Glowworm 56/2 User guide

221781A.07.00
Installation and Servicing Instructions
Hepworth Heating Ltd.,
Nottingham Road, Belper, Derbyshire. DE56 1JT
General/Sales enquiries:
Tel: [phone] Fax: [phone]
One Contact Local Service
To be left with the user
Customer Services:
Tel: [phone]
Fax: [phone]
8010
References 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.
This is a Cat I2H Appliance
BS 6332
BS 5258
For use with specially designed Glow-worm fire fronts only
Glow-worm 56/2 Back Boiler Unit
GC No 44 315 40

2
221781A
C
L
FLUE
C
L
FLUE
1 General
Dimension A B C D E F G H J K L M N P Q
'56/2' 345min 238min 88min
BACK BOILER 547 357 146 185 56 212 382 168 350 460 370max 263max 154 192 113max
Diagram 1.1
Theinstructionsconsistofthreeparts,InstallationandServicing
Instructions for the Back Boiler Unit, Installation and Servicing
Instructions for the Fire Front and Instructions for Use, which
includestheGuaranteeRegistrationCard. Theinstructionsare
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.
This boiler is for use only with a specially designed Glow-worm
Gas Fire Front, see Table 1.
The boiler is delivered in one pack which contains all the parts
necessary for the installation.
If installing the back boiler unit and fire front at the same time
please read both sets of instructions before starting.
1 General Notes and Information
IMPORTANT NOTICE
The back boiler is fitted with a safety device which will shut it
down if there is a lack of oxygen. If the back boiler shuts down
frequentlyfor noapparent reasonthe firstthings tobe checked
are the chimney and air inlets into the room. Any problems
foundmustbeputright,byacompetentperson,beforetheback
boiler is used again.
This back boiler is for use only on G20 gas.
Wherever possible, all materials, appliances and components
to be 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 back boiler care
should be taken when handling the edges of sheet metal parts
to avoid any possibility of personal injury.
1.1 Statutory Requirements
The installation of this back boiler unit must be carried out by a
competent person in accordance with the current issue and
relevant requirements of:
Manufacturer’s instructions, supplied.
TheGasSafety(InstallationandUse)Regulations,TheBuilding
Regulations, The Building Standards (Scotland) Regulations
(applicable in Scotland), Local Gas Undertaking, Byelaws of
theLocal WaterCompany,The HealthandSafety atWorkAct,
Control of Substances Hazardous to Health, The Electricity at
Work Regulations and any applicable local regulations.
Detailedrecommendationsarecontainedinthecurrentissueof
the following British Standards and Codes of Practice,
BS6891, BS5449, BS5546, BS6700, BS5871, BS5440 Part 1
and 2, BS6798, BS1251, BS7478, BS7593, BS7671.
Manufacturer’snotesmust notbetakenas overriding statutory
requirements.
1.2 Data
Gas connection Rc1/2(1/2inBSPT)
Water connection Rc1 (1inBSPT)
Electrical supply 230V~50Hz fused 3A
Weight, about 47.4kg (104.5lb)
Water content 6.28Litres (1.38gall)
Injector 3.7mm
Dimensions are given in millimetres (except as noted).
Data Label: Bottom left of control tray.
6070
C
N
A
PE
D
M
L
F
Q
H
J
G
GAS CONNECTION
Rc 1/2 (1/2in. BSPT)
WATER CONNECTION Rc1
(1in. BSPT) ON RIGHT-HAND
SIDE OR LEFT-HAND SIDE
(R.H. SHOWN)
INSIDE DIAMETER OF
SOCKET FOR 125mm (5in)
NOMINAL DIAMETER FLUE
GENERAL DIMENSIONS
All dimensions are in
millemetres
BK

3221781A
INJECTOR
MARKING
1 General
RANGE RATING
NOMINAL kW
HEAT INPUT
(GROSS) Btu/h
NOMINAL kW
HEAT
OUTPUT Btu/h
BURNER mbar
SETTING
PRESSURE in.w.g
18.5 20.2 21.9
63,200 69,000 74,800
RANGE RATING TABLE
3.7 203001
13.8 15.2 16.5
47,100 51,950 56,450
9.8 11.7 13.7
3.94 4.70 5.5
Minimum Medium Maximum
1.3 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 back boiler.
Oncompletiontestthe gasinstallationusingthepressure drop
method and suitable leak detection fluid, purge in accordance
with the current issue of BS6891.
1.4 Electrical Supply
WARNING. This back boiler must be earthed.
All system components shall be of an approved type and shall
be connected in accordance with the current issue of BS7671
and any applicable local regulations.
Connectionofthebackboilerandsystemcontrolstothemains
supply should be through a double pole isolating switch, fused
3Ahavingaminimumcontactseparationof3mminbothpoles.
Alternatively, a fused 3A 3 pin plug and unswitched socket
outlet to the current issue of BS1363 may be used.
Wiring to the back boiler must be PVC (85oC) insulated type to
the current issue of BS6500 Table 16, not less than 0.75mm2
(24/0.20mm).
1.5 Site Requirements
Refer to diagram 1.1 for dimensions appropriate to the back
boiler.
For all types of installation a standard sized builder’s opening
is required, see diagram 1.2.
It is important that the opening is cleared of debris and mortar.
It is recommended that the access hole for pipework into the
fireplace or builder’s opening is either at the left hand or right
hand side of the chimney breast. If access is required at both
sides then it may be necessary to prepare some of the
connections before fitting the back boiler into the builder’s
opening.
The prepared base for the back boiler must be level.
Refer to Table 2 for dimensions of fire front fixing wall face
which must be true.
1.6 Water System - Open Vented
This back boiler can be used on an unrestricted open vented
systemwith thewater supply taken from a feed andexpansion
cistern, having a head between 1m (3ft3in) minimum and 27m
(90ft) maximum.
Diagrammaticlayoutsofsystemsareshownindiagram1.3and
1.4.
1.7 Sealed Water System
A kit and instructions, part number 426520, is available to
enablethebackboilertobeusedonasealed watersystem.
Pleasegive theserial number ofthe backboiler when ordering
the kit.
Dimensions
for
minimum
flat area
(no fixtures)
Dimensions
for fixture or
surround
protection
clearance
3013
FRONT
OPENING
C
L
ALL DIMENSIONS IN MM
PREPARED
BASE
Y
X
G.C No.
Teak Mahogany
T a b l e 1
FIRE TYPE
Miami 3 BBU 37-047-04A 37-047-07A
Melody 3 BBU 37-047-06A
Black Ash 3 37-047-08
Saxony 3 37-047-09
Brown Ember 3 37-047-02
T a b l e 2
FIRE
TYPE
XY XY
Miami 3 BBU 642 698 750 836
Melody 3 BBU 642 698 750 836
Black Ash 3 700 660 840 890
Brown Ember 3 795 707 905 892
Saxony 3 700 625 840 860

4
221781A
FULLY PUMPED SYSTEM
(DIAGRAMMATIC) Diagram 1.4
The COLD FEED PIPE may be connected to the flow
pipe, adjacent to the open vent pipe as shown .
(THERE MUST ALWAYS BE A COLD WATER PATH
TO THE RETURN CONNECTION Of THE BOILER.)
C
L
BOILER
22mm MIN
OPEN VENT
INDIRECT
CYLINDER
MANUAL
AIR VENT
1 metre MIN
27 metres MAX
15mm
COLD
FEED
PUMP
HEATING
CIRCUIT
150mm
MAX
DRAIN COCK
1588
Diagram 1.3
PUMPED HEATING & GRAVITY
DOMESTIC HOT WATER
(DIAGRAMMATIC)
1587
C
L
BOILER
27 metres
MAX
PUMP
HEATING CIRCUIT
22mm
VENT
Refer to
B.S. 5546
28mm
INDIRECT
CYLINDER
15mm
COLD
FEED
DRAIN COCK
1 General
1.8 Hot Water Cylinder
The back boiler is suitable for open vented systems using an
indirect cylinder (including single feed self priming type). The
indirect cylinder must be fitted to the manufacturer’s
recommendations and the system must conform to the
requirements of the current issue of BS5546 and BS6700.
It is recommended that the indirect cylinder be fitted with some
form of temperature control.
1.9 Frost Protection
Ifthepositionofthebackboilerissuchthatitmaybevulnerable
to freezing it should be protected as specified in the current
issue of BS5422.
It is also recommended that a frost protection thermostat is
fitted.
1.10 Draining Tap
Adrainingtapmustbeprovidedatthelowestpointofthesystem
whichwillallowtheentiresystem,theback boilerandhotwater
cylinder to be drained.
Draining taps shall be to the current issue of BS2879.
1.11 Safety Valve
A safety valve need not be fitted to an open vented system.
1.12 Back Boiler Location
This back boiler MUST NOT be installed in a private garage or
in a room containing a bath or shower or in a room used or
intended to be used as sleeping accommodation.
1.13 BSI Certification
ThisapplianceiscertificatedtothecurrentissueofBS6332Part
1 invoking the current issue of BS5258 Part 8 for safety and
performance. It is, therefore, important that no alteration is
madetoitwithoutpermission,inwriting,fromHepworthHeating
Ltd.
Any alteration that is not approved by Hepworth Heating Ltd.,
couldinvalidatetheBSI Certificationoftheboiler,warranty and
could infringe the current issue of the Statutory Requirements.
C
L
C
L
3012/A
C
B
405mm
A
* CORNER IN-FILL
(not required to be full
depth of opening)
PREPARED
BOILER
BASE
100mm
Diagram 1.2
FRONT OPENING
A B C
Miami 3 BBU 350 405 to 580 560 to 590
Melody 3 BBU 350 405 to 580 560 to 590
Black Ash 3 350 406 to 460 560 to 590
*Brown Ember 3 350 510 to 580 560 to 590
Saxony 3 350 406 to 460 560 to 590

5221781A
1 General
CE Mark
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. Directive73/23/EEContheharmonizationoftheLawsofthe
Member States relating to 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.
_________________________________________
ThisboilerisexemptfromthegeneralrequirementsoftheBoiler
(Efficiency) Regulations (1993) and Directive 92/42/EEC by
reason of its conformity to Schedule 3.I.7 of those Regulations
and Article 4.3 of that Directive.
_________________________________________
1.14 Inhibitor
Attention is drawn to the current issue of BS5499 and BS7593
on the use of inhibitors in central heating systems.
If an inhibitor is to be used, contact a manufacturer for their
recommendations as to the best product to use.
Ifusinginanexistingsystemtakespecialcaretodraintheentire
system, including the radiators, then thoroughly cleaning out
before fitting the boiler whether or not adding an inhibitor.
2.1 With Non-combustible Hearth
Theback boiler mustbeinstalled levelwiththe hearthorabove
it, see diagram 2.1.
For minimum dimensions of a hearth see diagram 2.1.
2.2 Combustible Hearth
If the hearth is existing and made of a combustible material the
back boiler must be installed to the dimensions in diagram 2.2.
2.3 With Surround
The combined thickness of the surround and lintel must be
checked, to make sure that the back boiler can be positioned
within the opening to allow easy connection of the flue into the
back boiler flue socket, see diagram 2.3.
Thesurroundrequiresaminimumopeningforaccessasshown
in diagram 1.2.
2.4 Wall Mounted - that is - Without Surround
or Hearth
If there is to be any combustible material beneath the fire front,
forexample,carpetthenthebase ofthebuilder’sopeningmust
not be less than 75mm above the floor covering as shown in
diagram 2.2.
Diagram 2.3
LINTEL DIMENSION
Diagram 2.1
INSTALLATION WITH
HEARTH (NON-COMBUSTIBLE)
Diagram 2.2
COMBUSTIBLE HEARTH / WALL
MOUNTED INSTALLATIONS
1591 1590
FIRE FIXING WALL FACE
350mm
MIN.
TOP OF HEARTH
MUST NOT BE ABOVE
PREPARED BASE
13mm MIN NON-
COMBUSTIBLE
MATERIAL
50mm
MIN.
PREPARED BASE
350mm
MIN.
FIRE FIXING
WALL FACE
N.B. *Minimum dimension.
This dimension refers to
minimum clearance after
carpet or any floor
covering has been fitted.
PREPARED BASE
TOP OF
CARPET,FLOOR
COVERING OR
COMBUSTIBLE
HEARTH
*75mm
FLUE PIPE
MIN. 48mm
MAX. 73mm
FIRE FIXING
WALL FACE
*165mm N.B. *This dimension can
be increased up to 190mm
if builders opening depth
is at least 375mm deep.
1589
Thebuilder’sopening,withlintelmusthaveminimumdimensions
as shown in diagram 1.2 and 2.3.
2 Types of Installation

6
221781A
BACK
BOILER
UNIT
3 Flue and Ventilation
Diagram 3.1
Diagram 3.2
EXISTING FLUE FITTED WITH
APPROVED LINING
FLEXIBLE LINER
CONNECTION
1593
BACK BOILER
APPROVED
SEAL
RIGID
FLUE
LINER
FLEXIBLE
LINER
1592
600mm
SEALING
PLATE
SEALING AND
CLAMPING
PLATE
3.1 General
The general recommendations of the current issue of BS5440
Part 1 should be followed.
In all cases the flue should be lined, preferably with a flexible
liner.
It is essential that the flue has an equivalent height of at least
2.5m(8.2ft)measuredfromtheflueconnectionontheappliance.
The first 600mm, at least, above the draught diverter must be
vertical.
The flue socket is designed to take flue pipe to BS567. If flue
pipe conforming to a different standard is used a suitable
adaptermustbefittedandsecuredtothefluesocket. A flexible
flue liner may be used, with connection to the back boiler flue
socket made with a short vertical piece of flexible liner, see
diagram 3.2.
Theexistingfluemaynotbecompletelysound. Toprevent any
possibility of leakage, additional sealing MUST be carried out
between the base of the chimney and the flue liner.
The end of the liner at the chimney top must be adequately
sealed and clamped, using proprietary fittings suitable for the
flue liner used, see diagram 3.1.
The flue should, preferably, end above ridge height but at least
above the eaves of a pitched roof. Use a certificated terminal.
If the flue is to pass through or near any combustible material it
should be installed in accordance with the current issue of
BS5440 Part 1. If in doubt seek advice from the local gas
undertaking or Hepworth Heating Ltd.
3.2 Existing Chimney
An existing brick chimney must be thoroughly swept and all
debris cleared away before lining.
Removeanyregisterplates,dampersandthelike. Alternatively
it may be locked in the open position.
Aflexiblefluelinerispreferredbutarigidlinermaybeused,with
connection to the back boiler flue socket made with a short
vertical piece of flexible liner, see diagram 3.2.
Anyairsupplythatentersthebuilder’sopeningotherthanbythe
front opening, that is underdraught openings and the like must
be completely sealed off.
Thesealing platealsoprevents debrisfalling and givesthe flue
better insulation, reducing the possibility of condensation, see
diagram 3.1.
Check the flue system efficiency before installing the back
boiler.
3.3 New Chimney
A newly built chimney can be lined with a moisture resistant
lining, such as salt glazed pipe, of an appropriate diameter as
specified in the Building Regulations
In the case of a salt glazed lined flue, it is recommended that a
short vertical length of flue pipe, preferable flexible metallic be
used,fixedandsealedtothebackboilerfluesocket,madegood
withapprovedpackingandpargedwithfirecement,seediagram
3.2.
If a flue and false chimney breast are to be constructed all
openingsforpipeworktoupperfloorsetc.,mustbesealed. The
onlyopeningforthebackboilermustbeatthefront,beingofthe
dimensions as shown in diagram 1.2.
If a specially built compartment is constructed for the back
boiler, it must conform to the requirements of the current issue
of BS5440 Part 1 and BS5871.
The flue should, preferably, end above ridge height but at least
above the eaves of a pitched roof. Use a certificated terminal.
AIR SPACE

7221781A
3 Flue and Ventilation
3.4 Ventilation - Back Boiler and Fire Front
It is important that the room in which the back boiler unit is
installed has adequate air inlets to ensure correct operation as
specified in the current issue of BS5440 Part 2.
Ventilation requirement for this back boiler is:
97cm2(15in2)
Thisventilationareatakes intoaccountthetotalrequirement of
the back boiler unit and any of the specially designed gas fire
fronts.
The ventilation openings may communicate direct with outside
airorwithan internalroomorspace(such asahall)whichitself
isprovidedwithapermanentairventofthesameeffectivearea.
Thepermanentairventshouldbeinapositionwhichminimises
nuisance to occupants due to draughts.
This vent must NOT be placed in the builder’s opening.
If the appliance is to be installed in a room already containing
another fuel burning unit, the air supply required for this other
unit MUST be added to the figure above.
Any air vent taken through a cavity wall must be ducted.
4.1 Preparation
Remove draught diverter, flueway baffle and fittings pack from
carton.
Remove back boiler body assembly from carton.
4.2 Water Connections
IT IS EXTREMELY IMPORTANT THAT NO SERVICE PIPES
ARE ROUTED IN FRONT OF THE BACK BOILER.
If the builder’s opening was previously used for solid fuel all
pipework within should be protected with PVC tape or equal.
Pipework passing through walls of the opening should be
sleeved and made good.
The four heat exchanger connections are tapped Rc1 and are
all on one side of the heat exchanger, see diagram 1.1.
4.3 Pumped Heating with Gravity Domestic
Hot Water
All pipework must comply with the current issue
of BS5546.
The domestic hot water flow and return pipes must be 28mm.
Thedomestic returnmust beinto theconnection directlybelow
the domestic flow connection.
Refer to diagram 1.3 for a diagrammatic layout.
If it is necessary to route pipework from both sides of the
builder’sopening,itisrecommendedthattheheatexchangeris
positioned on the combustion chamber so that the gravity
circuits exit on the same side as the back boiler connections.
It is recommended that pumped heating connections are
prepiped as in diagram 4.2.
If the heat exchanger connections are opposite hand to that
required,theheatexchangercanbeturned,asfollows,remove
the four screws securing the heat exchanger to combustion
chamber, see diagram 4.1. Turn heat exchanger, refit the four
screws.
3.5 Extract Fans
Ifanextractfanisfittedinthepremises,thereisapossibilitythat
if adequate air inlet openings are not provided spillage of the
products of combustion could occur.
When openings are fitted in accordance with the
recommendationsofthecurrentissueofBS5440Part2,extract
fans should not cause spillage.
Where such a fan installation is found, a clearance of products
testmustbeconductedasdescribedinthefirefrontInstallation
Instructions.
This test must be carried out with the back boiler fitted with its
fire front.
See also Section 6.3 of these instructions.
Diagram 4.2
Diagram 4.1
PUMPED HEATING -
WITH GRAVITY HOT
WATER PRE-PIPING
5188
1595
HEAT
EXCHANGER
SECURING
SCREWS (2)
SECURING
SCREWS (2)
COMBUSTION
CHAMBER
28mm
168mm 22mm 30mm
MIN.
40mm
MIN.
380mm
MAX.
95mm
238
4 Installation

8
221781A
Diagram 4.5
5190
FLUE BAFFLE
FRONT OF
BACK BOILER
FLUEWAY
Diagram 4.4
8014
INSTALLATION
CENTRE LINE
'A'
'A'
'Y' LIMIT
MARKS
FIRE
FIXING
LIMIT
MARKS
INSTALLATION
CENTRE LINE
45
56
FIRE
FIXING
WALL
FACE
NOTCH
LIMIT
MARKS
VIEW ON
ARROWS
'Y'
VIEW ON
ARROWS
'A'
FIXING
HOLE(S)
7mm Drill
Mark through the fixing holes each side of the combustion
chamber, see diagram 4.4. Remove the back boiler. Drill two
holes to accept the plugs and fixings provided.
Ifaccesstothefixingholesshownindiagram4.4isdifficult,use
the alternative method described in Section 4.8 otherwise
proceed as Section 4.9.
4.8 Alternative Back Boiler Fixing
PositionthebackboilerasdescribedinSection4.7paragraphs
1 to 3.
Carefully disconnect the electrical plug from the gas valve and
undo the four screws securing the combustion chamber
extension and remove, see diagram 4.8.
Markposition of fixingholeson eachsideof thefloorprotection
plate, see diagram 4.9. Remove back boiler from the opening.
Drill two holes to accept the plugs and fixings provided.
4 Installation
Diagram 4.3
PUMPED HEATING
& HOT WATER PRE-PIPING
380mm
MAX.
30mm
MIN.
22mm
95mm
22mm
238
4.4 Pumped Heating and Hot Water
Thepumpedflowconnectionmustbe diametricallyoppositeto
the pumped return connection.
Refer to diagram 1.4 for a diagrammatic layout.
If it is necessary to route pipework from both sides of the
builder’sopeningitisrecommendedthattheheatexchangeris
positioned on the combustion chamber such that the flow pipe
exits on the same side as the back boiler connections.
It is recommended that the pumped return is prepiped as in
diagram 4.3.
If the heat exchanger connections are opposite hand to that
required, turn in the same manner as described in Section 4.3
paragraph 7.
4.5 Pump
Isolatingvalves, integralif possible, must be fitted each sideof
the pump.
4.6 Gas Supply
The gas installation must be fitted in accordance with the
recommendations of the current issue of BS6891.
See diagram 1.1 for position of gas connection.
It is recommended that the gas supply enters the builder’s
opening on the right hand side.
If the gas supply enters from the left hand side it will be
necessary to route the pipe behind the combustion chamber
before final fixing, see diagram 4.2 and 4.3.
4.7 Positioning the Back Boiler
Topositionthebackboilerliftbythecastingandplacecentrally
in the builder’s opening. The installation centre line is marked
on the combustion chamber extension and by a notch on the
front edge of the floor protection plate.
The back boiler must be positioned so that a line across the
openingofthefirefixingwallfacefallsbetweentheappropriate
front and rear limiting marks, see diagram 4.4.
The easiest method of aligning the back boiler is to use a
straight edge across the top of the combustion chamber
extension. It is important that the back boiler is square to the
fire front fixing wall face.
Check that the back boiler is level. If packing is required to
adjust the level of the back boiler, use metal shims and pack
under the full width of the base.

9221781A
4 Installation
Diagram 4.6
Diagram 4.7
5202
5203
FRONT OF
BACK BOILER
HEAT
EXCHANGER
DRAUGHT
DIVERTER
SCREW(4)
FLUE COLLECTOR
ASSEMBLY
SOCKET
FRONT
No.8 X 1/2
SCREWS
(BLACK)
Fully fit No.8 X 3/8
screw into rear of
socket.
Centralise flexible
flue liner using the
2 No. 8 x 1/2
screw
provided.
No.8 X 3/8
SCREWS REAR
4.9 Positioning the Back Boiler - continued
Fitthefluebaffleontop oftheheatexchangerensuringthatthe
fourcornersarecorrectlylocatedintotheflueways,seediagram
4.5. The flue baffle is marked “TOP FRONT”.
Fit the draught diverter onto the heat exchanger with the four
screws provided in the fittings pack, see diagram 4.6. taking
care not to damage the seal.
Whereaflexiblefluelinerisbeingused,fullyfittheNo8x3/8inself
tapping screw provided into the rear of the flue socket as in
diagram 4.7.
Repositionthebackboilerintothebuilder’sopeningandsecure
to the prepared base with the screws provided. Connect the
system pipework to the back boiler unit/preplumbed pipework.
Refitthecombustionchamberextension,ifpreviouslyremoved.
Connect gas supply to gas service cock. Leave gas service
cock in the Back Boiler/Fire “OFF” position, see diagram 6.2.
If a flexible liner is being used, position the liner in to the flue
socket. UsingtwoNo8x1/2inselftappingscrewscolouredblack,
fromthefittingspack,screwthrough thetworemainingholesin
the flue socket to centralise and secure the flue liner, see
diagram 4.7. Seal with a suitable fire clay cement.
Diagram 4.8
Diagram 4.9
8015
SECURING
SCREWS
UNION NUT
UNION
NUT
GAS VALVE
ELECTRICAL
PLUG
SECURING
SCREWS
ALTERNATIVE
FIXING HOLES
1602
COMBUSTION
CHAMBER
EXTENSION
AND BURNER
ASSEMBLY
FLOOR
PROTECTION
PLATE

10
221781A
Diagram 5.3
8019
CABLE
CLAMP
EARTH
Diagram 5.2
Diagram 5.1
5 Electrical Wiring
8011
MAINS
CABLE
THERMOSTAT
CAPILLARY TO R.H.
PHIAL
POCKET
CABLE
CLIPS
CAPILLARY
CLIPS
MAINS
FROM
R.H.S.
SECURING SCREW
8012
GAS VALVE
ELECTRICAL PLUG
5.1 General
WARNING. This boiler must be earthed.
ISOLATE THE ELECTRICAL SUPPLY BEFORE DOING ANY
WIRING.
Alloftheelectricalinstallationmustbecorrectlyearthedandbe
in accordance with the current issue of BS7671 and be carried
out by a competent person.
The mains supply required is 230V~ 50Hz, fused at 3A. A
double pole isolating switch, having a minimum contact
separation of 3mm in both poles should be used.
The mains cable should be PVC heat resistant to 85oC the
current issue of BS6500 Table 16, not less than 0.75mm2(24/
0.20mm).
Make sure that there is sufficient cable slack to ease future
servicing or replacement.
It is preferable to have the electrical supply cable coming from
the left hand side of the builder’s opening.
If however, it must come from the right hand side, it must be
secured under the front edge of the combustion chamber
extension using the two cable clips, from the fittings pack, as
shown in diagram 5.1.
Make sure that all cables are routed well clear of hot surfaces.
5.2 Access to the Boiler Control Box
Disconnectthegasvalveelectricalplug,(ifnotalreadyremoved)
see diagram 5.2.
Remove the electrical control box securing screw and lift the
box upwards to release, see diagram 5.5.
5.3 Control Box Wiring
Thread the cable through the rear of the box, see diagram
5.3.
The mains cable outer insulation must not be cut back external
to the clamp.
Whenmakingconnections,makesurethatthe earth conductor
ismadeofagreaterlengththanthecurrentcarryingconductors,
so that if the cable is strained the earth conductor would be the
last to become disconnected.
Connecttheincomingmainsearthconductortothe terminal
on the terminal block, see diagram 5.3 and 5.4.
Connect the incoming mains neutral conductor to N and boiler
control live to Ls.
CAPILLARY
CUT-OUT

11 221781A
5 Electrical Wiring
8082
Diagram 5.4
NL
E
N
GAS VALVE
BLUE
BLACK
E
N
THERMOSTAT
NC C
BROWN
BLACK
VIEW OF PLUG
WHEN REMOVED
GREEN/YELLOW
230V ~ 50Hz
MAINS SUPPLY
FUSED AT 3 AMP
GREEN/
YELLOW
5.4 Testing - Electrical
Checks to ensure electrical safety must 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 cable.
2. Test the earth continuity and short circuit of all cables.
3. Test the polarity of the mains.
5.5 Control Box Refitting
Refit the control box making sure that the control thermostat
capillaryispositionedsothatitpassesthroughthe cutout inthe
control box panel, see diagram 5.2.
Secure with screw previously removed, see diagram 5.2.
Refit the gas valve electrical plug.
5.6 Control Thermostat Phial
Unwindthecapillarysothat itwillbewellclearofany partofthe
backboilerwhichbecomeshotandinsertitfullyintothepocket,
see diagram 5.6.
Secure with location washer behind the split pin.
If the phial pocket is on the right hand side use the cable clips
supplied in the fittings pack. Secure the capillary, see diagram
5.1. Check that the capillary is not touching any hot surfaces.
Diagram 5.5
Diagram 5.6
1870 8021
PHIAL
POCKET
RETAINING
SPLIT PIN
LOCATION
WASHER
CONTROL
BOX
FLOOR
PROTECTION
PLATE
CONTROL
THERMOSTAT
CAPILLARY
L
Ls

12
221781A
6 Commissioning
Diagram 6.1
'D' PIEZO
UNIT BUTTON
'L'
BOILER
DATA
BADGE
SETTING
POINT
'M' VIEWING
WINDOW
6074
'E' PILOT BURNER
'N'
PILOT
ADJUSTMENT
SCREW
'F'
GOVERNOR
ADJUSTMENT
COVER
SCREW 'A'
GAS VALVE
CONTROL
KNOB
SETTING
POINT
OFF
PILOT/IGNITION
MAIN BURNER
'G'
BURNER
PRESSURE
TEST POINT
'K' GAS
SERVICE
COCK
'B'
THERMOSTAT
CONTROL
KNOB
6.1 Commissioning the Back Boiler
TheBackBoilerisfittedwithaflueblockagesafetydevicewhich
will shut it down if there is a lack of oxygen.
The flue blockage safety device assembly incorporates the
electrode, thermocouple and pilot assemblies.
Note:The flue blockagesafety devicesensing tube issupplied
with the fire front.
The lighting, testing of the boiler and commissioning of the
system can continue, but the lighting of the boiler must be
repeated after fitting the sensing tube.
Ifthe backboiler shutsdown frequentlyfor noapparent reason
thefirst things tobe checked arethe chimney andair inlets into
theroom. Anyproblemsfoundmustbeputright,byacompetent
person, before the back boiler is used again.
Also,whensensingtubeisfitted,checkthatthefilterisnotlinted
up, see diagram 9.4.
The flue blockage safety device MUST NOT be adjusted or
disconnected.
If replacing use only the correct and approved parts.
Beforecommissioning theback boiler,the wholeof the system
should be thoroughly flushed out with cold water with the
circulation pump removed. Replace the pump, fill the system
and examine for water soundness. Vent air from the system
and pump.
CAUTION. Thefollowingwork should bedonebya competent
person.
Identify the back boiler controls by reference to diagram 6.1.
Open windows and put out all naked lights, cigarettes etc.
Test the gas supply for soundness. Purge air in accordance
with the current issue of BS6891.
Check that the electrical supply to the back boiler is switched
off.
Set the control thermostat control knob “B” to “Off” that is, fully
anti-clockwise.
Makesure the controlthermostatphial iscorrectlylocated, see
Section 5.6.
Remove the back boiler burner pressure test screw “G” and
connect a suitable pressure gauge.
If flue blockage safety device sensing tube is not fitted, remove
the plastic ferrule from the bulkhead connector on the air duct,
replace ferrule after testing/commissioning.
Turngas servicecock “K” toBack Boileronly “On” position,see
diagram 6.2.
Push in slightly and turn gas valve control knob “A” anti-
clockwiseuntil*isagainstthesettingpoint,nowfullypushinand
hold, at the same time press and release piezo button “D” until
the pilot burner “E” lights, view through window “M”.
Note, at this stage air may be present in the pilot supply so this
operation may need to be repeated.
When the pilot burner lights, keep gas valve control knob “A”
fully pushed in for about 15 seconds. If the pilot burner fails to
stay alight, repeat the lighting procedure but now keep the
control “A” knob pushed in for a little longer.
Check that the pilot flame is stable and has a length as shown
in diagram 6.3.
Push in slightly and turn gas valve control knob “A” anti-
clockwise until is against the setting point.
Ifthegasvalvecontrolknob“A”isturneduntil isagainstthe
settingpoint,asafetylockpreventsitbeingturnedonagainuntil
the thermocouple has cooled. NO ATTEMPT SHOULD BE
MADETO TURN THECONTROL KNOB “A”UNTIL AT LEAST
3 MINUTES HAVE GONE BY.
Switch on electrical supply and set any remote controls that is,
clock, thermostats, and the like, for heating. Refer to control
manufacturers’ instructions for specific detail
Turn control thermostat knob “B” clockwise until “MAX” is
against the setting point. The main burner should now light.
Test for gas soundness using a suitable leak detection fluid.
Thebackboilerissuppliedpresettothemaximumheatinputbut
may be adjusted to suit design requirements. Refer to Data
Label or Range Rating Table for details.
If adjustment is required, TEN MINUTES after lighting, remove
cover “F” and turn adjustment screw, anti-clockwise to suit
system design heat input.

13 221781A
6 Commissioning
Diagram 6.2
3924 S
1.64 m/3h to 2.15 m3/h
58.0 ft3/h to 76.0 ft3/h
GAS SERVICE
COCK UNION
BACK
BOILER
ONLY 'ON'
TURNED
FULLY
CLOCKWISE
BACK
BOILER &
FIRE 'ON'
TURNED TO
MID POSITION
90°
'OFF'
TURN FULLY
ANTI-
CLOCKWISE
180°
Should any doubt exist, the gas rate should be checked at the
gas meter.
The rate of the back boiler should be within the range,
Note, if the gas rate is checked, make sure that all other gas
appliances and pilot lights are turned off.
Turn control thermostat knob “B” anti-clockwise to “O” “Off”
position. Removepressuregaugeandreplacetestpointscrew
make sure that a gas tight seal is made. Replace governor
cover screw “F”.
Relight the back boiler by turning control thermostat knob “B”
clockwise to “MAX”.
Use the self adhesive arrow from the fittings pack and stick it
against the relevant heat input figure on the Data label.
6.2 Testing the Back Boiler Controls
To check the operation of the flame failure device carry on as
follows:
With the main burner alight, slightly push in gas valve control
knob “A” and then turn it fully clockwise until is against the
settingpoint. Thiswillcausethemainandpilotburnertogoout.
Note, relighting will not now be possible as the safety device in
the gas valve has been activated.
Check that the flame failure device closes within 60 seconds,
indicated by a “click” from the valve.
DONOTATTEMPTTORELIGHTUNTILATLEAST3MINUTES
HAVE GONE BY.
Relight the pilot and main burner as described in the relevant
part of Section 6.1.
Check that the control thermostat and any external controls
operate the back boiler correctly.
6.3 Clearance of Products
Aclearance ofproducts(spillage) testmust be carriedout after
installation of the back boiler and its fire.
Before fitting the fire front check that the heat exchanger baffle
is fitted and seated correctly.
Makesure thatthere isnoflame disturbanceon theback boiler
burner immediately before carrying out test, look through pilot
window “M”, in diagram 6.1.
Details of the necessary procedure to be carried out will be
foundunder“TESTFORCLEARANCEOFPRODUCTS”inthe
fire front Installation Instruction Booklet.

14
221781A
Fire Front Installation and Servicing Instructions are packed
with the fire front.
7.1 Completion - After Installation of the Fire
Front
Instruct and demonstrate to the user, the efficient and safe
operationofthe backboiler,heating andhotwatersystem and
fire front.
Hand the Instructions for Use to the user, for their retention,
making sure that they are understood.
Advise the user that to ensure the continued efficient and safe
operationoftheappliance it isrecommendedthatitis checked
andservicedas necessaryatregularintervals. The frequency
of the servicing will depend upon the particular installation
conditions and usage, but in general once a year should be
enough.
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 person who let out any property
containing a gas appliance.
It is the Law that any servicing is carried out by a competent
person.
Advise that the boiler is fitted with a safety device and refer to
the instructions for use.
Setanyremotecontrolsforthesystemtosettingsrequestedby
the user.
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.
5197
6 Commissioning
Diagram 6.3
Diagram 6.4
20mm FLAME
DIMENSION
Pilot Shield
omitted for
clarity
5340
0
10
20
30
40
50
60
70
80
90
510 15 20 25 30
WATER PRESSURE LOSS (mm head of water)
WATER FLOW (litres/minute)
56/2 BACK BOILER
PRESSURE LOSS OF APPLIANCE
0
6.4 Commissioning the System
Setallcontrolstooperatetheheatingsystem. Adjustpumpand
balancethesystemtogiveatemperaturedropacrosstheboiler
of11oC(20oF). Attheappropriateflowrate,theresistanceofthe
back boiler can be found by reference to diagram 6.4.
There should be no undue noise in the pipework or heat
emitters. There must be NO pumping over of water or entry of
airatthe openventpipeabove thefeedand expansion cistern.
Make sure that the back boiler control knob “B” is turned
clockwise to “MAX” against the setting point, allow the water to
reachmaximumworkingtemperature. Examinethesystemfor
water soundness.
Do not attempt to adjust the thermostat calibration screw.
Turnthecontrolthermostatknob“B”anti-clockwiseto“Off”and
rapidlydrainthe systemwhilststillhot, to completetheflushing
process.
Refill the system, vent and check again for water soundness.
7 Fire Installation

15 221781A
Diagram 8.2
Diagram 8.1
SECURING
SCREWS
1613
BURNER
ELECTRODE
BURNER
LOWER
SENSING
TUBE NUT
GAS VALVE
SECURING
SCREW (2)
COMBUSTION
CHAMBER
EXTENSION
BURNER
SUPPORT
8.1 Servicing Notes.
(a) To ensure the continued efficient and safe operation of the
applianceitis recommendedthatit ischeckedandserviced as
necessary at regular intervals.
The frequency of the servicing will depend upon the particular
installation conditions and usage, but in general once a year
should be enough.
(b) It is the Law that servicing must be carried out by a
competent person.
(c) Remove the fire front.
(d) Refer to the Gas Fire Front Installation and Servicing
Instructions for full details of fire front removal.
(e)Aftercompletinganyservicingalwaystestforgassoundness
with a suitable leak detection fluid and carry out functional
check on controls.
(f) Unless stated otherwise reassembly of all components is in
the reverse order to that for removal.
(g)The flue blockage safety deviceMUST NOTbe adjustedor
disconnected. If replacing use only the correct and approved
parts.
8.2 Isolation of Services
Having removed the fire front.
Isolate the electrical supply to the back boiler.
Refer to diagram 6.1 to identify the controls.
Turnthegasvalvecontrolknob“A”to “Off”positionandturn
theappliancegasservicecockto“FireandBackBoilerOff”,see
diagram 6.2.
8.3 Controls Assembly and Burner.
Disconnecttheunionatthegasservicecock,see diagram6.2.
If necessary release the control thermostat capillary and the
mainscablefromtheclipsonthecombustionchamberextension,
see diagram 5.1.
Disconnect the electrical plug from the gas valve, see diagram
5.2.
Removethecontrolboxsecuringscrewandlifttheboxupwards
to release, see diagram 5.2.
Disconnect the ignition lead from the piezo unit and remove
from control box, see diagram 9.1.
Temporarily refit control box.
Note:Onreconnecting the ignitionleadtothe piezounit,itmay
necessary to temporally remove the control thermostat, see
Section 9.8. Ensure that the control thermostat capillary is
replacedbackinthecutoutofthe control box,seediagram5.2.
Undo union nut and disconnect the back boiler lower sensing
tube, undo the four combustion chamber extension securing
screws and slide the extension/burner assembly forward to
remove, see diagram 4.8.
Undo the two screws shown in diagram 8.1, which locate the
burner support to the combustion chamber extension.
Turn the combustion chamber extension/burner assembly
upside down.
Undo the lower sensing tube nut, see diagram 8.2.
Disconnect the ignition lead from the piezo unit.
Undothetwoscrewsshownindiagram8.2whichlocatethegas
valve control to the combustion chamber extension.
8 Servicing
Diagram 8.3
SHAKEPROOF
WASHERS PILOT SHIELD
MOUNTING
BRACKET
PILOT
SHIELD
NUTS
SCREW
1615 8017
The complete gas carrying assembly can now be lifted clear of
the combustion chamber extension.
Undothescrewsonthesideofthepilotshield,alsothetwonuts,
also remove the two shakeproof washers securing the pilot
shieldmountingbrackettotheburner,seediagram8.3. Remove
the pilot shield mounting bracket from the studs on the burner
and remove the pilot shield.
Inspect the pilot for damage or blockage, clean or replace flue
blockage safety device as necessary.
Make sure the spark gap is as diagram 8.4.

16
221781A
5199
5200
Diagram 8.4
Diagram 8.5
8 Servicing
SHAKEPROOF
WASHER (2)
LUG
LINT
ARRESTER
BURNER
SUPPORT
SLOT
SECURING
NUT (2)
MAIN BURNER
INJECTOR
SECURING SCREW (4)
SUPPLY PIPE
FLANGE
ELECTRODE THERMOCOUPLE
BBU
LOWER
SENSING
TUBE
PILOT TUBE
NUT
THERMOCOUPLE
NUT
PILOT TUBE
SECURING
NUT
IGNITION
LEAD
SPARK GAP
3+1
-0.5
FRONT VIEW
TOP VIEW
ELECTRODE
EARTH
POST
EARTH
POST
SILICONE
SLEEVE
SECURING
SCREW(2)
UNION NUT
AND LINER
Undothetwonutsshownindiagram8.5whichsecurethemain
gasmanifoldtotheburnerandremovetheshakeproofwashers,
disengage the lint arrester and then withdraw the main gas
manifold from the burner.
Clean the lint arrester as necessary.
Inspectthemain burnerinjectorfor damageorblockage,clean
or replace as necessary using a small amount of approved
jointing compound, on the external thread.
Inspect the ignition lead for wear or damage, clean or replace
as necessary, see diagram 8.4.
Inspectthethermocoupleforwearordamage,cleanorreplace
flue blockage safety device as necessary, see diagram 8.4.
Inspectthe electrodeforwear ordamage,clean orreplaceflue
blockage safety device as necessary, see diagram 8.4.
Inspect the flue blockage safety device sensing tube filter for
damage or blockage, clean or replace as necessary, see
diagram 9.4.
8.4 Refitting Burner Assembly
Whenrefittingthelintarrestermakesurethatthelugisfittedinto
the slot on the burner support bracket, see diagram 8.5.
Position the pilot shield around the pilot tube, ignition lead and
thermocouplebeforereplacingthepilotshieldmountingbracket,
see diagram 8.3.
Loosely replace the gas valve control securing screws, see
diagram8.2. Refitthetwo screws shownindiagram8.1,which
locatetheburnersupporttothecombustionchamberextension.
Refit the lower sensing tube nut into the bulkhead connection.
Then fully tighten the gas valve securing screws.
Before replacing the burner and controls assembly into the
back boiler the following servicing should be carried out.
8.5 Cleaning Back Boiler Flueways
Remove the burner assembly as Section 8.3.
Undo the two screws securing the fire front sensing tube, if
fitted, and remove, see diagram 8.6.
Undothetwosteelscrewssecuringthefluecollectorassembly,
see diagram 8.7 and remove the flue collector assembly.
Undothetwostainlesssteelscrewssecuringthediverterplate,
see diagram 8.8 and remove the diverter plate by sliding it
forward.
Lift out the flue baffle, see diagram 8.9.
Clean the back boiler flue ways with a suitable stiff brush.
Note. A sheet of paper placed in the back boiler combustion
chamber will help in collecting any debris.
To make sure that the flueways are clean, view with the aid of
a mirror or reflector.
8.6 Refitting Flue Collector Assembly and
Final Reassembly
Whenrefittingthefluebafflemakesurethatthefourcornerlugs
fit correctly into the back boiler flueways, see diagram 8.9.
When refitting the diverter plate make sure that the plate is
correctlyfittedintotheguidechannelsas shown indiagram8.8
and replace the two stainless steel securing screws.
Refit the flue collector assembly and if fitted the fire front
sensing tube. Refit the burner and controls assembly to the
back boiler.

17 221781A
5079
8 Servicing
Diagram 8.9
Diagram 8.8
Diagram 8.6
Diagram 8.7
5201
1620
1621
FLUE
BAFFLE
FLUEWAYS
FLUE COLLECTOR
ASSEMBLY
SECURING
SCREW
STAINLESS STEEL
SECURING SCREWS(2)
GUIDE
CHANNELS
FLUE
BAFFLE
DIVERTER
PLATE
FIRE FRONT
SENSING TUBE
SECURING
SCREW (2)
9.1 Notes on Replacing Parts.
(a) Replacement of parts must be carried out by a competent
person.
(b)Unlessstatedotherwiseallpartsarereplacedinthereverse
order to that of removal.
(c) After replacing any gas carrying parts always test for gas
soundness using a suitable leak detection fluid. Also carryout
functional check of controls.
(d) Refer to the Gas Fire Front Installation Instructions for
details of the removal of the fire front.
(e) Isolate the electrical supply to the back boiler.
(f) Remove the gas fire front plinth.
(g) Refer to diagram 6.1 to identify the back boiler controls.
Turn the gas valve control knob “A” clockwise to “Off”
position. Turn the appliance gas service cock anticlockwise to
“Off” position, see diagram 6.2.
9 Replacement of Parts
8033
Diagram 9.1
PIEZO
UNIT
IGNITION LEAD
(BLACK END)
RETAINING
TABS

18
221781A
9 Replacement of Parts
Diagram 9.2
8019
Diagram 9.3
NOTE: It is important that the thermostat is
fitted the same way as shown in diagram
CONTROL
KNOB
ELECTRICAL
CONNECTIONS
THERMOSTAT
SECURING
SCREW(2)
SENSING
TUBE
FITTING
ASSEMBLY
THREAD CUTTING
SCREW(Taptite)
1 mm
BACK
BOILER
SENSING TUBE
BULKHEAD CONNECTION
TUBING
NUT BOILER AIR DUCT
SENSING
TUBE
FITTING
ASSEMBLY
FRONT FACE
OF BOILER
CASTING
FILTER
Diagram 9.4
6129
9.2 Flue Blockage Safety Device Assembly
Gain access as the relevant part of Section 8.3.
Remove lead from electrode.
Pull off back boiler lower sensing tube.
Undothe pilottubesecuring nutsand the thermocouplenuts at
gas valve, see diagram 8.4.
Undotheflueblockagesafetydeviceassemblysecuringscrews
and withdraw, see diagram 8.4.
When refitting take care not to damage the lower sensing tube
adapter “O” rings.
9.3 Gas Valve
Gain access as the relevant part of Section 8.3.
Disconnect the thermocouple tube nut at the gas valve and
ease out of the valve, see diagram 8.4.
Disconnect the pilot tube nut at the gas valve.
Undo the securing screws to separate the gas valve from the
supply pipe flange. Take care not to damage the “O” ring seal
between the flanges.
Undo the two securing screws to release gas valve from the
combustion chamber extension, see diagram 8.2.
Transfer the union nut and liner to the replacement gas valve
using a small amount of approved jointing compound on the
external thread only.
When fitting the thermocouple only tighten the nut at the gas
valve a quarter turn beyond finger tight.
9.4 Ignition Lead
Gain access as the relevant parts of Section 8.3.
Remove the lead from the electrode and piezo unit.
Fit the silicone sleeve over the new lead.
Fit the black insulated end of the ignition lead to the piezo unit
and the clear end to the electrode.
Push the silicone sleeve into position, see diagram 8.4.
9.5 Main Burner Injector
Gain access as the relevant parts of Section 8.3.
Refer to diagram 8.4 and undo the thermocouple nut and
withdraw the thermocouple.
Undo the pilot tube nut at the gas valve control.
Refer to Section 8.3 paragraph eleven.
Whenreplacing themain burner injector use a small amountof
approved jointing compound on the external thread only.
9.6 Pilot Burner Injector
Should pilot burner injector need replacing, the whole pilot
burner assembly must be replaced.
9.7 Piezo Unit
Gain access as the relevant parts of Section 8.3.
Disconnect the ignition lead from the piezo unit, see diagram
9.1.
Note: To ease the removal of the piezo unit it is advisable to
temporarily remove the boiler thermostat from the control box,
refer to Section 9.8.
Depress the retaining tabs and remove the Piezo unit.
SELF ADHESIVE
ALUMINIUM FOIL
GASKET
MICA WINDOW
PEEL OFF
BACKING
PAPER
OPENING
(PILOT
BURNER)
7886

19 221781A
Diagram 10.1
FUNCTIONAL FLOW WIRING
8084
C
L s
GAS VALVE SOLENOID
THERMOSTAT
BLUE
BROWN
VIEW OF
PLUG WHEN
REMOVED
BLUE
NC
34
NL
E
NN
BLACK
9.8 Control Thermostat
Disconnect the gas valve electrical plug, see diagram 5.2.
Removethesplitpintoreleasethecontrolthermostatphial,see
diagram 5.6.
If the phial pocket and/or the electrical supply is on the right
hand side, release the capillary and/or the main lead from the
clips, see diagram 5.1.
Removethecontrolboxsecuringscrewandlifttheboxupwards
to release, see diagram 5.2.
Remove the control thermostat knob “B”, see diagram 9.2.
Remove the two securing screws and remove the control
thermostat body.
When fitting the new control thermostat, make sure that the
capillary connection to the control thermostat body is placed at
the top of the control box top.
Refit electrical connections.
Capillaryshouldpassthroughthecutoutonthecontrolboxtop,
see diagram 5.3. Care should be taken to make sure that the
side plate hooks onto the box before fitting the securing screw.
9.9 Viewing Window
Gain access as the relevant parts of Section 8.3.
Removetheoldselfadhesivealuminium foilgasketandtheold
mica window. Replace with a new mica window. Peel off the
backingpaperandsecurewithnewselfadhesivealuminiumfoil
gasket, see diagram 9.3. Ensure no air bubbles are trapped
underneath the foil.
Important
Make sure that the mica window fully covers the opening and
that the hole in the aluminium foil gasket is centred over
opening.
9.10 Flue Blockage Safety Device Sensing
Tube Fitting
Removefilter,unscrewthreadcuttingscrewandremovesensing
tube fitting assembly, see diagram 9.4.
When fitting new filter, take care not to damage the filter.
10.1 Electrical
Carryoutthepreliminaryelectrical systemchecksascontained
in a multimeter instruction book.
Referto functionalflow wiring diagram 10.1 and electrical fault
finding chart, diagram 10.2.
On completion of the fault finding task which has required the
breaking and remaking of electrical connections the checks
earth continuity, polarity and resistance to earth must be
repeated.
10.2 Thermocouple
To test the thermocouple, a meter with a range of 0 - 30mV is
required together with a thermocouple interrupter test unit.
Refer to thermocouple fault finding chart, diagram 10.3 and
diagnosis graph, diagram 10.4.
10.3 Back Boiler Pilot and Ignition
Tocheck backboiler pilotandignition, referto pilotfault finding
chart, diagram 10.5.
10.4 Flue Blockage Safety Device
If the device operates and the filter is clean, it indicates there is
a problem with the chimney. Make sure air vents are free from
obstruction, carry out spillage checks as Fire Front Installation
Instructions and put right as necessary.
10 Fault Finding
9 Replacement of Parts

20
221781A
Diagram 10.2
ELECTRICAL FAULT FINDING CHART
4484A
Isolate power supply to the control box. Gain access to the control box and physically check all wires and
connections. Check fuses.
Check that all remote controls, (eg room and / or cylinder thermostats), are making contact for duty.
Turn on the power supply to the control box. Turn on the boiler thermostat and measure the voltage
between C and N.
Is the voltage between 216 and 264 volts. Check control box wiring and mains supply
Isolate the power supply. Replace thermostat
Is there voltage between NC and N.
216 and 264 volts.
Isolate the power supply to the control box. Remove plug from gas valve and connect
voltmeter between L and N in plug, ensuring no short circuits (mains voltage). Turn on power supply and
measure voltage.
Is the voltage between 216 and 264 volts. Check control box wiring.
Isolate the power supply to the control box.
Reconnect gas valve. Turn on
power supply. Does main burner light.
Turn off boiler thermostat, measure voltage
across 3 and 4. Is the voltage zero.
Does the main burner extinguish.
Boiler electrical system operating satisfactorily
Isolate power supply.
Replace gas valve.
Isolate power supply. Replace thermostat.
Isolate power supply.
Replace gas valve.
YES
NO
NO
YES
NO
YES
YES
YES
YES
NO
NO
NO
Isolate power supply to the control box. Gain access to the control box and physically check all wires and
connections. Check fuses.Check Flue Blockage Safety Device filter is not blocked, clear if necessary.
Check that all remote controls, (eg room and / or cylinder thermostats), are making contact for duty.
10 Fault Finding