Heatstore HSUDC100 User guide

1
UNVENTED MAINS PRESSURE WATER HEATER
100, 120, 150, 170, 210, 250 AND 300 LITRE
DIRECT AND INDIRECT MODELS
INSTALLATION AND SERVICING INSTRUCTIONS
36 00 5944 Issue 1
PACK CONTENTS
zHeatstore unvented water heater incorporating immersion heater(s) and thermal controls zFactory
fitted Temperature/Pressure Relief Valve zCold Water Combination Valve zExpansion Vessel
zExpansion Vessel Mounting Bracket zTundish zMotorised Valve (Indirect models only) zCom-
pression nuts and olives zImmersion heater spanner zInstallation Instructions

2
HEATSTORE UNVENTED HOT WATER STORAGE CYLINDER INSTALLATIONAND
SERVICING INSTRUCTIONS.
PLEASE LEAVE THIS MANUALWITH THE UNIT FOR FUTURE REFERENCE.
CONTENTS
SECTION CONTENT PAGE
1 INTRODUCTION ....... 2
2 GENERAL REQUIREMENTS ...... 3
3 INSTALLATION - GENERAL ...... 4
4 INSTALLATION - DIRECT UNITS ...... 9
5 INSTALLATION – INDIRECT UNITS ..... 9
6 COMMISSIONING ....... 11
7 MAINTENANCE ....... 12
8 FAULT FINDINGAND SERVICING ...... 13
9 USER INSTRUCTIONS ...... 15
10 GUARANTEE ........ 16
1.0 INTRODUCTION
The Heatstore HSU is a purpose designed unvented
water heater. The unit has a stainless steel inner ves-
sel which ensures an excellent standard of corrosion
resistance. The outer casing is a combination of resil-
ient thermoplastic mouldings and plastic coated cor-
rosion proofed steel sheet. All Heatstore HSU units
are insulated with CFC free polyurethane foam to meet
the latest European heat loss requirements (see Table
3).
The unit is supplied complete with all the necessary
safety and control devices needed to allow connec-
tion to the cold water mains. All these components
are pre-adjusted.
NOTE: Prior to installation the unit should be stored
in an upright position in an area free from excessive
damp or humidity.
This appliance complies with the requirements of the
CE marking directive and is KIWA approved to show
compliance with Building Regulations (Section G3).
The following instructions are offered as a guide to
installation which must be carried out by a competent
plumbing and electrical installer in accordance with
Building Regulation G3, The Building Standards
(Scotland) Regulations 1990, or The Building Regu-
lations (Northern Ireland).
IMPORTANT: PLEASE READ ALL THESE INSTRUCTIONS BEFORE
COMMENCING INSTALLATION
TABLE 1: OPERATIONAL SUMMARY
Maximum water supply pressure to PRV 16.0 bar
Operating pressure of unit 3.5 bar
Expansion vessel charge pressure 3.5 bar
Expansion valve setting 6.0 bar
Nominal storage capacity of units (see Section 2 Table 2)
Max. primary working pressure 3.0 bar (indirects only)
Opening temperature of T&P Relief Valve 90deg C
Opening pressure of T&P Relief Valve 10 bar

3
2.0 GENERAL REQUIREMENTS
2.1 COMPONENTS SUPPLIED
1. Heatstore HSU unvented water heater incorporat-
ing immersion heater(s) and thermal controls
2. Factory fitted Temperature/Pressure Relief Valve
3. Cold Water Combination Valve.
4. Expansion Vessel and mounting bracket.
5. Tundish.
6. Motorised Valve (Indirect models only).
7. Compression nuts and olives
8. Immersion heater key spanner
2.2 SITING THE UNIT
The Heatstore HSU unvented water heater must be
installed vertically. Although location is not critical,
the following points should be considered:
•The Heatstore HSU should be sited to ensure
minimum dead leg distances, particularly to the point
of most frequent use.
•Avoid siting where extreme cold temperatures will
be experienced. All exposed pipework should be in-
sulated.
•The discharge pipework from the safety valves
must have minimum fall of 1:200 from the unit and
terminate in a safe and visible position.
• Access to associated controls and immersion
heaters should be possible to allow for periodic
servicing and maintenance.
•Ensure that the base chosen for the Heatstore
HSU is level and capable of permanently supporting
the weight when full of water (see Table 2).
2.3 WATER SUPPLY
Bear in mind that the mains water supply to the prop-
erty will be supplying both the hot and cold water re-
quirements simultaneously. It is recommended that the
maximum water demand is assessed and the water
supply checked to ensure this demand can be satisfac-
torily met.
NOTE:A high mains water pressure will not always
guarantee high flow rates.
Wherever possible the mains supply pipe should be
22mm. We suggest the minimum supply requirements
should be 1.5 bar pressure and 20 litres per minute
flowrate. However, at these values outlet flow rate may
be poor if several outlets are used simultaneously.
The higher the available pressure and flow rate the
better the system performance.
The Heatstore HSU has an operating pressure of 3.5
bar that is controlled by the Cold Water Combination
Valve. The Cold Water Combination Valve can be con-
nected to a maximum mains pressure of 16 bar.
2.4 OUTLET/TERMINAL FITTINGS (TAPS, ETC.)
The Heatstore HSU can be used with most types of
terminal fittings. It is advantageous in many mixer show-
ers to have balanced hot and cold water supplies. In
these instances a balanced pressure cold water con-
nection should be placed between the Cold Water
Combination Valve and the Heatstore HSU water
heater. Outlets situated higher than the Heatstore HSU
will give outlet pressures lower than that at the heater,
a 10m height difference will result in a 1 bar pressure
reduction at the outlet.
2.5 LIMITATIONS
The Heatstore HSU unvented water heater should not
be used in association with any of the following:
•Solid fuel boilers or any other boiler in which the
energy input is not under effective thermostatic con-
trol unless additional and appropriate safety measures
are installed.
•Ascending spray type bidets or any other class 1
back syphonage risk requiring that a type A air gap be
employed.
•Steam heating plants unless additional and appro-
priate safety devices are installed.
•Situations where maintenance is likely to be ne-
glected or safety devices tampered with.
•Water supplies that have either inadequate pres-
sure or where the supply may be intermittent.
•Situations where it is not possible to safely pipe
away any discharge from the safety valves.
•In areas where the water consistently contains a
high proportion of solids, e.g. suspended matter that
could block the strainer, unless adequate filtration can
be ensured.
Table 3: Standing heat losses
Table 2: Unit weights
Based on an ambient air temperature of 20oC and a stored
water temperature of 65oC
Type Model
reference
Nominal
capacity
(litres)
Weight of
unit full
(kg)
DIRECT HSUDC100 100 124
HSUDC120 120 146
HSUDC150 150 179
HSUDC170 170 201
HSUDC210 210 252
HSUDC250 250 295
HSUDC300 300 355
INDIRECT HSUIC100 100 125
HSUIC120 120 147
HSUIC150 150 181
HSUIC170 170 204
HSUIC210 210 257
HSUIC250 250 301
HSUIC300 300 360
Nominal
capacity per day per yea
r
(litres) (kWh/24h) (kWh/365d)
100 1.14 416.1
120 1.47 536.6
150 1.70 620.5
170 1.92 700.8
210 2.30 839.5
250 2.45 894.3
300 2.72 992.8
Standing Heat Loss

4
SECONDARY
RETURN
COLD
SUPPLY
CHECK
VALVE
SECONDARY
CIRCULATION
PUMP
COLD
INLET 
CONNECTION
SWEPT
TEE
3.0 INSTALLATION – GENERAL
(FIGS 3 & 5)
3.1 PIPE FITTINGS
All pipe fittings are made via 22mm compression
fittings directly to the unit. The fittings are threaded
3/4”BSP male parallel should threaded pipe
connections be required.
3.2 COLD FEED
A 22mm cold water supply is recommended however,
if a 15mm (1/2”) supply exists which provides suffi-
cient flow this may be used (although more flow noise
may be experienced).
A stopcock or servicing valve should be incorporated
into the cold water supply to enable the Heatstore
HSU and its associated controls to be isolated and
serviced.
3.3 COLD WATER COMBINATION VALVE (FIG 1)
The Cold Water Combination Valve can be connected
anywhere on the cold water mains supply prior to the
Expansion Vessel (see Fig. 5). The Cold Water Combi-
nation Valve is installed as a complete one-piece unit.
The valve incorporates the Pressure Reducer, Strainer,
Expansion Valve and Check Valve. Ensure that the
valve is installed with the direction of flow arrows
pointing in the right direction. No other valves should
be placed between the Cold Water Combination Valve
and the Heatstore HSU unit. The Expansion Valve con-
nection must not be used for any other purpose.
FIG. 1 Cold Water Combination Valve FIG. 2 Secondary circulation connection
3.4 DRAIN TAP
A suitable draining tap should be installed in the cold
water supply to the Heatstore HSU unit between the
Cold Water Combination Valve and the heater at as
low a level as possible. It is recommended that the
outlet point of the drain pipework be at least 1 metre
below the level of the heater (this can be achieved by
attaching a hose to the drain tap outlet spigot).
3.5 EXPANSION VESSEL
The Expansion Vessel accommodates expansion that
results from heating the water inside the unit. The unit
is pre-charged at 3.5 bar. The Expansion Vessel must
be connected between the Cold Water Combination
Valve and the Heatstore HSU (see Fig. 5). The loca-
tion of the Expansion Vessel should allow access to
recharge the pressure as and when necessary, this
can be done using a normal car foot pump. It is recom-
mended that the Expansion Vessel is adequately sup-
ported. An Expansion Vessel wall mounting bracket is
supplied for this purpose
3.6 SECONDARY CIRCULATION
If secondary circulation is required it is recommended
that it be connected to the Heatstore HSU as shown
in Fig. 2 via a swept tee joint into the cold feed to the
unit.
The secondary return pipe should be in 15mm pipe
and incorporate a check valve to prevent backflow. A
suitable WRAS approved bronze circulation pump will
be required. On large systems, due to the increase in
system water content, it may be necessary to fit an
additional expansion vessel to the secondary circuit.
this should be done if the capacity of the secondary
circuit exceeds 10 litres.
Pipe capacity (copper)
15mm o/d = 0.13 l/m (10 litres = 77m)
22mm o/d = 0.38 l/m (10 litres = 26m)
28mm o/d = 0.55 l/m (10 litres = 18m)
Secondary circulation is NOT recommended for direct
electric units being used on Off Peak electricity tar-
iffs.
3.7 OUTLET
The hot water outlet is a 22mm compression fitting
located at the top of the cylinder. Hot water distribu-
tion pipework should be 22mm pipe with short runs of
15mm pipe to terminal fittings such as sinks and ba-
sins. Pipe sizes may vary due to system design.
EXPANSION VALVE
COLD MAINS
CONNECTION
(22mm)
EXPANSION VALVE
OUTLET (15mm)
OUTLET
CONNECTION
(22mm)
PRESSURE
REDUCING
VA LV E
HOUSING
PRESSURE
REDUCING
VA LV E
CARTRIDGE (3.5 bar)

5
FIG. 3 General Dimensions
Model Heating time
15 to 65deg. C
70% Recovery
tim e
Notes
HSUDC100 2hours 08mins 1hour 17mins 3kW input
HSUDC150 1hour 33mins 1hour 08mins 6kW input (using both immersion heaters)
HSUDC210 2hours 21mins 1hour 51mins 6kW input (using both immersion heaters)
HSUIC100 21mins 15mins Indirectly heated. Primary flow 82deg. C at 15l/min
HSUIC150 24mins 20mins Indirectly heated. Primary flow 82deg. C at 15l/min
HSUIC210 32mins 29mins Indirectly heated. Primary flow 82deg. C at 15l/min
Test results obtained by WRc-NSF in accordance with Test Criteria 1-50-220 and 1-50-222
SURFACE
AREA
(sq.m)
RATING
(kW)
RECOVERY
(mins)
120 0.43 12.5 22 121
150 0.55 16.4 21 152
170 0.61 16.0 24 173
210 0.68 18.3 26 215
250 0.79 20.0 27 257
300 0.79 20.0 33 310
COIL
NOMINAL
CAPACITY
(litres)
HEATING
TIME IMM.
HTR. (mins)

6
Worked example of discharge pipe sizing
The example below is for a G1/2 temperature relief valve
with a discharge pipe (D2) having 4 No. elbows and
length of 7m from the tundish to the point of discharge.
From Table 4:
Maximum resistance allowed for a straight length of
22mm copper discharge pipe (D2) from a G1/2 tempera-
ture relief valve is 9.0m.
Subtract the resistance for 4 No. 22mm elbows at 0.8m
each = 3.2m
Therefore the permitted length equates to: 5.8m
5.8m is less than the actual length of 7m therefore
calculate the next largest size.
Maximum resistance allowed for a straight length of
28mm pipe (D2) from a G1/2 temperature relief valves
equates to 18m.
Subtract the resistance of 4 No. 28mm elbows at 1.0m
each = 4.0m
Therefore the maximum permitted length equates to: 14m
As the actual length is 7m, a 28mm (D2) copper pipe will
be satisfactory.
3.8 DISCHARGE PIPEWORK
It is a requirement of Building Regulation G3 that any
discharge from an unvented system is conveyed to
where it is visible, but will not cause danger to per-
sons in or about the building. The tundish and dis-
charge pipes should be fitted in accordance with the
requirements and guidance notes of Building Regula-
tion G3. The G3 Requirements and Guidance section
3.9 are reproduced in the following sections.
Information Sheet No. 33 available from the British
Board of Agrement gives further advice on discharge
pipe installation. For discharge pipe arrangements not
covered by G3 Guidance or BBA Info Sheet No.33
advice should be sought from either your local Build-
ing Control Officer or Heatstore.
G3 REQUIREMENT
“...there shall be precautions...to ensure that the hot
water discharged from safety devices is safely
conveyed to where it is visible but will not cause
danger to persons in or about the building.”
G3 GUIDANCE SECTION 3.9
The discharge pipe (D1) from the vessel up to and
including the tundish is generally supplied by the
manufacturer of the hot water storage system. Where
otherwise, the installation should include the discharge
pipe(s) (D1) from the safety device(s). In either case
the tundish should be vertical, located in the same
space as the unvented hot water storage system and
be fitted as close as possible and within 500mm of the
safety device e.g. the temperature relief valve.
The discharge pipe (D2) from the tundish should ter-
minate in a safe place where there is no risk to persons
in the vicinity of the discharge, preferably be of metal
and:
a. be at least one pipe size larger than the nominal
outlet size of the safety device unless its total equiva-
lent hydraulic resistance exceeds that of a straight
pipe 9m long i.e. discharge pipes between 9m and 18m
equivalent resistance length should be at least two
sizes larger than the nominal outlet size of the safety
device, between 18 and 27m at least 3 sizes larger , and
so on. Bends must be taken into account in calculat-
ing the flow resistance. Refer to Diagram 1, Table 1
and the worked example.
An alternative approach for sizing discharge pipes
would be to follow BS 6700:1987 Specification for
design installation, testing and maintenance of ser-
vices supplying water for domestic use within build-
ings and their curtilages, Appendix E, section E2 and
table 21.
b. have a vertical section of pipe at least 300mm long,
below the tundish before any elbows or bends in the
pipework.
c. be installed with a continuous fall.
d. have discharges visible at both the tundish and the
final point of discharge but where this is not possible
or is practically difficult there should be clear visibil-
ity at one or other of these locations. Examples of
acceptable discharge arrangements are:
i. ideally below a fixed grating and above the water
seal in a trapped gully.
ii. downward discharges at low level; i.e. up to 100mm
above external surfaces such as car parks, hard stand-
ings, grassed areas etc. are acceptable providing that
where children may play or otherwise come into con-
tact with discharges a wire cage or similar guard is
positioned to prevent contact, whilst maintaining vis-
ibility.
iii. discharges at high level; e.g. into a metal hopper
and metal down pipe with the end of the discharge
pipe clearly visible (tundish visible or not) or onto a
roof capable of withstanding high temperature dis-
charges of water and 3m from any plastics guttering
system that would collect such discharges (tundish
visible).
iv. where a single pipe serves a number of discharges,
such as in blocks of flats, the number served should
be limited to not more than 6 systems so that any
instalation discharging can be traced reasonably eas-
ily. The single common discharge pipe should be at
least one pipe size larger than the largest individual
discharge pipe (D2) to be connected. If unvented hot
water storage systems are installed where discharges
from safety devices may not be apparent i.e. in dwell-
ings occupied by blind, infirm or disabled people, con-
sideration should be given to the installation of an
electronically operated device to warn when discharge
takes place.
Note: The discharge will consist of scalding water and
steam. Asphalt, roofing felt and non-metallic rainwa-
ter goods may be damaged by such discharges.

7
Fixed grating
Discharge below
fixed grating
(Building Regulation
G3 section 3.9d gives
alternative points
of discharge)
Trapped
gully
Discharge pipe (D2) from tundish,
with continuous fall. See Building
Regulation G3 section 3.9d i-iv,
Table 4 and worked example
300mm
minimum
500mm maximum
Metal discharge pipe (D1) from
Temperature relief valve to tundish
Tundish
Safety device
(e.g. Temperature
relief valve)
Valve outlet size Minimum size of
discharge pipe
D1
Minimum size of
discharge pipe
D2 from tundish
Maximum
resistance
allowed,
expressed as a
length of straight
pipe (I.e. no
elbows or bends)
Resistance
created by each
elbow or bend
G1/2 15mm
22mm
28mm
35mm
up to 9m
up to 18m
up to 27m
0.8m
1.0m
1.4m
G3/4 22mm
28mm
35mm
42mm
up to 9m
up to 18m
up to 27m
1.0m
1.4m
1.7m
G1 28mm
35mm
42mm
54mm
up to 9m
up to 18m
up to 27m
1.4m
1.7m
2.3m
Table 4 Sizing of copper discharge pipe (D2) for common temperature relief valve outlet sizes
FIG. 4 Typical discharge pipe arrangement (extract from Building Regulation G3 Guidance
section 3.9)
3.9 WARNINGS
•Under no circumstances should the factory fitted
Temperature/Pressure Relief Valve be removed other
than by authorised personnel. To do so will invalidate
any guarantee or claim.
•The Cold Water Combination Valve must be fitted
to the mains water supply to the Heatstore HSU unit.
•No control or safety valves should be tampered
with.
•The discharge pipe should not be blocked or used
for any other purpose.
•The tundish should not be located adjacent to any
electrical components.

8
BROWN
BLUE
GREEN/YELLOW
FIG. 5 Typical installation - schematic
FIG. 6 Electrical Connections (Schematic)
DIRECT MODELS INDIRECT MODELS
Note: On models fitted with two or three elements each element must be
wired individually in accordance with the diagram above.
THERMOSTAT
EARTH
CONNECTION
FUSED (13A) DOUBLE
POLE ISOLATING
SWITCH
A
B
1.5mm23 CORE
HOFR SHEATHED
CABLE
12
GREEN/YELLOW
13 AMP MAINS
SUPPLY. 1.5mm2
MIN. CABLE SIZE
TO INDIRECT SYSTEM
CONTROLS JUNCTION
BOX - SEE FIGS. 7/8
GREEN/
YELLOW
BROWN
BLUE
3
DIRECT THERMOSTAT
B
A
11 223
INDIRECT THERMOSTAT
INDIRECT THERMAL CUT-OUT
EXPANSION
VESSEL
COLD WATER
COMBINATION
VALVE
T&P RELIEF
VALVE
TO HOT
OUTLETS
MAINS
WATER
SUPPLY
ISOLATING
VALVE (NOT
SUPPLIED)
TUNDISH
DISCHARGE
PIPE
DRAIN COCK
(NOT SUPPLIED)
PRIMARY
RETURN
PRIMARY
FLOW
ELEMENT /
CONTROLS
HOUSING
INLET
BOOST ELEMENT
CONTROL HOUSING
(HSUDC120 TO HSUDC300
MODELS ONLY)
NOTE: PRIMARY HEATING COIL
FITTED ON HSUIC100 TO HSUIC300
MODELS ONLY
SECONDARY
RETURN
TAPPING (IF
REQUIRED)
BALANCED
COLD WATER
CONNECTION
(IF REQUIRED)

9
4.0 INSTALLATION - DIRECT
UNITS
4.1 PLUMBING CONNECTIONS
Direct units require the following pipework connec-
tions.
•Cold water supply to and from inlet controls.
•Outlet to hot water draw off points.
•Discharge pipework from valve outlets to tundish.
4.2 ELECTRICALSUPPLY(FIG. 6)
The Heatstore HSUDC100 litre units are fitted with
one 3kW immersion heater, all other direct models are
fitted with two 3kW immersion heaters as standard. It
is recommended that these should be wired via a suit-
able controller to BSEN 60730. The Heatstore HSU
MUST be earthed. The 250 and 300 litre units have an
additional boss which has a blanking plug fitted. An
additional immersion heater can be fitted in place of
the blanking plug where a higher electrical input is
required for faster recovery times, order Part No. 95
970 510 if required.
All wiring to the unit must be installed in accordance
with the latest IEE Wiring Regulations and the circuit
must be protected by a suitable fuse and double pole
isolating switch with a contact separation of at least
3mm in both poles. The Live and Neutral connections
are made directly onto the combined thermostat and
thermal cut-out located under the terminal cover(s)
mounted on the side of the unit. The Earth connection
should be made to the earth connection located to
the side of the immersion heater boss(es). The supply
cable must be routed through the cable gland located
on the unit casing beneath the terminal housing.
DO NOT operate the immersion heaters until the
Heatstore HSU has been filled with water.
4.3 SAFETY
DISCONNECT FROM THE MAINS SUPPLY
BEFORE REMOVING ANY COVERS.
Never attempt to replace the immersion heater(s) other
than with the recommended Heatstore HSU immersion
heater(s).
DO NOT BYPASS THE THERMAL CUT-OUT(S) IN
ANY CIRCUMSTANCES. Ensure the two male spade
terminations on the underside of the combined
thermostat and thermal cut-out are pushed firmly onto
the corresponding terminations on the element plate
assembly.
In case of difficulty contact Heatstore, tel: [phone]
5375.
5.0 INSTALLATION - INDIRECT
UNITS
5.1 PLUMBING CONNECTIONS
Indirect units require the following pipework connec-
tions.
•Cold water supply to and from inlet controls.
•Outlet to hot water draw off points.
•Discharge pipework from valve outlets to tundish
•Connection to the primary circuit.
Primary connections are 22mm compression. However,
3/4”BSP parallel threaded fittings can be fitted to the
primary coil connections if required.
5.2 ELECTRICALSUPPLY (FIG. 6)
All Indirect units are fitted with a 3kW immersion
heater and a combined thermostat and thermal cut-
out to control the indirect heating source. The
Heatstore HSU MUST be earthed.
All wiring to the unit must be installed in accordance
with the latest IEE Wiring Regulations and the supply
circuits must be protected by a suitable fuse and double
pole isolating switch with a contact separation of at
least 3mm in both poles. All connections are made to
the terminal block located under the terminal cover
mounted on the side of the unit. The supply cable(s)
must be routed through the cable grip(s) in the terminal
housing.
DISCONNECT FROM MAINS SUPPLY BE-
FORE REMOVINGANY COVERS. DO NOT BY-
PASS THE THERMALCUT-OUTS INANY CIRCUM-
STANCES. Ensure the thermostat and thermal cut-
out sensing bulbs are pushed fully into the pockets
on the element plate assembly.
5.3 BOILER SELECTION
The boiler should have a control thermostat and non
self-resetting thermal cut-out and be compatible with
unvented storage water heaters.
5.4 PRIMARY CIRCUIT CONTROL
The 2 port motorised valve supplied with the Heatstore
HSUIC indirect units MUST be fitted to the primary
flow to the Heatstore HSU heat exchanger and wired
in series with the indirect thermostat and thermal cut-
out fitted to the unit.
Primary circulation to the Heatstore HSU heat ex-
changer MUST be pumped, gravity circulation WILL
NOT WORK due to the special design of the heat
exchanger.
5.5 SPACEAND HEATING SYSTEMS CONTROLS
The controls provided with the Heatstore HSU indi-
rect units will ensure the safe operation of the unit
within a central heating system. Other controls will be
necessary to control the space heating requirements
and times that the system is required to function. The
Heatstore HSU is compatible with most heating con-
trols, examples of electrical circuits are shown in Figs.
7 and 8. However, other systems may be suitable, refer
to the controls manufacturers’ instructions, supplied
with the controls selected, for alternative system wir-
ing schemes.

10
FIG. 7 Schematic wiring diagram - Basic 2 x 2 port valve system
FIG. 8 Schematic wiring diagram - 3 port mid position valve system. N.B. Must be used in
conjunction with 2 port zone valve supplied
PROGRAMMER BOILER PUMP
ROOM STAT
ZONE VALVE(DHW)
(SUPPLIED)
ZONE VALVE (HTG)
INDIRECT CONTROLS
TERMINAL BLOCK
JUNCTION BOX
12345678910
12345678910
LNLN
GBr Bl O
GY GBrBlO GY
132
L
N
23
HTG DHW
ON ON
12 23123
123
23
2
3
LN
(SUPPLY)
1
3

Control terminal numbering may
differ from those shown. Refer to
instructions with controls
selected
ADOUBLE POLE ISOLATING
SWITCH MUST BE INSTALLED
IN THE MAINS SUPPLY.
ALL EARTH CONNECTIONS
BE CONNECTED BACK TO
THE MAINS EARTH SUPPLY
PROGRAMMER
BOILER
PUMP
ROOM STAT
ZONE VALVE(DHW)
(SUPPLIED)
ZONE VALVE (HTG)
INDIRECT CONTROLS
TERMINAL BLOCK
JUNCTION BOX
12345678910
12345678910
LN
GBrBlO GY GWBl O GY
132
L
N
23
2
2
3123
23
2
3
LN
(SUPPLY)
1
3
LN
HTG DHW
ON ON
123
DHW
OFF
Control terminal numbering may
differ from those shown. Refer to
instructions with controls
selected
ADOUBLE POLE ISOLATING
SWITCH MUST BE INSTALLED
IN THE MAINS SUPPLY.
ALL EARTH CONNECTIONS
BE CONNECTED BACK TO
THE MAINS EARTH SUPPLY

11
6.0 COMMISSIONING
6.1 FILLING THE UNIT WITH WATER
•Check Expansion Vessel pre-charge pressure. The
vessel is supplied pre-charged to 3.5 bar to match the
control pressure of the Pressure Reducing Valve. The
pre-charge pressure is checked using a car tyre gauge
by unscrewing the plastic cap opposite the water con-
nection.
•Check all connections for tightness including the
immersion heater(s). An immersion heater key span-
ner is supplied for this purpose.
•Ensure the drain cock is CLOSED.
•Open a hot tap furthest from the Heatstore HSU.
•Open the mains stop cock to fill the unit. When
water flows from the tap, allow to run for a few min-
utes to thoroughly flush through any residue, dirt or
swarf, then close the tap.
•Open successive hot taps to purge the system of
air.
6.2 SYSTEM CHECKS
•Check all water connections for leaks and rectify
as necessary.
•Remove the Pressure Reducing Valve Cartridge
to access the strainer mesh (see Section 7.3 for de-
tails), clean and re-fit.
•Manually open, for a few seconds, each relief
valve in turn, checking that water is discharged and
runs freely through the tundish and out at the discharge
point.
•Ensure that the valve(s) reseat satisfactorily.
6.3 DIRECT UNITS
Switch on electrical supply to the immersion heater(s)
and allow the Heatstore HSU to heat up to normal
working temperature (60ºC recommended, approxi-
mately graduation 4 on the thermostat). If necessary
the temperature can be adjusted by inserting a flat
bladed screwdriver in the adjustment knob on top of
the immersion heater thermostat and rotating. The ad-
justment range 1 to 5 represents a temperature range
of 10oto 70oC. Check the operation of thermostat(s)
and that no water has issued from the Expansion Re-
lief Valve or Temperature/Pressure Relief Valve during
the heating cycle.
6.4 INDIRECT UNITS
Fill the indirect (primary) circuit following the boiler
manufacturer’s commissioning instructions. To ensure
the Heatstore HSU primary heat exchanger is filled,
the 2 port motorised valve (supplied) should be manu-
ally opened by moving the lever on the motor hous-
ing to the FLUSHING ONLY setting. When the pri-
mary circuit is full return the lever to the NORMAL
USE position. Switch on the boiler, ensure the pro-
grammer is set to Domestic Hot Water and allow the
Heatstore HSU to heat up to a normal working tem-
FIG. 9 Indirect thermostat and thermal cut-
out
perature (60oC recommended, approximately gradua-
tion 4 on the thermostat). If necessary the tempera-
ture can be adjusted by inserting a flat bladed screw-
driver in the adjustment knob (located on top of the
thermostat mounting bracket - see Fig.9) and rotating.
The minimum thermostat setting is 10oC. The adjust-
ment range 1 to 5 represents a temperature range of
30oto 70oC. Check the operation of the indirect ther-
mostat and 2 port motorised valve and that no water
has issued from the Expansion Relief Valve or Tem-
perature/Pressure Relief Valve during the heating cycle.
6.5 BENCHMARKTM LOG BOOK
On completion of the installation and commissioning
of the Heatstore HSU the BenchmarkTM “Installation,
Commissioning and Service Record Log Book” should
be completed and signed off by the competent in-
staller or commissioning engineer in the relevant sec-
tions.
The various system features, location of system con-
trols, user instructions and what to do in the event of
a system failure should be explained to the customer.
The customer should then countersign the
BenchmarkTM log book to accept completion.
The log book should be left with the customer along
with these instructions. The log book includes sec-
tions that should be filled out when any subsequent
service or maintenance operation is carried out on the
Heatstore HSU system.
CABLE CLAMPS TERMINAL BLOCK
INDIRECT
THERMOSTAT
THERMOSTAT
ADJUSTMENT
INDIRECT
THERMAL
CUT-OUT
INDIRECT THERMAL
CUT-OUT RESET
BUTTON
NOTE:
THE HOUSING COVER AND ELEMENT ASSEMBLY
HAVE BEEN REMOVED FROM THIS VIEW FOR
CLARITY

12
Carefully remove any scale from the surface of the
element(s). DO NOT use a sharp implement as dam-
age to the element surface could be caused. Ensure
sealing surfaces are clean and seals are undamaged, if
in doubt fit a new gasket.
Replace immersion heater(s) ensuring the lower (right
angled) element hangs vertically downwards towards
the base of the unit. It may be helpful to support the
immersion heater using a round bladed screwdriver
inserted into one of the thermostat pockets whilst the
backnut is tightened. Replace thermostat (Direct mod-
els) and thermostat capillaries into pocket (Indirect
models), rewire, check, close and secure immersion
heater housing cover(s).
7.5 EXPANSION VESSELCHARGE PRESSURE
Remove the dust cap on top of the vessel. Check the
charge pressure using a tyre pressure gauge. The pres-
sure (with system de-pressurised) should be 3.5bar. If
it is lower than the required setting it should be re-
charged using a tyre pump (Schrader valve type). DO
NOT OVER CHARGE. Re-check the pressure and
when correct replace the dust cap.
7.6 RE-COMMISSIONING
Check all electrical and plumbing connections are se-
cure. Close the drain cock. With a hot tap open, turn
on the cold water supply and allow unit to refill. DO
NOT switch on the immersion heater(s) or boiler un-
til the unit is full. When water flows from the hot tap
allow to flow for a short while to purge air and flush
through any disturbed particles. Close hot tap and then
open successive hot taps in system to purge any air.
When completely full and purged check system for
leaks. The heating source (immersion heater(s) or
boiler) can then be switched on.
7.7 BENCHMARKTM LOG BOOK
On completion of any maintenance or service of the
Heatstore HSU the BenchmarkTM “Installation, Com-
missioning and Service Record Log Book” should be
filled in to record the actions taken and the date the
work was undertaken.
7.3 STRAINER
Turn off the cold water supply, boiler and immersion
heaters. The lowest hot water tap should then be
opened to de-pressurise the system. Remove the Pres-
sure Reducing Valve cartridge by unscrewing from
the Pressure Reducing Valve Housing. The strainer
will be withdrawn with the Pressure Reducing Valve
cartridge. Wash any particulate matter from the strainer
under clean water. Re-assemble ensuring the seal is
correctly fitted, DO NOT use any other type of seal-
ant.
7.4 DESCALING IMMERSION HEATER(S)
Before removing the immersion heater(s) the unit must
be drained. Ensure the water and electrical supply
and boiler are OFF before draining. Attach a
hosepipe to the drain cock having sufficient length to
take water to a suitable discharge point below the level
of the unit. Open a hot tap close to the unit and open
drain cock to drain unit.
Direct models:
Open the cover(s) to the immersion heater housing(s)
and disconnect wiring from the thermostat mounted
on top of the immersion heater(s). Remove the ther-
mostat by carefully pulling outwards from the immer-
sion heater. Unscrew immersion heater backnut(s) and
remove immersion heater from the unit. A key spanner
is supplied with the Heatstore HSU unit for easy re-
moval/tightening of the immersion heater(s). Over time
the immersion heater gasket may become stuck to the
mating surface. To break the seal insert a round bladed
screwdriver into one of the pockets on the immersion
heater and gently lever up and down.
7.0 MAINTENANCE
7.1 MAINTENANCE REQUIREMENTS
Unvented hot water systems have a continuing main-
tenance requirement in order to ensure safe working
and optimum performance. It is essential that the Re-
lief Valve(s) are periodically inspected and manually
opened to ensure no blockage has occurred in the
valves or discharge pipework. Similarly cleaning of
the strainer element and replacement of the air in the
Expansion Vessel will help to prevent possible opera-
tional faults.
The maintenance checks described below should be
performed by a competent installer on a regular basis,
e.g. annually to coincide with boiler maintenance.
7.2 SAFETY VALVE OPERATION
Manually operate the Temperature/Pressure Relief
Valve for a few seconds. Check water is discharged
and that it flows freely through the tundish and dis-
charge pipework. Check valve reseats correctly when
released. NOTE: Water discharged may be very
hot!
Repeat the above procedure for the Expansion Valve.
Indirect models:
Open the cover(s) to the immersion heater housing(s)
and disconnect wiring from the thermostat mounted
on top of the immersion heater(s). Remove the ther-
mostat by carefully pulling outwards from the immer-
sion heater. Remove capillary sensors from the pock-
ets on the immersion heater. Unscrew immersion heater
backnut(s) and remove immersion heater from the unit.
A key spanner is supplied with the Heatstore HSU
unit for easy removal/tightening of the immersion
heater(s). Over time the immersion heater gasket may
become stuck to the mating surface. To break the seal
insert a round bladed screwdriver into one of the pock-
ets on the immersion heater and gently lever up and
down.

13
8.0 FAULT FINDING AND
SERVICING
8.1 IMPORTANT
•Servicing should only be carried by authorised
Service Engineers or Agents or by competent install-
ers in the installation and maintenance of unvented
water heating systems.
•Any spare parts used MUST be authorised
Heatstore parts.
•Disconnect the electrical supply before remov-
ing any electrical equipment covers.
•NEVER bypass any thermal controls or operate
system without the necessary safety valves.
•Water contained in the Heatstore HSU unit may
be very hot, especially following a thermal control fail-
ure. Caution must be taken when drawing water from
the unit.
8.2 SPARE PARTS
A full range of spare parts are available for the
Heatstore HSU range. Refer to the Technical Data la-
bel on the unit to identify the model installed and en-
sure the correct part is ordered.
Cold Water Combination Valve - Exploded view
Cable
Gland
Combined
Thermostat &
Thermal Cut-out
- Direct models
Spare Part No:
95 612 599
Description Part no.
Immersion heater (lower) 95 606 946
Immersion heater (upper) 95 606 947
Immersion heater gasket 95 611 822
Immersion heater backnut 95 607 869
Immersion heater key 95 607 861
Tundish 95 605 838
Expansion valve cartridge - 6bar 95 605 864
Expansion valve complete - 6bar 95 607 030
Cold water combination valve complete 95 605 022
Cold water combination valve body 95 605 030
Check valve housing 95 605 028
Pressure reducing valve cartridge 3.5bar 95 607 029
Pressure reducing valve housing 95 605 027
Temperature/Pressure Relief Valve 95 605 810
Expansion vessel 12 litre (100, 120
and 150 litre models) 95 607 863
Expansion vessel 18 litre (170 and
210 litre models) 95 607 864
Expansion vessel 25 litre (250 and
300 litre models) 95 607 612
Direct units only
Combined thermostat and thermal
cut-out 95 612 599
Terminal cover 95 607 836
Indirect units only
Indirect thermostat 95 612 697
Indirect Thermal cut-out 95 612 698
Motorised valve 2 port 95 605 819
Terminal housing 95 607 865
4 Way terminal block 95 607 902
Indirect thermostat
Spare Part No:
95 612 697
Indirect Thermal Cut-out
Spare Part No:
95 612 698
4 Way Terminal Block
Spare Part No:
95 612 697
Expansion Valve
Cartridge
Spare Part No.
95 605 864
Expansion Valve
Complete (6 bar)
Spare Part No.
95 607 030
Valve Body
Spare Part No.
95 605 030
Check Valve
Housing
Spare Part No.
95 605 028
Pressure Reducing
Valve Housing
Spare Part No.
95 605 027
Pressure Reducing
Valve Cartridge
(3.5 bar)
Spare Part No.
95 607 029
Strainer Mesh
Housing Securing
Screws (4 off)
Cold Water Combination Valve Complete
Spare Part No. 95 605 022

14
8.3 FAULT FINDING
The Fault Finding chart below will enable operational
faults to be identified and their possible causes recti-
fied. Any work carried out on the Heatstore HSU
unvented water heater and its associated controls
MUST be carried out by a competent installer for
unvented water heating systems. In case of doubt
contact Heatstore (see contact details at foot of page
16).
DO NOT TAMPER WITH ANY OF
THE SAFETY VALVES OR CON-
TROLS SUPPLIED WITH THE
HEATSTORE HSU AS THIS WILL IN-
VALIDATE ANY GUARANTEE
TABLE 5 Fault Finding Chart
FAULT POSSIBLE CAUSE REMEDY
No hot water flow 1. Mains supply off 1. Check and open stop cock
2. Strainer blocked 2. Turn off water supply.
Remove strainer and clean (see
Section 7.3)
3. Cold W ater Com bination
Valve incorrectly fitted
3. Check and refit as required
W ater from hot taps is
cold
1. DIRECT immersion
heater not switched on
1. Check and switch on
2. DIRECT immersion
heater therm al cut-out has
operated
2. Check. Reset by pushing
button.
3. INDIRECT programm er
set to Central Heating only
3. Check. Set to a Dom estic
Hot W ater programm e
4. INDIRECT boiler not
working
4. Check boiler operation. If fault
is suspected consult boiler
manufacturer's instructions
5. INDIRECT thermal cut-
out has operated
5. Check. Reset by pushing
button on cut-out. Check
operation of indirect thermostat
6. INDIRECT motorised
valve not connected
correctly
6. Check wiring and/or plumbing
connections to motorised valve
(see Fig. 7)
W ater discharges 1. INTERMITTENTLY
from Expansion Valve Expansion Vessel charge
pressure has reduced below
3.5bar
1. See Section 7.5 for re-
charging procedure
2. CONTINUALLY
a. Cold W ater Com bination
Valve Pressure Reducer not
working correctly
a. Check pressure from Cold
W ater Combination Valve. If
greater than 3.5bar replace
P res s ure R educ er c artridge
b. Expansion Valve seat
damaged.
b. Remove Expansion Valve
cartridge. Check condition of
seat. If necessary fit new
Expansion Valve cartridge.
W ater discharges from
T& P Relief V alve
1. Thermal control failure
NOTE water will be very hot
1. Switch off power to
immersion heater(s) and shut
down boiler. DO NOT turn off
water supply. W hen discharge
stops check all thermal
controls, replace if faulty.
"Milky" water Oxygenated water W ater from a pressurised
system releases oxygen
bubbles when flowing. The
m ilkiness will disappear after a
short while.
WARNING

15
9.0 USER INSTRUCTIONS
9.1 WARNINGS
IFWATER ISSUES FROM THE TEMPERATURE/
PRESSURE RELIEFVALVE ON THE HEATSTORE
HSU SWITCH OFFELECTRICALSUPPLYTO THE
IMMERSION HEATER(S) (DIRECT UNITS) OR
SHUT DOWN THE BOILER (INDIRECT UNITS). DO
NOTTURN OFFANYWATER SUPPLY. CONTACT
ACOMPETENT INSTALLER FOR UNVENTED WA-
TER HEATERS TO CHECKTHE SYSTEM.
DO NOT TAMPER WITH ANY OF THE SAFETY
VALVES FITTED TO THE HEATSTORE HSU SYS-
TEM. IFA FAULT IS SUSPECTED CONTACT A
COMPETENTINSTALLER.
9.2 TEMPERATURE CONTROLS – DIRECT UNIT
IMMERSION HEATER(S)
A combined adjustable thermostat and thermal cut-
out is provided for each immersion heater. The ther-
mostat is factory set to give a water storage tempera-
ture of approx. 55oto 60oC. Access to the thermostat
can be made by opening the immersion heater cover -
DISCONNECT THE ELECTRICAL SUPPLY BEFORE
OPENING THE COVER(S). Temperature adjustment is
made by inserting a flat bladed screwdriver in the slot
on the adjustment disc on top of the thermostat and
rotating. The adjustment range 1 to 5 represents a
temperature range of 10oto 70oC (60oC will be approxi-
mately position 4). If in any doubt contact a compe-
tent electrician.
DO NOT bypass the thermal cut-out(s) in any cir-
cumstances.
9.3 TEMPERATURE CONTROLS – INDIRECT
UNITS (Fig. 9)
The Heatstore HSU Indirect units are fitted with an
Indirect Thermostat and Thermal Cut-out. These con-
trols must be wired in series with the 2 port motorised
zone valve supplied to interupt the flow of primary
water around the heat exchanger coil when the con-
trol temperature has been reached. The controls are
located within the lower grey terminal housing along
with the immersion heater thermostat. The thermostat
is factory set to give a water storage temperature of
approx. 55oto 60oC. Access to the thermostat can be
made by opening the terminal housing cover - DIS-
CONNECT THE ELECTRICAL SUPPLY BEFORE
OPENING THE COVER. Temperature adjustment is
made by inserting a flat bladed screwdriver in the ad-
justment knob and rotating. The minimum thermostat
setting is 10oC. The adjustment range 1 to 5 repre-
sents a temperature range of 30oto 70oC (60oC will be
approximately position 4). If in any doubt contact a
competent electrician.
On indirect units an immersion heater is also provided
for use should the indirect heat source be shut down
for any purpose. The immersion heater control tem-
perature is set using the same adjustment knob as
that for the indirect heat source.
DO NOT bypass the thermal cut-out(s) in any cir-
cumstances.
9.4 FLOW PERFORMANCE
When initially opening hot outlets a small surge in
flow may be noticed as pressures stabilize. This is
quite normal with unvented systems. In some areas
cloudiness may be noticed in the hot water. This is
due to aeration of the water, is quite normal and will
quickly clear.
9.5 OPERATIONALFAULTS
Operational faults and their possible causes are de-
tailed in Section 8.0. It is recommended that faults
should be checked by a competent installer.
The air volume within the expansion vessel will peri-
odically require recharging to ensure expanded water
is accommodated within the unit. A discharge of water
INTERMITTENTLY from the Expansion Valve will in-
dicate the air volume has reduced to a point where it
can no longer accommodate the expansion.

16
10.0 GUARANTEE
This product is guaranteed against faulty materials
and manufacture for a period of 10 years from date of
purchase (with the exception of the Expansion Vessel
which is guaranteed for a period of 5 years and valves,
fittings and electrical parts which are guaranteed
for a period of 2 years) provided that:
• The unit has been installed in accordance with
the Installation and Service instructions and all rel-
evant Codes of Practice and Regulations in force at
the time of installation, and that all necessary inlet
controls and safety valves have been fitted correctly.
• Any valves and controls are of the Heatstore rec-
ommended type and specification.
• It has only been used for the storage of potable
water.
• The unit has not been modified or tampered with
in any way, and has been regularly maintained as de-
tailed in the Installation and Service instructions.
The unit is not guaranteed against damage by frost,
and the inner container with integral immersion
heater(s) is not guaranteed against excessive scale
build-up.
Periodic loss of charge pressure from the Expansion
Vessel is normal (indicated by an intermittent discharge
of water from the Expansion Valve) and is not cov-
ered under the product guarantee. Refer to Section 7.5
for details on how to restore the Expansion Vessel
charge pressure.
This guarantee does not affect your statutory rights.
ENVIRONMENTAL INFORMATION
The Heatstore HSU products are manufactured from many
recyclable materials. At the end of their useful life they
should be disposed of at a Local Authority Recycling Cen-
tre in order to realise the full environmental benefits.
Insulation is by means of an approved CFC/HCFC free
polyurethane foam with an ozone depletion factor of zero.
The policy of Heatstore is one of continuous product development and, as such, we reserve the right to change
specifications without notice.
Island Park
Bristow Broadway
BRISTOL
BS11 9FB
Tel: [phone]
Fax: [phone]