Glow-worm Ultimate 120FF Instructions For Use Installation And Servicing

Instructions for Use

Installation and Servicing

To be left with the user

100FF 120FF

G.C. No. 41 047 59 G.C. No. 41 319 75

221966B.04.03

4272

Fanned Flue Boiler

BS 6332
BS 5258

This is a Cat I2H Appliance

Reference in these instructions to British Standards and Statutory

Regulations/Requirements apply only to the United Kingdom.

The instructions consist of three parts, User, Installation and Servicing Instructions, which includes the Guarantee Registration

For Ireland the rules in force must be used.

Card. The instructions are an integral part of the appliance and must, to comply with the current issue of the Gas Safety

(Installation and Use) Regulations, be handed to the user on completion of the installation.

Guarantee Registration

Thank you for installing a new Glow-worm appliance in your home.

Glow-worm appliances' are manufactured to the very highest standard so we are pleased

to offer our customers' a Comprehensive First Year Guarantee.

In the centre pages are to be found your Guarantee Registration Card, which we recommend you complete and

return as soon as possible.

If this card is missing you can obtain a copy or record your registration by telephoning the Heatcall Customer

Service number 01773 828100.

Our Guarantee gives you peace of mind plus valuable protection against breakdown by covering the cost of:

✔

All replacement parts

❏

✔

All labour charges

❏

All call-out charges

✔

❏

One Contact Local Service

REGISTER YOUR GLOW-WORM APPLIANCE

FOR 1ST YEAR GUARANTEE PROTECTION

CALL 0208 247 9857

Customer Services:

Tel: [phone]

Fax: [phone]

Nottingham Road, Belper, Derbyshire. DE56 1JT

Tel: [phone] Fax: [phone]

Hepworth Heating Ltd.,

General/Sales enquiries:

Important Information

Testing and Certification

This boiler is tested and certificated for safety and performance. It is therefore important that no alteration is made to the boiler, without
permission, in writing, from Hepworth Heating Ltd.

Any alteration not approved by Hepworth Heating Ltd., could invalidate the certification, boiler warranty and may also infringe the
current issue of the Statutory Requirements, see Section 1.4.

CE Mark

This boiler meets the requirements of Statutory Instrument No. 3083 The boiler (Efficiency) Regulations, and therefore is deemed
to meet the requirements of Directive 92/42/EEC on the efficiency requirements for new hot water boilers fired with liquid or gaseous
fuels.

Type test for purposes of Regulation 5 certified by: Notified body 0086.

Product/productioncertifiedby: Notified body 0086.

The CE mark on this appliance shows compliance with:

1. Directive 90/396/EEC on the approximation of the laws of the Member States relating to appliances burning gaseous fuels.

2. Directive 73/23/EEC on the harmonization of the Laws of the Member States relating to the electrical equipment designed
for use within certain voltage limits.

3. Directive 89/336/EEC on the approximation of the Laws of the Member States relating to electromagnetic compatibility.

INFORMATION FOR THE INSTALLER AND SERVICE ENGINEER.

Under Section 6 of The Health and Safety at Work Act 1974, we are required to provide information on substances hazardous to
health.

REFRACTORY CERAMIC FIBRE

This product uses insulation material containing Refractory Ceramic Fibre (RCF), which are man-made vitreous silicate fibres.
Excessive exposure to these materials may cause temporary irritation to eyes, skin and respiratory tract, consequently, it makes
sense to take care when handling these articles to ensure that the release of dust is kept to a minimum.

To ensure that the release of fibres from these RCF articles is kept to a minimum, during installation and servicing we recommend
that you use a HEPA filtered vacuum to remove any dust accumulated in and around the boiler before and after working on the boiler.
When replacing these articles we recommend that the replaced items are not broken up, but are sealed within heavy duty polythene
bags, clearly labelled as RCF waste. This is not classified as “hazardous waste” and may be disposed of at a tipping site licensed
for the disposal of industrial waste. Protective clothing is not required when handling these articles, but we recommend you follow
the normal hygiene rules of not smoking, eating or drinking in the work area and always wash your hands before eating or drinking.

INSULATION PADS, GLASSYARN.

These can cause irritation to skin, eyes and the respiratory tract. If you have a history of skin complaint you may be susceptible to
irritation. High dust levels are usual only if the material is broken. Normal handling should not cause discomfort, but follow normal
good hygiene and wash your hands before eating, drinking or going to the lavatory. If you do suffer irritation of the eyes or severe
irritation to the skin seek medical attention.

THERMOSTATS

These contain very small amounts of xylene in the sealed phial and capillary. If broken, under normal circumstances the fluid does
not cause a problem, but in case of skin contact, wash with cold water. If swallowed drink plenty of water and seek medical attention

CUT-OFF DEVICES

These contain activated charcoal and a very small amount of chlorodifluormethane in the sealed phial and capillary. If broken, under
normal circumstances the fluid does not cause a problem. If there is irritation to the eyes or skin then seek medical attention.

Spare Parts

REMEMBER, When replacing a part on this appliance, use only spare parts that you can be assured conform to the safety and
performance specification that we require. Do not use reconditioned or copy parts that have not been clearly authorised by Hepworth
Heating Ltd.

221966B

2

Important Information

CONTENTS DESCRIPTION SECTION PAGE No.

INSTRUCTIONS

FOR USE

INSTALLATION

INSTRUCTIONS

SERVICING

INSTRUCTIONS

Introduction 3
Lighting the Boiler 5

General Data 1 6
Flue Terminal 2 9
Water Systems 3 10
Flue and Appliance Preparation 4 13
Boiler Installation 5 17
Flue Fixing 6 19
Electrical Connectors 7 20
Commissioning 8 21
Instructions to the User 9 24

Servicing 10 24
Fault Finding 11 27
Replacement of Parts 12 31
Spare Parts 13 34

Instructions for Use

Introduction

WARNING. It is important that the case (not the controls tray)
is not disturbed or removed other than for servicing by a
competent person.

Please read these instructions and follow them carefully for the
safe and economical use of your boiler.

The Ultimate FF series are fanned flue boilers designed to
provide central heating and indirect domestic hot water.

The boiler is fully automatic in operation having only one user
control, the control thermostat.

Important Notice

This boiler is for use only on natural gas (G20).

The Gas Safety (Installation and Use)
Regulations

In your interest and that of gas safety it is the law that ALL gas
appliances are installed by a competent person in accordance
with the above regulations.

Gas Leak or Fault

If a gas leak or fault exists or is suspected, the boiler must be
turned off, including the electrical supply and must not be used
until the fault has been put right.

Advice/help should be obtained from your installation/servicing
company or the local gas undertaking.

Electrical Supply Failure

Failure of the electrical supply will cause the burner to go out.
Should this occur, operation of the appliance will normally
resume after the electrical supply is restored.

If the boiler does not relight after an electrical supply failure the
overheat safety cutoff device may need resetting, remove the
controls cover and press the reset button, refer to diagram 1.

Overheat Safety Cutoff

If the overheat safety cutoff device operates on any other
occasion than an electrical supply failure, press the reset button
as in “Electrical Supply Failure”. If the overheat operates again,
turn the appliance off and contact your installation/servicing
company.

3 221966B

Instructions for Use

Maintenance

To ensure the continued efficient and safe operation of the
boiler it is recommended that it is checked and serviced as
necessary at regular intervals. The frequency of servicing will
depend upon the particular installation conditions and usage,
but in general once a year should be enough.

If this appliance is installed in a rented property there is a duty
or care imposed on the owner of the property by the current
issue of The Gas Safety (Installation and Use) Regulations,
Section 35.

It is the law that any servicing is carried out by a competent
person.

To obtain service, please call your installer or Heatcall (Glow­worm’s own Service Organisation) using the telephone number
given on the controls tray.

Please be advised that the ‘Benchmark’ logbook should be
completed by the installation engineer on completion of
commissioning and servicing.

All CORGI Registered Installers carry a CORGI ID card, and
have a registration number. Both should be recorded in your
boiler Logbook. You can check your installer is CORGI registered
by calling CORGI direct on :- 01256 372300.

Boiler Clearances

If fixtures are positioned close to the boiler space must be left
as shown in diagram 2. At least a minimum clearance of 500mm
must be left in front of the boiler to allow for servicing.

CONTROLS COVER

30FF to 60FF Ultimate User Controls illustrated, details
for the 70FF to 120FF are different but the controls are
the same.

DATA &

VIEWING WINDOW

4625

SERIAL
NUMBER
LABEL

RESET
BUTTON

4140

Boilers Installed in a Compartment or
Cupboard

If the boiler is installed in a compartment or cupboard do not
obstruct any ventilation openings.

Do not use the compartment or cupboard for storage.

Cleaning

WARNING. This appliance contains metal parts (components)
and care should be taken when handling and cleaning, with
particular regard to edges.

Clean the casing occasionally by wiping it over with a damp
cloth or dry polishing duster.

Do not use an abrasive cleaner.

Boiler Electrical Supply

WARNING. This boiler must be earthed.

The boiler must only be connected to a 230V~50Hz supply
protected by a 3A fuse.

All wiring must be in accordance with the current issue of
BS7671.

Wiring to the boiler must be PVC insulated type to the current
issue of BS6500 Table 16, not less than 0.75mm

The colours of three core flexible cable are:

Brown - live, Blue - neutral,

Green/yellow - earth.

As the markings on your plug may not correspond with these
colours continue as follows:

The cable coloured blue must be connected to the terminal
marked “N” or black.

2

(24/0.20mm).

CONTROL
THERMOSTAT
KNOB

SETTING POINT

GAS SERVICE
COCK (Shown
Off)

Diagram 1

The cable coloured brown must be connected to the terminal
marked “L” or red.

The cable coloured green/yellow must be connected to the
terminal marked “E”, or green or the earth symbol

.

221966B

4

Instructions for Use

To Light the Boiler

WARNING. Sealed Systems

A sealed water system must be filled and pressurised by a
competent person.

Only light the boiler when you are sure that the system has been
filled and pressurised.

The pressure gauge should show at least 0.7bar, anything less
than this figure could indicate a leak and you MUST contact your
installation/servicing company.

If there is any doubt about the boiler being full of water consult
your installation/servicing company.

ALL SYSTEMS.

Turn the electrical supply on to the boiler and check that all
remote controls are calling for heat.

To Turn the Boiler On

Remove the controls cover, by withdrawing it forward and off,
see diagram 1.

Turn the control thermostat knob clockwise to any position
between MIN and MAX. The maximum temperature setting is
about 82

The boiler lighting operation is now automatic as follows.

The fan operates, followed by an ignition spark until the pilot is
lit. When the pilot is alight the ignition system switches off and
the main burner lights. The flames can be seen through the
viewing window, see diagram 1.

The main burner will remain alight until switched off by the
control thermostat or any remote control.

If the boiler is switched OFF, by hand, wait at least 30 seconds
before switching on again.

When the boiler switches off, both the pilot and main burner go
out.

The automatic lighting sequence will operate again when heat
is required.

Refit the controls cover.

It should be noted that this is a fan flue appliance and fan
operation may be heard.

o

C (180oF), see diagram 1.

6mm

Additional clearances may be
required for installation

160mm

6mm

500mm

65mm

6mm

6mm

6mm

FRONT
VIEW

0208M

Diagram 2

To Turn the Boiler Off

For short periods, turn the control thermostat knob anti-clockwise
to “O” Off. To relight, turn the control thermostat knob to any
position between “MIN” and “MAX”.

For longer periods, turn the control thermostat knob fully anti­clockwise to “O” Off and switch off the electrical supply to the
boiler.

To relight follow the lighting sequence given above.

Protection Against Freezing.

If the boiler is to be out of use for any long period of time during
severe weather conditions we recommend that the whole of the
system, including the boiler, be drained off to avoid the risk of
freezing up. Make sure that, if fitted, the immersion heater in the
cylinder is switched off.

For the position of the serial number, see diagram 1.

5 221966B

B

AO

1 General

C

PUMPED

FLOW

PUMPED

RETURN

F

G

H

0301M

J

SIDE ELEVATION FRONT ELEVATION

MODEL

100FF,120FF

E

D

ABCDEFGHJKLMO

67 300 58 127 114 450 168 132.5 835 772 63 132 43

WATER CONNECTIONS
28mm COPPER PIPE

GAS CONNECTIONS

1

RC

/2 (1/2 in. BSPT)

P

C

L

K

M

Diagram 1.1

L

P

78.5

Important Notice

This boiler is for use only on G20 gas.

This boiler can be used on an open vented or sealed water
system.

When used on an open vented system domestic hot water can
only be provided by pumped circulation to the indirect cylinder.

Wherever possible, all materials, appliances and components
used shall comply with the requirements of applicable British
Standards.

Where no British Standard exists, materials and equipment
should be fit for their purpose and of suitable quality and
workmanship.

Sheet Metal Parts

WARNING. When installing or servicing this boiler care should
be taken when handling sheet metal parts, to avoid any possibility
of personal injury.

1.1 Statutory Requirements

The installation of the boiler must be carried out by a competent
person in accordance with the relevant requirements of the
current issue of:-

Manufacturer’s instructions, supplied.

The Gas Safety (Installation and Use) Regulations, The Building
Regulations, The Building Standards (Scotland) Regulations
(applicable in Scotland), Local Water Company Byelaws, The
Health and Safety at Work Act, Control of Substances Hazardous
to Health, The Electricity at Work Regulations and any local
regulations which may apply.

Detailed recommendations are contained in the current issue of
the following British Standards and Codes of Practice:-

BS6798, BS5440 Part 1 and 2, BS5546 Part 1, BS5449,
BS6891, BS6700, BS7478, BS7593, BS7671.

Manufacturer’s instructions must not be taken as overriding
statutory requirements.

1.2 Data

See Table 1

All dimensions are given in millimetres (except as noted).

The Seasonal Efficiency Domestic Boilers UK (SEDBUK) is
Ultimate 100FF = 79, Ultimate 120FF = 78.1.

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 B.S.I.

221966B

6

1 General

DATA TABLE 1.

MODEL

100FF

120FF

TOTAL DRY
WEIGHT
(Including

71.0 kg
(157 lb)

71.0 kg
(157 lb)

Terminal)

*

LIFT WEIGHT

WATER
CONTENT

GAS
CONNECTION

ELECTRICITY
RATING

WATER
CONNECTION

ELECTRICITY
SUPPLY

DATA LABEL

63.3 kg
(140 lb)

3.8 litres

(0.84 gal)

Rc 1/2 in.

71W 97W

Internal fuse F1 & F2 (F1A)

2x28mm copper pipes from

top of case

230V~50Hz, fused 3A

Bottom right hand side of case

63.3 kg

(140 lb)

3.8 litres

(0.84 gal)

1.3 Range Rating

This boiler is range rated and may be adjusted to suit individual
system requirements.

Table 2 gives the ratings and settings.

*Note: Lift weight is with Flue Elbow, Controls Cover and Front
Cover removed.

1.4 B.S.I. Certification

This boiler is certificated to the current issue of BS6332 Part 1,
invoking the current issue of BS5258 Part 1 for performance
and safety. It is, therefore, important that no alteration is made
to this boiler without permission, in writing, from Hepworth
Heating Ltd.

Any alteration that is not approved by Hepworth Heating Ltd.,
could invalidate the B.S.I. Certification of the boiler, warranty
and could also infringe the current issue of the Statutory
Requirements.

9072

TABLE 2. 100FF

RANGE RATING

NOMINAL
HEAT
INPUT(NETT)

NOMINAL
HEAT
OUTPUT

BURNER.
SETTING
PRESSURE

in. wg.

APPROX.
GAS
RATE

Btu/h

Btu/h

m bar

m

ft

kW

kW

3

/h

3

/h

Min.

26.44

90,210

23.45

80,000

9.2

3.7

2.8

100

29.24

99,760

26.38

90,000

11.6

4.7

3.1

111

BURNER INJECTOR MARKING:

BURNER INJECTOR SIZE:

Max.Med.

32.38

110,485

29.31

100,000

14.4

5.8

3.5

123

205727

4.7mm

TABLE 2. 120FF

RANGE RATING

NOMINAL
HEAT
INPUT(NETT)

NOMINAL
HEAT
OUTPUT

BURNER.
SETTING
PRESSURE

in. wg.

APPROX.
GAS
RATE

Btu/h

Btu/h

m bar

m

ft

Min. Max.

kW

33.43

114,066

kW

29.3

100,000

Medium.

124,608

110,000

9.9

4.0

3

/h

3.5

3

125

/h

36.52

32.24

12.0

4.8

3.9

137

39.6

135,150

35.17

120,000

14.2

5.7

4.2

148

BURNER INJECTOR MARKING: 205726

BURNER INJECTOR SIZE: 5.2mm

9715

1.5 Gas Supply

The gas installation shall be in accordance with the current
issue of BS6891.

The supply from the governed meter must be of adequate size
to provide a steady inlet working pressure of 20mbar (8in wg) at
the boiler.

On completion test the gas installation for soundness using the
pressure drop method and suitable leak detection fluid, purge
in accordance with the above standard.

1.6 Electrical Supply

WARNING. This boiler must be earthed.

All system components shall be of an approved type and shall
comply with and be connected in accordance with the current
issue of BS7671 and any applicable local regulations.

Connection of the boiler and system controls to the mains
supply must be through a common isolator and must be fused

3A, maximum. This method of connection must be by a fused
double pole isolating switch with a minimum contact separation
of 3mm on both poles. The switch should be readily accessible
and preferably adjacent to the appliance. It should supply the
appliance only and be easilyidentifiable as so doing.

Alternatively, an unswitched shuttered socket outlet and 3A
fused 3 pin plug both to the current issue of BS1363 may be
used, provided that they are not used in a room containing a
bath or shower.

Wiring to the boiler must be PVC insulated type to the current
issue of BS6500 Table 16.

1.7 Contents of Packaging

The boiler is delivered in one pack, refer to Section 4.1 for
contents.

Refer to Section 4.2 to check that the flue terminal assembly
supplied is suitable.

7 221966B

1 General

1.8 Water System

This boiler may be fitted to an open vented or sealed water
system.

It is recommended that plastic pipes for primary pipework
should not be used for this boiler.

1.9 Drain

System

A draining tap must be provided at the lowest points of the
system which will allow the entire system, boiler and hot water
cylinder to be drained.

Draining taps should be to the current issue of BS2879.

Boiler

A draining point is fitted at the bottom right hand side of the heat
exchanger.

Cover controls to avoid water damage.

If required remove the combustion chamber front cover to
improve access.

1.10 Safety Valve

A safety valve need not be fitted to an open vented system.

1.11 Location

This boiler is not suitable for outdoor installation.

This boiler may be installed in any room, although particular
attention is drawn to the requirements of the current issue of
BS7671 with respect to the installation of a boiler in a room
containing a bath or shower. Any electrical switch or boiler
control utilising mains electricity should be placed so that it
cannot be touched by a person using the bath or shower. The
electrical provisions of the Building Standards (Scotland) apply
to such installations in Scotland.

The boiler must be mounted on a flat wall which is sufficiently
robust to take its total weight.

The boiler may be fitted to a wall made of combustible material.

1.12 Boiler Clearances

Refer to diagram 1.2.

The boiler must be positioned so that at least the minimum
operational and servicing clearances are provided.

Additional clearances may be required for installation.

If fixtures are positioned next to the boiler they should be made
removable for access to pipework.

Sufficient clearance must be left in front of the boiler for
servicing.

1.13 Room Ventilation

The boiler is room sealed and does not require the room or
space containing it to have permanent airvents.

1.14 Boilers in a Compartment

Where the installation of the boiler will be in an unusual position,
special requirements are needed, the current issue of BS6798
gives detailed guidance on these requirements.

A compartment used to enclose the boiler must be designed
and constructed specifically for this purpose. An existing
cupboard or compartment modified for the purpose may be
used. Details of essential requirements for cupboard or
compartment design are given in the current issue of BS6798.

The doorway opening should be of sufficient size to allow for
easy removal of the boiler.

Where the boiler is fitted in a cupboard or compartment,
permanent high and low level ventilation must be provided. The
minimum ventilation areas are given in Table 3.

0208M

6mm

Additional clearances may be
required for installation

160mm

6mm

500mm

65mm

6mm

PLAN
VIEW

6mm

6mm

FRONT
VIEW

MINIMUM CLEARANCES FROM WALLS
CEILING, FLOOR, CUPBOARD, WORKTOPS,
AND INFLAMMABLE MATERIALS

TABLE 3. COMPARTMENT AIR VENTS

VENTILATION
REQUIREMENTS

MODEL

VENTILATION
FROM
ROOM
OR SPACE

VENTILATION
FROM
OUTSIDE

100FF

120FF

100FF

120FF

HIGH LEVEL
VENT AREA

2

cm

330 51 330 51

396 61.5 396 61.5

165 25.5 165 25.5

198 30.5 198 30.5

in2cm

Diagram 1.2

LOW LEVEL
VENT AREA

2

in

0209M

2

1.15 Timber Frame Building

If the boiler is to be installed in a timber frame building it should
be fitted in accordance with the Institute of Gas Engineers
document IGE/UP/7/1998. If in doubt seek advice from the local
gas undertaking or Hepworth Heating Ltd.

1.16 Heating System Controls

The heating system should have installed: a programmer and
room thermostat controlling the boiler.

Thermostatic radiator valves may be installed, however they
must not be fitted in a room where the room thermostat is
located.

Note: For further information, see The Building Regulations
1991 - Conservation of fuel and power, 1995 edition - Appendix
G, table 4b.

221966B

8

2 Flue Terminal

Note. Detailed recommendations for flues are given in the
current issue of BS5440 Part 1.

2.1 Terminal Position

The minimum acceptable siting dimensions for the terminal
from obstructions, other terminals and ventilation openings are
shown in diagram 2.1.

The terminal must be exposed to the external air, the position
allowing free passage of air across it at all times.

Car ports or similar extensions of a roof only, or a roof and one
wall, require special consideration with respect to any openings,
doors, vents or windows under the roof. Care is required to
protect the roof if it is made of plastic sheeting. If the car port
consists of a roof and two or more walls, seek advice from the
local gas company before installing the boiler.

If the terminal is fitted within 600mm below plastic guttering or
painted soffit an aluminium shield 1500mm long should be fitted
immediately beneath the guttering or eaves. If the terminal is
fitted within 450mm below painted eaves or a painted gutter, an
aluminium shield 750mm long should be fitted immediately
beneath the guttering or eaves.

2.2 Terminal Guard

A terminal guard is required if persons could come into contact
with the terminal or the terminal could be subject to damage.

If a terminal guard is required, it must be positioned to provide
a minimum of 50mm clearance from any part of the terminal and
be central over the terminal.

A suitable guard, reference Type K3, can be obtained from:

Tower Flue Components Ltd
Morley Road
Tonbridge
Kent
TN9 1RA

A

B,C

A

F

G

Under Car Port etc.

MINIMUM SITING DIMENSIONS FOR
FANNED FLUE TERMINALS POSITION

A DIRECTLY BELOW, ABOVE OR HORIZONTALLY

TO AN OPENING, AIR BRICK, OPENING WINDOWS,

AIR VENT OR ANY OTHER

VENTILATION OPENING. 300

B BELOW GUTTER, DRAIN/SOIL PIPE 75

C BELOW EAVES 200

D BELOW A BALCONY OR CAR PORT 200

E FROM VERTICAL DRAIN PIPES AND SOIL PIPES 25

F FROM EXTERNAL CORNERS 25

G ABOVE ADJACENT GROUND OR BALCONY LEVEL 25

H FROM A SURFACE FACING THE TERMINAL 600

I FACING TERMINALS 1200

J FROM OPENING (DOOR/WINDOW) IN

CAR PORT INTO DWELLING 1200

K VERTICAL FROM A TERMINAL 1500

L HORIZONTALLY FROM A TERMINAL 300

M FROM INTERNAL CORNERS 25

G

A

E

G

H,I

B,C

K

M

F

F

G

J

C

K

L

L

K

G

D

F

K

SPACING in mm

MINIMUM

0103M

4307

Diagram 2.1

9 221966B

Flow rate (litres/minute)

Water pressure loss

(mm head of water)

PRESSURE LOSS
OF BOILER 100FF/120FF

Design Flow Rate

0088(z)M

750

500

250

0

0 5 10 15 20 25 30 35 40 45

700mm (120FF)

450mm (100FF)

3 Water Systems

The installation of the boiler must comply with the requirements
of the current issue of BS6798.

It is recommended that plastic pipes for primary pipework
should not be used for this boiler.

3.1 Frost Protection

If the position of the boiler is such that it may be vulnerable to
freezing it should be protected as specified in the current issue
of BS5422. It is recommended that a frost protection thermostat
be fitted.

3.2 Pump

The pump, with integral valves, should be fitted in the heating
flow pipework from the boiler, it should be set to produce a
temperature difference of 11
return, with the control thermostat set at “MAX”, which is about
82oC (180oF).

The pressure loss of the boiler can be found from diagram 3.1.

High resistance microbore systems may require a higher duty
pump.

o

C (20o), between the flow and

Diagram 3.1

3.3 Bypass - Fully Pumped and Sealed Water
System

A bypass MUST be fitted to a fully pumped and sealed water
system.

Where the water system allows the boiler and pump to operate
on bypass only, the bypass connection must be at least 2.5metres
away from the boiler.

The flow through the boiler must not be allowed to fall such that
there is a temperature difference greater than 20
flow and return.

o

C between the

3.4 Water System

For an open vented system the boiler must be supplied from an
unrestricted water supply taken from a feed and expansion
cistern fitted at a maximum height of 27metres above the boiler.

The cold feed must be 15mm minimum size.

It is important that the relative positions of the pump, cold feed
and open vent are as shown in diagram 3.2.

The unrestricted open vent from the boiler must rise continuously
to over the feed and expansion cistern.

3.5 Domestic Hot Water System

General. The domestic hot water service must be in accordance
with the current issue of BS5546, refer also to the current issue
of BS6700.

3.8 Inhibitor

Attention is drawn to the current issue of BS5449 and BS7593
on the use of inhibitors in central heating systems.

If an inhibitor is to be used, contact a manufacturer or Hepworth
Heating Ltd., for their recommendations as to the best product
to use.

When installing in an existing system take special care to drain
the entire system, including the radiators, then thoroughly
cleaning out before installing the boiler whether or not adding an
inhibitor.

3.9 Sealed Water Systems

The installation should comply with the appropriate requirements
of the current issue of BS4814, BS5449, BS6759, BS6798 and
BS7074 Part 1 and 2, see diagram 3.4 for a suggested layout.

3.10 Safety Valve

A safety valve must be fitted to a sealed water system.

It shall be preset, nonadjustable with a lift pressure of 3bar,
incorporating seating of resilient material, a test device and a
connection for drain.

The drain from the safety valve must be routed clear of any
electrical fittings and positioned so that any discharge can be
seen.

3.6 Indirect Cylinder

For all systems supplying domestic hot water the cylinder must
be indirect. It is recommended that the indirect cylinder be fitted
with some form of temperature control.

3.7 Fully Pumped Heating and Domestic Hot
Water

The connections for this type of system MUST be as shown in
diagram 3.2 and 3.3.

221966B

10

3 Water Systems

OPEN VENTED FULLY PUMPED WATER SYSTEM
RECOMMENDED RELATIONSHIP BETWEEN
PUMP COLD FEED AND VENT

6349

22mm VENT
450mm
MIN.
HEIGHT

(MIN.)

FEED AND
EXPANSION
CISTERN

15mm (MINIMUM)
COLD FEED

1150mm
MIN.

RETURN

CYLINDER

FLOW

PUMP

There must
always be a
cold water
path to the
return
connection
of the boiler.

BOILER

150mm
MAX.

28mm (MINIMUM)

BY-PASS WITH

FLOW

HEATING

RET.

LOCKSHIELD VALVE

Diagram 3.2

3.11 Expansion Vessel

A diaphragm type expansion vessel, conforming to the current
issue of BS4814 (see also BS7074 Part 1 and 2) must be
connected at a point close to the inlet side of the circulating
pump, see diagram 3.4, unless laid down differently by the
manufacturer.

The expansion vessel volume depends upon the total water
system volume and the initial system design pressure. For any
system an accurate calculation of the vessel size is given in the
current issue of BS7074 Part 1.

Example. For an initial system design pressure of 0.7bar the
minimum total vessel volume required is 0.063xTotal System
volume.

Note. A higher initial design pressure requires a larger volume
expansion vessel.

Guidance on vessel sizing is also given in the current issue of
BS5449 and BS7074 Part 1.

The charge pressure must not be less than the static head of the
system, that is, the height of the highest point of the system
above the expansion vessel.

The water content of the boiler is given in Data Table 1.

3.12 Pressure Gauge

A pressure gauge with a set pointer and covering at least the
range of 0 to 4bar (0 to 60lb/in
the system in a position where it can be seen when filling the
system.

2

) shall be permanently fitted to

FLOW

28mm
PIPE

22mm VENT & 15mm COLD FEED
TO BE FITTED IN ACCORDANCE
WITH BS 5449

INDIRECT
CYLINDER

1metre Min.

27 metres

Max.

FULLY PUMPED CIRCULATION
BYPASS (DIAGRAMMATIC)

1metre Min.

27 metres

Max.

BYPASS 28mm
MIN WITH
LOCKSHIELD
VALVE

PUMP

22mm FOR COMBINED FEED & VENT
TO BE FITTED IN ACCORDANCE
WITH BS 5449

INDIRECT
CYLINDER

BYPASS 28mm
MIN WITH
LOCKSHIELD
VALVE

PUMP

RETURN

4273

6459

HEATING
SYSTEM

ALTERNATIVE
SYSTEM
CONTROL
VALVES

6466

HEATING
SYSTEM

ALTERNATIVE
SYSTEM
CONTROL
VALVES

FULLY PUMPED CIRCULATION
BYPASS (DIAGRAMMATIC)

Diagram 3.3

11 221966B