159979-10.pmd

istor system store -

Installation and Servicing

GENERAL

Boiler size

istor HE260

istor HE325

Gas supply

2H - G20 - 20mbar

Gas Supply Connection

Rc 1/2 (1/2" BSP female)

Injector size

Stereomatic 5.6mm dia.

Inlet Connection

Domestic Hot Water

22mm copper

Outlet Connection

Domestic Hot Water

22mm copper

Flow Connection

Central Heating

22mm copper

Return Connection

Central Heating

22mm copper

Flue Terminal Diameter

mm (in)

100 (4)

Average flue temp/mass flow rate

(DHW)

C / 20.3g/s

Maximum Working Pressure (Sealed Systems)

bar (lb/in

)

2.65 (38.5)

Maximum Domestic Hot Water Inlet Pressure

bar (lb/in

)

10.0 (145)

Minimum Domestic Hot Water Inlet Pressure

bar (lb/in

)

0.5 (7)

Maximum Domestic Hot Water Outlet Pressure

bar (lb/in

)

2.0 (29)

Temperature & Pressure relief valve

Preset 95

C / 4.0 Bar opening

Electrical Supply / Power consumption

230 V ~ 50 Hz. / 148 W

Fuse Rating

External : 3A

Internal : 3.15A TL250 V

Water content

Central Heating litre (gal)

2.0 (.44)

Domestic Hot Water

80 litre

120 litre

Packaged Weight - Boiler box

kg (lb)

58.5 (129)

Packaged Weight - Tank box

kg (lb)

66 (145)

73 (161)

Maximum Installation Weight -Boiler box

kg (lb)

55 (121)

Maximum Installation Weight -Tank box

kg (lb)

59 (130)

65 (143)

Boiler Casing Size

Height mm (in)

1400 (55)

1600 (63)

Width mm (in)

560 (22)

Depth mm (in)

600 (23.6)

Potable water components on tank module
Pressure reducing valve

preset to 2 bar

Thermostatic mixer

max inlet temp 85

C/max pressure 14 bar

Pressure and temp relief valve on cylinder

C and 4 bar

Pressure relief valve on inlet manifold

3 bar

DHW expansion vessel

19 litres, precharged to 2 bar

Table 1 - General Data

Note. Gas consumption is calculated using a
calorific value of 38.7 MJ/m

(1038 Btu/ft

)

gross or 34.9 MJ/m

(935 Btu/ft

) nett

To obtain the gas consumption at a different
calorific value:
a. For l/s - divide the gross heat input (kW) by

the gross C.V. of the gas (MJ/m

)

b. For ft

/h - divide the gross heat input (Btu/

h) by the gross C.V. of the gas (Btu/ft

)

Key to symbols
IE =

Ireland, GB = United Kingdom (Countries of destination)

PMS = Maximum operating pressure of water
C

= A room sealed appliance designed for connection via ducts to a

horizontal or vertical terminal, which admits fresh air to the burner
and discharges the products of combustion to the outside through
orifices which, in this case, are concentric. The fan is up stream
of the combustion chamber.

= An appliance designed for use on 2nd Family gas, Group H only.

* The value is used in the UK Government's Standard Assessment Procedure (SAP) for energy rating of dwellings. The test data from

which it has been calculated have been certified by a notified body.

CAUTION.

To avoid the possibility of injury during the installation, servicing or cleaning

of this appliance, care should be taken when handling edges of sheet steel components.

Table 2 - Performance Data - Central Heating

Maximum DHW Input :

Nett CV

30.2

(Btu/h)

(103 100)

Gross CV

33.5

(Btu/h)

(114 300)

Gas Consumption

l/s

0.87

(ft

/h)

(110)

Maximum DHW Output

29.3

(Btu/h)

(100 000)

DHW Storage Temp

DHW Delivery Temp

Factory set

Variable on Installation only

C-65

DHW Flow Rate

HE260 HE325

(Practical maximum assuming
suitable mains supply)

l/min

DHW Recovery from 15

min.

After 70% draw off

min.

Table 3 - Performance Data - Domestic Hot Water

Boiler Input :

Max.

Min.

Nett CV

24.4

9.1

(Btu/h)

(83 300)

(31 000)

Gross CV

27.1

10.1

(Btu/h)

(92 500)

(34 400)

Gas Consumption

l/s

0.70

0.26

(ft

/h)

(89.1)

(33.2)

Boiler Output :

Non Condensing

23.4

8.8

(Btu/h)

(80 000)

(30 000)

Condensing

25.1

9.6

(Btu/h)

(83 700)

(32 800)

Seasonal efficiency (SEDBUK)*

Band A [90.1]%

NOx Classification

Class 5

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Installation and Servicing

GENERAL

CONTENTS

Air Supply ....................................................................... 9
Benchmark Commissioning Checklist ..................... 68
Boiler Clearances ......................................................... 8
Boiler Exploded Diagram ................................. 15,16,17
Condensate Drain ....................................................... 11
Electrical Connections ............................................... 30
Electrical Supply ......................................................... 11
Extension Ducts - Fitting ............................................. 28
Fault Finding ........................................................... 58-61
Flow Wiring Diagram .................................................. 33
Flue Fitting

Rear outlet .............................................................. 25
Side outlet .............................................................. 25

Flue Installation ............................................................. 9
Gas Safety Regulations ................................................ 7
Gas Supply ..................................................................... 9
Installation ............................................................. 16-36
Mandatory Requirements ....................................... 7-15
Pump .......................................................................... 53
Safe Handling ................................................................ 6
Servicing ................................................................ 37-57
Short List of Parts ....................................................... 62
Thermostatic Radiator valves ................................... 11
Water and Systems .............................................. 12-14
Water Connections ............................................... 19-20
Water Treatment ......................................................... 15
Wiring Diagrams ................................................... 30-33

Destination Countries: UK, IE

oiler

Page

Make and model ....................................................... 5
Appliance serial no. on data badge ...................... 16
SEDBUK No. % ......................................................... 4

Controls

Time and temperature control to heating ............. 31
Time and temperature control to hot water .......... 31
Heating zone valves .............................................. n/a
TRV's ....................................................................... 11
Auto bypass ............................................................ 11
Boiler interlock ........................................................ 11

For all boilers

Flushing to BS.7593 .............................................. 13
Inhibitor .................................................................. 13

Central heating mode
Heat input ................................................ to be calculated

For assistance see Technical Helpline on the back page

Page

Burner operating pressure ...... measure and record
Central heating flow temp. ...... measure and record
Central heating return temp. ... measure and record

For combination boilers only

Scale reducer ......................................................... n/a

Hot water mode

Heat input ............................................................... n/a
Max. operating burner pressure .............................. n/a
Max. operating water pressure ............................. n/a
Cold water inlet temp ............................................ n/a
Hot water outlet temp. ........................................... n/a
Water flow rate at max. setting .............................. n/a

For condensing boilers only

Condensate drain .................................................. 22

For all boilers: complete, sign & hand over to customer

For GB, to comply with Building Regulations Part L1 (Part J in Scotland) the boiler should be fitted in accordance with the
manufacturer's instructions. Self-certification that the boiler has been installed to comply with Building Regulations can be
demonstrated by completing and signing the Benchmark Commissioning Checklist.

istor

Natural Gas only

Boiler size

G.C. Appliance No.

PI No.

(Benchmark No.)

HE260

41-394-13

0063 BM 3094

HE325

41-394-14

0063 BM 3094

BENCHMARK COMMISSIONING CHECKLIST DETAILS

NOTE TO THE INSTALLER: COMPLETE

THE BENCHMARK COMMISSIONING

CHECKLIST AND LEAVE THESE

INSTRUCTIONS WITH APPLIANCE

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Installation and Servicing

GENERAL

1 BOILER WATER CIRCUIT DIAGRAMS

INTRODUCTION

The istor HE260 & HE325 boilers are a fully automatically controlled,
condensing, system store, fanned flue, gas boiler.
Note. Due to the high efficiency of the boiler a plume of water vapour
will form at the terminal during operation.
Central heating (CH) output is fully modulating with a range of:

8.8 to 23.4kW (30,000 to 80,000 Btu/h)

Domestic hot water (DHW) output to the cylinder is also fully
modulating with a maximum of:

29.3kW (100,000 Btu/h)

The boiler is supplied fully assembled with an unvented DHW cylinder,
diverter valve, circulating pump, CH & DHW expansion vessels,
pressure gauge, safety valves, thermostatic mixer valve. A pressure
reducing valve is supplied for fitting externally to the boiler.
Variable CH temperature control is fitted on the user control.
A programmer is fitted as standard.
The boiler casing is of white painted zintec coated mild steel.
The boiler temperature controls are visible at the middle RHS of the
front panel.
The heat exchanger is of cast aluminium.
The DHW cylinder is made of copper with a rapid recovery coil and
produces mains pressure hot water to a maximum pressure of 2 bar.
The system pipework MUST include drain cocks in appropriate places.
A prepiping frame is provided with the boiler which allows pipework to
be made to the boiler before installation of the tank module and boiler
module.
Note. Prior to installation this appliance must be stored in a dry, upright
condition.
Due note should be taken of the carton labelling when handling this
appliance.

OPERATION

With no demand for CH the boiler fires only when DHW is drawn off, or
periodically for a few seconds without any DHW draw-off, in order to
maintain the DHW cylinder in a heated condition.
When there is a demand for CH, the heating system is supplied at the
selected temperature of between 30

C and 82

C, until DHW is drawn

off. The full output from the boiler is then directed via the diverter valve
to the cylinder coil to satisfy the cylinder store temperature of 70

DHW temperature is controlled to a factory set 60

C via a thermostat

mixer valve. This is adjustable on installation.

The boiler features a comprehensive diagnostic system which gives
detailed information on the boiler status when operating, and
performance of key components to aid commissioning and fault
finding.

SAFE HANDLING

This boiler may require 2 or more operatives to move it to its
installation site, remove it from its packaging base and during
movement into its installation location. Manoeuvring the boiler may
include the use of a sack truck and involve lifting, pushing and pulling.
Caution should be exercised during these operations.
Operatives should be knowledgeable in handling techniques when
performing these tasks and the following precautions should be
considered:
·

Grip the boiler at the base.

Be physically capable.

Use PPE as appropriate, e.g. gloves, safety footwear.

During all manoeuvres and handling actions, every attempt should be
made to ensure the following unless unavoidable and/or the weight is
light.

ist8330

Central Heating Circuit

C H Return

CH Flow

CH Pressure gauge

Pressure relief valve

Pump

Filling loop

Diverter valve

Domestic Hot Water Circuit

DHW Expansion

vessel

DHW

Thermostatic

mixer valve

ist8331

DHW Flow

Cold water in

Hot water out

DHW Temp

& Pressure

relief valve

DHW

Return

Keep back straight.

Avoid twisting at the waist.

Avoid upper body/top heavy bending.

Always grip with the palm of the hand.

Use designated hand holds.

Keep load as close to the body as possible.

Always use assistance if required.

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Installation and Servicing

GENERAL

OPTIONAL EXTRA KITS

Flue Kits (for more details see pages 10 & 11).
Condensate pump Kit.
90

Elbow Kit (max 4 elbows/ installation).

Remote User controls.

SAFETY

Installation of this boiler as an unvented hot water system falls
within the scope of the Building Regulations 1995 (Part G).
These require that installation of an `unvented' system shall be
notified to the local authority Building Control Department: also
that the work must be carried out by a competent person as
defined in the Approved Document G3.

Current Gas Safety (installation and use) regulations or rules
in force:

The appliance is suitable only for installation in GB and IE and
should be installed in accordance with the rules in force.

In GB, the installation must be carried out by a CORGI
Registered Installer. It must be carried out in accordance with
the relevant requirements of the:
·

Gas Safety (Installation and Use) Regulations

The appropriate Building Regulations either The Building
Regulations, The Building Regulations (Scotland), Building
Regulations (northern Ireland).

The Water Fittings Regulations or Water byelaws in
Scotland.

The Current I.E.E. Wiring Regulations.

Where no specific instructions are given, reference should be
made to the relevant British Standard Code of Practice.
In IE, the installation must be carried out by a Competent
Person and installed in accordance with the current edition of
I.S.813 "Domestic Gas Installations", the current Building
Regulations and reference should be made to the current ETCI
rules for electrical installation.
Detailed recommendations are contained in the following British
Standard Codes of Practice:
BS. 5440:1

Flues (for gas appliances of rated input not
exceeding 70 kW).

BS. 5440:2

Ventilation (for gas appliances of rated input not
exceeding 70 kW).

BS. 5449

Forced circulation hot water systems.

BS. 5546

Installation of gas hot water supplies for
domestic purposes (2nd Family Gases)

BS. 6798

Installation of gas fired hot water boilers of rated
input not exceeding 60 kW.

BS. 6891

Low pressure installation pipes.

Health & Safety Document No. 635.

The Electricity at Work Regulations, 1989.

The manufacturer's notes must NOT be taken, in any way, as
overriding statutory obligations.

IMPORTANT. These appliances are CE certificated for safety
and performance. It is, therefore, important that no external
control devices, e.g. flue dampers, economisers etc., are
directly connected to these appliances unless covered by these
Installation and Servicing Instructions or as otherwise
recommended by Caradon Ideal Limited in writing. If in doubt
please enquire.

Any direct connection of a control device not approved by
Caradon Ideal Limited could invalidate the certification and the
normal appliance warranty. It could also infringe the Gas Safety
Regulations and the above regulations.

SAFE HANDLING OF SUBSTANCES

Care should be taken when handling the boiler insulation
panels, which can cause irritation to the skin. No asbestos,
mercury or CFCs are included in any part of the boiler or its
manufacture.

LOCATION OF BOILER AND FLUE OUTLET

The boiler is floor mounted. The floor must be capable of
adequately supporting the weight of the boiler and any ancillary
equipment.

The boiler may be fitted on a combustible floor and insulation
between the floor and the boiler is not necessary, unless
required by the local authority.

For electrical safety reasons there must be no access available
from the back of the boiler.

The boiler must not be fitted outside.

Timber Framed Buildings
If the boiler is to be fitted in a timber framed building it should be
fitted in accordance with the Institute of Gas Engineering
document IGE/UP/7:1998.
Where installation will be in an unusual location, special
procedures may be necessary and BS 6798 gives detailed
guidance on this aspect.

Compartment Installations

A compartment used to enclose the boiler should be designed
and constructed specially for this purpose.

An existing cupboard or compartment may be used, provided
that it is modified for the purpose.

In both cases, details of essential features of cupboard /
compartment design, including airing cupboard installation, are
to conform to the following:

BS 6798 (No cupboard ventilation is required - see air supply
for details).

The position selected for installation MUST allow adequate
space for servicing in front of the boiler.

For the minimum clearances required for safety and
subsequent service, see Frame 2. In addition, sufficient
space may be required to allow lifting access for the boiler
module.

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Installation and Servicing

GENERAL

BOILER DIMENSIONS, SERVICES & CLEARANCES

all dimensions in mm (in)

The boiler connections are made on the boiler piping frame.
Refer to Frame 22.

The following minimum clearances must be maintained for
operation and servicing.

Additional space will be required for installation, depending
upon site conditions.

Side and Rear Flue
a Provided that the flue hole is cut accurately, e.g. with a core

drill, the flue can be installed from inside the building where
wall thicknesses do not exceed 600mm (24"). Where the
space into which the boiler is going to be installed is less
than the length of flue required the flue must be fitted from
the outside.

Front clearance
The minimum front clearance when built in to a cupboard is
5mm (1/4") from the cupboard door but 450mm (17 3/4")
overall clearance is still required, with the cupboard door open,
to allow for servicing.

ist8386

119.5 (4

") Cold mains feed

Installation from inside ONLY
b. If a core boring tool is to be used inside the building

the space in which the boiler is to be installed must
be at least wide enough to accommodate the tool.

Boiler

HE260 HE325

LH Flue Dim A

m m

1477

1677

RH Flue Dim B

m m

1480

1680

Rear Flue Dim C

m m

1476

1676

If fitted to minimum clearances, the following dimensions
apply:

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Installation and Servicing

GENERAL

TERMINAL

The terminal assembly can be adapted to accommodate
various wall thicknesses. Refer to Frame 26.

AIR SUPPLY

It is NOT necessary to have a purpose-provided air vent in the
room or internal space in which the boiler is installed. Neither
is it necessary to ventilate a cupboard or compartment in which
the boiler is installed, due to the low surface temperatures of
the boiler casing during operation; therefore the requirements
of BS 6798, Clause 12, and BS 5440:2 may be disregarded. In
IE the requirement of IS 813:2002 may be disregarded.

WATER CIRCULATION SYSTEM

The central heating system should be in accordance with BS.
6798 and, in addition, for smallbore and microbore systems,
BS. 5449.
Draining taps MUST be located in accessible positions, which
permit the draining of the whole system. They should be at
least 1/2" BSP nominal size and be in accordance with BS
2879.

WATER TREATMENT - see Frame 9

GAS SUPPLY

The local gas supplier should be consulted, at the installation
planning stage, in order to establish the availability of an
adequate supply of gas. An existing service pipe must NOT be
used without prior consultation with the local gas supplier.
The boiler MUST be installed on a gas supply with a governed
meter only.
A gas meter can only be connected by the local gas supplier or
by a registered CORGI engineer. In IE by a competent person.
An existing meter should be checked, preferably by the gas
supplier, to ensure that the meter is adequate to deal with the
rate of gas supply required.
N.B.

The principle of the 1:1 gas valve ensures that the istor
is able to deliver its full output at inlet pressures well
below those required by BS. 6891.

IMPORTANT.

Installation pipes must be fitted in accordance with BS.6891. In
IE refer to IS.813:2002. Pipework from the meter to the boiler
MUST be of an adequate size, i.e. no longer than 20m and not
less than 15mm O.D.
The complete installation MUST be tested for gas soundness and
purged as described in the above code.

FLUE INSTALLATION

Pluming will occur at the terminal so terminal positions where
this could cause a nuisance should be avoided.
The flue must be installed in accordance with the
recommendations of BS. 5440-1: 2000.
In IE refer to I.S. 813:2002.
Do not use pipes of a smaller size than the boiler inlet gas connection.
The following notes are intended for general guidance:
1. The boiler MUST be installed so that the terminal is exposed

to external air.

2. It is important that the position of the terminal allows the free

passage of air across it at all times.

3. Minimum acceptable spacing from the terminal to obstructions

and ventilation openings are specified in Table 4.

4. Where the lowest part of the terminal is fitted less than 2m

(6'6") above a balcony, above ground or above a flat roof to
which people have access then the terminal MUST be
protected by a purpose designed guard.
Terminals guards are available from boiler suppliers. In
case of difficulty seek advice from:

Grasslin (UK) Ltd.,
Vale Rise, Tonbridge, Kent TN9 1TB
Telephone No. 01732 359 888

Ensure that the guard is fitted centrally.

5. Where the terminal is fitted within 850mm (34") of a plastic or

painted gutter or 450mm (18") of painted eaves then an
aluminium shield at least 750mm (30") long should be fitted
to the underside of the gutter or painted surface fitted
centrally above the flue.

6. The air inlet/products outlet duct and the terminal of the

boiler MUST NOT be closer than 25mm (1") to combustible
material. Detailed recommendations on the protection of
combustible material are given in BS. 5440: Part 1, 2000. In
IE refer to IS 813:2002.

IMPORTANT. It is absolutely essential to ensure, in practice, that
products of combustion discharging from the terminal cannot re-
enter the building or any other adjacent building through
ventilators, windows, doors, other sources of natural air
infiltration, or forced ventilation / air conditioning.
If this should occur the appliance MUST be turned OFF, labelled
as 'unsafe' until corrective action can be taken.

Flue Terminal Positions

Min. Spacing*

1. Directly below or alongside an opening

window, air vent or other ventilation opening.

300mm (12")

2. Below guttering, drain pipes or soil pipes.

25mm ( 1")*

BS5440-1 2000

75mm (3")

3. Below eaves.

25mm (1")*

BS5440-1 2000

200mm (8")

4. Below balconies or a car port roof.

25mm (1")*

BS5440-1 2000

200mm (8")

5. From vertical drain pipes or soil pipes.

25mm (1")*

BS5440-1 2000

150mm (6")

6. From an internal or external corner or to a

25mm (1")*

boundary along side the terminal.

BS5440-1 2000

300mm (12")

7. Above adjacent ground, roof or balcony level.

300mm (12")

8. From a surface or a boundary facing the terminal.

600mm (24")

9. From a terminal facing a terminal.

1,200mm (48")

10. From an opening in a car port

(e.g. door or window) into dwelling.

1,200mm (48")

11. Vertically from a terminal on the same wall.

1,500mm (60")

12. Horizontally from a terminal on the wall.

300mm (12")

Vertical Terminals

13. Above the roof pitch with roof slope of all angles. 300mm (12")

Above flat roof.

300mm (12")

14. From a single wall face.

600mm (24")

From corner walls.

1000mm (40")

Twin Flue Applications

15. Centre distance between air inlet and flue

outlet ducts.

120mm (5")

Table 4 - Balanced Flue Terminal Position

* Only one reduction down to 25mm is allowable per installation
otherwise BS5440-1 2000 dimensions must be followed.

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Installation and Servicing

GENERAL

THERMOSTATIC RADIATOR VALVES (TRV)

Caradon Ideal Limited recommend that heating systems
utilising full thermostatic radiator valve control of temperature in
individual rooms should also be fitted with a room thermostat
controlling the temperature in a space served by radiators not
fitted with such a valve as stated in BS. 5449.

When thermostatic radiator valves are used, the space heating
temperature control over a living area having a heating
requirement of at least 0.9kW (3000Btu/h) of the boiler heat
output should be achieved using a room thermostat whilst other
rooms are individually controlled by thermostatic radiator valves.
A higher proportion of TRVs may be used, provided that a
bypass between the boiler flow and return is fitted, to ensure
adequate flow when all TRVs are closed - however this is NOT
recommended as a large proportion of TRVs can restrict water
circulation and inhibit the condensing mode of condensing
boilers, reducing fuel economy.

For further information refer to the 'Good Practice Guide 143', a
publication of the Energy Efficiency Office, available from the
Building Research Establishment, Garston, Watford WD2 7JR.
Tel: +44 (0) 1923 664258.

ELECTRICAL SUPPLY

WARNING. This appliance MUST be earthed,

Wiring external to the appliance MUST be in accordance with
the current I.E.E. (BS.7671) Wiring Regulations and any local
regulations which apply. For IE reference should be made to
the current ETCI rule for electrical installations.

The point of connection to the mains should be readily
accessible and adjacent to the boiler.

CONDENSATE DRAIN - Refer to Frame 20

A condensate drain is provided on the boiler. This drain must
be connected to a drainage point on site. All pipework and
fittings in the condensate drainage system MUST be made of
plastic - no other materials may be used.

IMPORTANT.

Any external runs must be insulated

The drain outlet on the boiler is standard 3/4in (21.5mm)
overflow pipe.

FLUING OPTIONS

Twin fluing kit.

80/80 kit to a maximum of 46m combined flue and air duct.

60/60 kit to a maximum of 20m combined flue and air duct
(horizontal applications only).

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Installation and Servicing

GENERAL

SYSTEM REQUIREMENTS - Central Heating

Notes

a. The method of filling, refilling, topping up or flushing sealed

primary hot water circuits from the mains via a temporary
hose connection is only allowed if acceptable to the local
water authority.

b. Antifreeze fluid, corrosion and scale inhibitor fluids suitable

for use with boilers having aluminium heat exchangers may
be used in the central heating system.

Advice should be sought from a local water treatment
company.

General
1. The installation must comply with all relevant national and

local regulations.

2. The installation should be designed to work with flow

temperatures of up to 82

3. All components of the system must be suitable for a working

pressure of 3 bar and temperature of 110

C. Extra care

should be taken in making all connections so that the risk of
leakage is minimised.
The following components are incorporated within the
appliance for the central heating:
a. Circulating pump.
b. Safety valve, with a non-adjustable preset lift pressure

of 3 bar.

c. Pressure gauge, covering a range of 0 to 6 bar.
d. A 8-litre expansion vessel, with an initial charge pressure

of 1.0 bar.

e. Diverter valve.
f.

Filling loop.

4. 'Make-up' Water. Provision is made for replacing water loss

from the system, via a filling loop supplied and fitted to the
appliance.
Note.
The maximum cold water capacity of the system should
not exceed 143 litres, if not pressurized. However, if the
system is to be pressurized, the efficiency of the
expansion vessel will be reduced and a larger vessel (or
smaller system volume) may be necessary. If the capacity
of the vessel is not considered sufficient for this, or for any
other reason, an additional vessel MUST be installed on
the return to the boiler.

Guidance on vessel sizing is given above.

5. Filling. The system should be filled by the following

method:
a. Through the filling loop fitted to the appliance.

Connecting the inlet manifold to the CH return.

Thoroughly flush out the whole system with
cold water.

ii.

Fill and vent the system until the pressure
gauge registers 1.5 bar, and examine for leaks.

iii. Check the operation of the safety valve by

raising the water pressure until the valve lifts.
This should occur within 0.3 bar of the preset lift
pressure.

iv. Release water from the system until the

minimum system design pressure is reached;
1.0 bar if the system is to be pre-pressurised.

Water Flow Rate and Pressure Loss

Max CH Output

23.4

(Btu/h)

(80 000)

Water flow rate

l/sec

0.37

(gal/min)

4.8

Temperature Differential

(

(27)

Head available for

m.w.g.

2.3

system pump.

(ft.w.g.)

7.5

Safety valve setting

bar

3.0

Vessel charge pressure

bar

0.5 to 0.75

System pre-charge pressure bar

None

1.0

System volume

Expansion vessel

(litres)

volume (litres)

1.6

1.8

3.1

3.7

4.7

5.5

100

6.3

7.4

125

7.8

9.2

150

9.4

11.0

175

10.9

12.9

190

11.9

14.0

200

12.5

14.7

250

15.6

18.4

300

18.8

22.1

For other system volumes
multiply by the factor across

0.063

0.074

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istor system store condensing -

Installation and Servicing

GENERAL

SYSTEM REQUIREMENTS - Domestic Hot Water

Domestic Hot Water Requirements (see note in Frame 15).
1. The domestic hot water service must be in accordance

with BS 5546 and BS 6700.

2. Refer to Table 1 for minimum and maximum working

pressures.

3. The boilers are suitable for connection to most types of

washing machine and dishwasher appliances.

4. When connecting to suitable showers, ensure that:

a. The cold inlet to the boiler is fitted with an approved

anti-vacuum or syphon non-return valve.

b. Hot and cold water supplies to the shower are of

equal pressure.

5. Hard Water Areas

Where the water hardness exceeds 200mg/litre, it is
recommended that a proprietary scale reducing device
is fitted into the boiler cold supply within the
requirements of the local water company.

Note.
Attention is drawn to the following extracts from the Building
Regulations 1991.
Regulation 11(1) (Giving of a building notice or deposit of
plans)
"Subject to the following provisions of this regulation, a
person who intends to carry out building work or to make a
material change of use shall:
a. Give to the local authority* a building notice in accordance

with 12; or

b. Deposit full plans with the local authority* in accordance

with regulation 13".

Regulation 12(4) (Particulars and plans where a building
notice is given)
".......a building notice shall be accompanied by a statement
which specifies:
*Attention is drawn to regulation 18 (supervision of building
work otherwise than by local authorities).
a. The name, make, model and type of hot water storage

system to be installed;

b. The name of the body, if any, which has approved or

certified that the system is capable of performing in a way
which satisfies the requirements of paragraph G3 of
Schedule 1;

c. The name of the body, if any, which has issued any current

registered operative identity card to the installer or
proposed installer of system."

Regulation 13(3) (Full plans)
"Full plans shall consist of:
a. Description of the proposed building work or material

change of use, and the plans, particulars and statements
required by paragraphs (1) to (4) of regulation 12: and...."

Note.
Bye-laws of the appropriate Water Undertake also apply.
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 persons in or about the
building. The tundish and discharge pipes should be fitted in
accordance with requirements and guidance notes of
Building Regulation 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 Building Control Officer or Caradon
Ideal Limited.
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.
Note.
The tundish is factory fitted during manufacture of the istor.
The discharge pipe (D2) from the tundish should terminate
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 equivalent
hydraulic resistance exceeds that of 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 calculating the flow
resistance. Refer to
An alternative approach for sizing discharger pipes would
be to follow BS 67100:1987 specification for design
installation, testing and maintenance of services
supplying water for domestic use within buildings and
their curtilages. Appendix E. section E2 and table 21.

b. Have a vertical section of 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 in not possible or is
practically difficult there should be clear visibility 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
standings, grassed areas etc. are acceptable
providing that where children may play or otherwise
come into contact with discharges a wire cage or
similar guard is positioned to prevent contact whilst
maintaining visibility.

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
discharges of water and 3m from any plastic
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
installation discharging can be traced reasonably
easily. The single common discharge pipe should
be at least on 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 dwellings occupied by blind , infirm
or disabled people, consideration should be given to

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Installation and Servicing

GENERAL

Valve

Minimum

Maximum resistance

Resistance

outlet

discharge discharge

allowed, expressed

created by

size

pipe D1

pipe D2

as a length of straight

each elbow

from tunish pipe (i.e. no elbow or bends) or bend
22mm

up to 9m

0.8m

G1/2

15mm

28mm

up to18m

1.0m

35mm

up to 27m

1.4m

28mm

up to 9m

1.0m

35mm

up to 18m

1.4m

G3/4

22mm

42mm

up to 27m

1.7m

35mm

up to 9m

1.4m

28mm

42mm

up to 18m

1.7m

54mm

up to 27m

2.4m

SYSTEM REQUIREMENTS - Domestic Hot Water (continued)

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 rain water goods may be
damaged by such discharges.
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 1:
Maximum resistance allowed for a straight
length of 22mm copper discharge pipe
(D2) from a G1/2 temperature 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 min (D2) copper pipe will
be satisfactory.
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
warranty claim.
Table 1. Sizing if copper discharge pipe (D2) for common
temperature relief valve outlet sizes.
Control and safety valves MUST NOT be tampered with.

The discharge pipe MUST NOT be blocked or used for
any other purpose.
The tundish must not be removed.
Electrical components must not be sited near the
tundish.

The boiler does not normally need a bypass but at least
some radiators on the heating circuit, of load of at least
10% of the minimum boiler output, must be provided
with tw