart requires several
variables to describe the system being modeled. These
include:
•
•
•
•
•
•
Location of installation (weather database)
Collector area
Collector efficiency intercept (FRta)
Collector efficiency slope (FRUL)
Collector slope
Collector azimuth
•
•
•
•
•
•
Collector flow rate
Storage tank volume
Effectiveness of collector/storage heat exchanger
Specific heat of collector circuit fluid
Space heating load
Domestic hot water load
Once a specific system is defined by these inputs, f-chart
calculates several outputs on a monthly and annual basis.
These include:
Each house is assumed to be located in Syracuse, New
York (a cold and relatively cloudy winter climate), as well
as in Colorado Springs, Colorado (a cold but relatively
sunny winter climate).
Each house has been analyzed with two different
combisystems: One built around four 4-foot by 8-foot
flatplate collectors with 256 gallons of water storage, and
the other built around eight of the same collectors and
512 gallons of storage.
Other specific data for each system is as follows:
• Total solar radiation incident on the collector area
• Space heating load of the building
• Domestic water heating load of the building
• Auxiliary energy needed for space heating and DHW
• Percentage of the monthly (space heating + DHW) load
supplied by solar
An output screen listing these outputs for a specific
combisystem is shown in figure 6-1. The lowest line is the
annual total of the monthly quantities listed above it, except
for the solar fraction (f), in which case the lower line gives
the annual solar fraction. For the results given in figure 6-1,
solar energy supplied 0.235 (e.g., 23.5%) of the annual total
space heating plus domestic water heating load.
Case Studies:
The performance of some representative solar combisystems will now be discussed. These combisystems
have been designed for two different houses: one with a
design heating load of 35,000 Btu/hr and the other with a
design heating load of 100,000 Btu/hr.
Figure 6-1
For the smaller house:
• Design heating load = 35,000 Btu/hr, with outdoor
temperature = 0ºF and indoor temperature is 70ºF
• Domestic water heating load = 60 gallons per day
heated from the local cold water temperature to 125ºF.
For the larger house:
• Design heating load = 100,000 Btu/hr, with outdoor
temperature = 0ºF and indoor temperature is 70ºF
• Domestic water heating load = 100 gallons per day
heated from the local cold water temperature to 125ºF.
• Each system uses drainback freeze protection with no
collector-to-storage heat exchanger
• Collectors are 4-foot by 8-foot, with a gross area of 32
square feet each
• Collector efficiency intercept is 0.76, and the efficiency
slope is 0.865 (Btu/hr/ft2/ºF)
• Collector arrays are sloped at local latitude +15º
• Collector arrays face directly south
• Storage volume is 2 gallons per square foot of collector
area
The performance estimates that follow
were all determined using f-chart
software.
Figure 6-2 shows the monthly solar
fractions for both combisystems in the
smaller house located in Syracuse, NY.
Notice that several bars representing the
solar fraction in mid-year reach 100%,
even for the smaller combisystem. This
happens because the collector array
can generate more heat than the load
requires at this time of year. During the
colder months, the larger system has
approximately double the solar fraction
of the small system. However, on an
annual basis, the four-collector system
meets 23.5% of the total load of the
smaller house, whereas the 8-collector
41
Figure 6-2
system meets 37.4% of the total load. Thus, the smaller
system produced about 63%of the savings associated
with the larger system. Although double in size, the
larger system did not double the energy savings. This is
largely because of the lack of load in warmer weather,
where the higher potential output of the larger system
is of essentially no use.
It follows that the economic return on investment of
the smaller system, per square foot of collector area,
is greater than that of the larger system. The choice
of which system to install should consider this, as well
as the goals of the owners and the available space
required for each system. If the choice is largely driven
by economic considerations, the smaller system is
the better choice. However, if the owner’s desire is to
cover a greater percentage of the load, and both the
space and funds are available, the larger system may
be selected. Ultimately, most combisystem sizes are
selected based on the owner’s weighted preferences
for performance, economic return and philosophical
commitment to renewable energy use.
Figure 6-3 shows the performance prediction for the
larger house in Syracuse, NY, with the same two
combisystems.
Figure 6-3
Notice that only one bar — that associated with the
larger (8 collector) system — reaches the 100% mark in
July. The larger load — especially that associated with
100 gallons per day of domestic hot water — makes
better use of the collected energy. The eight-collector
system still approximately doubles the monthly fraction
of the four-collector system from November through
March. The annual solar fraction of the smaller system
is 10.1% versus 18% for the larger system. Again,
having twice the collector and storage size does not
double the annual solar yield. However, the difference is
more significant in this application relative to the smallhouse application because there is less wasted solar
energy during warmer weather (e.g., the larger domestic
water heating load makes better use of the available
solar energy).
Moving both of these systems to Colorado Springs,
Colorado, increases both the monthly and annual solar
fractions, as shown in figure 6-4.
Given the more favorable solar climate, the system on
the smaller house experiences even more excess energy
in warmer weather, especially if the larger collector array
is used. The annual solar fraction for the four-collector
system is now 34.8% versus 54.6% for the eightcollector system. Using twice the collector area and
storage yields about 57% more collected energy on an
42
Figure 6-4
annual basis. The diminishing return on the larger system is
again attributable to lack of load in warmer weather.
It also requires assurance that underground aquifers will
not be carrying away that heat prior to its recovery.
The larger house, with its larger load reduces this
excess, but doesn’t eliminate it for the eight-collector
system in either July or August. The annual solar fraction
for the four-collector system on the larger house is now
15.1% versus 26.9% for the eight-collector system.
The potential for excess heat production in summer also
favors the use of drainback freeze protection versus
antifreeze in combisystem applications. When no more
energy can be delivered to storage, the drainback system
drains and the collector array “dry stagnates.” In an
antifreeze-based system, a heat-dumping subsystem
must be operational to prevent rapid thermal deterioration
of the antifreeze solution.
The most important point to be taken from these
comparisons is that large solar combisystems in typical
residential applications do not offer the same economic
advantages of smaller combisystems. This is due to loads
being far less than the potential amount of heat collection
from a large collector array.
In some installations, the greater summertime energy
delivery of a solar combisystem could be used to heat
to a swimming pool. Heated fluid from the collector array
would be sent through a stainless steel heat exchanger
connected to the pool’s filter system. Assuming this energy
displaced other conventional energy for pool heating, the
economic viability of the system would definitely improve.
Another way to add load to the system in summer is to
dissipate heat into the loop field used for a geothermal
heat pump system. This could allow some quantity of
solar-derived heat to be stored in the earth—heat that
could later be recovered and used during the heating
season. However, the feasibility of this concept precludes
situations where the geothermal loop field is also being
used to dissipate heat from a building cooling system.
Collector Orientation in Combisystems:
The theoretical optimum collector orientation for a combisystem is true (polar) south. However, site conditions
that create shading may justify different orientations.
Variations up to 30 degrees East or West of true South
typically result in less than 10% loss of annual solar
energy collection.
An accepted rule of thumb for collector slope in
combisystem applications is latitude plus 15 degrees.
The steeper slope, relative to collectors used solely for
domestic water heating, favors winter sun angles, and
improves performance when heating loads are greatest.
Steeper collector slopes also reduces solar radiation on
collectors during warmer weather when loads are small,
and thus reduce the potential for overheating. Collectors
mounted to a vertical, south-facing, unshaded wall (slope
angle = 90 degrees) yield approximately 20% less energy
gain than collectors mounted at an optimal slope.
43
Storage Tank Size in Combisystems:
The size of the combisystems’s storage tank affects its
annual performance. A rule of thumb is to size storage
tanks in combisystems within the range of 1.25 to 2.5
gallons per square foot of collector area. Tanks larger
than the upper end of this range usually show little return
on the extra investment. Research has even shown that
tanks larger than about 3.7 gallons per square foot of
collector can decrease annual system performance due
to increased heat losses.
Figure 6-5
Annual solar heating fraction (%)
• All combisystems must include mixing assemblies that
prevent potentially high-temperature water generated by
the solar subsystem from reaching low-temperature heat
emitters. This mixing device can be operated based on
outdoor reset control logic to allow the lowest possible
water temperatures to satisfy the load.
• All systems should include a simple and automatic means
of switching the distribution system from using the storage
tank as the heat source to some form of auxiliary heating
when necessary. Building occupants should not experience
any loss of comfort as the system transitions between these
heat sources. An outdoor reset controller that calculates the
lowest possible temperature at which the solar storage tank
can supply the load is ideal for selecting which heat source
supplies the distribution system.
27.5
27
26.5
26
• All solar combisystems benefit from the same state-ofthe-art hydronics technology used in non-solar hydronic
systems. These technologies include pressure-regulated
circulators in combination with valve-based zoning,
hydraulic separation, manifold-based distribution systems
and high-performance air separation.
25.5
25
1
1.5
2
2.5
3
storage tank size
(gallons/sq ft of collector)
Figure 6-5 shows the affect of storage tank size on the
annual solar heating fraction for the 8-collector system
on the larger house in Colorado Springs, as discussed
earlier in this section. There is an increase in annual solar
heating fraction as tank volume increases, but the rate of
increase goes down as the size of the tank increases.
SUMMARY:
Solar thermal combisystems are a natural extension of
solar domestic water heating. Their objective is to provide
a high percentage of the building’s domestic hot water
and some percentage of its space heating energy.
There are countless variations in how solar combisystems
can be designed. A system that’s “perfect” for one situation
may not be suitable for the next. However, all combisystems
should address the following considerations.
• For best performance, solar subsystems should be
interfaced with space heating delivery systems that operate
at low water temperatures. Do not simply assume that
44
a solar subsystem can interface directly to any existing
space heat distribution system. A suggested maximum
operating temperature for a space heating distribution
system that will interface to solar collectors is 120ºF.
• All combisystems should provide year-round preheating
of domestic water, and thus utilize solar-supplied heat at
its lowest possible temperature.
• For good performance, the effectiveness of the collectorto-storage heat exchangers in antifreeze-based systems
should be at least 0.55 (see appendix B for information on
calculating heat exchanger effectiveness).
• Systems should be designed with the assistance
of software. The latter can be used to estimate the
combined effects of many variables that vary from one
system to the next.
• All piping components should be well insulated to
minimize extraneous heat loss and optimize the delivery
of heat precisely where and when it’s needed.
• Optimum collector orientation in combisystem
applications is generally due south, with a slope angle of
latitude plus 15 degrees.
• Storage tanks in combisystem applications should be
sized between 1.25 and 2.5 gallons per square foot of
collector area. Tanks larger than this add very little to
annual system performance.
APPENDIX A: Piping Symbol Legend
GENERIC COMPONENTS
circulator
circulator w/
isolation flanges 3-way motorized
mixing valve
CALEFFI COMPONENTS
3-way thermostatic mixing
valve
4-way motorized
mixing valve
DISCAL central
air separators union
circulator w/
internal check valve
& isolation flanges flow-check valve
swing check valve
float -type
air vent
gate valve
spring loaded
check valve
globe valves
purging valve
Autoflow
balancing
valve
backflow preventer
pressure
reducing
valve
ball valve
pressure gauge
thermostatic
radiator valve
thermostatic
radiator valve
pressure
relief
valve
pressure &
temperature
relief valve
strainer
primary/secondary
fitting
zone valve
(2 way)
zone valve
(3 way)
pressure
relief valve
metered
balancing
valve
differential pressure
bypass valve
hose bib
drain valve
diverter tee
Hydro
Separator
brazed plate
heat exchanger
air & dirt
separator
DIRTCAL
dirt separator
cap
diaphragm-type expansion tank
Hydrolink
(3 configurations)
manifold station with
balancing valves
conventional boiler
solar
circulation
station
indirect water heater (with trim)
Modulating / condensing boiler
high temperature
solar DISCAL air separators high temperature
solar pressure
relief valve
solar collector array
high temperature
solar air vent
Modulating tankless water heater
high temperature
shut-off valve for
solar air vent
high temperature
solar 3-way thermostatic
mixing valve
isolar differential
temperature
controller
high
temperature
solar expansion
tank
45
APPENDIX B:
B: Performance:
Heat Exchanger
Heat APPENDIX
Exchanger
Where:
Performance:
(8.01 x D x c x f)min = the smaller of the two fluid
exchanger performance is often expressed as “effectiveness,”
whichrates.
is
Found by calculating the product (8.01
Heat Heat
exchanger
performance is often expressed as capacitance
defined as follows:
x D x c x f) for both the hot and cool side of the heat
“effectiveness,” which is defined as follows:
exchanger and then selecting the smaller of the two.
actual heat transfer rate
e=effectiveness = e =
Thin = inlet temperature of the hot fluid (ºF)
maximum possible heat transfer rate
Tcin = inlet temperature of the cool fluid (ºF)
The actual
rate
of
heat
transfer
can
be
determined
based
The actual rate of heat transfer can be determined based on the flow rate,
As the size of the heat exchanger increases relative to the
on thespecific
flow rate,
heat and change
temperature
change
ofshown
heatspecific
and temperature
of either
fluid, as
in figure B-1.
required rate of heat transfer, its effectiveness approaches
either fluid, as shown in figure B-1.
the theoretical limiting value of 1.0.
[insert figure B-1]
Figure B1
hot side cool side
Example: A heat exchanger in a solar combisystem
operates at the conditions shown in figure B-2. The
fluid in the collector loop is a 40% solution of propylene
fh
fc
glycol. The fluid on the cool side of the heat exchanger is
Thin
Tcout
water. Determine the rate of heat transfer across the heat
exchanger and its effectiveness under these operating
conditions.
Figure B2
Thout
hot side
Tcin
Qactual = (8.01× Dh × ch ) × fh × (Thin − Thout )
or
Qactual
= (8.01× Dc × cc ) × fc × (Tcout − Tcin )
Where:
4 gpm
130ºF
40%
propylene
glycol
cool side
6 gpm
116.3ºF
water
120ºF
110ºF
Qactual = actual rate of heat transfer across heat exchanger (Btu/hr)
Where:8.01 = unit conversion factor
Dh = density of fluid through hot side of heat exchanger (lb/ft3)
density
ofof
fluid
through
cool
side of
heatexchanger
exchanger (lb/ft3)
rate
heat
transfer
across
heat
QactualD=c =actual
(Btu/lb/ºF)
ch = specific heat of fluid through hot side of heat exchanger
Start
by finding the fluid properties of both the 40%
(Btu/hr)
= specific
heat of
fluid through cool side of heat exchanger
(Btu/lb/ºF)
propylene
glycol solution and water at the average
8.01 =chunit
conversion
factor
fh = flowof
rate
of fluid
through
heat
exchanger (gpm)
temperature of each fluid as it passes through the heat
fluid
through
hot hot
sideside
of of
heat
exchanger
Dh = density
3 fc = flow rate of fluid through cool side of heat exchanger (gpm)
exchanger.
(lb/ft )
Dc = density of fluid through cool side of heat exchanger
For the 40% propylene glycol solution:
(lb/ft3)
3
ch = specific heat of fluid through hot side of heat D = 64.0 lb/ft
c = 0.91 Btu/lb/ºF
exchanger (Btu/lb/ºF)
ch = specific heat of fluid through cool side of heat
For water:
exchanger (Btu/lb/ºF)
For the 40% propylene glycol solution:
3
61.8
lb/ftlb/ft
fh = flow rate of fluid through hot side of heat exchanger DD= =64.0
cc==
0.91
Btu/lb/ºF
1.00 Btu/lb/ºF
(gpm)
fc = flow rate of fluid through cool side of heat exchanger For water:
D
=(ºF)
61.8calculate
lb/ft
Next,
the actual rate of heat transfer across the
(gpm) T = temperatures at locations shown in figure
c = 1.00 Btu/lb/ºF
heat exchanger. This can be done using data from either
T = temperatures at locations shown in figure (ºF)
flowcalculate
stream.
Inheat
this
case,
data
from
theexchanger.
flow stream
Next,
the actual
rateexchanger
of heat the
transfer
across
the heat
This
The maximum possible rate of heat transfer through
the
can
be
can
be done using
either
this case, the data
from the
through
the data
hot from
side
offlow
thestream.
heatInexchanger
(using
the
The maximum
possible
rate
of
heat
transfer
through
the
calculated as follows:
flow stream through the hot side of the heat exchanger (using the 40%
40% propylene
glycol
solution) is used:
heat exchanger can be calculated as follows:
propylene
glycol solution)
is used:
3
3
Qmax = [ 8.01× D × c × f ] min × (Thin − Tcin )
46
Where:
Qactual = (8.01× Dh × ch ) × fh × (Thin − Thout ) = (8.01× 64.0 × 0.91) × 4 × (130 −120 ) = 18, 660Btu / hr
Next determine which side of the heat exchanger has the minimum fluid
capacitance rate (e.g., calculate the product (8.01 x D x c x f) for each flow
stream and determine which is smaller).
For the hot side of the heat exchanger:
Btu
(8.01 x D x c x f)min = the smaller of the two (8.01×
fluidD ×capacitance
Found
by
c× f)
= (8.01× 64.0rates.
× 0.91× 4) = 1866
40%PG
D = 61.8 lb/ft33
D = 61.8 lb/ft
c = 1.00 Btu/lb/ºF
c = 1.00 Btu/lb/ºF
Next, calculate the actual rate of heat transfer across the heat exchanger. This
Next, calculate the actual rate of heat transfer across the heat exchanger. This
For the 40%
glycol data
solution:
canpropylene
be done using
from either flow stream. In this case, the data from the
can be
done using data from either flow stream. In this case, the data from the
D = 64.0 flow
lb/ft3stream through the hot side of the heat exchanger (using the 40%
flow stream through the hot side of the heat exchanger (using the 40%
c = 0.91 Btu/lb/ºF
propylene glycol solution) is used:
propylene glycol solution) is used:
For water:Q
= (8.01× which
Dh × ch ) × side
fh × (Thinof
− Ththe
× 0.91) × 4 × (130
−120 ) =heat
18, 660Btu
/ hr
exchanger
used as a system, would
Next
determine
heat64.0
exchanger
has
out ) = (8.01×
3
Qactual
actual = (8.01× Dh × ch ) × fh × (Thin − Thout ) = (8.01× 64.0 × 0.91) × 4 × (130 −120 ) = 18, 660Btu / hr
D = 61.8 lb/ft
of the amount of solar energy compared
the
minimum
c = 1.00
Btu/lb/ºF fluid capacitance rate (e.g., calculate the
gather 95%
to the same
determine
the heat
exchanger
has the minimum
fluid
array without the heat exchanger. This could
productNext
(8.01
x D which
x c side
x f)of
each
flow stream
and collector
Next
determine
which
side
of for
the heat
exchanger
has the minimum
fluid
capacitance
rate
(e.g.,
calculate
the
product
(8.01
x D x c x This
f) for each flow
Next, calculate
the actual
rate
of heat
transfer
across
the heat
exchanger.
capacitance
rate
(e.g.,
calculate
the
product
(8.01
x
D
x
c
x
f)
for
each
flow
also
be
viewed
as a 5% performance penalty due to the
determine
which
is
smaller).
stream
is smaller).
can be done
usingand
datadetermine
from eitherwhich
flow stream.
In this case, the data from the
stream and determine which is smaller).
presence of the heat exchanger.
flow stream through the hot side of the heat exchanger (using the 40%
propylene
glycol
solution)
used:
hot side
of
the
heatexchanger:
exchanger:
For
theFor
hotthe
side
of isthe
heat
For
the
hot side
of the
heat exchanger:
Btu
Figure B-3 shows how the correction factor varies as a
(8.01×
D
×
c
×
f
)
=
(8.01×
64.0
× 0.91×
4) =× 1866
40%PG
Q
= (8.01×
D ×Dc ×) ×c ×f ×
Th − =Th(8.01×
× 0.91)
4 × (130Btu
−120 ) = 18, 660Btu / hr
) = (8.01×
(8.01×
f )(40%PG
64.0 ×64.0
0.91×
4) = 1866
hr•º
F
hr•º F
function of the heat exchanger’s effectiveness. This graph
Next the
determine
which
heat
exchanger
has the minimum fluid
is for a small combisystem using four 4-foot by 8-foot flat
For
cool
side
of ofthe
heat
exchanger:
For
the
coolside
side
ofthe
the
heat
exchanger:
Forrate
the(e.g.,
cool calculate
side of the
exchanger:
capacitance
theheat
product
(8.01 x D x c xBtu
f) for each flow
plate collectors, a 50% solution of propylene glycol as the
Btu
(8.01×
D
×
c
×
f
)
=
(8.01×
61.8
×1.00
×
6)
=
2970
stream and
determine
is smaller).
(8.01×
D × c ×which
f )water
water = (8.01× 61.8 ×1.00 × 6) = 2970 hr•º F
collector fluid and a flow rate of 1 gallon per minute per
hr•º F
For thefluid
hot side
of the heat exchanger:
The
capacitance
rate
on
the
hot
side
of
the
heat
The fluid capacitance rate on the hot
of the heat exchanger is collector.
the smallest.The collector’s efficiency line has a slope (FRUL)
Btu side
rate4)on
the hot
side of the heat exchanger is the smallest.
(8.01× D × The
c × f )fluid
=capacitance
(8.01×
64.0 × 0.91×
= 1866
of
0.865 Btu/hr/ft2/ºF.
exchanger
is the
smallest.
hr•º F
actual
h
h
h
in
out
40%PG
and
the entering
fluid.
This difference
called
capacitance
rate by thecool
difference
in temperature
between is
theoften
entering
hot
fluid and
the entering temperature
cool fluid. This difference
is often called the “approach”
the
“approach”
difference.
temperature difference.
Qmax = [ 8.01× D × c × f ] min × (Thin − Tcin ) = [8.01× 64.0 × 0.91× 4] × (130 −110 ) = 37, 320Btu / hr
collector performanc multiplier
Determine the maximum possible heat transfer across the heat exchanger. This
Determine the maximum possible heat transfer across the heat exchanger. This
corresponds
a thermodynamic
which the outlet temperature of the
For
the
cool
side
of maximum
the to
heat
exchanger:
Determine
the
possible limit
heatin
the
corresponds
to
a thermodynamic
limit
in transfer
which the across
outlet temperature
of the
Btu rate approaches the inlet temperature of
fluid
with
the lower
fluid× 6)
capacitance
(8.01×
D
×
c
×
f
)
=
(8.01×
61.8
×1.00
=
2970
fluid
with
the
lower
fluid
capacitance
rate
approaches
the inlet temperature of 1
water
heat exchanger.
This
corresponds
to
a
thermodynamic
hr•º
F
the other fluid stream. It is determined by multiplying the minimum fluid
other fluid stream. It is determined by multiplying the minimum fluid
limit inthe
which
the
temperature
of the between
fluid with
capacitance
rateoutlet
by the difference
in temperature
the entering hot
capacitancerate
rateonby
the
inheat
temperature
between
the entering hot0.95
The fluid capacitance
the
hotdifference
side
of the
exchanger
is the smallest.
fluid
and
thecapacitance
entering
cool
fluid.
Thisapproaches
difference
is often
“approach”
the lower
fluid
rate
thecalled
inletthe
fluid and
the entering cool fluid.
This difference is often
called
the “approach”
temperature
difference.
temperature
of the
other
fluid
stream.
It heat
is determined
difference.
Determinetemperature
the maximum
possible
heat
transfer
across the
exchanger. This
0.9
corresponds
to a thermodynamic
limit in whichcapacitance
the outlet temperature
of the
by
multiplying
the
rate
the ) = 37, 320Btu / hr
Qmax = [ 8.01×
D ×minimum
c × f ] min × (Thinfluid
− Tcin ) = [8.01× 64.0 × 0.91×
4] × (by
130 −110
fluid with Q
the
lower
fluid
capacitance
rate
approaches
the
inlet
temperature
of
=
8.01×
D
×
c
×
f
×
Th
−
Tc
=
[8.01×
64.0
×
0.91×
4]
×
130
−110
=
37,
320Btu
/
hr
]min (between
( fluid )
max
in
in )
difference
in[ temperature
the entering hot
the other fluid stream. It is determined by multiplying the minimum fluid
0.85
0.8
0.75
Finally, determine the effectiveness of the heat exchanger under these
Finally, determine
the effectiveness of the heat exchanger
conditions.
under these conditions.
0.7
0.65
Finally, determine
the
effectiveness of the heat exchanger under these
Q
18,
660
e = actual =
= 0.50
conditions.Q
37, 320
max
0.6
Qactual 18, 660
=
=Heat
0.50 Exchanger
Collector
37, 320
CollectorQmax
Heat
Exchanger
e=
0
Performance
Penalty:
0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9
1
heat exchanger effectiveness
Performance
Penalty:
The decrease
in solar energy collected as a result of having a heat exchanger
Collector Heat Exchanger
Performance
Penalty:
between the collector loop fluid and the storage
tank can be estimated using
The decrease in
solar energy
collected as a result of The graph shows that heat exchangers with low
the following
The decrease
in solarformula.
energy collected as a result of having
a heat exchanger
effectiveness
numbers (less than 0.55) create significant
having a heat exchanger between the collector loop
between the collector loop fluid and the storage tank can
be estimated
using (over 5% reduction in energy gain). It
performance
penalties
fluid and the
storage tank can be
1 estimated using the is suggested that all collector-to-storage heat exchangers
the following formula.
CF =
following formula.
 ( F U ) × Aca   1 
used in solar combisystems have effectiveness ratings of
1+  1 R L
 ×  −1
CF =
8.01× D × c × fca   ε 
0.55 or higher, and thus impose losses of not more than


 ( FRU L ) × Aca   1 
1+ 
5% on solar energy collection.
 ×  −1
 8.01× D × c × fca   ε

Where:
Where: Where:CF = correction factor (derating multiplier)
Ffactor
of collector
efficiency line (Btu/hr/ft2/ºF)
CF = correction
(derating
multiplier)
RUL = slope
CF = correction
factor
(derating
multiplier)
2 2
of collector
(ft
) /ºF) 2/ºF)
efficiency
linearray
(Btu/hr/ft
FRUL = slope
CA = area
FRULof
=Acollector
slope
of collector
efficiency
line
(Btu/hr/ft
2
2
ACA = areaAof
collector
arrayof(ftcollector
)
D = density
loop fluid (lb/ft3)
CA = area of collector array (ft )
3
3
D = density
ofdensity
collector
loopheat
fluid
D=
of collector
loop
fluid) (lb/ft
) fluid (Btu/lb/ºF)
c = specific
of(lb/ft
collector
loop
c
=
specific
heat
of
collector
loop
fluid
(Btu/lb/ºF)
c = specific heat
(Btu/lb/ºF)
fcaof
= collector
fluid flowloop
rate fluid
through
collector array (gpm)
rate through
array (gpm)heat exchanger.
rate
through
collector
array (gpm)
fca = fluid fflow
ca = fluid
e = flow
effectiveness
of collector
collector/storage
e = effectiveness
of collector/storage
heat exchanger.
e = effectiveness
of collector/storage
heat exchanger.
The correction factor is a derating multiplier. For example, if the correction
The correction
is a derating
multiplier.
For example, if the correction
The correction
factor
afactor
derating
multiplier.
Forarray
example,
factoriswere
0.95, the
collector
and heat exchanger used as a system,
factor were 0.95, the collector array and heat exchanger used as a system,
if the correctionwould
factorgather
were 0.95,
thethe
collector
and energy compared to the same
95% of
amountarray
of solar
would gather 95% of the amount of solar energy compared to the same
collector
array without
heat exchanger.
could
alsoas
bea viewed
as a 5%
collector
array without
the heatthe
exchanger.
This could This
also be
viewed
5%
performance
penalty
due
to
the
presence
of
the
heat
exchanger.
performance penalty due to the presence of the heat exchanger.
FigureFigure
B-3 shows
how thehow
correction
factor varies
as avaries
function
the heat of the heat
B-3 shows
the correction
factor
as of
a function
exchanger’s
effectiveness.
This graph
is for
a small
combisystem
using four 4-using four 4exchanger’s
effectiveness.
This
graph
is for
a small combisystem
47
h = height fluid in tank (inches)
APPENDIX C:
Tank and Piping
Volume Formulas:
Pipe Volume Data:
The following
table
cancalculating
be used to calculate
the volu
This section provides data and
formulas
for
the volume
Pipe
Volume
Data:
other types of hydronic systems.
tasks such as determining the drop in wa
The following table can be used to calculate the volume
of(Stephanie,
piping
in solarof
as water
well
as other
of as
hydronic
this
is the
same
table
appeared
in
This size
section storage
provides data and
formulas
for calculating
tank
when
a given
volume
is types
extracted
(such
systems.
the volumes of tanks and piping. This is useful for tasks
you can just pull it from the archive.)
collection
suchsystem
as determiningbegins
the drop in the
water level
of a specific cycle).
APPENDIX C: Tank and Piping Volume
Formulas:
piping. This is useful for
size storage tank when a given volume of water is
extracted (such as when a drainback system begins the
collection cycle).
H
diameter of tank
D
st
height of fluid
height ofheight
fluid of fluid
H
height ofheight
tank of tank
height of tank
Tube type / size
Gallons /foot
3/8" type
M copper:
Formula C-1 can be used to calculate
the
volume of0.008272
a cylindrical
Formula C-1 can be used to calculate the volume of a
1/2" type M copper:
0.0132
diameter
height:
cylindrical
storage tankand
of known
diameter and height:
3/4" type M copper:
0.0269
1" type M copper:
0.0454
APPENDIX C: Tank and Piping Volume Formulas:
1.25" type M copper:
0.068
APPENDIX
Tank data
and and
Piping
Volume
Formulas: the volumes of tanks and
This
sectionC:provides
formulas
for calculating
1.5" type M copper:
0.095
piping. This is useful for tasks such as determining the drop in water level of a specific
This
section provides
data
and formulas
for
calculating
the volumes
of2"
tankstype
size storage
tank when
a given
volume of
water
is extracted
(such as
when
aand
drainback
M copper:
0.165
piping.
is useful
for tasks
such as determining the drop in water level of a specific
system This
begins
the collection
cycle).
2.5"
M copper:
0.2543
size storage tank when a given volume of water is extracted (such as
when a type
drainback
Hsystem
the
cycle). the volume of a cylindrical storage tank of known
Formulabegins
C-1 can
becollection
used to calculate
3" type M copper:
0.3630
diameter and height:
h
Formula C-1 can be used to calculate the volume of a cylindrical storage tank of known
3/8" PEX
0.005294
diameter and height:
1/2" PEX
0.009609
5/8" PEX
0.01393
3/4" PEX
0.01894
diameter of tank
1" PEX
0.03128
D
1.25" PEX
0.04668
Formula C-1:
1.5" PEX
0.06516
Formula C-1:
2" PEX
0.1116
Formula C-1: 2
π (D ) H
V
=
3/8" PEX-AL-PEX
0.00489
Formula
C-1:
tank
π (924
D2 ) H
Vtank =
1/2" PEX-AL-PEX
0.01038
924
Where: Where:
5/8" PEX-AL-PEX
0.01658
V
= of
volume
tankgallons)
(US gallons)
tankof(US
Vtank = volume
Where:
D
= diameter of tank (inches)2
D = diameter
of
tank (inches)
3/4" PEX-AL-PEX
0.02654
V = height
= volume
of tank
(US gallons)
H
of tank
(inches)
H = heightDof
tank (inches)
= diameter
of tank (inches)
1" PEX-AL-PEX
0.04351
h
h
diameter of tank
D
tank
tank
V
=
π (D ) H
H
= height
tank
Formula
C-2ofcan
be(inches)
used to calculate the volume of liquid of known height h with a
cylindrical
storage
of known diameter
and height:
Formula tank
C-2
can be
usedtank
to calculate
the volume
of liquid
Formula C-2 can be used to calculate the volume of liquid of known height h with a
of known height h with a cylindrical storage tank of known
cylindrical
storage tank of known diameter and height:
Formula C-2:
diameter and height:
924
π ( D2 ) h
Formula C-2:
Formula C-2:
V fluid =
Where:π (924
D )h
V =
924
Vtank = volume
of tank (US gallons)
Where:
= diameter
of tank
= volume
of fluid in tank (U.S.
gallons) (inches)
Vfluid D
D = diameter of tank (inches)
H =fluid
height
of tank (inches)
h = height
in tank (inches)
2
fluid
48
Formula C-2 can be used to calculate the volume of liquid of know
cylindrical storage tank of known diameter and height:
APPENDIX D: Unit Conversion Factors:
49
Flat Plate Solar Thermal Collectors
CALEFFI
series NAS100
Function
Solar thermal collectors are used to capture energy from the sun
and efficiently transfer solar energy to heat the solar fluid in the
primary circuits of solar heating systems. This heated solar
fluid is circulated through a heat exchanger, thus heating domestic
water, which is stored in suitable tank. This heated water is then
delivered to a conventionalwater heater for final heating, if required,
or direct use.
Product range
Code NAS10406 Solar Flat Plate Solar Collector, 4' x 6.5' frame, SRCC rating Category C
Code NAS10408 Solar Flat Plate Solar Collector, 4' x 8' frame, SRCC rating Category C
Code NAS10410 Solar Flat Plate Solar Collector, 4' x 10' frame, SRCC rating Category C
Dimensions
Technical specifications
Materials: - absorber plate:
- absorber coating:
- absorptivity / emissivity
- header manifold:
- glazing:
- glazing seal:
7.5 kWh (25,000 Btu)
9.2 kWh (32,000 Btu)
11.7 kWh (40,000 Btu)
1/2" tube to fin copper
selective crystal coating
0.96 / 0.08
1" copper
low iron tempered glass
extruded “U” channel EPDM
B D
- insulation:
R-10 poly-isocyanurate foam board
- frame & battens:
type 6063-T6 extruded aluminum
- backing sheet: type 3105-H14 embossed aluminum
Medium:
Max. percentage of glycol:
Working temperature range:
Max. pressure:
Working pressure:
Typical transfer flow rate:
Connections:
Wind load rating:
50
water, glycol solutions
60%
C
A
E
-40 to 350ºF (-40 to 177ºC)
150 psi (10 bar)
90 psi (6 bar)
0.5 –1.8 gpm (1.8 – 7 lpm)
1" union thread (4' x 6.6')
1-1/4" union thread (4' x 8' & 4' x 10')
181mph / 291kph
G = gross glass area ft²
F = frontal aperture area ft²
Code
A
B
C
D
E
F
G
77 3/16” 47 3/16” 74 5/8” 50 1/2” 3 1/8” 23.6 25.35
10408 97 3/16” 47 3/16” 94 5/8” 50 1/2” 3 1/8” 29.9 31.91
10410 121 3/16” 47 3/16” 118 5/8” 50 1/2” 3 1/8” 37.4 39.79
10406
Wt (lb) Cap (gal)
90
0.79
113
0.88
160
1.05
Hydraulic characteristics
NAS10408
Univerisal Mount System (NAS10001)
NAS10410
0.120
0.280
0.100
0.230
0.080
0.185
0.060
0.140
0.040
0.090
0.020
0.045
0.000
0.000
0.050
1.000
1.500
2.000
Optional Tilt Mount Assembly
Head Loss (ft. w.c.)
Pressure Drop (PSI)
NAS10406
Universal mount system
1" Aluminum
Square Tube
(NAS10002)
0.000
2.500
Tilted
Installation
Side View
Flow Rate (GPM)
Construction details
Built-in temperature sensor well
Caleffi’s exclusive universal mounting systems allow for virtually
any collector orientation and mounting. Collectors can be mounted
to any roof, vertical wall, fascia boards, pre-constructed racks or
ground mount systems. The frame wall and mount have been certified to withstand 180 mph winds. The frame wall will accept the
mounts anywhere around the collector without drilling or tapping so
the integrity of the framewall is not violated. The rear struts can be
cut to any length allowing proper elevation and orientation.
Item
Code
Description
NAS10001
Universal foot mounts for solar
collectors, flush or tilt mount
(4 each with hardware)
NAS10002
6' extension square brace to
tilt collectors
Collector cross section
EPDM Glazing Gasket
Sensor Well
Copper Fintube
Brass Union Half
Flat Sealing Washer
51
SolarCon solar water heater tank
CALEFFI
series NAS200
Function
The solar water heater has either one or two internal coils and a
backup electric heating element in the single coil units. A heating
medium is passed through the solar panels and internal coil as long
as there is an adequate temperature difference between the heating medium and stored water in the tank. The internal coil is located
as close to the bottom to facilitate the transfer of heat even at lower
solar panel temperatures.
During periods of water flow through the water heater, hot water is
drawn from the top of the heater and cold water comes into the bottom of the tank (by a dip tube or bottom inlet). On single coil tanks,
if the hot water demand should exceed the solar heat input or there
is an insufficient temperature difference between the heating medium and stored water, the heating element thermostat will activate
the electrical heating element for backup heat. On double coil
tanks, the upper tank is connected to the boiler for backup heat.
Meets and exceeds CSA
C309 requirements
Solar heat output from the internal coil will vary depending on outside conditions and the temperature of the stored water.
Product range
NAS20053
NAS20083
NAS20123
NAS20082
NAS20122
NAS20124
Storage
Storage
Storage
Storage
Storage
Storage
tank
tank
tank
tank
tank
tank
with
with
with
with
with
with
lower
lower
lower
lower
lower
lower
coil
coil
coil
coil
coil
coil
and
and
and
and
and
and
back up electric element
back up electric element
back up electric element
top coil for boiler back up
top coil for boiler back up
top coil heat exchanger with back up electric element
Technical specifications
Tank materials:
porcelain coated steel
Tank insulation:
2" non-CFC foam
Tank external cover:
powder-coated steel (20-24 ga.)
Insulation thermal conductivity:
R16
Anode rods:
2 each magnesium
Internal heat exchanger coil (lower):
1-1/2" x 30' (50 gallon)
1-1/2" x 36' (80, 119 gallon)
Internal heat exchanger coil (top):
1-1/2" x 24' (80, 119 gallon)
50 gallon
80 gallon
119 gallon
80 gallon
119 gallon
119 gallon
Connections:
3/4" NPT (50 gal.), 1" NPT (80, 119 gal.)
Maximum working pressure:
150 psi
Testing pressure:
300 psi
Temperature and pressure relief valve:
210°F/150 psi max
Maximum tank temperature:
180°F
Recommended maximum delivery hot water temperature:
120°F
Power requirements (electric element):
240 VAC
Power consumption (electric element):
4.5 KW
Agency approval:
UL listed
Capacity and performance
Model
Actual Tank
Volume
(gal)
Coil Volume
Solar/Boiler
(gal)
Coil Surface Area
Solar/Boiler
(ft 2)
Coil Friction Loss*
Solar/Boiler
(ft. of head)
First Hour Rating
(gal)
Standby
Loss Rating
(°F/hr)
NAS20053
45
2.30/ -
11.78/ -
0.50/ -
91
51
1.1
NAS20083
75
2.76/ -
14.14/ -
0.60/ -
126
56
0.8
NAS20123
110
2.76/ -
14.14/ -
0.60/ -
158
56
1.2
NAS20082
73
2.76/1.84
14.14/9.42
0.60/0.40
226
158
0.8
NAS20122
108
2.76/1.84
14.14/9.42
0.60/0.40
258
158
1.2
NAS20124
108
2.76/1.84
14.14/9.42
0.60/0.40
282
182
1.2
NOTES: * Based on 5 GPM flow rate.
# Based on solar input of 140ºF @ 2 GPM. Depending on model, backup heat recovery is calculated with either
a 4500W heating element or a boiler with output of 180ºF at 14 GPM. Potable water temperature rise is 77ºF.
52
Recovery Rate
Solar & Backup#
(gal/hr)
Dimensions
ANODE
HOT OUT
(1" NPT)
COLD IN
(3/4" NPT)
HOT OUT
W/ ANODE
(3/4" NPT)
ANODE
HOT OUT (1" NPT)
ANODE
ANODE
ANODE
NAS20053 TOP
NAS20083, NAS20123 TOP
Plug
Top Sensor
Immersion Well
Electric
Heating
Assembly
T&P RELIEF
VALVE
FROM BOILER (1" NPT)
Aquastat Location
(for backup heating)
FROM SOLAR
(1" NPT)
TO BOILER (1" NPT)
B
D
B
C
Bottom Sensor
Immersion Well
D
F
F
E
TO SOLAR
(1" NPT)
COLD IN
(1" NPT)
C
Bottom
Sensor
Immersion
Well
FROM SOLAR
(1" NPT)
E
G
H
I
G
TO SOLAR
(1" NPT)
COLD IN
(1" NPT)
J
H
K
A
B
C
A
Figure 2: NAS20082, NAS20122, NAS20124
Figure 1: NAS20053, NAS20083, NAS20123
Model
A
G
H
I
J
K
NAS20053
22"
481⁄4" 393⁄4" 393⁄4" 311⁄2" 163⁄4"
61⁄2"
n/a
n/a
n/a
n/a
NAS20083
24"
64"
571⁄8" 571⁄8" 311⁄2" 191⁄4"
61⁄2"
5"
n/a
n/a
n/a
NAS20123
28"
65"
573⁄4"
83⁄4"
61⁄2"
n/a
n/a
n/a
NAS20082
24"
64"
57 ⁄8" 57 ⁄8" 49 ⁄2" 46 ⁄8" 36 ⁄2"
31 ⁄2"
19 ⁄4"
1
6 ⁄2"
5"
NAS20122
28"
65"
57 ⁄4" 57 ⁄4" 51 ⁄4" 49 ⁄8" 38 ⁄4"
33 ⁄4"
16 ⁄4"
3
8 ⁄4"
61⁄2"
NAS20124
28"
65"
573⁄4" 573⁄4" 513⁄4" 491⁄8" 383⁄4"
333⁄4"
161⁄4"
83⁄4"
61⁄2"
1
3
D
573⁄4"
1
3
E
F
333⁄4"
1
161⁄4"
7
3
1
1
1
3
1
3
1
Application diagrams
Single tank system with electric backup
air vent
w/ shut off
valve
Single tank system with boiler backup
air vent
w/ shut off
valve
sensor S1
so
la
sensor S1
so
rc
la
ol
le
ct
or
ar
rc
ol
le
ra
ct
or
y
ar
ra
y
ASSE 1017
approved
mixing valve
ASSE 1017
approved
mixing valve
programmable
control
timer
HW
solar pump
station
ON
boiler
circulator
(w/ check)
delta T
controller
HW
solar pump
station
CW
delta T
controller
3
P&TRV
CW
potable
expansion
tank
P&TRV
3
potable
expansion
tank
electric
heating
element
fill / purge
valves
fill / purge
valves
expansion
tank
sensor S2
solar storage tank
with internal heat exchanger
and electric back up heating element
expansion
tank
sensor S2
solar storage tank
with internal heat exchanger
and boiler backup heat exchanger
53
Flexible stainless steel insulated piping
SolarFlex
NA3500
CALEFFI
Function
SolarFlex is a system solution with pre-insulated flow and return
pipes for solar hot water heating systems used to connect the solar
collector with the storage tank in an easy, quick and professional
way. It optimizes thermal efficiency of the entire system. The preinsulation solution of two flexible stainless steel pipes inside two
EPDM closed cell insulation and the integrated sensor cable, saves
time and reduces cost of installation. SolarFlex is packaged in a 50foot continuous coil with a complete range of accessories to ensure
a smoothand secure installation.
General
• Easy to install, enabling pipes to be run without using a torch
in confined spaces or on the roof.
• Ensures a leak-free installation.
• Easy to separate, without damaging the tubes.
• External copolymer foil protects against UV radiation
and mechanical strain.
• Identification mark for flow and return.
• Meets highest requirements for modern solar heating systems.
• Pre-insulated feed and return pipes can be joined easily
without special tools.
Product range
NA3520-15
NA3540-15
NA3540- B
NA3560-15
1/2" SolarFlex pipe 50' coil including (2) double nipples, (4) union nuts, 4 segment rings and 4 washers
3/4" SolarFlex pipe 50' coil including (2) double nipples, (4) union nuts, 4 segment rings and 4 washers
3/4" SolarFlex pipe bulk cut to length up to 164 foot. Without connection fittings.
1" SolarFlex pipe 50' coil including (2) double nipples, (4) union nuts, 4 segment rings and 4 washers
Technical specifications
Dimensions
Materials:
- pipe:
two corrugated stainless steel 316L
- insulation:
two closed cell elastomer UV resistance EPDM
- outer cover:
UV resistant polyolefin copolymer foil
Insulation thickness:
5/8 inch (16mm)
Thermal conductivity:
0.215 BTU-in/hr-ft2-°F (0.031 W/mK)
Thermal resistance:
R-4.2
Max. working pressure:
150 psi (10 bar)
Max. fluid temperature:
350ºF (175ºC)
Min. surface temperature:
-60ºF (-50ºC)
Length per coil:
50 feet (15m)
Fluid capacity per foot:
1/2" - 0.0219 gallons (0.08 liters)
3/4" - 0.0346 gallons (0.13 liters)
1" - 0.0509 gallons (0.19 liters)
Min. bending radius:
5 inch (130mm)
Pessure loss: Approx. 25% more than in a comparable smooth pipe
Flammability:
Class VO
Flame spread/smoke density
25/50
Agency approvals:
ASTM D 635
ASTM C 177
A
D
C
Code
NA3520 -15
NA3540 -15
NA3560 -15
54
B
A
1/2"
3/4"
1"
B
11/16"
15/16"
1 - 1/4"
C
4"
4 - 3/8 "
4 - 7/16 "
D
2"
2 - 1/8 "
2 - 1/2 "
Weight (lb/f)
0.4
0.5
0.7
Hydraulic characteristics
Construction details
Flexible stainless steel pipe
Feet of head curve for 1 foot of 1/2" SolarFlex
0.15
0.13
Integrated
two-wire
sensor cable
Feet of Head
0.11
0.09
0.07
0.05
0.03
0.01
Closed cell
elastomeric
EPDM foam
insulation
0 .125 .25 .325 .50 .625 .75 .875 1.0 1.25 1.375 1.5 1.625 1.75 1.875 2.0 2.25 2.5
Volume flow is gpm
Medium: Glycol/water 40/60 temperature 100ºF
Feet of head curve for 1 foot of 3/4" SolarFlex
0.15
0.13
Feet of Head
0.11
0.09
0.07
UV resistant protection film
0.05
0.03
0.01
0 .025 .50
.75
1.0 1.25 1.5 1.75 2.0 2.25 2.5 2.75 3.0 3.25 3.5 3.75 4.0 4.5
Volume flow is gpm
Medium: Glycol/water 40/60 temperature 100ºF
Feet of head curve for 1 foot of 1" SolarFlex
0.15
0.13
Feet of Head
0.11
0.09
0.07
0.05
0.03
0.01
0 .50
1.0
1.5
2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0 6.5 7.0
Volume flow is gpm
Medium: Glycol/water 40/60 temperature 100ºF
Item
Code
7.5 8.0
9.0
Flow and return pipes are easy to separate without damaging the
insulation or sensor cable.
Description
SolarFlex pipe hangers
NA12132
Pipe hangers 1/2" pack of 4 hanger for 1/2" SolarFlex
NA12133
Pipe hangers 3/4" pack of 4 hangers for 3/4" SolarFlex
NA12134
Pipe hangers 1" pack of 4 hangers for 1" SolarFlex
SolarFlex extra connection kits
NA12102
Connection Kit for 1/2" SolarFlex with 4 nuts, 4 segment rings and 4 flat sealing washers
NA12103
Connection Kit for 3/4" SolarFlex with 4 nuts, 4 segment rings and 4 flat sealing washers
NA12104
Connection Kit for 1" SolarFlex with 4 nuts, 4 segment rings and 4 flat sealing washers
SolarFlex insulating tape
NA35001
Insulating EPDM foam tape (UV resistant) to wrap exposed piping, 50 ft roll x 2" wide x 1/8" thick
NA35002
Black film tape (UV resistant) to wrap foam tape, 50 ft roll x 2" wide
NA35007
Black braid sleeve (UV & Vermin resistant), to protect exposed split piping outside, (2) 4' braid
with (1) 30 ft roll x 2" wide black film tape
55
Solar pump stations
CALEFFI
series 255 & 256
Function
Solar pump stations are used on the primary circuit of solar heating
systems to control the temperature of the hot water storage.
The pump inside the unit is activated by the signal from a differential temperature controller. The unit contains the functional and
safety devices for an optimal circuit control, and is available with
both flow and return connection or with return connection only.
General
The solar pump station is a pre-installed and leak-tested unit with
fittings for transferring heat from the collector to the storage tank.
It contains important fittings and safety devices for the operation of
the solar thermal system:
• Ball valves in flow and return in combination with check valves
to prevent gravity and thermo circulation.
• Ports for flushing, filling and emptying the system.
• Air vent for manual bleeding of the solar thermal system.
• Flow meter for displaying and setting the flow rate.
• Thermometer in flow and return for displaying
both temperatures.
• Pressure gauge for displaying the system pressure.
• Safety relief valve to prevent overpressure.
• Three-speed solar pump for wide range of flow rates.
Product range
Code
Code
Code
Code
255050A
255056A
256050A
256056A
Dual line pump station, 3 speed, flow and return connection, flow meter scale: 1/2–5 gpm
Dual line pump station, without pump, flow and return connection, flow meter scale: 1/2–5 gpm
Single line pump station, 3 speed, return connection, flow meter scale: 1/2–5 gpm
Single line pump station, without pump, return connection, flow meter scale: 1/2–5 gpm
Technical specifications
Body:
Temperature gauge:
Seals:
O-Rings:
Union gaskets:
Insulating shell:
Pump
brass
steel / aluminium
PTFE / EPDM
EPDM / Viton
AFM 34, asbestos free
EPP, thermal conductivity value = R4
Medium:
Max. percentage of glycol:
Max. working temperature:
Max. working pressure:
water, glycol solutions
50%
360°F (180ºC)
150 psi (10 bar)
Safety relief valve temperature range: -20 to 360°F (-30 to 180ºC)
Safety relief valve factory setting:
90 psi (6 bar)
Min. opening pressure for check valve:
Δp: 1/4 psi (2 kPa)
Adjustment range of flow meter:
Max return flow meter temperature:
Pressure gauge scale:
Temperature gauge scale:
Connections:
Filling/drain hose connections:
Expansion tank connection:
Wilo solar model:
Body:
Power supply:
Max. pressure:
Max. temperature:
Agency approval:
Star S-16 U15
cast iron
115 V - 60 Hz
150 psi (10 bar)
230°F (110ºC)
cULus
Wilo Star S-16 U15 hydraulic characteristics
Performance
56
3/4" female
3/4" female
3/4" female
3/4" female
1/2 to 5 gpm (1 to 20 l/min)
265°F (130ºC)
0–90 psi (0—6 bar)
32–320°F (0—160ºC)
3/4" female straight thread
3/4" male hose thread
1/2" male straight thread
Dimensions
Construction details
Shut-off and check valve
The shut-off and check valves are built into the ball valves of the
temperature gauge connectors.
A. In normal system operation, the ball valves must be fully open.
B. To allow the fluid to flow in both directions, it is necessary to rotate
the respective ball valve to 45°.
C. To close ball valve, rotate 90º.
0°
45°
A
B
Check valve in operation,
flow-through only in
flow direction
Characteristic components
90 °
Check valve not operating,
flow-through in
both directions
C
Ball valve closed,
no flow-through
Air vent
The solar pump unit version with flow and return connection is
equipped with an air vent on the flow line. The air, separated from
the fluid, is collected at the top of the vent.
The collected air must be released from time to time — every day
after the initial installation; however, it can eventually be done weekly
or monthly, depending on the quantity of the air. The collected air is
released using the manual air vent with a screwdriver.
Flow meter
1
2
3
4
5
6
Wilo-Solar circulation pump
Safety relief valve 253 series
Filling/drain valve
Pressure gauge
Flow meter
Air trap and vent
7
8
9
10
11
12
Flow temperature gauge
Return temperature gauge
Pre-formed insulation shell
Shut-off and check valve
Expansion Tank connection kit
3/4" cap (used if no expansion
tank is installed)
The Flow meter is for measurement and display of the flow rate of 1/2
to 5 gpm (1-20 l/min). For accurate function of the measuring device
the system must be flushed and free from foreign substances.
1/2 – 3.5 gpm
(1-13 l/min)
4 – 5 gpm
(15-20 l/min)
Left scale:
Upper edge
of the
propeller
Right scale:
Lower edge
of the
propeller
Example display = approx. 3 gal/min
57
Solar pump stations
CALEFFI
series NA255
Function
Solar pump stations are used on the primary circuit of solar heating
systems to control the temperature of the hot water storage.
The pump inside the unit is activated by the signal from a differential temperature controller. The unit contains the functional and
safety devices for an optimal circuit control, and is available with
both flow and return connection or with return connection only.
General
The solar pump station is a pre-installed and leak-tested unit with
fittings for transferring heat from the collector to the storage tank.
It contains important fittings and safety devices for the operation of
the solar thermal system:
• Ball valves in flow and return in combination with check valves
to prevent gravity and thermo circulation.
• Ports for flushing, filling and emptying the system.
• Air vent for manual bleeding of the solar thermal system.
• Flow meter for displaying and setting the flow rate.
• Thermometer in flow and return for displaying
both temperatures.
• Pressure gauge for displaying the system pressure.
• Safety relief valve to prevent overpressure.
• Three-speed solar pump for wide range of flow rates.
Product range
Code NA255160 Dual line pump station, 3 speed, flow and return connection, flow meter scale: 1–10 gpm
Technical specifications
Body:
Temperature gauge:
Seals:
O-Rings:
Union gaskets:
Insulating shell:
Pump
brass
steel / aluminium
PTFE / EPDM
EPDM / Viton
AFM 34, asbestos free
EPP, thermal conductivity value = R4
Medium:
Max. percentage of glycol:
Max. working temperature:
Max. working pressure:
Safety relief valve factory setting:
Min. opening pressure for check valve:
Adjustment range of flow meter:
Max return flow meter temperature:
Pressure gauge scale:
Temperature gauge scale:
Connections:
Filling/drain hose connections:
Wilo solar model:
Body:
Power supply:
Max. pressure:
Max. temperature:
Agency approval:
Star S-30 U25
cast iron
115 V - 60 Hz
150 psi (10 bar)
230°F (110ºC)
cULus
Wilo Star S-30 U25 hydraulic characteristics
Performance
58
1" male
water, glycol solutions
50%
360°F (180ºC)
150 psi (10 bar)
Pressure [ft head] [mWC]
30 9
27
8
24
7
21
6
18
5
15
4
12
9 3
3
2
90 psi (6 bar)
0.66 ft head (0.2 mWC)
1
1 to 10 gpm (4 to 38 l/m)
265°F (130ºC)
0–90 psi (0—6 bar)
32–320°F (0—160ºC)
Pump station
pressure drop
1" male thread
3/4" male
6
2
3
1
0
0
1
2
3
4
0
250
500
750
1000
5
6
1250
7
1500
8
9
1750
2000
0
10 Flow [gpm]
2250
Flow [l/h]
Dimensions
Construction details
Shut-off and check valve
B
The shut-off and check valves are built into the ball valves of the
temperature gauge connectors.
C
A
A
A. In normal system operation, the ball valves must be fully open.
B. To allow the fluid to flow in both directions, it is necessary to rotate
the respective ball valve to 45°.
C. To close ball valve, rotate 90º.
0°
45°
90 °
B
C
E
G
D
A
Check valve in operation,
flow-through only in
flow direction
Check valve not operating,
flow-through in
both directions
Ball valve closed,
no flow-through
Air vent
The solar pump unit version with flow and return connection is
equipped with an air vent on the flow line. The air, separated from
the fluid, is collected at the top of the vent.
A
Code
NA255160
A
1”
B
C
F
D
A
E
The collected air must be released from time to time — every day
after the initial installation; however, it can eventually be done weekly
or monthly, depending on the quantity of the air. The collected air is
released using the manual air vent with a screwdriver.
F
G
4 7/8” 4 1/2” 11 1/2” 20 1/2” 9 5/8” 22 1/2”
W (lb)
20
Characteristic components
Flow meter
The Flow meter is for measurement and display of the flow rate
of 1 to 10 gpm (4 to 38 l/m). For accurate function of the measuring
device the system must be flushed and free from foreign substances.
1 – 8 gpm
(4 – 30 l/m)
9 –10 gpm
( 34 – 38 l/m)
Left scale:
1 Wilo-Solar circulation pump
2 Safety relief valve 253 series
3 Filling/drain valve
4 Pressure gauge
5 Flow meter
6 Air trap and vent
7 Flow temperature gauge
8 Return temperature gauge
9 Pre-formed insulation shell
10 Shut-off and check valve
Upper edge
of the
propeller
Right scale:
Lower edge
of the
propeller
Example display = approx. 7 gal/min
59
DC-EMCstainless
solar pump
Flexible
steel insulated piping
SolarFlex
CALEFFI
CALEFFI
NA26711
NA3500
Function
SolarFlex is a system solution with pre-insulated flow and return
pipes for solar hot water heating systems used to connect the solar
Application
collector
with the storage tank in an easy, quick and professional
way.
optimizessolar
thermal
efficiency
the for
entire
system.
The preTheIt DC-ECM
pump
can be of
used
most
circulation
pump
insulation
solution
of connection
two flexibletostainless
two
applications
without
the powersteel
grid.pipes
Highlyinside
efficient,
the
EPDM
closed
cellpump
insulation
the integrated
sensor
saves
DC-ECM
solar
can and
be connected
directly
to cable,
a photovoltaic
time
andand
reduces
cost of installation.
in a 50panel
is characterized
by its SolarFlex
small size,is packaged
high efficiency,
and
foot
continuous
withconsumption.
a complete range
accessories
to ensure
extremely
low coil
power
The of
shaftless
spherical
motor
a smoothand
secure installation.
technology provides
maintenance free andprovides quiet service and
maintenance free life.
This pump is ideal for single family home thermal solar systems or any
General
circulation pump application where conventional power is not
• available.
Easy to install, enabling pipes to be run without using a torch
in confined spaces or on the roof.
• Ensures a leak-free installation.
• Easy to separate, without damaging the tubes.
• External copolymer foil protects against UV radiation
and mechanical strain.
• Identification mark for flow and return.
• Meets highest requirements for modern solar heating systems.
• Pre-insulated feed and return pipes can be joined easily
without special tools.
(Shown with two 3/4” sweat unions)
(not included, see page 2)
Product range
Product range
NA3520-15
1/2" SolarFlex pipe 50' coil including (2) double nipples, (4) union nuts, 4 segment rings and 4 washers
NA3540-15
3/4" SolarFlex
pipe pump
50' coiloperates
including
nipples, (4) union nuts, 4 segment rings and 4 washers
Code: NA26711
DC-ECM solar
on (2)
8 todouble
25 VDC
NA3540- B
3/4" SolarFlex pipe bulk cut to length up to 164 foot. Without connection fittings.
NA3560-15
1" SolarFlex pipe 50' coil including (2) double nipples, (4) union nuts, 4 segment rings and 4 washers
Dimensions
Dimensions
A
C
1” male union half threads
5 1/8”(130 mm)
NA3520
Code-15
NA3540
-15
NA26711
NA3560 -15
60
B
D
Code
Connections:
Face to face dimension:
B
A
D
Technical specification
Technical specifications
Materials
Materials:
Pump
- pipe:body:
two corrugated stainless steel brass
316L
- insulation:
two closed cell elastomer UV resistance
EPDM
Bearing:
ceramic
ball
- outer cover:
UV resistant polyolefin copolymer
foil
Seals:
EPDM
Insulation
5/8 inchwet
(16mm)
Impeller:thickness:
rotor
2
Thermal
0.215 BTU-in/hr-ft
-°F (0.031
W/mK)
Motor:conductivity:
permanent
magnet
ECM
Thermal resistance:
R-4.2
Performance
Max. working pressure:
150 psi (10 bar)
Voltage:
8 - 25
VDC
Max.
fluid temperature:
350ºF
(175ºC)
Power
consumption:
- 55W
Min.
surface
temperature:
-60ºF3 (-50ºC)
Current
0.13
2.1 A
Length
perdraw:
coil:
50
feet- (15m)
Insulation
IP 42(0.08
/ Class
Fluid
capacityclass:
per foot:
1/2" - 0.0219 gallons
liters)F
Suitable fluids:
water,
glycol
solution
3/4" - 0.0346
gallons
(0.13
liters)
Max percentage of glycol:
50%
1" - 0.0509 gallons (0.19 liters)
Min.
bending
radius:
5 inch
Max.
working
pressure:
150
PSI(130mm)
(10 bar)
Pessure
loss: Approx. 25% more than
in aF comparable
smooth
pipe
Max. temperature:
-10°
to 230° F (-10
to 110°C)
Flammability:
VO
Flow rates:
12V up to 5 gpm Class
(19 lpm)
Flame spread/smoke density
24V up to 7 gpm (26.525/50
lpm)
Agency
ASTM
D 635
Pumpapprovals:
head:
12V up to 10
ft (3.0
m)
ASTM
C
24V up to 15 ft (4.6177
m)
1” male union thread
A
1/2"
A
3/4"
1”
1"
C
B
11/16"
B
15/16"
5 1/8”
1 - 1/4"
C
4 "C
"”
4 -33/8
1/8
4 - 7/16 "
D
2 "D
" ”
2 -31/8
1/4
2 - 1/2 "
Weight (lb/f)
0.4 (lb)
Weight
0.5
3.0
0.7
Hydraulic characteristics
Installation
24 Volt in red, 12 Volt in black
50
Pump head [ft]
12
10
40
8
30
6
20
4
10
2
0
0
1
2
3
4
Flow rate [GPM]
5
6
- - - - - Power consumption [W]
60
14
0
The pump can be fitted either vertically or horizontally, with the motor in
any position, except the motor up.
7
Operating principle
The single moving part in a spherical motor is a hemispherical
rotor/impeller unit. The rotor/impeller rides on an ultra-hard, wearresistant ceramic sphere. There are no conventional shaft bearings or
seals. This eliminates the possibility of bearing-play which is commonly
associated with increased noise and the seal-less design eliminates a
potential leak path. These pumps are particularly robust and provide an
exceptionally long service life in excess of 50,000 hours.The selfrealigning bearing is lubricated and cooled by the fluid media. Maintenance is not necessary under normal conditions. Even after lengthy
shutdown periods a reliable start-up is virtually guaranteed. Parts
exposed to the fluid are completely corrosion resistant even with
aggressive fluids.
Construction design
favored
acceptable
not permitted
Electrical connection
Important note: Electrical installations may only be performed by a
properly licensed electrician observing all applicable general and local
codes.
- Connect to a 8-25 V co-current flow power supply, the red wire has
to be connected with positive terminal, the black wire has to be
connected with the negative terminal.
- If the system is not filled with water yet, reduce the time of a function
test to an absolute minimum. Extended dry operation of the pump will
damage the bearing.
Before startup
Flush the system to remove dirt, make sure the system is filled and the
air has been purged. The pump can be switched on. If you hear air
noises initially, these should stop after a short time. Power cycling the
pump several times accelerates the air removal. If the air noise does not
disappear or at least decrease substantially, repurge the system. Avoid
dry run in any case, this will damage the pump.
Startup
- The starting current is much higher than the operating current for a
very short time until the pump is running.
- If the voltage drops because of the high starting current, the pump will
startup.
Pump station installation
The
pump housing brass is for use in
·
both solar systems and potable
water. The pump motor is fixed to the
pump housing by the screw ring,
which enables easy removing and
disassembly.
The
motor
has
electronic integrated thermal overload
protection, interference suppressor
and integrated reverse polarity
protection. Power cord double-wire is
red/black for polarity. The pump
motor and the integrated electronic
parts are moisture resistant.
The DC-ECM solar pump is a direct fit
into the 255 and 256 series solar pump
stations. The DC pump face to face
dimensions and the male union thread
are exactly the same 120V version.
Simply select the 255 or 256 solar pump
station configured without the pump. To
install, remove the pump space pipe and
mount the DC-ECM directly with the
union half nuts. The iSolar 12V and 24
VDC controllers will fit into the front
insultation cover of the 255 and 256
series pump station.
In-line sweat fittings
Integrated overtemperature protection
The pump comes with an integrated overtemperature safety device,
which shuts the pump electronics off when reaching overtemperature.
A complete shutdown after reaching an overtemperature condition can
result in adverse effects on the solar system. Since the temperature of
the electronic components is influenced by the temperature of the
pumped media, the pump will lower its speed automatically after
reaching a critical temperature level in order to avoid a total system
shutdown. However, if the temperature continues to rise because of
too hot of pumped media, the pump will eventually shut down
completely. After cooling down, the pump will restart automatically.
Item
Code
Description
255056A
Dual-line solar station without pump
256056A
Single-line solar station without pump
NA10002
NA10003
R50055
R61008
59834A
1/2” sweat tail piece, use nut and washer
3/4” sweat tail piece, use nut and washer
Sealing washer, use with nut and tail piece
Union nut 1” thread, use washer, tail piece
1” sweat tail piece with nut, use washer
61
Differential temperature controllers
iSolar
CALEFFI
series 257
Function
The iSolar series solar thermal controllers are multi-functional temperature differential controllers
that provide complete control of the solar thermal system for safe and long-lasting operation. The
iSolar microprocessor controller monitors and controls thermal solar energy systems by means of
a collector sensor and a storage tank sensor. The controllers also implements important system
monitoring and safety functions. The system parameters and measured values can be viewed and
altered by the large LCD display. The controller is equipped for up to four temperature sensor
inputs and one or two outputs (some models) for activating the solar circuit pump and second
output for activating a valve or second pump.
Tested and Approved by TÜV Rheinland as an approved U.S. Nationally Recognized
Testing Laboratory (NRTL) Exceeds or is equivalent to:
UL 60730-1A
CAN/CSA E60730-1
Product range
Code 257210A
Code 257220A
Code 257230A
Code 257240A
Code 257260A
Code 257260A PV1
Code 257260A PV2
iSolar 1 with 1 pump control relay, includes 2 temperature sensors, data connection
iSolar 2 with 1 pump speed control triac, includes 2 temperature sensors, data connection
iSolar 3 with 2 control relays for solar pump and second pump or valve, includes 2 sensors, data connection
iSolar 4 with 1 pump speed triac and 1 control relay for second pump or valve, includes 2 sensors, data connection
iSolar Plus with 2 pump speed triacs, for second pump or valve, includes 4 sensors, data connection
iSolar Plus 12V with 2 pump control relay, for second pump or valve, includes 4 sensors, data connection
iSolar Plus 24V with 2 pump control relay, for second pump or valve, includes 4 sensors, data connection
Technical specifications
Housing plastic:
Protection type:
Mounting:
Display:
Interface:
Inputs:
Outputs:
Switching relay capacities:
Power supply:
Power consumption:
Data connection:
Resistance values for sensors subject to the temperature
PC-ABS
Indoor only
wall or in 255 series pump station
LCD with symbols and text
three soft push buttons
4 temperature sensors
1 or 2 triac or standard relays
1 (1) A 115VAC
115 VAC – 60 Hz
12V – 24V
1W, 1.5VA
V-Bus
°F
Ω
14
961
23
980
32
1000
41
1019
50
1039
59
1058
68
1078
77
1097
86
1117
°F
Ω
95
1136
104
1155
113
1175
122
1194
131
1213
140
1232
149
1252
158
1271
167
1290
°F
Ω
176
1309
185
1328
194
1347
203
1366
212
1385
221
1404
230
1423
239
1442
248
1461
Dimensions
A
C
ΔT adjustment range:
2–40º ΔT (1– 20ºK)
Min. temperature differential:
2º ΔT (1ºK)
Hysteresis:
2º ΔT, ± 1º ΔT (1ºK, ± .5ºK)
Max. tank temperature range:
35 – 205°F (2– 95ºC)
Max. collector temperature range:
210 – 375°F (100 –190ºC)
Emergency shut down of the collector:
230 –395°F (110 – 200ºC)
Min. collector temperature range:
50 –195ºF (10– 90°C)
Antifreeze temperature option:
15 – 50°F (-10–10ºC)
kWh (BTU) flow input:
0–5 gpm (0 –20 lpm)
Agency approvals:
cTÜVus
B
Performance
Temperature sensors
Platinum RTD type:
Collector sensor working range:
Tank sensor working range:
Length of collector black cable:
Length of tank sensor gray cable:
62
1,000 ohm
-58 – 355ºF (-50 –180°C)
15 –175ºF (-10– 80°C)
60 in. (1.5 m)
95 in. (2.5 m)
D
Code
257series
A
4
3/8"
B
6 3/4"
C
6"
D
2"
Weight (lb)
0.9
Characteristics
User-friendly operation
Pump speed control functions (iSolar 2, 4 & Plus)
System screen LCD display
with 16-segment display and
8 symbols for system status
Pump speed control can improve system efficiency by reducing
the flow to the collectors on cloudy days to improve solar thermal
transfer and reduce electrical consumption. This is achieved
by the differential temperature value between the collectors
and storage tank.
!
ê
?
?
F
R
Operating LED control lamp
–
+
SET
3 push-button controls
If the value for the ΔT switch-on is reached (e.g. ΔT on = 9º),
the pump will start with 100% pump speed for 10 seconds, then
reduce the speed to the adjusted minimum pump speed (min.
pump speed = 30 %, adjustable). If the temp-erature difference
reaches the set value (e.g. ΔT Set = 18º), pump speed will increase by 10 %. At any further rise of 3º ΔT the pump speed will
increase by 10% until the maximum of 100% is reached.
Attractive design and
compact dimensions
+
Easy to install
Standard operation functions
iSolar 1
120V
iSolar 2
120V
iSolar 3
120V
iSolar 4
120V
iSolar Plus iSolar Plus PV
12 or 24V
120V
Selectable programs
1
1
3
3
10
10
Standard relay output
1
0
2
1
0
2
Speed control triac output (30 to 100%)
0
1
0
1
2
0
Sensor inputs (temperature)
4
4
4
4
4
4
Max. solar collector arrays
1
1
1
1
2
2
Max. solar storage tanks
1
1
1
1
2
2
Two tank priority logic
no
no
no
no
yes
yes
Second deltaT-function
no
no
no
no
yes
yes
Drainback pump speed control
no
yes
no
yes
yes
no
Drainback booster pump (second relay)
no
no
yes
yes
yes
yes
Thermostat function (second relay)
no
no
yes
yes
yes
yes
Backup heat function (second relay)
no
no
yes
yes
yes
yes
Heat dump function (second relay)
no
no
yes
yes
yes
yes
Real time clock (timer function)
no
no
yes
yes
yes
yes
Collector freeze protection
yes
yes
yes
yes
yes
yes
Evacuated tube collector function
yes
yes
yes
yes
yes
yes
Min. collector temperature
yes
yes
yes
yes
yes
yes
Collector cooling functions
yes
yes
yes
yes
yes
yes
Tank (night time) cooling
yes
yes
yes
yes
yes
yes
Emergency shutdown functions
yes
yes
yes
yes
yes
yes
Operating hours counter
yes
yes
yes
yes
yes
yes
Energy metering measurement
yes
yes
yes
yes
yes
yes
Vbus data commincation
yes
yes
yes
yes
yes
yes
257240A
257260A
257260A
PV1 or PV2
Code
257210A 257220A 257230A
63
Sensor
Flexibleprotection
stainless steel insulated piping
SolarFlex
SP10
NA3500
CALEFFI
CALEFFI
Function
SolarFlex is a system solution with pre-insulated flow and return
Functionpipes for solar hot water heating systems used to connect the solar
collector with the storage tank in an easy, quick and professional
The SP10 sensor protection device should be used to protect the sensitive
way. It optimizes thermal efficiency of the entire system. The precollector temperature sensor against external over-voltages. In the case of
insulation solution of two flexible stainless steel pipes inside two
thunderstorms, lightning strikes can destroy the collector sensor and differential
EPDM closed cell insulation and the integrated sensor cable, saves
temperature controller. The SP10 protector diodes limit these over-voltages and
time and reduces cost of installation. SolarFlex is packaged in a 50maintains a stable noise-free connection between sensor and controller.
foot continuous coil with a complete range of accessories to ensure
a smoothand secure installation.
The best way to protect the collector sensor is to install the SP10 device close
to the collector sensor. The SP10 is designed as a weather-resistant connecting
terminal block
in a dripping water-protected housing which can be used
General
outdoors. Soft thermoplastic elastomers in the bottom of the lower housing
• sensor
Easy tocables
install,
enabling
pipes
to be run without using a torch
protects the
and
allow easy
installation.
in confined spaces or on the roof.
• Ensures a leak-free installation.
• Easy to separate, without damaging the tubes.
• External copolymer foil protects against UV radiation
and mechanical strain.
• Identification mark for flow and return.
Product range
• Meets highest requirements for modern solar heating systems.
Code NA15006 SP10 sensor protection device for protecting collector sensor •and
controller from
lightning
or other
over-voltages
Pre-insulated
feed
and return
pipes
can be joined easily
without special tools.
Technical specifications
Mounting
For optimum protection against moisture, the SP10 sensor protection
Upper
housing:
ASA thermoplastic
Product
range
device must be fitted vertically. Unscrew the housing screw and
Lower housing:
thermoplastic elastomers
NA3520-15
(2) double
nipples, (4)remove
union nuts,
4 segment
and 4 washers
the upper
part ofrings
the housing.
Mark the fastening points on
Protection
type: 1/2" SolarFlex pipe 50' coil including
NEMA
4 (IP 65)
NA3540-15
3/4" SolarFlex pipe 50'
(2)...
double
nipples, (4)vertical
union nuts,
4 segment
rings and
4 washers
surface
and drill. Attach
the lower
part of the housing using the
Ambient
temperature:
-15coil
... including
160ºF (-25
+70ºC)
NA3540- B
3/4" SolarFlex pipe bulk cut to length up tovertically
164 foot. Withoutscrews.
connection
Installfittings.
the upper part of the housing onto the lower part and
Mounting:
NA3560-15
1" SolarFlex pipe 50' coil including (2) doubleCE
nipples, (4)attach
union housing
nuts, 4 segment
screw. rings and 4 washers
Agency
approvals
Materials:
- pipe:
two corrugated stainless steel 316L
A two closed cell elastomer UV resistance EPDM
- insulation:
- outer cover:
UV resistant polyolefin copolymer foil
Insulation thickness:
5/8 inch (16mm)
Thermal conductivity:
0.215 BTU-in/hr-ft2-°F (0.031 W/mK)
Thermal resistance:
R-4.2
Max. working pressure:
150 psi (10 bar)
Max. fluid temperature:
350ºF (175ºC)
B
Min. surface temperature:
-60ºF (-50ºC)
Length per coil:
50 feet (15m)
Fluid capacity per foot:
1/2" - 0.0219 gallons (0.08 liters)
3/4" - 0.0346 gallons (0.13 liters)
1" - 0.0509 gallons (0.19 liters)
Min. bending radius:
5 inch (130mm)
Pessure loss: C
Approx. 25% more than in a comparable smooth pipe
D
Flammability:
Class VO
Flame spread/smoke density
25/50
Agency approvals:
ASTM D 635
ASTM C 177
A
fig. 1
Code
Code
NA15006
64
A
2
1/2”
B
4 3/8”
C
2
5/8”
D
1
1/2
Weight (lb)
0.3
B
Electrical connection
Pierce the lower housing with a pointed object (fig.1). Insert the cables
into the holes and pull them slightly back, such that the edge of the
material is slightly turned to the outside. Thus the device is protected
C cable to the terminals 1 and 2
against moisture. Connect the sensor
with either polarity (fig. 2). Connect the cable which leads to the
controller at the terminals 3 and 4 and to the corresponding controller
terminals.
D
Technical specifications
Dimensions
upper part of
the housing
lower part of
Dimensions
the housing
fig. 2
1
2 3
4
A
B
C
D
Weight (lb/f)
0.4
NA3520 -15
1/2"
11/16"
4"
2"
NA3540 -15
2 - 1/8 "
3/4"
15/16"
4 - 3/8 "
0.5
Note: If the connecting box is used outdoors, it is recommended to pierce a condensation
NA3560
-15bottom1"
0.7
2 - 1/2 "
1 - 1/4"
4 - 7/16 "
water
hole at the
after the device
has been installed.
Flexible
stainless steel insulated piping
Alarm module
SolarFlex
AM1
NA3500
CALEFFI
Function
SolarFlex is a system solution with pre-insulated flow and return
pipes for solar hot water heating systems used to connect the solar
Function
collector with the storage tank in an easy, quick and professional
The AM1 way.
alarmItmodule
is designed
signal system
It is connected
to
optimizes
thermal to
efficiency
of the failures.
entire system.
The prethe VBus insulation
data connection
of of
thetwo
iSolar
controllers
and steel
issuespipes
an optical
solution
flexible
stainless
insidesignal
two
via the redEPDM
Flash-LED
a failure
has occurred.
The AM1 also
has cable,
a dry contact
closedif cell
insulation
and the integrated
sensor
saves
output relay,
can be connected
to an additional
signaling
deviceinora to
timewhich
and reduces
cost of installation.
SolarFlex
is packaged
50-a
building management
system.Thus,
multi-modal
error
can to
beensure
issued
foot continuous
coil with a acomplete
range
of message
accessories
in the case
of a system failure.
a smoothand
secure installation.
Depending on which iSolar controller and the sensors connected, different fault
conditionsGeneral
can be signaled. For example sensor failures, excess system
temperature,
excess
collector
or tankpipes
temperature,
aswithout
well as using
errors aintorch
the flow
• Easy
to install,
enabling
to be run
rate, such asinaconfined
dry run ofspaces
the pump.
Thethe
AM1
ensures that occurring failures can
or on
roof.
be immediately
recognized
and repaired,
even if the system and the controller
• Ensures
a leak-free
installation.
are difficult
access
or locatedwithout
in a remote
place.the tubes.
• to
Easy
to separate,
damaging
• External copolymer foil protects against UV radiation
and mechanical strain.
• Identification mark for flow and return.
Product range
• Meets highest requirements for modern solar heating systems.
• Pre-insulated
Code NA15009 AM1 alarm module with red Flash-LED light and one dry contact
output relayfeed and return pipes can be joined easily
without special tools.
D
D
1
1/2
Weight (lb)
0.3
D
Dimensions
Technical specifications
Product range
Housing plastic:
PC-2207 UV
NA3520-15
1/2" SolarFlex pipe 50' coil including (2) double
nipples, (4) union nuts, 4 segment rings and 4 washers
Protection type:
Indoor only
NA3540-15
3/4" SolarFlex pipe 50' coil-15
including
(2)(-25
double
nipples, (4) union nuts, 4 segment rings
Ambient temperature:
... 160ºF
... 70ºC)
A and 4 washers
NA3540B
3/4" SolarFlex pipe bulk cut to length up to 164 wall
foot. Without connection fittings.
Mounting:
NA3560-15
1" SolarFlex pipe 50' coil including (2) double
nipples, (4) union nuts, 4 segment rings and 4 washers
Display:
1 Red LED
Interface:
VBus data connection
Power supply:
VBus
Technical
Outputs: specifications
1 dry contact relay
Dimensions
Switching relay capacities:
1 A, 24V AC/DC
Materials:
Agency
CE
A
B B
- pipe:approvals
two corrugated stainless steel 316L
- insulation:
two closed cell elastomer UV resistance EPDM
Operating
sequence
- outer cover:
UV resistant polyolefin copolymer foil
Insulation thickness:
5/8 inch (16mm)
When theconductivity:
AM1 is operational, the0.215
LED will
glow continuously
to W/mK)
signal
2
Thermal
BTU-in/hr-ft
-°F (0.031
operational readiness. If the LED does not glow, check the connection
Thermal resistance:
R-4.2
of the device. The AM1 receives the VBus data packets of the device
Max. working pressure:
150 psi (10 bar)
connected. In the case of a failure signal, the integrated Flash-LED
C
Max. fluid temperature:
350ºF (175ºC)
flashes and the AM1 activates the dry contact output relay. The relay
Min. surface temperature:
-60ºF (-50ºC)
can be used to connect an additional signaling device, or to a building
Length
per coil:
50 feet (15m)
management
system.
C
Fluid capacity per foot:
1/2" - 0.0219 gallons (0.08 liters)
Code
A
B
C
3/4" - 0.0346 gallons (0.13 liters)
NA15009
2 1/2”
4 3/8”
2 5/8”
Data communication example1" - 0.0509 gallons (0.19 liters)
Min. bending radius:
5 inch (130mm)
Pessure loss: Approx. 25% more than in a comparable smooth pipe
Data connections
Flammability:
Class VO
Flame spread/smoke density
Agency approvals:
iSolar
25/50
ASTM D 635
ASTM C 177
Alarm
Optional
Datalogger
Relay output
The AM1 is designed for easy connection
to all iSolar controllers through the VBus
Connection terminals
data connection. Connect VBus wires to
A
B with either
C
D
Weight (lb/f)
theCode
terminals marked
“VBus”
polarity.
The bus
wire can
be extended
0.4
NA3520 -15
1/2"
11/16"
4"
2
"
RELAY
VBUS VBUS
with
two-15conductor
(bell wire).The
NA3540
2 - 1/8 "
3/4" wire15/16"
4 - 3/8 "
0.5
2
wire must be at least 20 AWG (0.5 mm ) and can be extended up to
NA3560 -15
0.7
2 - 1/2 "
1"
1 - 1/4"
4 - 7/16 "
150 feet. To the “Relay” terminals, a load can be connected with either
polarity.
65
Flexible
stainless steel insulated piping
Energy meter
SolarFlex
WMZ-G1
NA3500
CALEFFI
Function
SolarFlex is a system solution with pre-insulated flow and return
pipes for solar hot water heating systems used to connect the solar
Function
collector
the meter
storage
in ansolar
easy,
quick and
The WMZ-G1
is anwith
energy
fortank
thermal
systems
and professional
conventional
way. It optimizes
thermal
efficiency
of the
entire system.
heating systems.
The WMZ-G1
calculates
energy
by integrating
flow The
rate preand
insulation
of two
flexible
stainless
steel
pipes
inside
temperature
from a solution
Vortex Flow
Sensor
(VFS)
Grundfos
Direct
Sensors
™ two
and
EPDM
closedincell
thepiping
integrated
cable,
saves
temperature
difference
theinsulation
flow andand
return
usingsensor
a Relative
Pressure
time Grundfos
and reduces
cost
of installation.
SolarFlex isheat
packaged
a 50™. The calculated
energy in
value
is
Sensor (RPS)
Direct
Sensors
continuous
with
a complete
accessories
to guaranensure
displayed foot
in kWh
(kilowatt coil
hours)
and
stored. A range
power of
failure
protection
smoothand
tees that athe
adjusted secure
systeminstallation.
parameters and the calculated heat energy
quantity are maintained in the case of power loss.
(shown with optional 3/4” sweat unions)
(not included)
Product range
Code 257202A
Code NA15014
Code NA15015
Code NA15016
Product range
Grundfos
Direct Sensors™ Technology
General
The VFS combines
established
with
the direct
• Easy tothe
install,
enablingvortex
pipesprinciple
to be run
without
usingexposure
a torch of
the sensor chip
to the media
gives
sensitivity and fast response. The
in confined
spaces
or aonsuperior
the roof.
VFS sensor
detects athe
pressure
pulsation generated by the vortices and
• Ensures
leak-free
installation.
converts the
pulsation
and temperature
into an electrical
output signal. The VFS
• Easy
to separate,
without damaging
the tubes.
sensor has
tocopolymer
be 5 timesfoil
higher
in accuracy
faster flow response
• shown
External
protects
against with
UV radiation
than most common
turbine strain.
flow meters. The RPS sensor transforms the
and mechanical
pressure and
temperaturemark
of the
electrical signals. The pressure
• Identification
formedium
flow andinto
return.
signals are• linearized
to
compensate
for
temperature
Meets highest requirements for modernvariations.
solar heating systems.
• Pre-insulated feed and return pipes can be joined easily
without special tools.
WMZ-G1 Heat energy meter functions with VFS flow/temperature sensor and RPS pressure/temperature sensors
RPS Grundfos Direct Sensors 2 in 1 Pressure / temperature sensor 0 - 150 psi / up to 250º F, includes connecting wire
VFS Grundfos Direct Sensors 2 in 1 Flow / temperature sensor 1/4 - 3 gpm / up to 250º F. includes connecting wire
VFS Grundfos Direct Sensors 2 in 1 Flow / temperature sensor 1/2 - 10 gpm / up to 250º F. includes connecting wire
NA3520-15
1/2" SolarFlex pipe 50' coil including (2) double nipples, (4) union nuts, 4 segment rings and 4 washers
Technical specifications
System
NA3540-15
3/4" SolarFlex pipe 50' coil including (2) double nipples, (4) union
nuts,diagram
4 segment rings and 4 washers
NA3540- B
3/4" SolarFlex pipe bulk cut to length up to 164 foot. Without connection fittings.
WMZ-G1 energy meter
NA3560-15
1" SolarFlex pipe 50' coil including (2) double nipples, (4) union nuts, 4 segment rings and 4 washers
Housing plastic:
PC-ABS
Display:
4 lines LCD
Inputs:
2 Grundfos Direct Sensors
Technical
specifications
Dimensions
Output:
1 relay
Optional
Datalogger
Switching relay capacities:
2 (1) A 24V=
Materials:
A
B
Interface:
VBus
data connection
- pipe:
two corrugated
stainless
steel 316L
Power
supply:
24V AC or
DC
- insulation:
two closed cell elastomer UV resistance
EPDM
- outer
cover:
Vortex
Flow
Sensor (VFS) UV resistant polyolefin copolymer foil
Insulation
thickness:
inch
(16mm)
Flow measuring
range:
NA15015 0.25 - 35/8
gpm
(1-12
lpm)
2
Thermal conductivity:
0.215
BTU-in/hr-ft
-°F
(0.031
W/mK)
NA15016 0.50 - 10 gpm (2-40
lpm)
Thermal
resistance:
R-4.2
Flow accuracy:
1.5%
Max.
150 psi<(10
bar)
Flow working
responsepressure:
time:
1 sec.
RPS sensor
Max. fluid temperature:
350ºF (175ºC)
Relative Pressure Sensor (RPS)
Min. surface temperature:
-60ºF (-50ºC)
Pressure measuring range:
0 - 150 psi (0-10 bar)
VFS sensor
Length per coil:
50 feet (15m)
Pressure accuracy:
2% FS
C
Fluid capacity per foot:
1/2" - 0.0219 gallons (0.08 liters)
Multinode network
Pressure response time
< 1 sec.
3/4" - 0.0346 gallons (0.13 liters)
Additional WMZ-G1 energy meters can be cascaded together on the
VFS and RPS temperature specifications
1" - 0.0509 gallons (0.19 liters)
VBus connection. One WMZ-G1 is configured as the master and
Max.bending
fluid temperature:
250º F(130mm)
(120ºC)
Min.
radius:
5 inch
additional WMZ-G1 meters are configured as slaves. Up to 16
Temperature
accuracy
range:
32
210ºF
(0-100ºC)
Pessure loss: Approx. 25% more than in a comparable smooth pipe
meters can be cascaded together with two conductor wire (bell wire) at
Temperature accuracy:
Flammability:
Class2%
VO
least 20 AWG and up to 150 feet for transmission of data values to a
Temperature
responsedensity
time:
< 1sec.
Flame
spread/smoke
25/50
connected PC or DL2 datalogger.
Suitable fluids:
water, glycol solution
Agency approvals:
ASTM D 635
Max percentage of glycol:
50%
ASTM C
177
Materials: - Body:
brass
Code
A
B
C
D
Weight (lb/f)
- Seals:
EPDM
0.4
NA3520 -15
1/2"
11/16"
4"
2"
- Sensor housing:
composites (PPS, PA66)
Connection:
1” male union thread
NA3540 -15
2 - 1/8 "
3/4"
15/16"
4 - 3/8 "
0.5
Optional separate fittings: 1/2”, 3/4” & 1” sweat tail pieces and union nuts
The
connection
is1arbitrary,
16 can
together
" be2 cascaded
NA3560
-15 sequence
0.7
- 1/2 "
1"
- 1/4" up4to- 7/16
balance values
heatmeter
heat
6235 KWh
D
WMZ-G1
DataLogger
The trademark Grundfos Direct Sensors™ is owned and controlled by the Grundfos group.
66
Flexible
stainless steel insulated piping
DataLogger
SolarFlex
DL2
NA3500
CALEFFI
Function
D
A
SolarFlex is a system solution with pre-insulated flow and return
pipes for solar hot water heating systems used to connect the solar
Function
collector with the storage tank in an easy, quick and professional
optimizes
thermal
efficiencyand
of the
entireofsystem.
The preThe DL2 way.
data Itlogger
enables
the acquisition
storage
large amounts
of
insulation
of and
two recorded
flexible stainless
pipes
insideover
twoa
data (such
as energysolution
metering
values of steel
the solar
system)
The Relative Pressure Sensor (RPS) and Vortex
FlowEPDM
Sensor
(VFS)
are
closed
insulationtoand
the integrated
cable,
saves
long period
of time
whencell
connected
an iSolar
controller.sensor
The DL2
is compatcombined temperature sensors intended forible
use with
withtime
boilers
acontrollers
centralcostwith
andinreduces
of installation.
SolarFlex
is packaged
a 50-is
all iSolar
VBus data
connection
terminalsinand
heating circuit. The Relative Pressure Sensor
0-10
foot
continuous
coil
with
a complete
of accessories
to ensure
connected
tobar
the The
VBusdirect
with
two
conductor
wirerange
(bell wire)
at least 20 AWG
up to
exposure of the sensor chip to the media gives
a superior
sensitivity
and installation.
a of
smoothand
a distance
150
feet. secure
thereby fast pressure response. Dry-running protection in solar systems
The DL2, when connected to a network through the integrated ethernet socket,
and gas boilers
can be configured
General and viewed with any standard internet browser via its
integrated web interface. A configuring IP address and password protection
Relative Pressure Sensor:
•access
Easy to
install,
enabling
to connection
be run without
using amonitoring
torch
allows for
from
any
anpipes
internet
for system
The heart of the sensor is a coated SMART sensor,
which
thePC with
intransforms
confined
spaces
or on the
roof.performance, without additional
of
energy
metering
or
for
reviewing
system
pressure in and temperature of the medium into electrical
signals.aThese
•Download
Ensures
leak-free
software.
data
throughinstallation.
the web interface or an SD memory card for
signals are calibrated, conditioned and presented
in •analogue
digital
Easy
toor
separate,
without damaging
further
data
processing
in
spreadsheet
programs the tubes.
format by means of a microprocessor. The pressure signals
are tempera• External
copolymer foil protects against UV radiation
ture compensated and linearized for the influence and
of temperature
mechanical strain.
variations.
• Identification mark for flow and return.
• Meets highest requirements for modern solar heating systems.
Product range
• Pre-insulated feed and return pipes can be joined easily
The Vortex Flow Sensor 1-20 liter per minute The sensorwithout
has shown
a 5tools.
special
Code 257201A DL2 data
logger
connects
to
VBus
data
terminals
on
iSolar
controllers
times higher accuracy than most common turbine flow meters available and a faster flow response. A compact solution enables flexible design
possibilities, minimal permanent pressure loss and a vibration tolerable
sensor.The sensor is unaffected by the temperature, density and viscosProduct range
ity of the media.
Connection
Technical specifications
Housing:
PC-ABS (2)
Thermoplastic
NA3520-15
1/2" SolarFlex pipe 50' coil including
double nipples, (4) union nuts, 4 segment rings and 4 washers
Vortex
Flow
Sensor:
Protection type:
indoor
NA3540-15
3/4" SolarFlex
pipe
50'
coil including (2) double
nipples, (4) union nuts, 4 segment rings and 4 washers
By
combining
(von Karman,
1912)
with
NA35403/4" SolarFlex pipe bulkthe
cutestablished
to32
length
upvortex
foot.
connection
fittings.
AmbientBtemperature:
... 100º
Fto
(0 164
... principle
40º
C) Without
Router
the unique
metal-glass
coating,
Silicoat®
from Grundfos
affordable,
NA3560-15
1" SolarFlex
pipe 50'
coil including
(2) double
nipples,
(4) unionan
nuts,
4 segment rings and 4 washers
Mounting:
wall
accurate and direct flow sensor forbar
aggressive
media is now available.
Display:
LED
The flow sensor is without any5V
moving
Input voltage:
DC ± 5parts,
% which can deteriorate or
Vortex
Street
two series of
Power voltage
adapter:commence clogging. The 100
... 240
V~ generates
Technical
specifications
Dimensions
turbulence
(vortices)
shedding
behind
a
bluff
body
By
increasing
flow the
Rated current:
350 mA
Materials:
will increase
and the frequency increases
Ethernet connection: frequency of the vorticesintegrated
socket
A
B
- pipe:
two corrugated
stainless
directly proportional
to the
flow insteel
aSD
full316L
pipe. The Vortex Flow Sensor
Data access
integrated
slot
- insulation:
two closed
cell
elastomer
UV resistance
EPDM
consists
of
a
sensor,
Vortex
Tube
and
element.
The
sensor
detects
the
Memory:
180 MB internal memory
- outer cover:
UV pulsation
resistant generated
polyolefin by
copolymer
foil and converts the pulsation
pressure
the vortices,
Insulation
thickness:
5/8The
inch
(16mm) of the pressure pulsation is
into an electrical output signal.
frequency
Dimensions
2
Thermal conductivity: a measurement
0.215 BTU-in/hr-ft
-°Fand
(0.031
W/mK)
of the velocity
in the
defined flow pipe the actual flow
Thermal resistance:
R-4.2
is measured.
Integrated Web interface
Max. working pressure:
150 psi (10 bar)
Max. fluid temperature:
350ºF (175ºC)
Min. surface temperature:
-60ºF (-50ºC)
2in1 Flow and Temperature Sensor.
Length per coil:
50 feet (15m)
C
response
thru direct
Fluid capacity per foot: Fast temperature
1/2" - 0.0219
gallons
(0.08media
liters)contact.
1.5% FS accuracy.
3/4" - 0.0346 gallons (0.13 liters)
Compact, robust
and cost-effective
solutions
1" - 0.0509
gallons (0.19
liters)
2in1 Pressure and Temperature
Sensor.
Min. bending radius:
5 inch
(130mm)
?Accurate,
linearized
and temperature-compensated
pressure reading.
Pessure loss: Approx. 25%
more than
in a comparable
smooth pipe
Flammability:
Class VO
Flame spread/smoke density
25/50
Agency approvals:
ASTM D 635
B ASTM C 177
C
Code
Code
257201A
A
5 1/8”
B
1
3/4”
C
4
7/16”
Ø
1/4” mount
Weight (lb)
NA3520 -15
NA3540 -15
3.0
NA3560 -15
A
1/2"
3/4"
1"
B
11/16"
15/16"
1 - 1/4"
C
4"
4 - 3/8 "
4 - 7/16 "
D
2"
2 - 1/8 "
2 - 1/2 "
Weight (lb/f)
0.4
0.5
0.7
67
Solar Flat Plate Collectors
• 25,000, 32,000 & 40,000 Btu/day
(SRCC Cat. C)
Universal mounts for flush roof or
ground mount.
• Durable, 1/8”, low iron tempered glass.
• Selective crystal coating absorber coating.
• Attractive bronze extruded aluminum frame.
SRCC certified and listed.
• 10-year warranty.
SolarCon™ Storage Tank
• 50, 80 & 119 gallon tanks with lower heat
exchanger coil and electrical element for
backup heating.
• 4,500 watt, UL listed backup element
with aquastat.
• 80 & 119 gallon tanks with lower heat
exchanger coil and upper heat exchanger
coil for boiler backup heating.
• Durable porcelain enamel lining, with
protective cobalt.
• Heavy gauge powdered coated steel
outside jacket.
• Dual heavy-duty anode rods protection.
• Thick 2” non CFC foam insulation.
• 6-year warranty.
SolarFlex™ Insulated Flexible Stainless
Steel Piping
•
•
•
•
•
1/2”, 3/4” and 1” sizes in continuous coils.
High temperature EPDM insulation UV resistant.
Heavy durable UV resistant film outside jacket.
Sensor wire between flow and return pipes.
6-year warranty.
iSolar™ Differential Temperature
Controller and Solar Station
•
•
•
•
•
•
•
•
•
•
•
•
SOLAR WATER HEATING SYSTEMS
LCD user friendly graphic display.
Variable pump speed control.
Collector overheat protection.
Storage tank cooling.
kWh energy measurement.
Adjustable delta T function.
Shut off valves with built-in flow checks.
Fill and purge plus safety valves.
Flow meter and flow adjustment.
Temperature and pressure gages.
Three speed pump, UL listed.
4-year warranty with authorized installer.
www.caleffi.us
Caleffi Solar offers several complete, integrated Solar Water Heating Systems that makes the most of the
sun’s abundant energy. The systems are engineered of highly reliable components that work together to
ensure superior system performance. As an added benefit, having all the components from one manufacturer provides the advantage and convenience of reducing system planning and installation time. Caleffi’s
Solar Water Heating Systems can be installed quickly, with “plug and flow” components that are ready to
screw together, without lighting a torch for soldering. All mounts, fittings, connectors and pre-mix glycol
included.With their simple, reliable, environmentally friendly technology, the systems are suitable for all types
of l buildings and geographic areas. The first complete Solar Water Heater in a Box.
Caleffi North America Inc. - Milwaukee, WI - Tel 414.238.2360 - [email protected]
CALEFFI
SOLAR SOLUTIONS
68
Was this manual useful for you? yes no
Thank you for your participation!

* Your assessment is very important for improving the work of artificial intelligence, which forms the content of this project

Download PDF

advertisement