Glowworm Economy Plus 50C Operating manual

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Hepworth Heating Ltd.,
Nottingham Road, Belper, Derbyshire. DE56 1JT
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All replacement parts
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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.
Attached to the center of these instructions is 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:
Guarantee Registration
Open Flue Boiler
This is a Cat I2H Appliance
BS 6332
BS 5258
Reference in these instructions to British Standards and Statutory
Regulations/Requirements apply only to the United Kingdom.
For Ireland the rules in force must be used.
Tobeleftwiththeuser
❏
✔
❏
✔
❏
✔
Instructions for Use
Installation and Servicing
G.C. No. 41 319 39
REGISTER YOUR GLOW-WORM APPLIANCE
FOR 1ST YEAR GUARANTEE PROTECTION
CALL 0181 380 2555
50
C
2402
The instructions consist of three parts, User, Installation and Servicing Instructions, which includes the Guarantee Registration
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.

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Important Information
Introduction 3
Lighting the Boiler 4
General Data 1 5
Flue and Ventilation 2 7
Water Systems 3 8
Installation 4 10
Electrical Wiring 5 11
Commissioning 6 12
Servicing and Replacement Parts 7 14
Fault Finding 8 19
Spare Parts 9 24
CONTENTS DESCRIPTION SECTION PAGE No.
INSTRUCTIONS
FOR USE
INSTALLATION
INSTRUCTIONS
SERVICING
INSTRUCTIONS
Testing and Certification
Thisboileristestedandcertificatedforsafetyandperformance. Itisthereforeimportantthatnoalterationismadetotheboiler,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 1.3.
CE Mark
This boiler meets the requirements of Statutory Instrument No. 3083 The boiler (Efficiency) Regulations, and therefore is deemed
tomeettherequirementsofDirective92/42/EEContheefficiencyrequirementsfornewhotwaterboilersfiredwithliquidorgaseous
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
thatyouuseaHEPAfilteredvacuumtoremoveanydustaccumulated inandaroundtheboilerbeforeandafterworkingontheboiler.
Whenreplacing these articleswe recommend thatthe replaced itemsare not brokenup, but aresealed within heavyduty 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
notcauseaproblem,but in caseofskincontact,washwithcold water. Ifswalloweddrinkplentyofwaterand seek medical attention.
COMBUSTION PRODUCTS DISCHARGE SAFETY DEVICE
These contain very small amounts of ethylene glycol and methanol in the capillary. If broken, under normal circumstances the fluid
doesnotcauseaproblem,butincasesofskinoreyecontact,washwithcoldwater.Ifingested,drinkplentyofwaterandseekmedical
attention.

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Instructions for Use
General Notes and Information
Please read these instructions and follow them carefully for the
safe and economical use of your boiler.
Important Notice
This boiler is for use only on G20 gas.
The convection air openings on the boiler must NEVER be
obstructed.
The Gas Safety (Installation and Use)
Regulations
In your interests and that of gas safety it is the Law that ALL gas
appliances are installed by a competent person in accordance
with the current issue of the above regulations.
Maintenance
To ensure the continued efficient and safe operation of the boiler
it is recommended that it is checked and serviced at regular
intervals.Thefrequencyofservicingwilldependupontheparticular
installation and usage, but in general once a year should be
enough.
To obtain service, please call your installer, or Heatcall (Glow-
worm’s own service organisation) using the telephone number
given on the controls tray.
If the appliance is installed in a rented property there is a duty of
careimposedon the owner of thepropertyby the current issue of
the Gas Safety (Installation and Use) Regulations, Section 35.
It is the Law that servicing is carried out by a competent person.
Please be advised that the ‘Benchmark’ logbook should be
completed by the installation engineer on completion of
commissioning and servicing.
AllCORGIRegisteredInstallerscarryaCORGIIDcard,andhave
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.
Gas Leak or Fault
Ifagasleakorfaultexistsorissuspectedtheboilermustbeturned
offalsotheelectricalsupply. Advice/helpshouldbeobtainedfrom
your installation/servicing company or the local gas company.
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. If an immersion heater is fitted in the domestic hot
water cylinder make sure that it is switched off.
If you have a sealed water system you should contact your
installer/servicingcompanyasasealedwatersystemshouldonly
be drained, refilled and pressurised by a competent person.
Boiler Clearance
The boiler must be positioned so that at least the minimum
operational and servicing clearances are provided, see diagram
1.
If fixtures are positioned close to the boiler they should be made
removable for access to pipework.
Enough space must be left in front of the boiler for servicing.
Boiler in a Compartment
If the boiler is fitted in a compartment or cupboard, purpose built
ventilation must be provided and kept clear.
Do not use the enclosed space for storage.
Boiler Identification
The type of boiler and its output can be checked against the
details inside the controls cover.
Overheat Cutoff Device
The boiler is fitted with a safety device to prevent damage
throughoverheating. Shouldthe boiler go out togetherwiththe
pilotfornoapparentreason,allowthesystemtocooldown,then
relight the boiler.
Should the problem persist, turn the boiler off and consult your
installation/servicing company.
Electrical Supply
WARNING. The boiler must be earthed.
The boiler must only be connected to a 240V~50Hz supply,
protected by a 3A fuse, maximum.
All wiring must be in accordance with the current issue of
BS7671.
Heat resistant cable having a conductor size of 0.75mm2, (24/
0.20mm) to BS6500 Table 16 must be used.
The colours of three core flexible cable are, Brown - live, Blue -
neutral, Green and yellow - earth.
As the marking on your plug may not correspond with these
colours continue as follows:
The wire coloured brown must be connected to the terminal
marked “L” or “Red”.
The wire coloured blue must be connected to the terminal
marked “N” or “Black”.
The wire coloured green and yellow must be connected to the
terminal marked “E”, Green or the earth symbol .
AL.H. and R.H. side of casing 25
BTop of casing 75
CBottom of casing 150
DFront of boiler (from a
permanent surface 305
OPEN FLUE BOILERS
Minimum Clearances from
Walss, Ceiling, Floor, etc.
Diagram 1
MINIMUM
CLEARANCES
A
B
2390
A
C

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Instructions for Use
Safety Device
Thisapplianceisfittedwithaflueblockage safety device which
will shut down the appliance in the event of abnormal flue
conditions.ThisdeviceisNOTasubstituteforanindependently
mounted Carbon Monoxide detector.
Thesafetydevice isreset,afterthreeminutesbypushinginthe
button “ F ” shown in diagram 3.
Note: The pilot will stay alight but the device must be reset.
Shut down can occur during certain climate conditions, but if it
recurs the chimney flue and air inlet into the room must be
checked and any problems found corrected by a competent
person, before the boiler is used again.
Lighting the Boiler
CAUTION
Ifthepilotflamegoesout,eitherintentionallyorbyaccident,no
attempt should be made to relight for at least three minutes.
Slide the controls cover off and clear, see diagram 2.
Makesurethattheelectrical supply totheboilerisswitchedoff.
Identify the controls by referring to diagram 3.
Turn the control thermostat knob “A” fully anticlockwise to the
“OFF” position.
Pushandholdingascontrolknob“B”. Pushandreleaseigniter
button “C” until the pilot burner lights, look through window “D”.
When the pilot is alight keep gas control knob “B” pushed in for
about 15 seconds and then release.
Ifthepilotdoesnotlightorfailstostayalight,waitthreeminutes
and repeat the lighting operation, only this time keep knob “B”
pushed on for a little longer.
The flue blockage safety device may also need resetting, refer
to safety device instructions.
Make sure that the pilot is alight and stable.
Switch on the electrical supply to the boiler.
Check that all external controls are calling for heat.
Turn control thermostat knob “A” fully clockwise to “MAX” and
themainburnerwilllightfullyinaboutthreetofiveseconds,look
through window “D”.
Ifthemainburnerdoesnotlight,theflueblockagesafetydevice
may need resetting, refer to Safety Device instructions.
Adjustthecontrolthermostatknobtothedesiredsettingbetween
“MIN” and “MAX”. “MAX” is about 82oC (180oF).
Replace controls cover.
To Turn the Boiler Off
Forshortperiods,turncontrolthermostatknob“A”anticlockwise
until “O” is against the setting point. The pilot will stay alight, to
relightthemainburnerturncontrolthermostatknob“A”clockwise
to the desired setting between “MIN” and “MAX”.
For longer periods, turn the control thermostat knob “A”
anticlockwise until “O” is against the setting point. Slide gas
controlknob“B”toleftandrelease,thecontrolwillautomatically
reset. Switch off the electrical supply.
To relight, follow the full lighting procedure given above.
Cleaning
WARNING. Thisappliancecontainsmetalparts(components)
and care should be taken when handling and cleaning, with
particular regard to edges.
Clean the casing by wiping it over occasionally with a wet cloth
or dry polishing duster.
Do not use abrasive cleaners.
Diagram 2
CONTROLS
COVER
2391
BOILER
CONTROLS Diagram 3
A
D
C
MODEL AND
SERIAL
NUMBER
PLATE
F
A. CONTROL THERMOSTAT KNOB
B. GAS CONTROL KNOB
C. IGNITER BUTTON
D. VIEWING WINDOW
F. FLUE BLOCKAGE SAFETY DEVICE
RESET BUTTON
B
5354

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1 General Data
1.1 Important Notice
This boiler is for use only on natural gas G20.
The boiler is delivered in one pack.
Wherever possible, all materials, appliances and components
to be used shall comply with the requirements of applicable
British Standards.
Where no British Standards exist, materials and equipment
should be fit for their purpose and of suitable quality and
workmanship.
This boiler must have fully pumped circuits, but is suitable for
use with open vented or sealed water systems.
This boiler is not suitable for fitting out of doors.
The boiler must not be installed in a bedroom, bed sitting room
or a room containing a bath or shower.
Open flue boilers must not be installed in private garages.
1.2 Sheet Metal Parts
WARNING. When installing or servicing the boiler care should
betakenwhenhandlingsheetmetalpartstoavoidanypossibility
of personal injury.
1.3 Statutory Requirements
Theinstallationofthisboilermustbecarriedoutbyacompetent
person in accordance with the relevant requirements of the
current issue of:
Manufacture’s instructions, supplied.
TheGasSafety(InstallationandUse)Regulations,TheBuilding
Regulations, The Building Standards (Scotland) Regulations
(applicable in Scotland), local Water Company Byelaws, The
HealthandSafetyatWorkAct,ControlofSubstancesHazardous
to Health, The Electricity at Work Regulations and any local
applicable regulations.
Detailed recommendation are contained in the current issue of
the following British Standards and Codes of Practice:
BS4814, BS5400 Part and 2, BS5449, BS5446, BS6700,
BS6798, BS6891, BS7074 Part and 2, BS7478, BS7593,
BS7671.
Manufacturers’ instructions must not be taken as overriding
statutory requirements.
1.4 Data
Weight of boiler: 50C - 20.7kg (45.7lb)
Water content: 50C - 0.60Litre (0.13gal)
Gas connection: Rc1/2
Water connection: 22mm copper flow at right
Electrical supply: 240V - 50Hz fused at 3A
Data label: Bottom of inner case door.
Injector: 50C - Cat 98 - 1400
The Seasonal Efficiency Domestic Boilers UK (SEDBUK)
is 72.4%.
ThevalueisusedintheUKGovernment’sStandardAssessment
Procedure (SAP) for energy rating of dwellings. The test data
from which it has been calculated have been certified by B.S.I.
1.5 Range Rating
The boiler is range rated and may be adjusted to suit individual
system requirements.
The respective Table 1 gives the ratings and settings.
,
,
,
,










INSIDE DIAMETER
OF SPIGOT FOR
100 mm (4in) NOMINAL
DIAMETER FLUE
242
115
DIA.
RETURN FLOW
WATER
CONNECTIONS
11
GAS CONNECTION 40
36
600
360
FLUE
C
L86
43
WATER
CONNECTIONS
490
GAS
CONNECTION
110
225
98
300
*
*
Diagram 1.1
OVERALL DIMENSIONS (given in millimetres)
2409

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1 General Data
1.6 B.S.I. Certification
This boiler is certificated to the current issue of BS6332 Part 1,
invoking the current issue of BS5258 Part for performance and
safety. It is, therefore, important that no alteration is made to
boiler without permission, in writing, from Hepworth Heating
Ltd.
Any alteration that is not approved by Hepworth Heating Ltd.,
couldinvalidatetheB.S.I.,certificationoftheboiler,thewarranty
and could also infringe the current issue of the Statutory
1.7 Gas Supply
The gas installation must be in accordance with the current
issue of BS6891.
The supply from the governed meter must be of adequate size
toprovideasteadyinletworkingpressureof20mbar(8inwg)at
the boiler.
Oncompletion,testthegasinstallationforsoundnessusingthe
pressure drop method and suitable leak detection fluid, purge
in accordance with the current issue of BS6891.
1.8 Electrical Supply
WARNING. This boiler must be earthed.
All system components shall be of the approved type and be
wired and connected in accordance with requirements 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
3Amaximum. Thismethod of connection should be byafused
double pole isolating switch, which has a minimum contact
separationof3mmonbothpoles. This switchshouldbereadily
accessible and preferably adjacent to the appliance. It should
supplytheapplianceonlyandbeeasilyidentifiableassodoing.
Wiring to the boiler must be insulated PVC flexible type to the
current issue of BS6500 Table 16, not less than 0.75mm2(24/
0.20mm).
1.9 Draining Tap
A draining tap must be provided at the lowest points of the
system which will allow the entire system, boiler and domestic
hot water cylinder to be drained.
Draining taps shall be to the current issue of BS2879.
1.10 Safety Valve
A safety valve need not be fitted to an open vented system.
1.11 Clearances
Theboilerpositionshouldbesuchthattheclearancesshownin
diagram 1.2 are achieved.
Additional clearances may be required for installation.
Iffixtures are positioned next to the boilerthey should be made
removable for access to pipework.
Sufficient clearance must be left in front of the boiler for
servicing.
The casing side grilles must be kept clear at all times.
The boiler must be mounted on a flat wall which is sufficiently
robust to take its weight.
AL.H. and R.H. side of casing 25
BTop of casing 75
CBottom of casing 150
DFront of boiler (from a
permanent surface) 305
Minimum Clearances
from Walls, Ceiling,
Floor, Cupboard, Worktops etc.
Diagram 1.2
BOILER FIXING DIMENSIONS
AND MINIMUM CLEARANCES
B
518
232 200 200 C
A
46
300
Boiler
Outline Minimum
clearance
limit
0003M
1.12 Timber Frame Buildings
If the boiler is to be installed in a timber frame building it should
be fitted in accordance with the Institute of Gas Engineers
documentIGE/UP/7/1998. Ifindoubtseekadvicefromthelocal
gas undertaking or Hepworth Heating Ltd.
1.13 Heating System Controls
The heating system should have installed: a programmer and
room thermostat controlling the boiler.
Thermostatic radiator valves may be installed in addition to the
room thermostat.
Note: For further information, see The Building Regulations
1991-Conservationoffuelandpower,1995edition-Appendix
G, table 4b.

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2 Flue and Ventilation
Important note
The boiler is fitted with a Flue Blockage Safety Device, which
will shut down the boiler if there is an unacceptable spillage of
products at the draught diverter.
This safety device MUST NOT under any circumstances be
interferred with or put out of action.
Thesafetydevicemust only be replaced with the Glow-worm
parts.
2 Flue Connection
Theintegraldraughtdiverterontheboilermakesthecombustion
performance independent of the conditions in the secondary
flue,butincommonwithotherfuelsanefficientflueisnecessary
to ensure a trouble free installation.
The flue outlet on the boiler is designed to take flue pipes to
BS567. If a flue pipe to BS715 is to be used an adapter must
be fitted to the boiler flue socket.
The flue must be in accordance with the current issue of
BS5440 Part 1.
Give maximum possible vertical rise from the boiler, at least a
minimum of 600mm, before any offset or bend. The use of 90o
bends is not recommended.
An existing flue must be lined and end, at least above ridge
height, with a certificated terminal.
Achimneypreviouslyusedforsolidfuelmustbesweptandany
damper or register plate left in the locked open position or
removed.
2.1 Boilers in a Compartment
Wheretheinstallationoftheboilerwillbeinanunusuallocation,
specialproceduresarenecessary,thecurrentissueofBS6798
gives detailed guidance on this aspect.
A compartment used to enclose the boiler must be designed
and constructed specifically for this purpose.
Anexistingcupboard or compartment modified for thepurpose
may be used. Details of essential features of 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 required are given in Table “A”.
2.2 Boiler Installed in a Room or Space
Apurposedesignedventilationopeningmustbeprovidedonan
outside wall of the premises, refer to the current issue of
BS5440 Part 2 for further information.
The opening may be either, directly into the room or space
containing the boiler or into an adjacent room or space which
hasaninternalpermanentairventofthesamesizeastheroom
containing the boiler.
DONOTventilatethroughaprivategarage,bedroom,bedsitting
room or a room containing a bath or shower.
Air vents through a cavity wall must be ducted.
Whentheboiler is installed in a spacealreadycontainingafuel
burning appliance account must be taken of the TOTAL air
requirement.
2.3 Extract Fans
Ifanextractfanisfittedinthepremisesthereisapossibilitythat
if adequate air openings are not provided spillage of products
from the boiler may occur.
When openings are fitted in accordance with the
recommendationsofthecurrentissueofBS5440Part1andthis
Section,extractfansshouldnotcausespillage,butwheresuch
an installation is found spillage tests as the current issue of
BS5440 Part 1 must be carried out.
The necessary action should then be taken.
See also Section 6.6.
Range Rating
Nominal kW
Heat
Input (GROSS) Btu/h
14.73 16.60 18.46
50,250 56,600 63,000
min medium max
Burner m bar
Setting
Pressure in.w.g
Nominal kW
Heat
Output Btu/h
11.72 13.19 14.65
40,000 45,000 50,000
8.8 10.7 13.2
3.5 4.3 5.3
Table 1 ECONOMY PLUS 50C
Burner Injector Marking: 1.35
Burner Injector Size: 1.35 X 7
Pilot Injector Marking: 7218
TABLE "A" COMPARTMENT AIR VENTS
ECONOMY PLUS 50C
High Level
Vent Area Low Level Vent Area
Ventilation
Requirements
Air from room or
internal space 167cm2333cm2
Air direct from
outside 83cm2167cm2
ECONOMY PLUS 50C
TABLE "B" ROOM/SPACE AIR VENTS
Effective area
of vent 52cm2

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Notes:
PUMP
Thepumpwithintegralvalves,ifpossible,shouldbefittedinthe
flowpipeworkfromtheboiler,toproduceatemperaturedifference
across the boiler of 11oC (20oF).
See diagram 3.1 for pressure loss across the boiler.
High resistance microbore systems may require a higher duty
pump.
BYPASS
A bypass must be fitted, see diagram 3.2.
The flow through the boiler must not be allowed to fall below:
50C - 13.2L/min (2.9gall/min)
whilst the burner is alight.
3.1 Open (Vented) Water System
For an open (vented) water system the boiler must be supplied
from an unrestricted water supply taken from a cold feed and
expansioncistern situatedatamaximumheightof27.5 metres
(90ft) above the boiler.
The cold feed supply must be 15mm minimum size.
It is important that the relative position of the pump, cold feed
and open vent are as shown in diagram 3.2.
3.2 Domestic Hot Water Cylinder
Thedomestichotwatercylindermustbeofthedoublefeed,fully
indirect type. Single feed, self priming cylinders are not
recommended.
3.3 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 for their
recommendations for the best product to use.
When installing a boiler in an existing system, whether or not
using an inhibitor, take special care to drain the entire system,
including the radiators, then thoroughly cleaning out before
fitting the boiler and adding the inhibitor.
3.4 Sealed Water Systems
Theinstallationshouldcomplywiththeappropriaterequirements
ofthecurrent issue of BS4814, BS5449,BS6759,BS6798 and
BS7074 Part 1 and 2.
See diagram 3.3 for a diagrammatic layout.
3.5 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 a 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.
Diagram 3.1
PRESSURE LOSS OF BOILER
Diagram 3.2
Open (vented) system.
Recommended
relationship between
pump, cold feed and
vent.
22 mm (MIN) VENT
FEED AND
EXPANSION
CISTERN
15mm (MINIMUM)
COLD FEED
15mm (MINIMUM)
BY-PASS WITH
LOCKSHIELD VALVE
450mm
MIN.
HEIGHT
1150mm
MIN.
150
mm
MIN.
BOILER
PUMP
150mm
MAX
FLOW
RET.
ALTERNATIVE
PREFERRED
RET.
CYLINDER
FLOW
HEATING
0392
3 Water Systems
GALLONS/MINUTE
LITRES/MINUTE
FUELSAVER 50C
WATER PRESSURE LOSS
(m head of water)
WATER PRESSURE LOSS
(in head of water)
0124
35
0510 15 20 25
55
50
45
40
35
30
25
20
15
10
5
0
1.4
1.2
1.0
0.8
0.6
0.4
0.2
0
6928

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3 Water Systems
3.6 Expansion Vessel
A diaphragm type expansion vessel, conforming to the current
issue of BS4814 (see also the current issue of BS7074 Part 1
and2)must beconnectedata pointclosetothe inletsideofthe
circulating pump, see diagram 3.3, unless laid down differently
by the manufacturer.
The expansion vessel volume depends on the total water
systemvolumeand theinitialsystemdesign pressure. For any
system an accurate calculation of vessel volume 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.
Guidance is also given in the current issue of BS5449.
Thechargepressuremustnotbelessthanthestaticheadofthe
system, that is, the height of the highest point of the system
above the expansion vessel.
The water capacity of the boiler is given in Section 1.
3.7 Pressure Gauge
A pressure gauge with a set pointer and covering at least the
range of 0 to 4 bar (0 to 60lb/in2) shall be permanently fitted to
the system in a position where it can be seen when filling the
system.
3 LITRES (0.66 gals)
MAKE-UP BOTTLE
(if required)
NON-RETURN
VALVE
AUTO
AIR
VENT
FLOW
DRAIN
COCK BOILER
SAFETY
VALVE
(Make-up
alternatives) EXPANSION
VESSEL
PRESSURE
GAUGE
CIRCULATING
PUMP
FILLING POINT
AIR
RELEASE
POINT
HEATING CIRCUIT
15mm (min)
BY-PASS WITH
LOCKSHIELD
VALVE
RETURN
SEALED WATER SYSTEM DIAGRAMMATIC LAYOUT
EXPANSION VESSEL SYSTEM
EXPANSION VESSEL
PRESSURE (BAR)
A = SYSTEM VOLUME Diagram 3.4
INTIAL SYSTEM
PRESSURE (BAR)
EXPANSION VESSEL
VOLUME (LITRES)
INTIAL SYSTEM
PRESSURE (BAR)
EXPANSION VESSEL
VOLUME (LITRES)
EXPANSION VESSEL
PRESSURE (BAR) 0.5
1.0
A X 0.075 A X 0.126
A X 0.098 A X 0.171
0.5 1.0
1.0 1.5
Diagram 3.3
5812

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3 Water Systems
Diagram 3.5
FILLING SEALED
WATER SYSTEMS
METHOD 1
METHOD 2
METHOD 3
SUPPLY STOP
VALVE
SUPPLY
PIPE
HOSE
UNIONS SERVICING
VALVE
TEMPORARY
HOSE
HEATING
SYSTEM
HEATING
SYSTEM
TEMPORARY
HOSE
HOSE
UNIONS SERVICING
VALVE
SUPPLY
PIPE
SUPPLY STOP
VALVE
DOUBLE CHECK
VALVE ASSEMBLY
HEATING
SYSTEM
SERVICING
VALVE
SUPPLY
STOP VALVE
SUPPLY
PIPE
HOSE
UNIONS DOUBLE CHECK
VALVE ASSEMBLY
OVERFLOW
CISTERN
COMBINED
CHECK VALVE
AND VACUUM
BREAKER
PRESSURE
REDUCING
VALVE
3132
3.8 Domestic Hot Water Cylinder
SINGLEFEEDINDIRECTCYLINDERSARENOTSUITABLE.
Thedomestichotwatercylindermustbeoftheindirectcoiltype.
It must be suitable for working at a gauge pressure of 0.35bar
above the safety valve setting.
3.9 Water Make-up
Provision should be made for the replacing the water loss from
thesystemusingamake up bottlemountedinapositionhigher
than the top point of the system, connected through a non-
return valve to the return side of either the heating circuit of the
domestic hot water cylinder.
Alternatively, provision for make up can be made by using a
filling loop.
3.10 Filling a Sealed Water System
Provisionforfillingthesystematlowlevelmustbemade. Three
methodsareshownindiagram3.5. Theremustbenopermanent
connection to the mains water supply, even through a non-
return valve.
4.1 Appliance Preparation
Remove the controls cover by pulling it forwards and off, see
diagram 4.1.
Remove the boiler from the carton and lay it on its back.
The side grilles are packed in the bottom of the carton.
Remove the outer case by undoing the screws at the bottom
and unhooking at the top, see diagram 4.1.
Remove the two screws and attach the side grilles by hooking
over the top of the side panel and secure, see diagram 4.1.
4.2 Appliance Fitting
Refer to diagram 1.2 for fixing screw positions and minimum
clearances.
Mark position of the three fixing screws.
Drill and plug the holes, suitable for No10x2in woodscrews.
Fit the screws, leave about 6mm proud.
Hook the boiler on to the lower screw and keyhole slots at the
top, tighten all screws.
Connect the system pipework to the boiler.
Fixthefluetothe flue hoodinaccordancewithnormalpractice.
4 Installation

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4 Installation
4.3 Gas and Water Connection
Connect the gas supply to the Rc1/2in gas cock.
Thewholeofthegasinstallation,includingthemeter,shouldbe
inspected,testedforsoundnessandpurgedinaccordancewith
the current issue of BS6891.
Connectthe water to theboiler,using nuts and olivessupplied,
to BS2871 copper tube.
4.4 Casing
Refittheoutercasingbyhookingonatthetopandsecuringwith
the screws previously removed, see diagram 4.1.
Make sure that the side grilles are kept clear.
Diagram 4.1APPLIANCE PREPARATION
CONTROL
COVER
SECURING
SCREW
SIDE
GRILLE
OUTER
CASE
2410
SECURING
SCREW
5.1 Electrical Connection
WARNING. Theboilermustbeearthedandhavea permanent
mains supply.
To remove the control box release the two screws at the front,
see diagram 5.1, lower the box until it is clear then push
backwardstodisengagethehingeattherear,seediagram5.1.
Take care not to damage the thermostat and capillaries.
Thread the mains lead through the clamp in the rear of the
control box cover and connect to the terminal strip.
The mains cable outer insulation must not be cut back external
to the cable clamp.
Whenmakingconnections,makesurethattheearth conductor
ismadeofagreaterlengththanthecurrentcarryingconductors,
so that if the cable is strained the earth conductor would be the
last to become disconnected.
5.2 Pump and External Controls Connections
Thepumpmustbewiredintotheboilercontrolboxasshown in
diagram 5.2.
AnyexternalcontrolsmustonlybewiredtointerrupttheRedlink
between terminals 9 and SL.
Take the strain relief grommets from the loose items pack.
Placearoundtheexternalcontrolsandpumpconnectioncables
respectively.
Squeezethesidesofthegrommetswhenpushingthemintothe
obround holes in the rear of the control box, see diagram 5.1.
Makesurethesupplycableandallexternalcablesaresecured.
Diagram 5.1CONTROL BOX
SECURING
SCREWS
EARTH
POST
TERMINAL
STRIP
RETAINING
STRAP
FASTENER
5352
STRAIN
RELIEF
GROMMET
5.3 Testing - Electrical
Checks to ensure electrical safety should be carried out by a
competent person.
After installation of the system, preliminary electrical system
checks as below should be carried out.
1. Test insulation resistance to earth of mains cables.
2. Test the earth continuity and short circuit of all cables.
3. Test the polarity of the mains.
The installer is requested to advise and give guidance to the
user of the controls scheme used with the boiler.
5 Electrical Wiring

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5 Electrical Wiring
6.1 All Systems
Makesurethatthesystemhasbeenthoroughlyflushedoutwith
cold water without the pump in place. Refit the pump, fill the
system with water, making sure that all the air properly vented
from the system and pump.
Before operating the boiler make sure that all external controls
are calling for heat.
6.2 Sealed Water Systems Only
Flush the whole system with cold water without the pump in
place. Refitthepumpandfill until thepressuregaugeregisters
1.5bar (21.5lbf/in2). Clear any airlocks and check for water
soundness.
Check the operation of the safety valve, by allowing the water
pressure to rise until the valve opens. The valve should open
within +/-0.3bar (+/-4.3lbf/in2) of the 3bar preset pressure.
Where this is not possible conduct a manual check and test.
Release cold water to initial system design pressure.
Thesetpointeronthepressuregaugeshouldbesettocoincide
with the indicating pointer.
6.3 Initial Lighting and Testing - All Systems
Refit the outer case, see diagram 4.1.
Identify the controls be reference to diagram 6.1.
Turn the control thermostat control knob “A” to “O” the Off
position, see diagram 6.1.
Diagram 5.2WIRING DIAGRAM FOR CONTROL BOX.
SWITCHED
CONTROL
TIME SWITCH
PROGRAMMER
ETC.
(if fitted)
CIRCULATION
PUMP
240V~ 50Hz
PERMANENT
MAINS SUPPLY
FUSED AT 3A
L
N
L
N
BROWN
BLUE
GRN/YEL
GAS VALVE
BROWN
BROWN
RED
RED
PURPLE
BLUE
BROWN
BLUE
GRN/YELLOW
CHASSIS
EARTH
POST
3
7
6
89
Remove Red Link
between 9 and SL
when fitting a time
control etc.
(If link is not
removed the
circulation pump
will run constantly. )
7
89
7
89
NLSL
NLSL
COMBINED THERMOSTAT AND
PUMP OVERRUN
5353
GRN/YELLOW
BROWN
BLUE
WHITE
F.B.S.D.
Remove the pressure test point screw “K” and fit a suitable
pressure gauge.
Turn the electrical supply on and check that the pump is
working.
Openallwindowsandputoutanynakedlights,pipes,cigarettes
and the like.
Turn on the main gas supply and purge in accordance with the
current issue of BS6891.
Turn the boiler gas service cock “J” to On.
Note. Make sure that the flue blockage safety device reset
button “M” is fully pushed in.
Pushincontrolbutton“B”,keeppushedinandatthesametime
operatethepiezobutton“C”untilthepilotburnerlights. Afterthe
pilot burner lights keep the button “B” pushed in for about 15
seconds. If the pilot burner fails to light or stay alight a safety
deviceprevents immediate relighting. Do not attempttorelight
until the safety device has reset.
Note. Should the boiler fail to operate correctly refer to Fault
Finding Section.
Check the length of the pilot flame, it should envelop the
thermocoupletipasshownindiagram7.7. Thepilotratecanbe
adjusted by turning screw “H”, having first removed the gas
valve cover by releasing the screws, see diagram 6.1.
Testpilotsupplyconnectionsforsoundnesswithasuitableleak
detection fluid.
6 Commissioning

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6 Commissioning
Fit the outer case, secure with the screws previously removed.
Make sure that the pilot is alight and stable, view through
window “G”.
Set the control thermostat knob “A” between “MIN” and “MAX”
(“MAX” is about 82oC (180oF) and check that the burner lights
smoothly. Check all gas connections for soundness with a
suitable leak detection fluid.
Note. Should the boiler fail to operate correctly refer to Fault
Finding Section.
To set the burner pressure operate the boiler for 10 minutes,
remove the gas valve cover, if not already removed, adjust the
gaspressurebyscrew“H”untiltherequiredpressureisobtained,
see the relevant Table 1 for setting pressures.
Stick the self adhesive arrow, from the loose items pack, in the
appropriate space beneath “MIN” and “MAX” column on the
data label.
Should any doubt exist about the gas rate this should be
checked at the meter, using a stop watch to time at least one
cubic foot of gas consumption.
Replace the gas valve cover.
Removethepressuregaugeandrefitthescrew,makesurethat
a gas tight seal is made.
6.4 Testing
Check the operation of the flame failure device on the boiler to
make sure that the gas valve shuts down within 60 seconds,
indicated by a “click” from the valve.
MODEL AND SERIAL
NUMBER PLATE
A
KL
G
HBJ. (Shown Off)
C
A. CONTROL THERMOSTAT KNOB
B. GAS CONTROL KNOB
C. IGNITER BUTTON
G. VIEWING WINDOW
H. GAS RATE ADJUSTMENT SCREW
(UNDER COVER SCREW)
J. GAS SERVICE COCK
K. PRESSURE TEST POINT
L. PILOT BURNER
ADJUSTMENT SCREW
M. FLUE BLOCKAGE SAFETY DEVICE
RESET SWITCH
M
Diagram 6.1
5354
6.5 Flushing
Allow the system to reach maximum working temperature and
examine for water leaks.
The boiler should then be turned off and the system drained as
rapidly as possible whilst still hot.
Refill the system and vent and check for water soundness as
before.
6.6 Adjustment - All Systems
Whencommissioning the system the boilershouldfirst be fired
on full service, that is, central heating and domestic hot water.
The system should then be balanced, adjusting the pump and
lockshield valve as necessary. Having achieved a satisfactory
condition operate the boiler with the bypass fully closed on
minimum load, normally this will be central heating with one
radiator,inthemainliving area working. Thevalveshouldthen
be gradually opened to achieve a flow rate of 7.8L/min (1.7gal/
min).
Under no circumstances should this valve be left in the fully
closed position.
Operatetheboileragainonfullserviceandcheckthebalancing,
making further adjustments as necessary.
If thermostatic radiator valves are fitted care must be taken to
make sure adequate flow through the boiler when they close,
refer to the current issue of BS7478.
Do not attempt to adjust the thermostat calibration screw.
Test the boiler for spillage of the flue products at the draught
diverter as detailed in the current issue of BS5440 Part 1. See
also Section 2.3.

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6 Commissioning
6.7 Adjustment - Sealed Water Systems
Sealed water systems should be adjusted to the initial design
pressure and the set pointer repositioned.
6.8 Instruct the User in the Correct Operation
of the Boiler
Hand the User Instructions to the user for their use.
Instruct and demonstrate the safe and efficient operation of the
boiler, heating system and domestic hot water system.
Advise the user, that to ensure the continued efficient and safe
operation of the boiler it is recommended that it is checked and
serviced at regular intervals. The frequency of servicing will
dependupontheparticularinstallationandusage,butingeneral
once a year should be enough.
ItistheLawthatservicingiscarriedoutbyacompetentperson.
Draw attention, if applicable, to the current issue of the Gas
Safety (Installation and Use) Regulations section 35, which
imposes a duty of care on all persons who let out any property
containing a gas appliance.
Advise that the boiler is fitted with a safety device and refer to
the instructions for use.
Advisetheuseroftheprecautionsnecessarytopreventdamage
to the system and building in the event of the heating system
being out of use during frost and freezing conditions.
Reminder. Leave these instructions with the user.
Advise the user that the ‘Benchmark’ logbook should be
completed by the installation engineer on completion of
commissioning or servicing.
For the continued efficient and safe operation of the boiler it is
recommendedthatitischeckedandservicedatregularintervals.
The frequency will depend upon the particular installation and
usage, but in general once a year should be enough.
It is the Law that any servicing be carried out by a competent
person.
Replacement of parts must be carried out by a competent
person.
Before starting a service or replacing parts isolate the gas and
electrical supplies.
Unless stated otherwise all parts are replaced in the reverse
order to removal.
7.1 Heating Body - Service
Remove the controls cover by pulling it forwards and off.
Remove the outer casing by releasing the screw at the bottom
and unhooking at the top.
Remove the inner casing by releasing the wing nuts at the top
and the screws at the bottom, see diagram 7.1.
Removethecombustionchamberfrontbyunscrewingthewing
nut at the bottom front and the four screws, see diagram 7.2.
Disconnect the ignition lead from the electrode and unscrew
thermocouple nut to release, see diagram 7.3.
Supportthemainburnerandreleasepilottubingnutatthebase
of burner, release pilot tube. The pilot injector can now be
removed by unscrewing, see diagram 7.3.
Disengage the main burner from the main injector. Raise the
burner up through the combustion chamber to remove. Take
care not to damage the side insulation.
Place the burner to one side.
Cover the combustion chamber and injector with a sheet of
paper.
Remove the flue cleaning door, see diagram 7.1.
Remove the screws securing the draught diverter baffle and
lower out as shown in diagram 7.4.
Brush away any deposits from the heat exchanger paying
particular attention to the gap between the fins.
Remove the paper together with any debris.
When replacing parts make sure that the draught diverter is
refitted correctly. Diagram 7.1
ACCESS FOR SERVICING
FLUE CLEANING DOOR
INNER
CASE
INNER CASING
SECURING
SCREWS
WING
NUT(S)
2398
7.2 Main Burner - Service
Generally follow the instructions given in Section 7.1.
With the main burner removed brush or vacuum any deposits
away, make sure that the flame ports are clear.
Do not use a brush with metallic bristles.
Note. Alternative type of burner are fitted to some models.
Remove lint arrester from main burner and clean it thoroughly
bybrushingorvacuuming,seediagram7.5forBrayburnerand
diagram 7.6 for Furigas burner.
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7 Servicing and Replacement of Parts
7.3 Main Injector
Generally follow the instructions given in Section 7.1.
With the main burner removed the injector can be unscrewed
and replaced as necessary, using a new sealing washer.
If cleaning do not use a wire or sharp instrument on the hole.
Whenreplacingthemainburnermakesurethatitispushedfully
home onto the injector and that the guides are engaged on the
injector manifold.
Diagram 7.2
ACCESS FOR SERVICING
Diagram 7.3
PILOT ASSEMBLY
PILOT
INJECTOR
ADAPTOR
OLIVE
PILOT
TUBING
NUT THERMOCOUPLE
NUT
IGNITION
LEAD
(clear end)
ELECTRODE
THERMOCOUPLE
SECURING
SCREWS
PILOT
SHIELD
MICA WINDOW
M3
SCREW
COMBUSTION
CHAMBER
FRONT
PANEL
SIDE BAFFLES
SECURING
SCREWS
WING NUT
23971049
Diagram 7.4
DRAUGHT DIVERTER
AND BAFFLE
BAFFLE
SECURING
SCREW(S)
DRAUGHT
DIVERTER
BAFFLE
0929
Diagram 7.6
LINT ARRESTER
(FURIGAS)
Diagram 7.5
LINT ARRESTER
(BRAY)
SCREW-
LOOSEN ONLY
BURNER
ASSEMBLY
LINT ARRESTER
SECURING PLATE
LINT
ARRESTER
LINT ARRESTER
LINT ARRESTER
SECURING SCREW
AND WASHER
BURNER
ASSEMBLY
09280927

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7 Servicing and Replacement of Parts
7.4 Pilot Burner and Injector - Service
Generally follow the instructions given in Section 7.1.
Withthemaincase,innercaseandcontrolscoveretc.,removed
as above, pull off ignition lead from the electrode.
Unscrewthetubingnutatthebaseofthepilotburner,releasing
thepilotpipe. Removethepilotinjectorbyunscrewingfromthe
pilot burner.
Unscrew the thermocouple nut to release the thermocouple
from the pilot burner.
Support the main burner and remove the two screws and
washers securing the pilot burner and shield to burner.
Remove the complete assembly.
Lift the pilot burner off.
Take care not to damage the electrode.
Whenreplacingmakesurethesparkgapisasshownindiagram
7.7.
Check the pilot burner flame lengths are as shown in diagram
7.7.
7.5 Thermocouple
Generally follow the instructions given in Section 7.1.
Unscrew the thermocouple nut to release from the pilot burner,
see diagram 7.3.
Disconnect the thermocouple from the gas valve, see diagram
7.9.
Usetheoldthermocoupleasapatternwhenfittingthenewone.
Donottightenmorethanaquarterturnbeyondfingertightatthe
gas valve.
Check the electrode spark gap, see diagram 7.7.
Diagram 7.7
PILOT FLAME AND
SPARK GAP
14 to 17mm
14 to 17mm
THERMOCOUPLE
ELECTRODE
SPARK GAP
3 TO 4mm
1053
Diagram 7.8
THERMOSTAT
PHIAL/OVERHEAT
CUT-OFF
OVERHEAT
CUT-OFF
HEAT
EXCHANGER
RETAINING
CLIP
THERMOSTAT
PHIAL
CUT-OFF
SECURING
SCREW(S)
0951
GAS VALVE ASSEMBLY Diagram 7.9
GAS SERVICE
COCK
(Shown Off)
'O' RING
INTERRUPTER
EXT. SCREW (4)
'O' RING
PILOT
TUBE
NUT
GAS
VALVE
CONNECTORS
THERMOCOUPLE NUT
ELECTRICAL
CONNECTOR
2414
EXT.
SCREW (4)

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7 Servicing and Replacement of Parts
7.6 Electrode
Generally follow the instructions given in Section 7.1.
Unscrew the electrode from the pilot shield.
When refitting check that the spark gap is as diagram 7.7.
7.7 Over Heat Cutoff Device
Generally follow the instructions given in Section 7.1.
Remove the screws securing the over heat cutoff device to the
clamp, see diagram 7.8.
Releasethecutoffconnectorsatthegasvalve,seediagram7.9.
Removethescrewretainingthegrommetplatetotherearpanel
to release plate, see diagram 7.10.
Carefullyremove,oneat a time,thecablesofthecutoff through
the grommet.
When reassembling use a little of the heat sink compound,
supplied,onthefaceofthecutofftomakesureofagoodcontact
with the pipe also make sure it is correctly located.
7.8 Gas Valve
Generally follow the instructions given in Section 7.1.
Remove screw to release gas valve cover.
Disconnect all leads and pipes at valve.
Undo the four screws each side of the valve to release the
service cock and burner supply tube, take care not to damage
the “O” rings.
Remake all connections.
Do not tighten the thermocouple nut more than a quarter turn
beyond finger tight.
It will be necessary to purge pipework and gas valve before
relighting, refer to Commissioning.
7.9 Electrical Control Box
Remove controls cover and outer casing as above.
Remove retaining clip from boiler thermostat phial pocket and
withdraw the phial, see diagram 7.8.
Removethe control box byundoing the two fixingscrews at the
front and lower the front of the box until it is clear of the cover.
Pushtheboxtowards therearoftheboilertodisengagethehinge
and lower, see diagram 5.1.
Withdrawthecontrolthermostat capillary through the bottom of
the air duct.
Disconnectcables(a)mains,L.NandE(b)pumpatterminal8,
7 and earth stud, (c) cables at gas valve, (d) disconnect any
remote controls at terminals 9 and SL.
When replacing refer to diagram 5.2 for electrical connections.
Smear the control thermostat phial with heat sink compound
and make sure it is secured with the retainer, in the pocket.
7.10 Piezo Unit
Gain access generally as Section 7.1.
Disconnect ignition lead and remove backing nut from piezo
unit.
7.11 Ignition Lead
Gain access generally as Section 7.1.
Disconnect the ignition lead at both ends.
When replacing the clear end fits to the electrode.
7.12 Control Thermostat
Gain access generally as Section 7.1.
Remove and support the control box.
Remove the control knob and electrical connections from the
control thermostat body.
Pull off the connectors from the control thermostat terminals.
Remove the two screws securing the control thermostat to the
control box. The control thermostat can now be removed.
When replacing smear the control thermostat phial with a little
heat sink compound, supplied, before fitting into the pocket.
Diagram 7.10
OVERHEAT CUT-OFF
REMOVAl
GROMMET
GROMMET
PLATE
(behind duct)
SECURING
SCREW for
Grommet Plate
0787
Diagram 7. 11
GAS VALVE
COVER
SOLENOID
SECURING
SCREW
RETAINING
CLIP
ELECTRICAL
CONNECTORS
3782

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7 Servicing and Replacement of Parts
Diagram 7.12
SECURING
SCREW for
Grommet Plate
GROMMET
PLATE
(behind duct)
PHIAL
BRASS
KNURLED
NUTS
INSET C
FLUE BLOCKAGE
SAFETY DEVICE
LOCKNUT
PLASTIC
RETAINING
CLIP
5400
5389
5390
BRACKET INSET BINSET A
CAPILLARY
7.13 Replacement of Flue Blockage
Safety Device
Gain access generally as section 7.1 and Diagram 7.12
InsetA. Removephialassemblybyremovingthebrassknurled
screw(s).
Inset B. Carefully remove phial and capillary through back of
boiler.
Inset C. Having opened control box remove the electrical
connections from the flue blockage safety device, the locknut
and capillary retaining clip. Fit new flue blockage safety device
in reverse order, making sure that the capillary is secure and
there is sufficient slack at the control box to allow the box to be
opened and closed without damaging the capillary.
Important. Makesurethephialassemblyiscorrectlylocatedon
the two locating studs.
When refitting make sure that the capillary is clear of hot
surfaces, to avoid nuisance shut down of boiler.

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8 Fault Finding
Remedy
Fault and Cause
8.1 Pilot Goes Out after a Period
of Remaining Alight
Front cover not correctly fitted. Fit parts correctly.
Flue parts not fitted or sealed properly. Seal cavity or fit flue parts correctly as described in
Installation Instructions.
Electrical supply failure causing
over heat device to operate. Relight pilot.
Pump incorrectly wired. Connect pump in accordance with diagram 5.2.
Overheat cutoff operating. Refer to Section 8.3.
8.2 Main Burner Will Not Light
External, remote controls not “On.” Check that any remote controls are calling for heat.
Control thermostat not on. Check control thermostat is in an “On” position, see also
Section 8.9.
Flue Blockage Safety Device tripped. Reset, refer to section 6
If Flue Blockage Safety Device repeatedly requires resetting, call a service engineer
8.3 Control Thermostat Will Not Cut Out
Control thermostat phial not fitted in pocket. Fit phial in pocket.
Faulty control thermostat. Replace control thermostat.
8.4 Overheat Cutoff Device
Cuts Out Prematurely
Air in heating body. Vent system. Alter system layout if necessary.
Water circulation low or stopped. Pump not functioning correctly. Check pump is
wire directly to the boiler. Alter system if necessary.
Overheat cutoff device operates before boiler
cycles on maximum control thermostat setting. Change faulty overheat cutoff device.
The correctly set overheat cutoff device operates
prematurely. There is no air in the heating body
and water circulation satisfactory. Change faulty heating body.
Pump not functioning correctly. Check pump is wire directly to the boiler.
Alter system if necessary.
8.5 Insufficient Heat
Control thermostat set too low. Increase setting.
Inlet gas pressure inadequate. Increase gas pressure.
Governor setting incorrect.
(make sure control thermostat is on maximum setting). Check burner pressure against data label.
Reset only if more than 10% away from required figure.
8.6 Appliance Noisy in Operation*
Overgassed. Check burner pressure against data label and adjust only if
more than 10% away from stated required figure.
Complete lack of water. Check system controls for correct installation or correct type
of controls.
Air in system. Remove air from system. When system is first commissioned
the air dissolved may take some time to boil out, therefore
attempts should be made to vent air during the first weeks of
the installation. Check venting of system, as air bubbles can
remain suspended in the water if system is not well vented.
Water flow rate. Check that flow rate is correct. Check that pump is correct
size and is correctly adjusted. Bypass not fitted or set
correctly.
* There remains on most boilers a residual noise more noticeable at high temperatures. Normal operation of the boiler over a period should remove most noise.

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8 Fault Finding
Diagram 8.1
THERMOCOUPLE
Diagram 8.2
GAS VALVE
CONNECTION 'E'
CONNECTION 'D'
BOILER
OVERHEAT
CUT-OFF
CONNECTION 'B'
CONNECTION 'C'
CONNECTION 'A'
2487
2327\A
Re-connect boiler overheat cut-off to points
A and B. Disconnect thermocouple at point
D of the gas valve. Test continuity between
point C and the body of the gas valve.
Is there continuity?
Test continuity of thermocouple between inner
connection point D and point E.
Is there continuity?
Faulty boiler overheat cut-off,
renew.
Thermocouple and boiler overheat circuit
satisfactory.
NO
YES
YES
Faulty cut-off connectors into gas
valve, either at A or C.
Renew where faulty.
Faulty thermocouple, renew.
With the boiler cold, check connections of the thermocouple, boiler overheat cut-off and gas valve.
Disconnect overheat cut-off connectors at points A and B at the gas valve, see diagram 3.4.
Test continuity of the overheat cut-off. Is there continuity?
YES
NO
NO
8.7 Thermocouple and Overheat Cutoff Device
To test the thermocouple, a meter with a range of 0 to 30 mV is
required.
Symptom: The pilot burner fails to stay alight. Test the
thermocouple, overheat cutoff and thermocouple connectors,
as described in fault finding chart 8.2, see also diagram 8.1.
Check the millivoltage of the thermocouple closed circuit at
points “A” and “E”, see diagram 8.1. This should be within the
range of 6 to 13mV.
8.8 Electrical
Important: The preliminary electrical systems checks in a
multimeterinstructionbookarethefirstcheckstobecarriedout
duringafaultfindingprocedure.Oncompletionoftheservicing/
faultfindingtaskwhichhasrequiredthebreakingandremaking
of electrical connections then checks, earth continuity, polarity
and resistance to earth must be repeated.
Tocheckthecontrolthermostatandgasvalve,seediagram8.3
and functional flow wiring diagram 8.4.
Tocheckcontrolthermostatpump over runcutoffdevicecircuit
see diagram 8.3 and functional flow wiring diagram 8.5.
8.9 Pilot
Refer to fault finding for pilot, see diagram 8.5.