Performance Specification for Thermal Stores

Performance Specification
for Thermal Stores
Direct integrated thermal stores
Indirect integrated thermal stores
Hot water thermal stores
Buffer stores
Performance Specification
for Thermal Stores
• Direct integrated thermal stores
• Indirect integrated thermal stores
• Hot water thermal stores
• Buffer stores
This document specifies the performance requirements
and the test procedures for the primary (non-potable
water) thermal energy stores listed below:1.1
1.2
Integrated thermal stores, which use the
stored energy (i.e. the preheated primary hot
water) directly for space heating and indirectly
for producing instantaneous domestic hot water
and which are suitable for:-
Thermal stores with factory fitted electrical wiring must
also comply with the current and relevant IEE and BS3456
requirements.
• Individual dwellings.
• Thermal storage group heating schemes for
blocks of flats.
The construction of the thermal store and the fittings
and the components used or specified must also comply
with the requirements of the ‘Model Water Bylaws’ and
the relevant British Standards.
Hot water only thermal stores, that use stored
energy (i.e. the pre-heated primary hot water)
indirectly for producing instantaneous domestic
hot water only and which are suitable for:-
Where a thermal store is unvented i.e. intended for
a sealed heating system application, it must comply
with the Building Regulations Approved Document G3
Hot Water Storage, 1992 Edition and relevant British
Standards e.g. BS5449: 1990.
• Individual dwellings.
• Thermal storage group heating schemes for
blocks of flats.
At the time of publication, this document took account
of the standards, regulations, etc prevailing at the time.
No responsibility can be taken for subsequent changes
or product developments.
Buffer stores, which supply preheated water
to integrated thermal stores in the individual
apartments in thermal storage group heating
schemes for blocks of flats.
SCOPE
1.3
It does not cover the materials and manufacturing of the
thermal stores and the associated components but the
manufacturer must comply with the requirements of BS
EN ISO 9002 or must be in the process of applying for
approval.
Page 1
Scope
Appendices
2
Definitions
A
Definition of terminology
Definition of thermal stores
Test rig and test procedures for evaluating the
performance of the hot water heat exchanger of
integrated thermal stores (DITS and IDITS) and hot
water thermal stores (HWTS).
3
General Requirements
B
Thermal store data badge
Thermal store design and installation manuals
Flow and return connection
Thermostat pockets
Labelling of connections
Size of connections
Descaling of hot water heat exchanger
Test rig and test procedures for evaluating the
performance of the primary heat exchanger of
an indirect integrated thermal stores (IDITS) and
indirect buffer store (IDBS).
C
Test rig and test procedures for measuring the
standby heat loss of a thermal store and the
temperature of the water in the integral feed and
expansion tank.
4
Performance Specification
D
Details of the coded information for the thermal
store ‘data badge’.
Domestic hot water performance
E
Hot water performance without temperature
control device
Performance of a domestic hot water temperature
control device
Pressure loss through a domestic hot water heat
exchanger
Performance and design information to be
included in the design and installation manuals.
Performance of a primary heat exchanger
Heat transfer capacity of a primary heat
exchanger
Pressure loss through a primary heat exchanger
Standby heat loss from a thermal store
Heat losses with pipe work
Heat losses without pipe work
Heat losses for SAP Calculations
Temperature of water in the integral feed and
expansion tank.
5
Specification of Components
CONTENTS
Store thermostat pockets
Expansion vessel
Hot water temperature limiting device
Pump over-run control
Anti vacuum and air release valves
2-Port charge control (e.g. zone) valve
Metering systems
Page 2.1
DEFINITIONS OF TERMINOLOGY
2.1.1 Capacity of a thermal store
Net volume of primary water in a thermal store
used for storing the primary heat energy for
domestic hot water and/or space heating.
2.1.2 Store Thermostat
One or more thermostats used to control the
temperature of the primary water in the thermal
store by either controlling the operation of
the boiler in an individual dwelling or a charge
control valve in a group heating scheme.
2.1.8 Data badge
A badge fitted to the thermal store, which gives
information about safety, identification and
essential performance information in the coded
form.
2.1.9 Installation and design manual
One or more comprehensive sets of documents
supplied with every thermal store containing
system design,installation and service information
for that store.
1
4
2.1.3 Primary heat exchanger
A heat exchanger in an indirect thermal store,
which transfers energy from a heat source e.g. a
boiler to the primary water in the store.
2.1.4 Natural convection hot water heat exchanger
A water to water heat exchanger inside a thermal
store (figure 2.1) which transfers heat from the
primary water to the domestic hot water during
a hot water draw-off without using motive power
(e.g. a pump) to circulate primary water.
5
3
2
Figure 2.1: Natural convection
hot water heater exchanger
1
2.1.5 Forced convection hot water heat exchanger
A water to water heat exchanger inside (figure
2.2) or outside a thermal store (figure 2.3) which
requires a motive power (e.g. a pump) to circulate
the primary water through the heat exchanger
during a hot water draw-off.
The pump used for circulating the primary water
through the heat exchanger during the hot water
draw-off may also act as a boiler and/or a heating
circuit pump.
6
2
4
3
5
Figure 2.2: Forced convection
external hot water heat exchanger
6
DEFINITIONS
2.1.6 Domestic hot water temperature controller
A device (e.g. a thermostatic non electric
blending valve) which is fitted to thermal store
for regulating the domestic hot water outlet
temperature and which also limits the ‘hot slug’
of water reaching the outlets.
2.1.7 Hot slug
The volume of hot water above 60°C passed
during a domestic hot water draw-off when the
temperature-regulating device is set to control
the outlet temperature at 55°C.
Page 4
5
3
2
1
Figure 2.3: Forced convection
internal hot water heat exchanger
1
2
3
4
5
6
Thermal store
Primary water
Mains cold water inlet
Hot water to taps
Hot water heat exchanger
Primary pump
2.2
DEFINITIONS OF THERMAL STORES
(c) 2.2.1 Integrated thermal store (ITS)
(a) (b) A thermal store designed to store primary hot
water, which can be used directly for space
heating and indirectly for domestic hot water.
In a group, heating scheme the primary water
in DITS is heated by one or more boilers or is
supplied with pre-heated water from one or more
buffer stores.
2.2.3 Indirect integrated thermal store (IDITS)
(a) An integrated thermal store (ITS) which complies
with the requirements of section 2.2.1. and in
which the primary water is heated indirectly by
means of an internal primary heat exchanger
(figure 2.5).
(b) The indirect integrated thermal store (IDITS) is
normally used in a thermal storage group heating
scheme and is heated by the central boilers.
In an integrated thermal store (ITS) the heating
primary water is circulated to the space heating
e.g. radiators. Therefore, the minimum storage
volume given by equation 1 must be available for
space heating.
VH = 45 + 0.25VS ----- (1)
Where:-
2.2.4 Domestic hot water thermal store (HWTS)
(c) In an Integrated thermal store (ITS), the
domestic hot water is heated instantaneously
by transferring the heat from the primary stored
water to the domestic hot water flowing through
the heat exchanger. The domestic hot water heat
exchanger may be:-
(a) A thermal store designed to provide domestic
hot water only and is heated directly or indirectly
by a heat source e.g. a gas boiler. Typical direct
and indirect domestic hot water thermal stores
(HWTS) are shown schematically in figures 2.6
and 2.7 respectively.
(b) In a hot water thermal store (HWTS), the
domestic hot water is heated instantaneously
by transferring the heat from the primary stored
water to the domestic hot water flowing through
the heat exchanger. The domestic hot water heat
exchanger may be:-
• An internal natural convection type shown
schematically in figure 2.1.
• An external forced convection type shown
schematically in figure 2.2.
• An internal forced convection type shown
schematically in figure 2.3.
(d) • An internal natural convection type shown
schematically in figure 2.1.
• An internal forced convection type shown
schematically in figure 2.2.
• An external forced convection type shown
schematically in figure 2.3.
The ITS acts as a buffer between the heat energy
source (e.g. boiler) and the ever changing space
heating and hot water energy demands of a
dwelling.
(c) Both direct and indirect HWTS are suitable for
individual dwellings.
(d) Indirect HWTS are also suitable for group heating
and district heating schemes.
2.2.2 Direct integrated thermal store (DITS)
(a) An integrated thermal store (ITS) which complies
with the requirements of section 2.2.1 and in
which the primary stored water is heated directly
by an internal or an external heat source.
(b) In an individual dwelling, the primary water in
DITS is heated by dedicated heat source e.g. a gas
boiler as shown in figure 2.4.
Page DEFINITIONS
VH = Minimum storage volume available for
space heating (l)
VS = Storage capacity of the thermal store (l)
1
V1
3
7
1
V1
4
V2
6
V2
10
9
3
Figure 2.4: Direct integrated thermal
store (DITS) with natural convection
hot water heat exchanger and
thermostatic mixing valve for regulating
the hot water outlet temperature
1
3
5
8
9
Figure 2.5: Indirect integrated thermal
store (IDITS) with external forced
convection hot water heat exchanger
and electronic controls for regulating
the hot water outlet temperature
1
4
3
5
11
10
2
4
5
6
10
9
6
9
3
Figure 2.6: Direct hot water only thermal
store (HWTS) with natural convection
hot water heat exchanger and
thermostatic mixing valve for regulating
the hot water outlet temperature
DEFINITIONS
3
6
7
2
4
2
8
10
1
4
7
10
V1:
V2:
10
5
2
11
3
10
12
Figure 2.7: Indirect hot water only thermal
store (HWTS) with forced convection hot
water heat exchanger and boiler fitted
with sealed system kit
Thermal store
2 Hot water heat exchanger
Hot water outlet
5 Mains cold water inlet
Thermostatic mixing valve 8 Space heating pump
Boiler
11 Diverter valve
Thermal store volume NOT available for space heating
Thermal store volume available for space heating
Page 3
6
9
12
Primary water
Boiler/system pump
Space heating circuit
Sealed system kit
2.2.5 Direct buffer store (DBS)
2.2.6 Indirect buffer store (IDBS)
(a) A thermal store heated directly by one or more
boilers in a group-heating scheme (1) shown
schematically in figure 2.8. In these heating
systems, the DBS is used for supplying primary
hot water to direct integrated thermal store
(DITS) located in the individual dwellings.
(a) A thermal store heated indirectly by one or
more boilers by means of an internal primary
heat exchanger and is used in a group heating
scheme (figure 2.8) for supplying hot water to
direct integrated thermal stores (DITS) located in
individual dwellings.
(b) The buffer store thermostats control the operation
of one or more boilers in a thermal storage group
heating scheme.
(b) The buffer store thermostats control the operation
of one or more boilers in a thermal storage group
heating scheme.
(c) A direct buffer store does not have a built in heat
exchanger for supplying domestic hot water.
(c) An indirect buffer store cannot have a built in heat
exchanger for supplying domestic hot water.
Note:
(i) The details of the thermal storage group
heating systems are contained in a separate
publication.
1
1
8
6
1 Indirect integrated thermal
stores in individual dwellings
2 Direct buffer store (DBS)
3 Indirect buffer store (IDBS)
4 Boiler
5 Boiler pump
6 Buffer store charge control valve
7 IDBS primary heat exchanger
8 Distribution pump
2
1
1
3
6
4
7
4
5
5
Figure 2.8: Schematic diagram of a thermal storage group heating scheme
Page DEFINITIONS
8
2.2.7 Integrated thermal stores (DITS & IDITS) for
individual dwellings
(a) A typical integrated thermal store (ITS) heating
system for an individual dwelling is shown in
figure 2.9. The design of an ITS for individual
dwellings must ensure that:• One or more store thermostats control the
operation of the boiler and the boiler pump.
(b) Both direct and indirect integrated thermal
stores (DITS and IDITS) having either a natural or
a forced convection hot water heat exchangers
are suitable for individual dwellings.
(c) Thermal stores designed for an open system and
for individual dwellings may have an integral or
remote feed and expansion tank.
(d) Thermal stores designed for sealed heating
(i.e. closed) system and for individual dwellings
must be fitted with safety devices and controls
specified in the Building Regulations Approved
Document G3.
• The user space heating controls e.g. a room
thermostat, heating programmer, must control
the operation of the space heating pump and
not the operation of the heat generator.
• It meets the requirements of sections 3 and 4.
Figure 2.9: Typical integrated thermal store (DITS) based heating system for individual dwellings
13
7
6
5
1
3
2
17
4
10
12
8
9
11
14
DEFINITIONS
15
1
3
5
7
9
11
13
15
17
Hot water outlet to taps
Expansion Vessel (1)
Heating programmer
Thermostatic mixing valve
Boiler pump
Boiler circuit check valve (2)
Integrated feed and expansion cistern
Boiler pump over-run timer
Hot water heat exchanger check valve
16
2
4
6
8
10
12
14
16
Mains cold water inlet
Space heating pump
Room thermostat
Heating circuit check valve (2)
Boiler
Store thermostat/sensor
Wiring centre
Mains supply 1 x 230V ac, 50Hz
Notes
(1) Expansion vessel can be integral part of the hot water heat exchanger
(2) To be fitted on site if required
Page 2.2.8 Hot water thermal stores for individual
dwellings
• It meets the requirements of sections 3 and 4.
(b) (a) Both direct and indirect HWTS designed for
individual dwelling may have an integral or
remote feed and expansion tank or may be
fitted with sealed system components, which
must comply with Building Regulations and
appropriate British Standards.
Typical heating systems based on direct and
indirect hot water only thermal stores (HWTS)
are shown in figures 2.10 and 2.11 respectively.
The design of HWTS for individual dwelling must
ensure that:-
Note:
• If the hot water has priority then the store
thermostat controls the operation of the boiler,
system pump and the 3-port diverter valve.
(i) In a heating system incorporating an HWTS,
if the domestic hot water has a priority then
if space heating is ON and the thermal store
control thermostat(s) calls for heat, the space
heating is switched OFF until the thermal
store is satisfied.
• If a flow share arrangement is used then
the user space heating controls e.g. a room
thermostat, heating programmer, should
control the operation of the boiler, system
pump and the position of the 3-port diverter
valve together with store thermostat.
(ii) Compared to an integrated thermal store,
an HWTS system increases the boiler cycling
when the space heating is ON.
13
7
17
9
6
5
1
3
2
8
12
4
10
14
15
16
Figure 2.10: Typical direct hot water thermal store (HWTS) based heating
system for individual dwellings
13
7
17
6
5
1
3
2
18
10
12
13
14
15
16
17
9
8
1
2
3
4
5
6
7
8
9
10
11
12
18
4
15
14
16
Figure 2.11: Typical indirect hot water thermal store (IHWTS) based heating
system for individual dwellings
Page Hot water outlet to taps
Mains cold water inlet
Expansion Vessel (1)
Bypass valve
Heating programmer
Room thermostat
Thermostatic mixing valve
3-Port valve
Boiler/system pump
Boiler
Air vent and anti-vacuum
valve
Store thermostat/sensor
Integrated feed and
expansion cistern
Wiring centre
Boiler pump over-run timer
Mains supply 1 x 230V ac, 50Hz
Hot water heat exchanger
check valve
Sealed system kit
DEFINITIONS
11
2.2.9 Integrated thermal stores for group heating
(a) (b) Both direct and indirect integrated thermal
stores (DITS and IDITS) with natural or forced
convection hot water heat exchangers are
suitable for thermal storage group heating
systems. Typical configurations of DITS and IDITS
for this application are shown in figures 2.12 and
2.13 respectively.
(c) A thermal store for group heating system is
normally fitted with a metering system for
apportioning the running costs.
(d) A direct integrated thermal store (DITS) for a
group-heating scheme can not have an integral
or remote feed and expansion tank.
(e) An indirect integrated thermal store (IDITS) for
a group-heating scheme must have an integral
or remote feed and expansion tank or must be
suitable for a sealed system and be fitted with
appropriate system components.
(f ) Integrated thermal stores (DITS and IDITS) must
comply with the requirements of sections 3 and 4.
A thermal store for group heating system does
not directly control the operation of the boilers
but the store thermostat(s) control the operation
of the charge control valve.
17
19
18
15
6
10
7
1
2
11
9
5
3
12
8
1
7
13
DEFINITIONS
4
14
Figure 2.12: Typical direct integrated thermal store (DITS) based heating system for
an apartment in a group heating scheme
1 Isolating valve
2 In line filter
3 Balancing valve
4 Heat meter
5 Store charge control valve
16
6 Distribution network
7 Store thermostat
8 Space heating pump
15
9 Cold water inlet
10 Hot water outlet to taps
10
6
11 Hot water heat exchanger
11
12 Space heating circuit
9
13 Wiring and controls
7
5
14 Mains electricity supply
1 2
3
230V ac, 50 Hz
15 HW heat exchanger pump
1
8
16 F & E cistern
17 Air vent / anti-vacuum valve
18 Programmer
19 Room thermostat
4
Figure 2.13: Typical indirect integrated thermal store (IDITS) based heating system for
an apartment in a group heating scheme
Page 10
2.2.10 Hot water only thermal stores (HWTS) for
group heating
(b) Only indirect hot water only thermal stores are
suitable for group or district heating systems.
Typical configuration for the application is shown
in figure 2.14.
A HWTS for group heating scheme may be fitted
with a metering system for apportioning the
running costs.
(d) Hot water thermal store must comply with the
requirements of sections 3 and 4.
A hot water thermal store does not control the
operation of the central boilers directly but the
store thermostat(s) control the operation of the
charge control valve.
Figure 2.14: Typical indirect hot water only thermal store (HTS) based heating system
for an apartment in a group heating scheme
15
17
16
14
Vp
6
7
1
1
2
8
5
3
11
7
5
12
4
1
3
5
7
9
11
13
15
17
9
10
Isolating valve
Balancing valve
Store charge control 3-port valve
Store thermostat
Hot water outlet to taps
Space heating circuit
Mains electricity supply 230V ac, 50Hz
F & E cistern
Room thermostat
2
4
6
8
10
12
14
16
13
In line filter
Heat meter
Distribution network
Cold water inlet
Hot water heat exchanger
Wiring centre and controls
HW heat exchanger pump
Programmer
DEFINITIONS
(a) (c) Page 11
3.1
THERMAL STORE DATA BADGE
3.2
The following minimum information shall be
provided in the form of a Data Badge fixed to
the thermal store. The badge must be accessible
without the use of tools.
THERMAL STORE SYSTEM DESIGN AND
INSTALLATION MANUAL
These manuals should be provided with all
thermal stores and should include (where
appropriate) the following information:-
• Section 3.1.1 applies to all types of thermal
stores i.e. DITS, IDITS, HWTS, DBS and IDBS.
(a) Performance and design information as defined
in appendix E of this document.
• Section 3.1.2 applies to direct and indirect
integrated thermal stores (DITS and IDTS) and
both direct and indirect hot water thermal
stores (HWTS).
(b) Installation
examples.
(c) Recommended space heating system designs
and control.
(d) Recommended hot and cold water distribution
networks in a dwelling (e.g. supply to shower and
pipe sizes).
3.1.1 For all types of thermal stores
3.3
FLOW AND RETURN CONNECTIONS
(a) (b) (a) These should be designed to prevent short circuit
of flow and return in the store for both the boiler
circuit and the space heating circuit.
(b) The aim should be to achieve uniform flow (up
or down) across the diameter of the store. This
can be achieved by using sparge pipes, diffusers
or other similar methods.
3.4
THERMOSTAT POCKETS
(a) The thermostat pocket should be designed and
located to sense the bulk water temperature in
the active zone of the store.
(b) Thermal stores of capacity up to 210 litres should
be fitted with ONE store thermostat pocket and
thermal stores of capacity greater than 210 litres
should be fitted with TWO thermostat pockets as
shown in figure 3.1.
(c) The position of the store thermostat pockets
must comply with equation 2 or 3a and 3b.
• Section 3.1.3 applies to indirect integrated
thermal stores (IDITS), indirect hot water
thermal stores and indirect buffer stores
(IDBS).
(c) (d) (e) (f ) (g) Manufacturers name and address etc. [….]
Complies with Performance Specification for
Thermal Stores [….]
The model and identity number […]
Primary water storage capacity (l)
Maximum working head for the store [bar]
Maximum working temperature (if special
components fitted) [°C]
Store thermostat settings [°C]
and
service
instructions
with
GENERAL REQUIREMENTS
3.1.2 Additional data for integrated thermal stores
(a) (b) Maximum working pressure for hot water heat
exchanger [bar]
Code-A (Coded information as defined in
appendix D)
3.1.3 Additional data for indirect stores
(a) (b) Maximum working pressure for primary heat
exchanger [bar]
Code B (Coded information as defined in appendix
D)
For VS < 210l; 0.25 VS < VB < 0.35VS ..... (2)
For VS > 210l; 0.05 VS < VB < 0.10VS ..... (3a)
0.60 VS < VT < 0.70VS ..... (3b)
Page 12
Where:-
3.5
LABELLING OF CONNECTIONS
VS = Nominal storage capacity of a thermal store (l)
VB = Volume of water below store thermostat _ 1 (l)
VT = Volume of water below store thermostat _ 2 (l)
(a) The thermal store should have clearly labelled
connections where applicable for:•
•
•
•
•
•
•
•
•
Figure 3.1: Position of store temperature control
thermostats or sensors
VS > 210 litres
_ 210 litres
VS <
VT = 0.70VS
VT = 0.60VS
VT
1
VB
VB = 0.35VS
VB = 0.25VS
1
VB = 0.10VS
VB = 0.05VS
VB
1 Lower store thermostat
2 Top store thermostat
3.6
SIZE AND TYPE OF CONNECTIONS
(a) The pipe connections should be designed to
minimise the heat losses from the thermal store.
(b) The size of connections will depend upon the
capacity and the type of store. Normally 22mm for
stores up to 140 litres, 28mm for stores up to 210
litres, 35mm for stores up to 350 litres and 42mm
for stores up to 500 litres will be adequate.
3.7
DESCALING OF HOT WATER HEAT EXCHANGER
VS = Volume of the thermal store
VB = Volume of water below store thermostat 1
VT = Volume of water below store thermostat 1
(d) The two store thermostats should be wired as
shown in figure 3.2 so that the boiler only fires
when both thermostats are calling for heat
and continue to fire until both thermostats are
satisfied. (Note: The same control action should
be achieved by electronic logic if non-mechanical
thermostats are used.)
A means of descaling the hot water heat
exchanger in the field must be provided and the
procedure must be outlined in the design and
installation manuals.
N
L
3
L
SL
6
5
4
1
1
4
Bottom thermostat
Pump over run timer
2
2
5
Top thermostat
Boiler pump
3
6
2-Pole CO relay
Boiler
Figure 3.2: Schematic wiring diagram for twin thermostat control of thermal stores
Page 13
GENERAL REQUIREMENTS
2
Boiler or system flow
Boiler or system return
Heating circuit flow
Heating circuit return
Mains cold water inlet
Domestic hot water outlet
Cold feed and open vent
Automatic air vent and anti-vacuum valve
Pictorial labelling of components is acceptable
provided it is securely fixed to the thermal
store.
4.1
DOMESTIC HOT WATER PERFORMANCE
Table 2 : Minimum average temperature rise of hot water
draw-off
4.1.1 General requirements
(a) (b) (c) The requirements of sections 4.1.2., 4.1.3 and 4.1.4
apply to both the direct and indirect integrated
thermal stores and the hot water thermal stores
(DITS, IDITS and HWTS) having forced or natural
convection heat exchangers defined in section 2
of this document.
For both individual dwellings and group heating
applications, the hot water flow rate and volume
are related to the type of dwelling for which a
thermal store is designed.
The hot water performance of a thermal
store should be measured using a test rig and
test procedures set out in appendix A of this
document. The flow rates and draw-off volumes
listed in table 1 should be used for these tests.
Test schedule (Appendix 1)
Minimum average
temperature rise of a draw-off
A1: No heating load
45°C
A2: Design heating load
40°C
4.1.3 Hot water performance without hot water
temperature control device
The effectiveness of a thermostatic mixing valve
or a similar device in preventing a hot slug of
water reaching an outlet should be measured
using the test procedure A3 in appendix A.
(a) The maximum peak temperature and the volume
of the hot slug (see section 2.1.7) shall not be
more than the values specified in table 3.
(b) The hot water performance of the thermal
store with and without a mixing valve or other
temperature regulating device (set at 55°C)
should be presented as shown in figure A2 in the
installation and design manual of that store.
PERFORMANCE SPECIFICATION
Table 1 : Hot water draw-off volumes and flow rates
Thermal
store
classification
Type of
thermal store
Draw-off
volume (l)
Draw-off
flow rate
(l/s)*
SC1:
Dwellings
For showers
only
40
0.13
SC2:
Dwellings
For 1
bathroom
67
0.30
SC3:
Dwellings
For 2
bathrooms
133
Table 3: Maximum peak temperature and volume of hot slug
of water at draw-off point.
Flow rate (l/s)
Maximum peak
temperature (°C)
Maximum volume
of hot slug (l)
0.1
65
0.15
0.2
65
0.20
0.3
65
0.25
0.5
65
0.30
0.50
* Normal flow rate (QN)
4.1.2 Hot water performance without hot water
temperature control device
(a) (b) The domestic hot water performance of a thermal
store should be measured without a thermostatic
mixing valve or a similar temperature regulating
device using the procedures and tests A1 and A2
set out in appendix 1 of this document.
The average temperature rise of the hot water
draw-off of a specified volume and the specified
flow rate must not be less than 45°C and 40°C for
tests A1 and A2 respectively (see table 2).
The temperature rise of the hot water from a
thermal store at the end of a draw-off must not
be less than 35°C in the tests A1 and A2.
4.1.4 Pressure loss of hot water heat exchanger
(a) The pressure loss measurements of the domestic
hot water heat exchanger (internal or external)
should be carried out using the test procedure
A4, defied in appendix A.
(b) The pressure loss at nominal water flow rate
given in table 1, should be declared on the store
data badge in the coded form.
(c) Full pressure flow characteristics of the hot water
heat exchanger should be presented in the
design manual in the format shown in figure A3.
Page 14
4.2
PERFORMANCE OF PRIMARY HEAT EXCHANGER
4.3
STANDBY HEAT LOSS FROM A THERMAL STORE
AND ENERGY RATING
4.2.1 General
4.3.1 General
(b) The requirements of this section apply to both the
indirect integrated thermal store (IDITS) and the
indirect buffer store (DBS) as defined in section 2.
The test rig and the test procedure for measuring
the performance of the primary heat exchanger
of indirect stores are defined in appendix B.
(a) This section applies to all types of thermal stores
including buffer stores.
(b) The 24-hour average heat loss rate QHL, measured
using the test rig (figure C1) and the procedure
C2 and C3 given in appendix C, shall not be
greater than the value, QHL-MAX, given by equation
4. Alternatively, the maximum permitted heat loss
rate, QHL-MAX, can be read from figure 4.
QHL-MAX = 1.6 x [0.2 + (0.051 x (VS)2/3] ---- (4)
Where:-
4.2.2 Heat transfer capacity of primary heat
exchanger
(a) (b) The UA value i.e. the heat transfer capacity of the
primary heat exchanger shall be determined using
the test procedure B1 outlined in appendix B.
The nominal flow rate (QN) and the UA value for
an average temperature difference of 6°C shall be
declared on the store ‘data badge’ in the coded
form.
The complete design data as shown in figure B2
shall be presented in the design manual.
4.2.3 Pressure loss of primary heat exchanger
(a) The hydraulic characteristics of the primary heat
exchanger should be measured using the test
procedure, B2 outlined in appendix B.
(b) The nominal flow rate (QN) and the pressure loss
at the nominal flow rate shall be declared on the
store ‘data badge’ in the coded form.
The full design information in form shown in
figure B3, shall be presented in the system design
manual for the store.
QHL-MAX = Maximum permitted heat loss from a
thermal store [kWh/24h]
VS
= Declared capacity of thermal store (l)
Note:
(i) This figure should be regarded as an absolute
maximum and efforts should be made to reduce
it.
(ii) The actual measured value shall be declared on
the data badge in the coded form and also in the
appliance manuals etc.
Page 15
PERFORMANCE SPECIFICATION
(a) Figure 4 : Maximum permitted heat loss from a thermal store
6.0
Heat loss rate (kWh/24h)
5.0
4.0
3.0
2.0
1.0
0.0
0
100
200
300
400
500
600
Nominal volume (litres)
4.3.2
for SAP calculations
4.3.2
Heat Heat
loss forloss
SAP calculations
PERFORMANCE SPECIFICATION
(a)
(a) (b)
(b) (c)
(d)
(c) (d) Therefore its 24h average heat loss is lower than
ITS.
The heat
In-Use
heat
losses
The In-Use
losses from
thermal
storesfrom
will be thermal stores will be less than the
measured
values
(see
This
less than
the measured
values
(see4.3.1.
4.3.1. This
is is
because:The heat loss factors for Hot Water Only and
because:Integrated Thermal Stores (HWS and ITS) for
The thermal stores are normally installed
airing
cupboards
a
use ininSAP
procedures
must belike
calculated
Theconventional
thermal stores arecylinder.
normally installed
in airing the ambient
Therefore,
temperature
will
be
higher
using appropriate equations as detailed in the
cupboards
likeoaCconventional
Therefore,
specifiedcylinder.
for the
test procedures
and loose
therefore
the heat
than 20
separate
sheet contained
at thelosses
back of this
the ambient
will be higher than 20°C
will be temperature
lower.
document.
specified for the test procedures and therefore
the The
heat losses
will be storage
lower.
thermal
systems are now being installed with two channel
4.4 heating
WATER TEMPERATURE
IN AN
INTEGRATED
programmers for controlling both space
and hot water.
Therefore,
Thethe
thermal
storagestore
systems
are now
being
FEED ANDmaximum
EXPANSION temperature
TANK
thermal
is not
maintained
at nominal
of
installed
two channel
programmers
the boiler
is not for
charging the thermal store, it will provide
75 o C.withWhen
controlling
bothofspace
hot water.in 4.4.1
This section
applies in
to all
stores fitted
40-50%
hot heating
water and
demands
a dwelling
resulting
a thermal
significantly
Therefore,
the
thermal
store
is
not
maintained
at
with an integral feed and expansion tank. The
lower 24h mean store temperature.
nominal maximum temperature of 75°C. When
24-hour average temperature of water in the
the The
boilerfield
is not studies
charging the
thermal
store,that
it
feed and
expansion
during storage
the heat loss
have
shown
the usage
pattern
of tank
thermal
will heating
provide 40-50%
of hotiswater
demands
in a for conventional
measurements
(see appendix C).
systems
similar
to that
systems.
dwelling resulting in a significantly lower 24h
mean
store temperature.
The measured
average
temperature
of the
Unlike
the integrated thermal stores,4.4.2
the hot
water only
thermal
stores
arewater
the feed heating
and expansion
tank should
not exceed
not maintained at high temperature wheninspace
is on.
Therefore
Theits
field
studies
have shown
that the
usage than ITS.
50°C.
24h
average
heat loss
is lower
pattern of thermal storage heating systems is
similar
to that
for conventional
systems.
4.4.3
design
of the feed
and expansion
The
heat
loss factors
for Hot Water
OnlyThe
and
Integrated
Thermal
Storestank,
the lid and
the be
overflow
pipe connection
(HWS and ITS) for use in SAP procedures
must
calculated
using (e.g.
Unlike
the integratedequations
thermal stores,
the hot in thedipped)
shouldloose
be such
that the
water loss due
appropriate
as detailed
separate
sheet
contained
wateratonly
stores
not maintained
to evaporation is minimised.
thethermal
back of
thisare
document.
at high temperature when space heating is on.
Page 16
HWA Specification for thermal stores
Draft: ID_01/010208
21/43
5.2
GENERAL
5.4
The integrated thermal store can either be
supplied with all the components ready fitted
and wired or full wiring details and list of
recommended components (e.g. pumps, delay
timers) must be provided.
5.4.1 Direct and indirect integrated thermal stores (DITS
and IDITS) and hot water thermal stores (HWTS)
must be supplied with a domestic hot water
outlet temperature regulating device to prevent
a hot slug reaching the hot water outlets.
Store thermostat(s)
5.4.2 The performance of the hot water temperature
control device must meet the requirements of
section 4.1.2.
5.2.1 The specified store thermostat setting should
prevent the boiler cycling on its internal
thermostat for efficient operation.
5.5
5.2.2 All types of thermal stores must be supplied with
one or more thermostats with an adjustable
range of up to 90°C and span not greater than
70°C. The switching differential of the thermostat
should be 6±1°C.
5.2.3 A strap on surface cylinder thermostat is not
considered suitable for this application.
5.2.4 The store control thermostats should be either:(a) Or
(b) Non user adjustable and pre-set to switch off
at the specified temperature to guarantee the
performance.
Capable of being locked in the correct user
zone and should switch off at the specified
temperatures within the zone to guarantee the
performance.
5.2.5 The thermal stores of capacity greater than 210
litres shall be fitted with two thermostats and
wired as shown in figure 3.2 to switch a boiler or
a zone valve.
5.3
HOT WATER TEMPERATURE CONTROL DEVICE
PUMP OVER-RUN CONTROL
5.5.1 If an integrated thermal store intended for an
individual dwelling is used with a boiler that
requires pump over-run, then it must be supplied
with a suitable additional pump over-run delay
timer or similar device.
5.5.2 The normal boiler flow temperature sensing
thermostat used in majority of boilers to control
the pump over-run is not suitable for this
application.
5.5.3 Integrated thermal stores for group heating
applications do not require a pump over-run
delay timer.
5.6
ANTI-VACUUM AND AIR RELEASE VALVE(S)
5.6.1 Direct integrated thermal stores (DITS) intended
for group heating schemes must have connections
for fitting an air vent and anti-vacuum valves.
These items must be supplied with the store.
5.6.2 Indirect integrated thermal stores (DITS) may be
supplied without these devices.
DOMESTIC HOT WATER BACK EXPANSION
5.3.1 The thermal stores DITS, IDITS and HWTS must be
supplied with a suitable expansion vessel for the
domestic hot water heat exchanger if necessary.
5.7
5.3.2 This expansion vessel is required to accommodate
the expansion of water (due to heating) in the heat
exchanger because expansion back in to the mains
may not always be possible. (For example, a double
check valve may be fitted in the mains supply).
5.7.1 An integrated thermal store (DITS and IDITS) that
is intended for group heating scheme must be
supplied with a 2-port motorised (zone) valve
controlled by the store thermostats (figures 2.12
and 2.13).
5.3.3 The method and equipment provided or specified
for accommodating the expansion must comply
with the Model Water Bylaws and relevant
standards.
5.7.2 The performance specification of this valve e.g.
maximum working pressure differential and flow
rate must be included in the installation and
design instructions.
Page 17
2-PORT MOTORISED CHARGE CONTROL (I.E.
ZONE) VALVE
SPECIFICATION OF COMPONENTS
5.1
5.8
METERING SYSTEMS
5.8.1 Unless the customer specifies otherwise, an
integrated thermal store that is intended for
group-heating scheme must be supplied with a
metering system for apportioning the running
costs.
5.8.2 Typical metering options are:(a) Heat meter for recording the heat energy
delivered to the thermal store in the individual
dwelling.
(b) Timer based devices for recording the length
of time the zone valve is open i.e. the store has
received heat.
(c) Volume based devices for recording the volume
of hot water delivered to the thermal store in
the individual dwellings from the central boiler
plant.
SPECIFICATION OF COMPONENTS
5.8.3 Details of the metering systems are set out in
a Watson House publication ‘Thermal Storage
Group Heating Design Guide’.
Page 18
Test rig and the test procedures for evaluating the
performance of a hot water heat exchanger of an
integrated store (DITS and IDITS) and hot water
thermal store (HWTS).
A1
TEST RIG AND TEST CONDITIONS
The schematic layout of the test rig for determining
the hot water performance of direct and indirect
integrated thermal stores (DITS and IDITS) and
hot water thermal stores (HWTS) is shown below
in figure A1.
A1.1
The hot water performance of the thermal store
should be presented in the graphical form as
shown in figure A2.
Either a gas boiler or an in-line electric heater
heats a thermal store under test. A mixing pump
is used to ensure that the thermal store is heated
uniformly from top to bottom. Alternatively,
an immersion heater may be used to heat the
A manometer or pressure gauges may be used for
measuring the pressure drop across the domestic
hot water heat exchanger.
A1.3
Although the cold water inlet temperature during
a test can be allowed to vary between 9°C and
11°C, the average temperature over a complete
draw-off should be 10±0.5°C.
A1.4
The maximum uncertainty in the measurement of
water temperature should not exceed ±0.25°C.
A1.5
The maximum uncertainty in the measurement
of the draw-off volume and the draw-off flow rate
should not exceed ±0.5 litres/minute respectively.
A1.6
The maximum uncertainty in the measurement of
pressure drop across the heat exchanger should
not exceed 3% of the measured value.
T5
3m of 22mm copper pipe
(0.95 / minimum volume)
T3
A1.2
4
T2 P2
V1
7
1
8
V2
5
9
T1 P1
6
2
T4
3
Figure A1: Test rig for measuring the hot water performance of a thermal store
1
2
3
4
5
6
7
8
9
V1:
V2:
T1 - T5:
P1 - P2:
Thermal store under test
Gas or electric boiler for heating a thermal store
Alternative internal heat source for heating a thermal store
Hot water temperature control device e.g. thermostatic mixing valve (Test A3 only)
Volume flow rate meter - Should be calibrated and certified
Cold water inlet as 10±1°C
Volume measurement (An alternative method)
Weighing machine
Mixing pump
On/Off valve
Regulating valve
Temperature sensors immersed in water
Pressure measuring points
Page 19
APPENDIX A
thermal store but a mixing pump would still be
required.
A2
TEST_A1 : Hot water performance without
domestic hot water temperature control
device and no space heating load.
This test applies to the following thermal
stores with natural or forced convection heat
exchangers:-
off rate should be calculated as shown below in
equation a1.
A2.2.2 The calculated rating of the heat exchanger
should be declared on the ‘data badge’ in the
coded form and in the design manual.
HR.W = (CP ρ QW(TAH – TAC)/1000 ---- (a1)
• Direct integrated thermal store (DITS)
• Indirect integrated thermal store (IDITS)
• Hot water thermal store (HWTS)
Where:HR.W = Rating of hot water heat exchanger (kW)
þ = Average density of water (kg/m3)
Cp = Average specific heat of water (kj/kgoC)
QW = Average water flow rate (l/s)
TAH = Average hot water outlet temperature (°C)
TAC = Average cold water inlet temperature (°C)
The object of this test is to determine the
performance of the hot water heat exchanger
without temperature regulating device (e.g.
thermostatic mixing valve) and with no simulated
design space heating load.
A2.1 Test procedure
A3
TEST A2 : HOT WATER PERFORMANCE WITHOUT
HOT WATER TEMPERATURE CONTROL DEVICE
AND WITH SIMULATED SPACE HEATING LOAD.
This test applies to the following thermal
stores with natural or forced convection heat
exchangers:-
A2.1.1 Before a hot water test is started, the temperature
of the water in the store at both top and bottom
(figure A1) should be 75±0.5°C and stable.
A2.1.2 For thermal stores having a natural convection
heat exchanger, the boiler or an electric heater,
the boiler pump and the mixing pump are
switched off before commencing a test and the
charge circuit is isolated.
A2.1.3 The cold water inlet and the hot water outlet
temperatures shall be continuously recorded at
intervals not greater than 10 seconds during a
test so that the average temperature rise can be
calculated to an accuracy of ±0.5°C.
• Direct integrated thermal store (DITS)
• Indirect integrated thermal stores (IDITS)
A2.1.4 The hot water draw-off tests without the
temperature control device should be carried out
at flow rate specified in table 1.
APPENDIX A
A2.1.5 The hot water draw-off should be continued until
at least the appropriate volume stated in table 1
has been drawn off.
A2.1.6 The average temperature rise of a hot water
draw-off shall not be less than 45°C (see table 2).
In addition, the temperature rise of the hot water
at the end of the draw-off shall not be less than
35°C.
A2.2 Hot water heat exchanger rating
The object of this test is to determine the
performance of the hot water heat exchanger
when the space heating is switched on and the
space-heating pump is cycling on the room
thermostat. Under these conditions, the hot
water in the bottom of the thermal store is
periodically replaced by the cold water from the
space heating circuit (e.g. radiators) and thus
reducing the average temperature of the water
in the thermal store.
A3.1 Initial store charge temperature
The initial store charge temperature for this test is
calculated from the equation a2.
TSC = (75VS – 120QR)/VS ---- (a2)
Where: -
TSC = Initial store charge temperature (°C)
VS = Volume of thermal store under test (l)
QR = Maximum recommended radiator capacity for the test store (kW)
A2.2.1 The rating of the hot water heat exchanger for the
specified draw-off volume at the specified drawPage 20
A3.2 Test procedure
A4
A3.2.1 The test procedure is the same as for test A1
described in section A2 but before a hot water
test is started, the temperature in the store at both
the top and the bottom (see figure A1) should be
equal to TSC±0.5°C.
TEST A3: Hot water performance with a hot
water temperature control device and no
simulated space-heating load.
This test applies to the following thermal
stores with natural or forced convection heat
exchangers:-
A3.2.2 For thermal stores with natural convection
domestic hot water heat exchangers, the boiler or
an electric heater, the boiler (heat source) pump
and the mixing pumps are switched off and the
charge circuit is isolated before commencing a
test.
• Direct integrated thermal store (DITS)
• Indirect integrated thermal store (IDITS)
• Hot water thermal store (HWTS)
A3.2.3 If a thermal store has forced convection heat
exchanger, then an appropriate circulation pump
is allowed to run but no heat input is allowed
during the hot water draw-off.
The object of this test is to assess the effectiveness
of a domestic hot water temperature control
device (e.g. a thermostatic mixing valve) in
preventing the hot slug of water at temperature
greater than 60°C reaching a draw-off point.
A4.1 Test conditions
A3.2.4 The cold water inlet and the hot water outlet
temperatures shall be continuously recorded
at intervals not greater than 10 seconds during
a test so that the average temperatures can be
calculated to an accuracy of ±0.5°C.
A4.1.1 For these tests, the domestic hot water
temperature control device e.g. a thermostatic
mixing valve should be set to control at 55°C.
A3.2.5 The hot water draw-off test shall be carried out at
flow rates specified in table 1.
A4.1.2 The average store charge and the cold water
inlet temperatures should be 75°C and 10°C
respectively (as per previous tests).
A3.2.6 The hot water draw-off shall be continued until
at least the volumes stated in table 1 have been
drawn off.
A4.1.3 The volume of water in the draw-off pipe from
the thermal store to the tap (i.e. the dead leg)
should be 1±0.1 litres.
A3.2.7 The average temperature rise of a hot water
draw-off shall not be less than 40°C (see table 2)
and also the temperature rise of the hot water at
the end of a draw-off shall not be less than 35°C.
A4.1.4 The temperature of the water in the dead leg
should be 20±2°C before commencing a hot
water draw-off test.
APPENDIX A
A4.1.5 Fast acting recorders and temperature sensors
must be used for this test.For example unsheathed
thin wire thermocouples.
Page 21
A4.2
Test procedure
A4.2.1
This test should be carried out at all of the flow rates specified in
table 3, section 4.1.2.
A4.2 Test procedure
A4.2.3 The data for the nominal test flow rate should be
presented as shown in figure A2 in the system
A4.2.2
The hot water draw-off test should be started by opening the valve V1
A4.2.1 This test should be carried out at all of the flow
design and installation manual for that store.
(figure A1) and the hot water outlet temperature T 3 and T 4 (see figure
rates specified in table 3, section 4.1.2.
A1) are continuously recorded to determine the volume and the
A4.2.4 The volume and the average temperature of the
temperature of the hot water slug.
A4.2.2 The hot water draw-off test should be started
hot slug of water should not exceed the values
by opening the valve V1 (figure A1) and the hot
presented in table 3.
A4.2.3
The data for the nominal test flow rate should be presented as shown in
water outlet temperature T3 and T4 (see figure
figure A2 in the system design and installation manual for that store.
A1) are continuously recorded to determine the
volume and the temperature of the hot water
A4.2.4
slug. The volume and the average temperature of the hot slug of water
should not exceed the values presented in table 3.
Figure A2: Example of presentation of hot water performance of a
thermal store
80
Temperature oC
70
60
50
40
30
20
10
0
0
2
4
6
8
10
Time and draw -off volume
With mixing valve
With mixing
valve
Without
mixing
valve
Without mixing valve
A5
TEST A4 : MEASUREMENT OF PRESSURE LOSS THROUGH THE HOT
WATER HEAT EXCHANGER
This test applies to the following thermal stores with natural or forced
convection heat exchangers:-
APPENDIX A
x
x
x
Direct integrated thermal store (DITS)
Indirect integrated thermal stores (IDITS)
Hot water thermal stores (HWTS)
A5.1
The pressure loss across the hot water heat exchanger should be
measured without the inline temperature control device (e.g. thermostatic
mixing valve) and when the store temperature is cold i.e. with no
significant extraction of heat.
A5.2
The cold water inlet temperature should be 10 + 0.5 o C.
HWA Specification for thermal stores
Page 22
Draft: ID_01/010208
30/43
A5
TEST A4 : MEASUREMENT OF PRESSURE LOSS
THROUGH THE HOT WATER HEAT EXCHANGER
A5.3 The pressure loss should be measured at the
following flow rates. QN is the nominal domestic
hot water flow rate for the thermal store under
test.
This test applies to the following thermal
stores with natural or forced convection heat
(a) at 0.5Q
A5.3 exchangers:The pressure loss should be measured
the N following flow rates. Q N is
(b) for
0.75Q
the nominal domestic hot water flow rate
the
N thermal store under test.
• Direct integrated thermal store (DITS)
(c) QN
Indirect
(d) 1.10QN
(a) • 0.5Q
N integrated thermal stores (IDITS)
•
Hot
water
thermal
stores
(HWTS)
(e)
1.25Q
(b)
0.75Q N
N
(c)
QN
A5.1
pressure
loss across the hot water heat A5.4 The data should be presented in the design
(d) The
1.10Q
N
exchanger
should
be measured without the inline
manual in a graphical form as shown in figure
(e)
1.25 Q N
temperature control device (e.g. thermostatic
A3.
mixing
valve)
and
when
the
store
temperature
is
A5.4 The data should be presented in the design manual in a graphical form as
cold
i.e. withinnofigure
significant
A5.5 The pressure loss at nominal flow rate, QN, should
shown
A3.extraction of heat.
be declared on a thermal store ‘data badge’.
A5.2
The
cold
water
inlet
temperature
should
be
A5.5 The pressure loss at nominal flow rate, Q N , should be declared on a
10±0.5°C.
thermal store ‘data badge’.
Figure A3 : Example of presentation of pressure loss
characteristics of hot water heatexchanger
1
0.9
QN = Nominal design flow rate
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0
0
0.2
0.4
0.6
0.8
Flow rate x Q N
1
1.2
1.4
(l/s)
APPENDIX A
Pressure drop (bar)
0.8
Page 23
Test rig and the test procedures for evaluating the
performance of a primary heat exchanger of an
indirect integrated thermal stores (IDITS) and an
indirect buffer store (IDBS)
B1.3 The maximum uncertainty of in the measurement
of temperatures should not exceed ±0.2°C. The
maximum uncertainty in the measurement of
flow rate through the heat exchanger should not
exceed ±1.5%.
B1
B1.4 If a certified accurate flow meter is not available
then the continuous weighing of the water as
shown in figure B1 may be used.
TEST RIG AND TEST CONDITIONS
B1.1 The schematic layout of the test rig for determining
the rating of the heat exchanger used for heating
indirect integrated thermal stores and indirect
buffer stores is shown in figure B1.
B1.5 The maximum uncertainty in the measurement
of pressure loss across the heat exchanger should
not exceed 3% of the measured value.
B1.2 The indirect thermal store under test should be
heated by passing hot water from a pre-heated
tank at a constant temperature and flow rate to
determine the UA value (i.e. the capacity) of the
heat exchanger.
T5
T3
6
9
1
4
P1 T1
5
4
10
2
T4
P2 T2
T4
7
3
8
APPENDIX B
Figure B1: Test rig for measuring the performance of a primary heat exchanger of an
indirect thermal store
1
2
3
4
5
6
7
8
9
10
V1:
V2:
T1 - T6:
P1 - P2:
Thermal store under test
Gas or electric boiler for heating a thermal store
Alternative internal heat source for heating a thermal store
Store mixing pump
Volume flow rate meter - Should be calibrated and certified
Cold water inlet when weighing method is used for measuring the flow rate
Volume measurement (An alternative method)
Weighing machine
Hot water storage vessel
Diverter valve
On/Off valve
Regulating valve
Temperature sensors immersed in water
Pressure measuring points
Page 24
B2
TEST B1 : DETERMINING THE UA-VALUE OF THE
PRIMARY HEAT EXCHANGER
This test applies to indirect integrated thermal
store (IDITS) and indirect buffer store (DBS).
Q =
TA1 =
TA2 =
T W =
TS.t2 =
TS =
UA =
B2.1 Test procedure
(Qt1 _Qt2)/2
(T1.t1 + T1.t2)/2
(T2.t1 + T2.t2)/2
(TA1 +TA2)/2
TS.t1 + ((QρCP(TA1-TA2)/δt)/VS ρCp)
(TS.t1 + TS.t2)/2
(QρCP(TA1-TA2)/δt/(T W – TS)
(b1)
(b2)
(b3)
(b4)
(b5)
(b6)
(b7)
Where:B2.1.1 Heat the thermal store with the mixing pump on
to a uniform temperature of 65±0.5°C.
B2.1.2 The hot water storage tank shall be heated to
supply hot water at 82±1°C during the test.
B2.1.3 Set the flow rate, Q, through the primary heat
exchanger to the nominal charge flow rate, QN, for
the store under test and stop the mixing pump.
B2.1.4 Start heating the thermal store and at one-minute
(60s) intervals read and record flow and return
temperatures (T1 and T2) and the flow rate, Q.
B2.1.5 Continue the test until the difference between
flow and return temperatures, T1 and T2 is
4±0.5°C.
B2.1.6 Repeat the tests (steps 1-5) at maximum charge
flow rate, QMAX and at minimum charge flow rate
QMIN.
Where:-
QMAX = 1.5 QN
QMIN = 0.5 QN
Note: If a certified reference flow meter is not used
then the primary water flow should be directed to
the weighing machine and the readings taken every
minute to determine the average flow rate.
Q =
Qt1 =
Qt2 =
TA1 =
T1.t1 =
T1.t2 =
TA2 =
T2.t1 =
T2.t2 =
T W =
Ts.t1 =
Ts.t2 =
ρ =
Cp =
δt =
VS =
TS =
UA =
Average flow rate through the
primary heat exchanger
(l/s)
Flow rate through the primary
heat exchanger at time, t1
(l/s)
Flow rate through the primary heat
exchanger at time, t2
(l/s)
Average flow temperature to
primary heat exchanger (°C)
Flow temperature to primary
heat exchanger at time, t1
(°C)
Flow temperature to heat
exchanger at time, t2 (°C)
Average return temperature from
primary heat exchanger (°C)
Return temperature from heat
exchanger at time, t1 (°C)
Return temperature from heat
exchanger at time, t2 (°C)
Average primary water
temperature
(°C)
Average store temperature
at time, t1
(°C)
Average store temperature
at time, t2
(°C)
Average density of water
(kg/m3)
Average specific heat of water
(kj/kg°C)
Time interval (t2-t1)
(s)
Volume of thermal store
under test
(l)
Average temperature of
thermal store (°C)
Heat exchanger capacity
(W/°C)
B2.2.1 The instantaneous UA-Value i.e. the heat
exchanger capacity should be calculated for every
time step using equations b1-b7 and presented
in the system design and installation manual as
shown in figure B2.
B2.2.2 The UA-Value of the heat exchanger at nominal
flow rate, QN, and for an average temperature
difference of 6°C should be declared on the store
‘data badge’.
Page 25
APPENDIX B
B2.2 Calculations and presentation of results
T s.t1 = average store temperature at time, t1
T s.t2 = Average store temperature at time, t2
ȡ = Average density of water
C p = Average specific heat of water
įt = Time interval (t2-t1)
V S = Volume of thermal store under test
T S = Average temperature of thermal store
UA = Heat exchanger capacity
( C)
( o C)
(kg/m3)
(kj/kg o C)
(s)
(l)
( o C)
(W/o C)
Figure B2: Example of a presentation of the primary heat exchanger
of an indirect thermal store
90
UA value (W/oC)
80
70
60
50
40
30
20
10
0
0
5
10
15
20
Average temperature difference (Tw - Ts), oC
0.5QN
QN
1.5QN
B3
TEST
MEASUREMENTS
OF MEASUREMENTS
B3.2 The data shouldOF
be presented
in a system design
B3 B2 : PRESSURE
TEST B2LOSS
: PRESSURE
LOSS
THE INDIRECT
THE INDIRECT
(PRIMARY)
HEAT
EXCHANGER
manual
in
the
format
shown
in figure B3. The
(PRIMARY) HEAT EXCHANGER
data at nominal primary flow rate, QN, through
B3.1 The
pressure
drop
across thedrop
primary
indirect
heatprimary indirect
B3.1
The
pressure
across
the
exchanger
be on the
the heatheat
exchanger
should should
be declared
+ o
at an average
of flow
temperature
of 70
exchangermeasured
should be measured
at an average
of and return
thermal
store ‘data badge’
. 2 C at the
following
flow rates:flow and return
temperature
of 70±2°C at the
following flow rates:B3.1.1
B3.1.2
B3.1.3
B3.1.4
B3.1.5
B3.1.1
0.50 Q N
B3.1.2
0.75 Q N
0.50 QN
B3.1.3
QN
0.75
QN
B3.1.4
1.10Q N
QNB3.1.5 1.25Q
N
B3.2N The data should be presented in a system design manual in the format
1.10Q
1.25QN shown in figure B3. The data at nominal primary flow rate, Q N , through
the heat exchanger should be declared on the thermal store ‘data badge’.
HWA Specification for thermal stores
Draft: ID_01/010208
34/43
Figure B3 : Example of presentation of pressure loss
characteristics of primary heatexchanger
0.7
Pressure drop (bar)
APPENDIX B
0.6
QN = Nominal design flow rate
0.5
0.4
0.3
0.2
0.1
0
0
0.2
0.4
0.6
0.8
Flow rate x Q N
Page 26
1
(l/s)
1.2
1.4
Test rig and the test procedures for measuring
the standby heat loss of a thermal store and the
temperature of the water in the integrated feed and
the expansion tank (if fitted).
GENERAL
C1.1 The objectives of this test are to determine the
standby heat loss from a thermal store and the
temperature of water in the integral feed and
expansion cistern (if fitted) at reference test
conditions without any components fitted. This
C1.2 During this test, all exposed pipe work, which
is integral part of a thermal store, should be
insulated as recommended in the installation
instructions supplied with the test sample.
C1.3 If the thermal store (e.g. ITS & HWTS) is fitted with
an external hot water heat exchanger as shown
in figure C1.1 then it should be tested with this
heat exchanger and the associated components.
ITS
Figure C1.1 Thermal stores fitted
with external hot water heat exchanger
should be tested with it and its
associated components fitted
HW out
HW heat exchanger
CW in
Figure C1: Schematic diagram of heat loss test rig
25±5mm
1
TFE
>
_700mm
2
TA1
TA2
h
TA2
TA1
3
TW
h/2
4
450±100
1
3
Integral feed & expansion cistern
Boiler control or solar controller
sensor pocket
2
4
Page 27
350±25mm
>
_700mm
TA3
Thermal store under test
Immersion heater
APPENDIX C
C1
test applies to all types of thermal stores (i.e.
integrated, hot water only and buffer stores).
C2
TEST RIG AND TEST SAMPLE
C2.1 The standing heat loss measurement test shall
be performed on a thermal store (i.e. primary
water storage vessel of types covered by this
document) fitted with a horizontally mounted
immersion heater or a fixed electrical element of
3kW output mounted so as to heat at least the
storage volume specified in table A1. For primary
stores of up to 250l total storage volume (VT ), a
3kW element shall be used. For larger primary
stores (VT > 250l) an element of greater output
can be used as specified by the manufacturer.
This condition shall be checked by heating
the primary store under test by means of the
immersion heater or an element until the
temperature at the measuring point (T W on figure
A1) reaches 75±1°C.
The thermal store temperature, T W, is measured
using the boiler control sensor pocket (Lower
pocket if a thermal store has two boiler control
sensor pockets). If suitable sensor pockets for
measuring temperature, T W, is not provided on
the test sample, then these temperatures nay
be measured on the metal surface of the vessel
(under the insulation).
C2.2 Apart from the introduction of the immersion
heater or element in the test sample, all other
aspects of the primary store design shall be as
identical as possible to the production model,
particularly with regard to the insulation
characteristics and hydraulic connections.
APPENDIX C
C2.3 In circumstances where it is impossible to fit an
immersion heater, then an external electrical flow
heater and a circulating pump can be substituted
as indicated in figure A2. The electric flow heater
shall be controlled such that it energises in
response to temperature T WH and the temperature
difference between T WL and T WH should not be
greater than 2°C.
The circulator shall operate whilst the flow heater
is energised but only the electrical input to the
flow heater shall be measured.
All connecting pipes, the flow heater and the
circulator shall be well insulated.
above the floor level. Units without the integral
feed and expansion cistern should be provided
with a temporary means of filling and well
insulated vent/overflow pipe of 22mm diameter
as shown in figure A.2. After filling the inlet valve
used for filling can be covered with temporary
insulation if desired (units without integral feed
and expansion cisterns only).
The test rig shall be in a draught free environment
where it is shielded from direct radiation and
has controlled ambient temperature of 20±2°C
during the test period.
The thermal store test sample shall be positioned
at least 700 mm from any wall or other vertical
surface.
C2.5 Three thermocouples (TA1, TA2 and TA3) or similar
temperature measuring devices capable of
measuring temperature to an accuracy of ±1°C
shall be positioned at a height equating to half
way to the storage vessel (±25 mm) and at a
distance of 350±25 mm from the outside of the
vessel insulation/casing. These devices shall be
positioned away from any wall or vertical surface
as shown in figures A.1 and A.2. A thermocouple
(T W ) or similar temperature measuring devices
capable of measuring temperatures to an
accuracy of ±1°C should be positioned on or
inside the storage vessel as follows: C2.5.1 T W should be positioned at a point approximately
100±20 mm above the top of the test immersion
heater if no suitable pockets have been
provided.
C2.5.2 For units fitted with integral feed and expansion
cistern, a thermocouple (TFE) or a similar
temperature measuring device capable of
measuring temperature to an accuracy of ±1°C
should be positioned in the feed and expansion
cistern 25 – 30 mm below the water level (figure
A.1).
C2.6 The electricity supply to the immersion heater
shall be connected via a kilowatt hour meter with
an accuracy of ±0.01 kWh.
C2.4 The primary store sample to be tested shall
be mounted on a base of 20mm thick medium
density fibreboard at a height of 400±100mm
Page 28
TEST PROCEDURE
C3.1 Fill the test sample of a thermal store with cold
water via temporary connection to a valve
connected to the feed and expansion cistern or
other suitable connection on the test appliance
or thermal store.
C3.4 Calculate the mean temperature of water in
the feed and expansion cistern using same 24h
periods used for calculating the standing loss of
the appliance.
C4
CALCULATION RESULTS
In units without integral feed and expansion
cistern, when the storage vessel is full, water will
flow from the vent/overflow and the water supply
can be disconnected. [Note: In these types of units,
water will drip out of overflow during initial stages
whilst heating occurs and therefore a suitable
temporary receptacle or a drain arrangement may
be required]
C4.1 Calculate the heat loss for each test period,
corrected for a 55°C differential between stored
hot water and the ambient temperatures as
follows:
Heat loss rate, QHL = E[55/(T W – TA)]
In units with integral feed and expansion cistern,
fill the storage vessel and the cistern up the water
mark level specified by the manufacturer.
E = Energy consumed in 24 h test period [kWh]
T W = Mean water temperature over a
[°C]
24h test period measured by T WH
TA = Mean ambient temperature over a
24h test period
[°C]
= (TA1 + TA2 + TA3)/3
C4.2 Calculate the average temperature of water in the
feed and expansion (F & E) cistern as follows:
TAFE= (TFE1 + TFE2 + TFE2) /3
C3.2 The immersion heater shall be switched on
and the temperature control adjusted to give a
temperature at T W of 75±2°C.
C3.3 Determine the heat losses over successive 24h
test periods as follows: C3.3.1 After a stabilisation period of at least 24h,
confirmed by consistent temperature readings,
record an initial kilowatt hour reading to the
nearest 0.01 kWh.
Where:-
C3.3.2 Record the subsequent meter readings at
24h intervals and determine the energy
consumptions (E1, E2, E3 etc) for each 24h test
period by subtraction.
C3.3.3 For each 24h period calculate and record the
mean ambient temperature TA (which is the mean
of TA1, TA2 and TA3), mean water temperatures T WH
and T WL and mean feed and expansion cistern
temperature TFE.
C3.3.4 Continue the test regime until the standing loss
calculated as per section A.4. is within 2% for the
at least two successive 24h periods. The standing
loss shall be taken as the mean of these results.
C3.3.5 If it is not possible to achieve a variation of less
than 2% between the results, then continue the
test for at least 168h and record the results for the
last three 24h periods. The standing loss shall be
taken as the mean of these three results.
Page 29
Where:
TAFE= Average temperature in F & E
cistern during test period TFE1= Mean temperature of water in F & E
cistern for 24h test period 1
TFE2= Mean temperature of water in F & E
cistern for 24h test period 2
TFE3= Mean temperature of water in F & E
cistern for 24h test period 3
(°C)
(°C)
(°C)
(°C)
APPENDIX C
C3
Details of the coded information for the thermal store
‘Data Badge’
D1
Code-A
This code refers to the performance of the
domestic hot water heat exchanger. The coded
information should be presented as follows:A:aa-bb.b-cc.c-dd.d-ee.e-f.f
Example
A: 18-25.5-2.5-2.1-10.2-2.8
Where : aa = Nominal domestic hot water
flow rate (l/min)
bb.b = Rating of the hot water heat
exchanger (kW)
cc.c = Pressure loss at nominal flow
rate (bar)
dd.d = Water content of the heat
exchanger (l)
ee.e = Maximum recommended
radiator capacity used in test A2(kW)
f.f =24 hour heat loss as per
section 4.3.2
(kWh)
D2
Code-B
This code refers to the performance of the primary
heat exchanger of the indirect thermal store.
The coded information should be presented as
follows:B:aa.a-b.bb-cccc-dd.d
Example
APPENDIX D
B:11.1-1.11-450-1.2
Where:aa.a =
bb.b =
cccc =
dd,d =
Nominal charge flow rate (litres/minute)
Pressure loss at nominal flow rate (kPa)
UA-Value of the heat exchanger (W/°C)
Water content of the heat exchanger(l)
Page 30
E7
Hot water heat exchanger
E7.1
Nominal flow rate (l/s)
E7.2
Hot water performance at nominal flow rate as
shown in figure A2, appendix A.
E1
Direct integrated thermal stores (DITS)
E1.1
Maximum installed radiator capacity (kW)
E1.2
Maximum recommended boiler power (kW)
E7.3
Pressure flow characteristics of the heat exchanger
as shown in figure A3, appendix A
E1.3
Plus performance specification listed in sections
E6 and E7
E7.4
Rating of the hot water heat exchanger as (kW)
calculated using equation a1, appendix A
E2
Indirect integrated thermal store (IDITS)
E7.5
Maximum working pressure (bar)
E2.1
Maximum installed radiator capacity (kW)
E8
Primary heat exchanger
E2.2
Plus performance specification listed in sections
E6, E7 and E8
E8.1
Thermal performance of the primary heat
exchanger as shown in figure B2, appendix B
E3
Hot water thermal store (HWTS)
E8.2
Pressure flow characteristics of the primary heat
exchanger as shown in figure B3, appendix B
E3.1
Maximum installed radiator capacity (kW)
E8.3
Maximum working pressure (bar)
E3.2
Maximum recommended boiler power (kW)
E3.3
Plus performance specification listed in sections
E6 and E7.
E4
Direct buffer store (DBS)
E4.1
Information specified in section E6
E5
Indirect buffer store (IDBS)
E5.1
Information specified in sections E6 and E8
E6
All types of thermal stores
E6.1
Maximum working head (m)
E6.2
Overall dimensions of the unit (mm)
E6.3
Clearances required for installation and service
(mm)
E6.4
Size and type of connections
Page 31
APPENDIX E
Performance and design information to be included in
the design and installation manuals.