Domestic Hot Water - Devi A S

Domestic Hot Water - Devi A S
Domestic hot water
Domestic Hot Water
Application manual
Intelligent solutions
with lasting effect
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Index
Let DEVI do the work
1. Application briefing 4
2. System Description
5
3. System Design
7
4. Product Selection 8
5. Installation 10
6. Cases
12
DEVI - an abbreviation of Dansk El-Varme Industri - was established in
Copenhagen, Denmark, in 1942. As from January 1st 2003 DEVI has become
a part of the Danfoss Group - Denmark's largest industrial Group. Danfoss
is one of the world's leading companies within heating, cooling and airconditioning. The Danfoss Group has more than 23.000 employees and
serves customers in more than 100 countries.
DEVI is Europe’s leading brand of electrical cable heating systems and electric
pipe heating systems with over 70 years of experience. The development of
electric floor heating system takes place in Denmark, where the head office
is situated while heating elements (cables and mats) are manufactured by
Danfoss in EU (in France and Poland).
Domestic Hot Water temperature
maintenance system
This design guide presents DEVI’s recommendations for design and
installation of Domestic Hot Water system. It provides guidance for a heating
cable layout, electrical data and system configurations.
Following DEVI’s recommendations will ensure energy efficient, reliable and
maintenance free solution for constant wattage heating cables with 20 year
warranty, self-limiting heating cables with 5 years of warranty.
Our quality management
system
and compliances
ISO 9001
TS 16949
ISO 14001
PED
Along with full compliance with EU
directives and product approvals
3
1. Application
briefing
Modern living requires buildings to
have hot water available whenever
and wherever needed – and
preferably immediately. The latest
building regulations (ASHRE 1882015) demand domestic hot water
systems to ensure best comfort and
efficiency as well as the Legionella
control measures.
DEVI Electric heat tracing systems
ensure instant and reliable supply
of the Legionella-free domestic hot
water (DHW). DEVIhotwatt™ is a selflimiting heating cable that is used
for temperature control of hot water
supply.
DEVIhotwatt™ is mainly used in the
DHW system without circulation
(“One pipe system”). The heat tracing
complies with IEC 62395-2, CIBSE
TM13 and ASHRE 188-2015.
Benefits
• DEVI pipe tracing systems ensure hot water
in all taps and savings when a circulating pipe
system is unnecessary.
• DEVI heating cable reduces water waste as you
can get hot water immediately.
• High protection against the Legionella – DEVI
system maintains water supply at the required
temperature level and provides appropriate
disinfection to suppress the Legionella bacteria.
• Perfect partner system to be used in domestic
hot water (DHW) systems supplied by the Lowtemperature district heating (LTDH), which is
a cost and energy efficient way of building
water supply in urban areas.
• Lower initial investment of DHW system
without circulation – appx. 50% less pipes,
insulation, valves, and pumps to be installed as
no return pipes and insulation are required.
• Space saving – no need for return pipe gives
more room in service ducts.
• Energy efficient - heating cables provide
power only where needed adapting output
according to the ambient temperature. Also,
less pipes and smaller boilers requirements for
the DHW means less heat losses in the system.
• The heating cable is flexible and easy to
install as it can be cut to length right on site
and installed directly on the pipe system.
• Long lifetime – with over 70 year experience in
the field, the lifetime of DEVI pipe tracing cables
is exceeding twenty years.
4
Application manual · Domestic hot water · VGLUA102 · ©DEVI
2. System Description
Since 1998 the EU Drinking Water
Directive (98/83/EG) in EN 806-2 has
established standards for hot water
in pipes that should not drop below
50 °C. The latest building regulations
(IEC 62395-2:2013 and ASHRAE
188-2015) as well as global trends
are demanding domestic hot water
(DHW) systems to provide the best
comfort, energy efficiency and the
Legionella mitigation measures.
General design principles
aim to provide uniform water
temperature, which should also
avoid temperatures enabling the
Legionella growth. The general
recommendation for DHW is
to maintain the heat source
temperature between 50-60 °C (IEC
62395-2:2013).
Recommendations for hot water services and water temperature regulation (IEC 62395-2:2013)
Application
Temperature,
°C
Safety showers and eyewashes
16 to 35
Hot service without mixing valves
40
Nursing homes and hospitals
40 to 46
General purpose
49 to 60
Laundry service
71
Kitchen sanitization
82
Water heating is often provided by
means of centralized or decentralized
installations with a large distribution
network. To avoid the Legionella
formation and unnecessary water
loss the DHW circulation should
be operated at 55 °C. According to
IEC 62395-2:2013 guidelines: ”For
disinfection purposes min 55 °C
is typically required for hot water
installations fitted with mixing
valves”.
However, the temperature of
domestic hot water cannot achieve
the recommended level if the supply
temperature from the source is lower
than that. Considering the above
there is a concern about occurrence
of possible water waste or hygiene
problems (Legionella) therefore a
supplementary electrical tracing
system is recommended.
The reason behind the required
disinfection is the Legionella bacteria,
which is commonly found in many
types of water worldwide and creates
potentially a fatal type of pneumonia
for people.
The Legionella bacteria multiply best
where temperatures are between
20-45 °C and nutrients are available.
The bacteria are dormant below 20 °C
and don't survive above 65 °C. The
primary method used, to reduce
the risk from the Legionella, is water
temperature control, which is easy
to do with help of DEVIhotwatt™
system.
The DEVI pipe heating system for
domestic hot water (DHW) replaces
the heat lost on hot water supply
pipes, to maintain the water at the
desired nominal temperatures when
needed.
Usually the DHW pipe
tracing will be required
in the following cases:
•
Low-temperature
district heating, heat
pump or another
source is supplying
DHW at around 55 °C
•
DHW system without
circulation used
•
The ambient
temperature
variation is greater
than 3 °C
•
DHW tap is located
further than 8 m
from circulation loop
Application manual · Domestic hot water · VGLUA102 · ©DEVI
5
Heat tracing in DHW system
DHW system without circulation
(a single pipe) - the temperature of
the cable adjusts, at any point along
the pipe, dependent upon the local
conditions on the pipe network. This
means that the DHW pipe is heated
everywhere in proportion to how
much it cools down.
The more often the hot water tap
is turned on, the less the hot water
temperature maintenance system
needs to be activated.
Self-limiting heating cable
DHW system with circulation continuous circulation of hot water
to insure that hot water is available at
any of the taps.
In case of DHW with circulation the use of pipe tracing can only be
required if the DHW tap is located
farther than 8 m from the circulation
loop
Self-limiting heating cable
The electric pipe tracing in DHW
system without circulation requires
less pipes, less valves, less pumps and
installation labor compared to the
Recirculating system.
The DEVIhotwatt™ system insures
that domestic hot water is supplied,
independent of the pipes length,
and reduces the risk of localized
temperature fluctuations.
• Appx. 50% less pipes – less water
volume in the pipes, so smaller
boiler can be used.
6
• Energy consumption reduction, as
heat losses from the pipes will be
reduced by min 50%.
Area of Use
• Less maintenance cost, as less
mechanical parts and pumps.
• Hospitals & Nursing homes
• Energy consumption reduction
during the night time, with help of
intelligent controls.
• Schools & Universities
• Saving water – DEVI tracing system
attached to the pipes keeps water
at the desired temperature along
the whole pipe system, so hot water
is immediately provided, when
demanded, and with minimum
water loss.
• Residential building
• Hotels & Prisons
• Multi-store buildings
• Sports facilities
Application manual · Domestic hot water · VGLUA102 · ©DEVI
DEVI pipe heating system is insuring
automatic maintenance of the
required temperature 24/7.
3. System
Design
Heat loss, W/m
Linear output of a heating cable
(W/m), which is installed on hot water
pipe, should be at least the same as
heat loss (Q, W/m) of this insulated
pipe. Heat loss depends on the following: pipe diameter, insulation thickness and temperatures inside pipe
and outside insulation.
Calculated heat losses for pipes, with
insulation thickness equal to pipe diameter, are presented on the diagram.
One line of the heating cable installed
along the water pipe is preferred. The
table and the graph show the calculated heat losses for corresponding
heating cables.
If technical conditions for hot water
pipe differ from the mentioned above,
the heat loss should to be calculated
using the formula below. Increased
heat loss will lead to the necessitation
of installation of 2 or more lines of
heating cable along 1 pipe length.
15
12,1 W/m
10
8,8 W/m
6,6 W/m
5
20
30
40
trr
Insulation
thickness
d
D
70
Maintain
temperature
Calculated
heat loss*
DEVIhotwatt™
nominal output
45 °C
6,6 W/m
7 W/m @ 45 °C, DEVIhotwatt™ 45
55 °C
8,8 W/m
9 W/m @ 55 °C, DEVIhotwatt™ 55
70 °C
12,1 W/m
12 W/m @ 70 °C, DEVIhotwatt™ 70
Controller
DEVIreg™ Therm Control DHB 330
Insulation
DEVIhotwatt™
heating cable
Heat loss calculation formula:
tu
60
Insulated pipe temperature, °C
* Calculation conditions: insulation thickness equal to pipe diameter,
insulation λ = 0,035 W/m·K, ambient temperature 15°C, safety factor 1,1.
Heat loss calculation for pipe heating
The formula below is an approximation of heat loss calculation and
should only be used as a reference.
Pipe dimensions, insulation thickness,
and the ambient temperature are
crucial for the dimensional output.
-t )
Q [W/m] = 2 · π · λ · (tr u · 1,3,
In (D/d)
where
D -Insulation outer diameter, [m];
d -Pipe outer diameter, [m];
π -Pi (3,14);
tr -Temperature of the liquid
inside the pipe, [°C];
tu -Ambient temperature, [°C];
λ -Thermal conductivity for
insulating material, [W/m·K];
1,3-Safety factor.
50
Fig. 1 - Heat loss of Insulated pipes.
Example
A ¾” (outer Ø 27 mm) water pipe
with 50 mm insulation and
λ = 0,04 W/m·K.
The pipe length is 15 m.
d = 27 mm;
D = 27 + 50 + 50 = 127 mm;
tr = 70 °C;
tu = 15 °C.
The temperature inside the pipe may
drop down to 35 °C, but needs to be
maintained at min. 55 °C. Once per
week, the temperature rise up to
70 °C is required.
The ambient temperature can drop
down to 15 °C, resulting max. Δt is
Δt = 70 – 15 = 55 °C .
The heat loss is calculated as follows:
Q=
2 · π · 0,04 · 55 · 1,3 = 11,6 W/m
ln (0,127 / 0,027)
In this example a 15 m self-limiting
DEVIhotwatt™ 70 cable with an
output of 12 W/m @ 70 °C is chosen.
Output for 15 m pipe:
11,6 · 15 = 174 W.
Application manual · Domestic hot water · VGLUA102 · ©DEVI
7
4. Product Selection
Emission of heat, W/m
The pipe tracing system consists of
a self-limiting heating cable (SLC),
installed straight on a pipe along
its whole length, and providing
hot water instantly, even at faucets
placed far away from pipe draw off.
The system is controlled by an
electronic regulator to maintain the
temperature and to run disinfection
insuring safe and Legionella-free
water supply.
35
30
DEVIhotwatt™ 45
DEVIhotwatt™ 55
25
DEVIhotwatt™ 70
The DEVIhotwatt™ is a self-limiting
heating cable that is used for
temperature maintenance of hot
water and other fluids which require
certain temperature levels.
The self-limiting capability of
the cable ensures cable output
regulation according to water
temperature in the pipes and the
ambient temperature, hence the selflimiting effect.
20
15
12 W/m
9 W/m
10
7 W/m
5
e
Pipe h
5
10
15
20
25
at los
30
s
35
40
45
50
55
60 65 70
Pipe temperature, °C
Fig. 2 - Heat emissions.
Curve on Fig. 2 represents Pipe heat loss, the same as Fig. 1 on previous page.
Self-limiting heating element
• 1,3 mm² nickel plated cooper bus wires
• Radiation Cross-linked Semiconductive
Heating Matrix
Overjacket
Bus wires
Protective braid
• Radiation Cross-linked Primary Dielectric
insulation
• Tinned copper braid
Insulation
• Polyolefin overjacket
Fig. 3 - SLC construction
Type
Value
Operation voltage:
230 V AC
Output, color:
7 W/m @ 45 °C, black (DEVIhotwatt™ 45)
9 W/m @ 55 °C, green (DEVIhotwatt™ 55)
12 W/m @ 70 °C, red (DEVIhotwatt™ 70)
Maximum permissible use
temperature
65 °C, powered
100 °C, unpowered
Minimum use temperature
- 30 °C
Cable dimensions
11,8 × 5,8 mm
Outer sheath
TPE
Minimum braid coverage
70%
Maximum resistance protective 18,2 Ω/Km
braid
8
Bending radius
25 mm (radius to the inside of the tape)
Max. length, with 10 A
circuit breaker:
55 m (DEVIhotwatt™ 45)
40 m (DEVIhotwatt™ 55)
35 m (DEVIhotwatt™ 70)
Warranty
5 years
Application manual · Domestic hot water · VGLUA102 · ©DEVI
Benefits
•
The cables can be
cut to length on
site providing quick
installation.
•
Automatic
compensation for
heat loss along the
pipe
•
Economical, selflimitting
•
PVC free
•
Limitted pre-planing
of the installation
The DEVIreg™ Therm Control DHB 330
The DEVIreg™ Therm Control DHB 330
is designed for controlling
DEVIhotwatt™ self-limiting heating
cables used for temperature
maintenance inside pipes. The
temperature can be regulated within
a range of 35 to 70 °C.
once a week to run disinfection and
suppress the Legionella bacteria.
Compared to the control method
without timer, smart control is
helping to save up to 20% of the total
electricity consumption.
Due to the built-in timer it is possible
to switch the system off once every
24 hours e.g. at night as usually there
is not a great demand for hot water,
however this will of course affect
the comfort. The system can be set
up to operate at max. temperature
A power limiter has been built-in in
order not to overload the fuse. After
switching the system on it will slowly
start up (about 8 min.).
Type
Value
Adjustment range
Hb 09: 45 to 60 °C = Typ 1 (factory adjustment) - DEVIhotwatt 55
Hb 12: 45 to 70 °C = Typ 2 - DEVIhotwatt 70
Operating voltage
230 V~ +10 to -15%
Breaking capacity
16 A
Clock operating reserve
12 h
Protection class
IP 20
Permissible ambient temperature
Benefits
•
Legionella
protection
•
Up to 20% energy
savings
-10 to 50 °C
•
Compact size
Maximum cable length
DEVIhotwatt™ 55: 88 m @ 16 A
DEVIhotwatt™ 70: 70 m @ 16 A
•
DIN rail mounting
Size
90 x 71 x 58 mm
•
Weight
0,30 kg
Built-in power
limiter
Attachment
on DIN rail
•
Timer
Alutape
Glued aluminum tape, 38 mm x 50 m
19805076
DEVIconnecto™
Item code Type
Description
19808360
DEVIconnecto B-A
Connection to supply cable
19808361
DEVIconnecto B-C
Heating tape connection
19808362
DEVIconnecto B-E
End termination
19808363
DEVIconnecto B-S
Connection to supply cable and end termination as set
19808364
DEVIconnecto B-T
T-branch for 3 x heating tape 1 I/O
19808365
DEVIconnecto B-TE2 T-branch with power connection and 2 x heating tape 2 I/O
19808366
DEVIconnecto B-TE3 T-branch with power connection and 3 x heating tape 3 I/O
19808367
DEVIconnecto B-X
X-branch for 4 x heating tape 2 I/O
Application manual · Domestic hot water · VGLUA102 · ©DEVI
9
5. Installation
Pipe diameter and recommended insulation
Calculation of cable length
Heating cable length is calculated
as minimum pipe length plus
extra length for some pipe system
construction elements, if any.
mm
15
20
25
32
40
50
65
inch
½"
¼"
1"
1¼"
1½"
2"
2½"
Calculation formula:
mm
50
65
Heated pipe length
+ Number of connections x 0,3 m
heating cable
+ Number of specials x 0,5 m heating cable
+ Number of T-junctions x 1 m
heating cable
+ Heating cable length for flanges,
fittings and measured pipe extensions
The cable installed throughout the
pipe length needs to be covered
along its whole length with
aluminum tape to ensure good
contact with the pipe.
All cables must be installed in parallel
passes; no spiral wrapping is allowed.
Hot water pipes shall be pressure
tested prior to installation of heating
cable and thermal insulation. Thermal
insulation shall not be installed until
heating cable installation is complete
and tested.
Pipe diameter,
mm
Recommended
number of
cable lines
Ø 20 – 100
1
Ø 125 – 200
2
Ø 250 – 400
3
Ø 450 – 600
4
Advised minimum insulation thickness
20
20
30
30
40
Conditions for table:
Ambient temperature = min. 18 °C,
Insulation = min. 0,035 W/m²·K.
DEVIhotwatt™ heating cable maximum length
DEVIhotwatt™ 55
DEVIhotwatt™ 70
Temperature
10 °C
Fuse
10 A
16 A
20 A
10 A
16 A
20 A
70 m
88 m
117 m
56 m
70 m
90 m
Insulation
Aluminium tape
Aluminum tape is recommended.
When using aluminum tape the heat
transfer is improved.
Heating cable
Straight cables must be fitted as
shown at 5 or 7 o’clock positions.
When the heating cable is installed
on pipes, the insulation should be
clearly marked with a warning sign,
e.g. “WARNING: 230 VOLT HEATING
CABLES“.
The recommended ways to mount the cable lines on the pipe
10
Application manual · Domestic hot water · VGLUA102 · ©DEVI
Notes
Application manual · Domestic hot water · VGLUA102 · ©DEVI
11
SU ZHOU CENTER
Su Zhou, China
Project scale: 2 apartment buildings.
Apartment quantity: 600.
Product: DEVIhotwatt™ 55.
Total length: 10,000 m.
Thermostat: 600 pcs.
Project finished : 2016.
The Main DHW system is a circulating
system, but the decision was made
for all the branch pipes indoor to use
pipe tracing by self-limiting cables,
about 20 meters for each apartment.
PROMENADA SHOPPING CENTRE
Warsaw, Poland
Project scale: shopping center.
Product: DEVIhotwatt™ 55.
Total length: 150 m.
Project finished: 1996.
DHW system without circulation.
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with lasting effect
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0809XXXX &VGLUA102
6. Cases
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