Bosch Worcester 240 Combi OF User guide

....--~~~ORCESTER-----.
BOSCH
240 Combi OF
WALL MOUNTED COMBINATION BOILER FOR CENTRAL HEATING AND
MAINS FED DOMESTIC HOT WATER
INSTALLATION AND
SERVICING INSTRUCTIONS
GC NUMBER 47 311 09
BOILER OUTPUT
Automatic Modulating Control
To Domestic Hot Water and Central Heating
Minimum 9.2 kW (31 ,400 Btu/h)
Maximum 24.0 kW (82,000 Btu/ h)
IMPORTANT: THIS APPUANCE IS FOR USE WITH NATURAL GAS ONLY
THESE INSTRUCTIONS APPLY IN THE UK ONLY
THESE INSTRUCTIONS ARE TO BE LEFT WITH THE USER OR AT THE GAS METER

Contents
1. Installation Requirements .... ..... ........ . ................. . ......... Page 2
2.
General Information .... . .. ........ ... .................................. .. Page 2
3.
Technical Data ................ .. . ...... ........... ..... .................. ..... Page 4
4.
Siting the Appliance .............................. . ....................... Page 5
5.
Siting the Flue Terminal .................. .. ...... ............. .... . .... Page 6
6.
Air Supply .... ........................................................ .. ... .. .... Page 6
7.
Sealed System .................................... .. ...... .. ...... .. .... ...... Page 7
8.
Open Ven t Pr im ary Water System ...... ............... ......... Page 8
9.
Domestic Hot Water .............................. . .. .. .... ............... Page 8
1. Installation Regulations
1.1 Gas Safety (Installation and Use) Regulations 1984
All gas appliances must be installed by a competent person in
accordance with the above regulations. Failure to install appli·
ances correctly could lead to prosecution.
1.2
The manufacturers notes must no t be taken ,i n any way ,as
overrid ing statutory obligations.
1.3
The compliance with a British Standard does not. of itself. con ·
fer immunity from legal obligations. In particular the installation
of this appliance must be in accordance with the relevant require ·
ments of the Gas Safety (Install ati on and Use) Regulations 1984 as
amended, current
lEE Wiring Regulations, local Building Regu la ·
tions, Building Standards ( ScotlandXConsolidation) and byel a ws of
the local Water Company . Health and Safety Document No . 635
(
Electridty at Work Regulat ions ). !t should be in accordance w ith
the relevant recommendations of the f ollowing B ritish Standards.
BS 6798:1987 Specifi cati on for installati on ofgas fired hot water
b
oilers of rated input no t exceeding 60 kW.
BS 5449 :19 90 Centra l Hea t ing for Domestic Premises.
BS 5546:1990 Installation of gas hot water supp li es for domes·
tic purposes.
BS 5440 :1 :1990 Flues and Ven tilati on for gas appliances of rated
in put not exceedi ng 60 kW: Flues .
BS 5440:2:1989 Flues and Ventilation for gas appliances of rated
input not exceeding
60kW : Air Supply.
BS 6891 :1988 Installa ti on of l ow pressure gas pipework installa·
t ions up to 28 mm (R 1).
1
.4 To ensure that the installation will perform to the highest
standards, t
he system and components should conform to any
other relevant
Br itish Standards in addition to those mentioned
in the instructions.
2. General Information
2.1 This appliance is not suitable for external installation.
2.2
The appliance controls are set to provide a maximum
output
for the domestic hot water of 24 kW and a central
heating load
of up to 16 .1 kW .
2.3 The appliance has a permanent pilot.
2.4 PRINCIPLE APPLIANCE COMPONENTS See Fig . 1.
A
low thermal capacity Gas to Water heat exchanger.
A
Water to Water heat exchanger to provide domest ic hot water.
Fully modulating controls in the central heating and domes tic
ho t water modes of operation.
An expansion vessel, pressure gauge and pressure relief valve .
A
by ·pass for the central heati ng system.
Temperature safety cut·out controls.
Awater
flow regulator.
2
10. Electrical .......... .. ..... ... ....... .... . ...... .. .... ..................... ........ Page 10
11 . Installation ........ .. ...... .... .... .. ...... . ...... ................ .... .. .. ...... Page 13
12 . Commissioning .. .... .. ............... .. .................. ...... .. .... .. ..... Page 15
13. Instructions to the User ........................................... ... .. Page 16
14 . Inspection and Servidng .......... .......................... ........ ..Page 17
15 . Replacement of Parts ..... . .. .. . ........................... ... .. .... . .... Page 19
16 . Short Parts List ... ............... .... .......................... .... . .... .....Page 25
17 . Operational Flow Diagram . .. ......... .. .... .. .. ... .............. . .... Page 26
18.
Fault Finding . .. . ... . ... . ........ ..... ..................... .. .............. .. ... Page 28
An optional facia mounted programmer instead of the standard
Operating
Switch .
2.5 ELECTRICAL SUPPlY
Mains supply: 240V -, 50 Hz, 150 watts. External fuse 3A.
Internal fuses: T2A (F1) and T315mA (F 2).
2.6 GAS SUPPLY
The boiler requires 2. 82 m' /h (9 6.8 ft '/hr) of gas. The gas meter
and supply pipes must be capable
of supplying this quantity of
gas in addition to the demand from an y other appliances being
served.
The table below gi ves an i nd icati on of limiting gas pipe
lengths and the allowance to be made for fittings.
Refer to
BS6891 f or further information.
The meter gov ernor should deliver a dynamic pressure of 20
mbar (B in wg .) at the appliance.
The complete installation, includ i ng the gas meter, must be test·
ed for soundness and purged. Refer to BS 6891 .
TOTAL LENGTH OF
GAS SUPPLY PIPE (metres) Pipe
Diamet er
3 6 9
(mm)
Gas Discharge Rate (m3 /h)
2.9 - - 15
8.7 5.8 4.6
22
18.G 12.0 9.4 28
Note:
Each fitting used in the gas line from the meter is equivalent to a
length of straight p ipe which mus t be added to the straight pipe
length to give the total length .
ie : Elbow = 0.5 metres, Tee = 0.5 metres, 90 ° Bend = 0.3 metres.
2.7 GENERAL INSTALLATION
The appliance: is supplied for connec tion to a sea led system but
is suitable for use with an open vent system. The connections
are suppl
ied as an option al kit.
The spec ified vent il a ti on openings must not be ob st ruc te d.
Do not pla ce anything on top of the appliance.
The clearances specified for servici ng must be maintai ned .
2.8 FLUE
The flue mu st be generally verti cal and have no horizontal runs.
The flue must end with a British Gas approved term i nal.
2.9 CONTROLS
T he electronic control system and gas valve modulate the heat
input
in response to t he central heati ng and domestic hot water
temperature settings between minimum and
max imum.
The Operating Switch provides for the selecti on of domestic hot

Fig. 1. Appliance water flow diagram.
Automat ic air vent
Gas to Water
heat exchanger
Waterflow
man i fold
L_
Ce n tra l hea ri ng
by · pass ad j uster
t__ - - ..
Boile r
- - -- - Water div erter
v alve
---,-- -:
I
I
Pr ess u re reli ef v al ve
- Oo mes t oe hot wate rout
-- Ma i ns col d water in
-
Ce nt ra l he at i ng retu rn
-- Cen tra l he at i ng flow
water only (WATER) or central heating and domestic hot water
(HEATING & WATER) or OFF .
A fac ia mounted programmer is ava ilable as an optional extra. A
remote mounted prog rammer may be connected to the appli-
ance.
The integral fac ia displays i nd icate the status of the appliance.
There is
prov ision for the connection of a mains voltage room
thermostat and/or a frost thermostat.
The electronic controls prevent rapid cycling of the appliance in
the central heating mode.
2.1 0
SYSTEM NOTES
WARNING
Check that no dirt is left in either the gas and water pipework
as this could cause
damage to the appliance. Thoroughly flush
the heating system and the cold water mains supply. Purge
the gas supply before finally connecting theappliance ..
The water pipe connections throughout a sealed system must
be capable
of sustaining a pressure of upto 3 bar.
Radiator valves must conform
to the requirements of BS2767
(10) : 1972 .
The relief valve discharge must be directed away from any elec -
trical components or where it would cause a hazard to the user.
Adrain cock to BS 2879 must be fitted to the lowest point of the
system.
For circu it design purposes it is important that due note is taken
of the informati
on gi ven in Table 3 relating to the available
pump head.
3
2.11 SHOWERS, BIDETS, TAPS AND MIXING VALVES
Hot and cold taps and mixing valves used in the system must
be suitable for operating at a mains pressure of up to 10 bar.
Thermostatically controlled or pressure equalising shower
valves will guard against the
flow of water at too higb a temper-
ature. I
Hot and cold mains fed water can be supplied direct to an over-
rim flushing bidet subject to local Water Company requirements.
With all mains fed systems the flow of water from the individual
taps will vary with the number
of outlets operated simultane-
ously and the cold water mai ns supply pressure to the property.
Flow balancing using 'Ball - o-Fix' type valves is recommended to
avoid an excessive reduction in flow or even starvation to indi -
vidual outlets. For further information contact Worcester Heat
Systems
Ltd .
2.12 SAFETY CONSIDERATIONS
The appliance must not be operated in a waterless condit ion .
The appliance must not be operated wi th the boiler inner casing
cover removed.
Work must not be carried out on the appliance without the gas
and electricity supplies
be i ng switched off .
Checks must be made to ensure that the ventilation openings
made into
walls and partitions are of the correct size and are not
obstructed.
2.13 OPERATION
Domestic Hot Water: With a demand for hot wa ter the burner
will light at its maximum setting and then automatically adjust
its output to maintain the temperature rise of the delivered
water.
When hot water is no longer required, the burner will
extinguish. The pump will continue to run for a short period to
dissipate the residual heat from the appliance.
Central Heating: With a demand for heating the burner will light
at its min i mum setting and gradually increase to give the maxi -
mum output. The output of the appliance is then automatically
adjusted to maintain the temperature
of the system. The output
can reduce down to a minimum of ?.2
kW. If the system no
longer requires even the minimum output to maintain the
desired
room temperature the burner will extinguish. The pump
will continue to run to dissipate the residual heat from the appli -
ance. The appliance will remain off for a fixed period of two min -
utes before re -lighting to automatically meet the system require-
ments.
Domestic Hot Water
and Central Heating: The ·appliance will
supply heat to the central heating system as required. A
demand for domestic hot water at a tap or shower will override
the central heating requirement
for the period of the domestic
hot water demand.
When hot water is no longer required the
burner will extinguish and the appliance will return to the cen -
tral heating state and its normal mode of operation. The pump
will continue to run to dissipate the residual heat from the appli·
ance as necessary.

3. Technical Data
The Data Plate is fixed to the control box casing.
TABLE 1
TABLE 5
NOMINAL BOILER RATINGS
OUtput Input
Burner Setting
Gas Rate
Pressure
Flue Di ameter
125mm
kW Btu/h kW Btu /h
mbar. in . wg . m3/h
tt
3/h
9.2 31 , 400 12 .6
43,000
2.7 1.1
1.17 40.2
Flue Pipe
BS 4543
16 .1
54 , 900 212 72,300 73 2.9 2. 03 69 .6
24 .0
82,000
30 .1
102,700
15 .0 6.0 2. 82
96 .8
TABLE2
AVAILABLE PUMP HEAD
Boiler Output
Head
Min. Flow Rate Temp . rise across
kW Btu /h
metres
feet
litres/min
gal / min
heating flow
and return
9.2 31 , 400 4.9 15 Q
120
2. 64
11 •c ( 20"FJ
16 .1 54 ,9 00 2. 54
8. 25 23.0 5. 07
11 •c (20"FJ
24 .0
82 , 000 2.0 6.5
23.0 5. 07 15 °C { 28 °F)
TABLE 3
SPECIFICATIONS
CENTRAL HEATING FLOW FriTING 22
mm Compression
CENTRAL HEATING RETURN FmiNG 22
mm Compression
COLD WATER MAINS INLET FrrnNG 15
mm Compression
DOMESTIC HOT WATER OUTLET FmiNG
15 mm Compression
GAS INLET FrrnNG Rc 1'2
PRESSURE RELIEF VALVE DISCHARGE FriTING 15
mm Compression
CASING HEIGHT
900 mm (35.4 in.)
CASING WIDTH
450 mm (17 .7 in.)
CASING DEPTH
360 mm (14.2 in.)
WEIGHT (including water) 48 kg (10Sib)
INSTALLATI ON WE IGHT 46 kg (101 lb)
PACKAGED WEIGHT 49 kg (1 08 lb)
TABLE4
SPECIFICATIONS
PRIMARY WATER CAPACITY 2.7 litres (0 .6 galls.)
MAXIMUM
COLD SUPPLY PRESSURE 10 Bar (1 50 psi)
MINIMUM
COLD SUPPLY PRESSURE (WORKING) FOR MAXIMUM HOT WATER FLOW
1.6 Bar (23.5 psi)
MINIMUM
COLD SUPPLY PRESSURE (WORKI NG ) TO OPERATE THE APPLIANCE 0.6 Bar (9 psi)
MAXIMUM
CENTRAL HEATING FLOW TEMPERATURE Nominally 82°C (180°F)
MAXIMUM STATIC HEAD (PRIMARY)
25 metres ( 81 ft)
MIMIMUM STATIC HEAD (PRIMARY) 0.3 me tr es (1 ft)
OUTPUT TO DOMESTIC HOT WATER Modulating 9. 2-24 .0 kW
(31 ,40Q-82,000 Btu /h)
OUTPUT TO CENTRAL HEATING Modulating 9.2 -24 .0 kW
(31 ,400-82,000 Btu /h)
MAXIMUM DOMESTIC HOT WATER FLOW RATE FROM THE APPLIANCE Nominally 8.51itres /min (± 15%)
(1 .87 gallons/min)
EQUIVALENT DOMESTIC HOT WATER FL OW RATE
Nominally 9. 8litres /min
TO GIVE A TEMPERATURE RISE OF 35°C (2.16 gallons /min)
4

4. Siting The Appliance
4.1 The appliance must not be installed in any room contain-
ing a bath or shower or in a bedroom, bed-sitting room or
garage. Particularattention is drawn to the requirements of the
current I.E.E. Wiring Regulations and, in Scotland, the electrical
provisions of
the Building Regulations applicable in Scotland.
4.2
The appliance is not suitable for external installation.
4.3
The appliance does not require any special wall protection.
4.4
The wall must be capable of supporting the weight of the
appliance. See
Table 3.
4.5
If the appliance is to be fitted in a timber framed building,
refer to the British
Gas publication "Guide for Gas Installations in
Timber Framed Housi ng ".
4.6 The following clearances must be available for installation
and
for servicing. See Fig. 2.
Installation Servicing
Above 300mm 300mm
In front 600mm 600mm
Below*
900mm
230mm
Right hand side 100mm 100mm
Left hand side 100mm 100mm
4.7 No combustible surface must be within 75 mm of the cas·
ing . See BS476:4.
4.8 Always consider the possible need to disconnect the pipes
from the appliance after installation.
4.9 Boilers in roof
spaces or in understair locations require
special conditions.
Refer to BS 6798.
* 4. 10 The appliance must have a minimum clearance of900 mm
between the bottom
ofthe appliance and the floor.
Fig. 2. Appliance casing dimensions and required clearances.
106mm
SlOE VIEW
Space required above
for i nstallalion and servicing .
f----- -----------~
Space requ i red in front
fo r installat i on and servicing .
I
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:---- __ f _________ _j
////~/////J/~
I I
I I
I I
I :
I ~--~
I
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------~- - ~----
~225mm
FRONT VIEW
~-----4~mm----~
Fixing holes
~413mm CAS . ___,
I
I
II
900mm
~ I Space required below
/). 1 for installation and serv ici ng .
/)~ ____ ____ j t 1 I
Space required at left hand side -+1 I+- -+1 il
,,, ... , • •M .. ,...... . i L_ ______________ j! I
5
Space required at right hand side
for installa tion and servicing .

Fig. 3. Appliance pipework connections.
-· ·
-· "'
"": rr-;J
__ ,_::D
Centra l heating flow
55
mm Jj
Central hearing return i 08 mm
Ma i ns cold water in --114-- -- 161mm
Domest ic hot water out -1-- ---- 216 mm -----< ~
Pressure relief valve discharge -1-- ------- 306 mm -- ~
tt\·r:!\
-w·o
_,....,..YI.III_
Gas cock - 1-- ----------- 405mm ------ -~
5. Siting the Flue Terminal
The flue diameter is 125 mm Refer to BS 4543.
5.1
The flue must be installed as specified in BS 5440: Part 1.
5.2 A means of dis -connection of the flue should be provided
and positioned immediately above the appliance draught divert·
er .
5.3 Horizontal flue runs should be avoided and the flue should
terminate in accordance with the requirements of BS 5440 :1.
The terminal must be of a type approved by Br itish Gas and
must not be
within 600 mm (24 in) of an openable window. air
vent or other ventilation opening.
5.4 If the flue is to be taken through the wall behind the appli·
ance t hen adequate space must be available to allow the fitting
of a suitable flue bend. A right· angle bend is not acceptable. A
minimum of 600 mm of verti cal flue pipe is required before the
introduction
of a bend. If the flue is taken through the ceiling
and i nto the roof ·space or room above then a sleeve of non · com ·
bustible material allowing an air-space of at least 25 mm
between the flue and the sleeve must be provided. The flue pipe
must be held in the centre of the sleeve .
6. Air Supply
6.1 The room in which an appliance is installed must have a per ·
manent air vent to outside air or to a room which itse lf ha s
6
direct access to outside air. The minimum effect i ve area of t he
air vent(s) must be 104 cm
2.
6.2 There must be sufficient clearance around the appliance to
allow proper circulation of ventilation air. The clearances
required for Installat ion and Servicing will normally be adequate
for ventilation. See Section 4.6.
6.3 The minimum free areas required are g iven below .
Position of
Air from
Air direct
air vents the room
from outside
High Level 271 cm
2•
135 .5 cm
2.
(42 in
2.)
(21 .5 in2)
Low Level
542 cm
2•
271 cm
2•
( 84 in
2.)
(42 in
2.)
6.4 Refer to BS 6798 and BS 5440:2 for additional information.
6.5 A spillage test, as detailed in 855440:1, must be carried out
and any remedial acti on taken to ensure that the installation
meets the standard. The effect of any type of extract fan in the
premises must
be considered and an additional air inlet may be
needed from outside to counter the effect of the fan .

7. Sealed System
7.1 The system must comply with the requirements of BS 6798
and
BS 5449: 1.
7.2 The appliance must not be operated without the system
being
full of water, properly vented and pressurised.
7.3 The pressure relief valve operates
at 3 bar (45lb/in").The dis-
charge must be directed away from electrical components or
where it might be a hazard to the user.
7.4 The pressure gauge indicates the system pressure which
must be maintained.
7.5 The 10 litre expansion vessel is charged to 0.5 bar and is
suitable for a static head of 5 metres (17 . 5ft) . The pressure can
be increased
if the static head is greater than 5 metres (17 .Sft) .
7.6
With an initial system pressure of 0.5 bar, a system capacity
of about 104litres can be accommodated. Refer to BS 7074 Pt. 1
for more information. The charge pressure can be increased but
with a decrease
in system volume.
7.7
The filling point must be at low level. See Fig. 4.
Fig. 4 Sealed primary water system.
L ocl<shield valve . Radiator valve .
l 11111 111 J IIIIIllI
Note .A dtm c:oc:1t should be installed at
the lowest point of the heating cir cuit and
beneath the appliance .
Fig. 5. System filling and make-up.
Heating Return
Non return
valve
....
Worcester Combi-Fill System
Non return
va~ ~ Hose union l
1-----t..•- ... -t..•-"" : =: zr, ::u I 1 ~ ~
!l i~ Stop cock
II II
Test cock · : ~==•.] :
Temporary hose
7
7.8 Water loss must be r~placed . See Fig 6. The connection
should
be made in the central heating return as close to the
appliance as possible.
7.9 The make-up vessel,
if fitted, mus t be fitted with a non-
return valve.
7. 10 Repeated venting loses water from the system. it is essen·
tial that this water is replaced and the system pressure main-
tained.
7.11 Connections
to the mains water supply must not be made
without the authority of the local Water Company.
7.12 The pump is set at maximum and must not be adjusted.
7.13 Connections
in the system must resist a pressure of up to 3
bar.
7.14 Radiator valves must conform to BS 2767(10):1972.
7.1 5 Other valves used should conform to the requirements of
BS 1010.
7. 16 To make use of the extra heating available from the appli-
ance at the end of any demand, it is recommended that a single
small radiator be left permanently open.
Central heat i ng
Suled system
--expansion vessel
-· Water to Wa t er
heat excltlnger
by-pass ad j uster - ~+----l-+--+----J
Fill po i nt ----
Heamg return
Heating flow .
Heating Return
'
I
I
l
Nola . The mains cold i nlet
connection to the app li ance
must come before any other
connection from the cold supply .
Auto
air vent
.... ....,..__ FiiiPoint
' Heating Return
Domestic
cold water .
._ British Standard
stop valve .
Fi xed spindle type.
- Wa t er mai n.
JOOmm ( 12 inl min .
above the hi ghest
po i nt of the system .

8. Open Vent Primary Water System
See Fig . 7
8.1
The size of the flow and return pipework is given in Section
3 -
Thble 4. The components required to connect the appliance
to an open vent system are available as an optional extra
kit.
8.2 The feed and expansion cistern should be arranged so that
there
is a minimum static head of 0.3 metres (12in.) above the
top of the appliance
or above the highest point in the heating
circuit, whichever
is the higher. See F ig . 6.
8.3 The feed and vent pipe should be 22 mm diameter
and rise
continuously
from the appliance to the feed and expansion cis·
tern.
Fig. 6. Open ventwater system.
Feed and expansion tank
8.4 Apressure relief valve is not required on an open vented sys·
tern. If the pressure relief valve is left in position then a discharge
pipe must be fitted which terminates
in a position such that any
water or steam discharge does not cause a hazard to the occu·
pants or damage electrical components.
8.5 Air w
it hin the appliance will be expelled via the feed and
vent connection or dissipated into the rest of the system which
must be fitted with manual air vents
at any high point.
8.6 The pump is set to maximum and must not be reset.
8.7
To make use of the extra heating ava il able from the appli·
ance at the end of any demand, it is recommended that a single
small radiator be left permanently open.
- Overflow .
S.H .- Mnmum statiC hud 300 mm 11 2 111 .1
me85Uied from the top surface of the
appliance or t.ghest point in the heattng
system to the wat er level in the feed ill1d
expansiOn tank .
-r ·- ·- ·- · :-_-:_-==: -·- ·r
S .H .
j Primary feed ill1d vent S.H.
;~-;--;jj
1
-
1
jl r- -- - ----, pipel22mmlmustrise-
l " " I • I I I : I I : II : : I I contiooously .
I I I I I I I I I I ::I I I' I
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,tl . I'! I I I ~ .!., I I II I' I I . ...
\' - ---- ---~ ~---------'~
'T • I I
----- - - - t- - -- - - - _; - - - ~ - -- - -- - ~ --- - ...,
0 I
- - --L - _________ .:. __ - --- - ---,
lockstoeld v...,• . Radllltor valvt.
l tlll llll J llllllll
Nott .A dr0111 cock should be InStalled at
the lo west poont of the heat tng c1r cut ill1d
beneath the appliance .
9. Domestic Hot Water
9.1 The following are gener al requirements and, if necessary,
reference should be made to the local Water Company before
fit ·
ti ng the appliance.
9.2
MAINS COLD WATER INLET . Devices capable of preventing
the
flow of expansion water must not be fitted unless separate
arrangements have been made.
An expansion vessel connection
point
is provided within the appliance.
A 15mm connection is provided on the domestic
water inlet
elbow. A Zilmet Z160 is the preferred type. A thread
sealant
compatible with potable water must be used.
9.3
The final 600 mm ofthe mains cold water connection to the
appliance should be made
in copper tube only.
9.4
The appliance is suitable for a mains pressure of up to 10
bar (150 lb/ in ").
I
I
8
Central h ea un g
-· Water to Wate r
h eat ex changer
by - pass ad ju ste r- ~±--t+-1----'
,
F ill point -- ---'
Heating return
Heat ing f low .
'
Nota . The ma.ns cold 1 nle1
connection to the appfta nce
must come before any other
connection from the cold supp ly .
Domest ic
cold water .
._. B rinsn St andard
stop valve .
Fixed spindle type .
.... Waterma 111 .
9.5 The appliance is fitted with a mains supply isolating valve.
9.6
The maximum domestic hot water flow rate is 8.5
litres/min (±15
%) (1 .87 gallons/min).
9.7
In winter (when the mains inlet water temperature is lower)
a reduced
flow rate at the taps will be required to achieve the
maximum hot water delivery temperature available
in warmer
weather.
9.8
It is a requirement that long pipe runs to the taps or shower
should be insulated to prevent the rapid cooling of domestic hot
water after a tap or shower has been turned off. Refer to
BS5546:1990.
Pipe diameter: up
to 12mm. Max.length 20 metres.
Pipe diameter: up to 22mm . Max. length 12 metres.
9.9 Hot and cold taps
and mixing valves used with this appli·
ance must be suitable for operating at a pressure of up to 10 bar
(150 lb/in ').

9.10 No anti·syphonage arrangements are necessary except for
someloose head showers. See also Section 9.12 following.
9.11 Thermostatically controlled or pressure equalising shower
valves
will guard against the flow of water at too high a temper·
ature.
9.
12 The head of a loose head shower must not fall doser than
25mm
(1 in) above the top edge ofthe bath to prevent its immer·
sion in bath water. Alternatively the shower must be fitted with
an anti·syphonage device at the point of the
flexible hose con·
nections.
9.
13 The supply of hot and cold mains water direct to a bidet is
permitted, (subject to local Water Company requirements), pro-
vided that the bidet is of the over-rim flushing type. The outlet(s)
9
should be shroucded and unable to have any temporary hand
held spray attached.
No anti-syphonage arrangements are nee·
essary.
9.14 As the maximum temperature of the Water to Water heat
exchanger is limited by the control drcuit, there
is normally no
need for
water treatment to prevent scale accumulation. In
exceptional drcumstances a device to prevent scale formation
can be fitted.
Installation of a scale inhibitor assembly should be
in accor·
dance with the requirements of the local Water Company. An
isolating valve should be fitted to allow servidng. The water
hardness can be determined using a standard test paper or by
reference to the local Water Company.

1 0. Electrical
See Figs . 7, 8, 9, 10 and 11 .
1
0.1 MAINS SUPPlY 240 V - , 50 Hz, 150 watts.
External Fuse 3A Internal Fuses : T2A (F1) and T315mA (F2) .
10.2 It must be possible to completely isolate the appliance.
1
0.3 Connection to the mains supply should be via a double
pole isolator
with a contact separation of 3mm in all poles and
supplying the appliance and controls
only.
10.4 The appliance must be earthed.
10.5 Mains Cable. 0. 75 mm • (24 x 0. 20 mm) to BS 6500 Thble
16 .
If a new cable is needed it must be connected into the terminals
marked L
(Brown or Red lead), N (Blue or Black lead) and -t
(Green/'rellow or Green) and be held securely in the cable clamp.
Fig. 7. Wiring Diagram -Control panel and facia.
For access refer to Section 14 . NOTE : Ensure the earth lead is
longer than the live and neutral leads.
1
0.6 The wiring between the appliance and the electrical supply
shall comply with current lEE Wiring Regulations and any local
regulations which apply .
1
0.7 If a room and/ or frost thermostat is to be fitted refer to
Figs. 10 and 11 . The thermostats must be suitable for use on
mains voltage .
1
0.8 A facia mounted programmer is available as an extra.
Instructions
are supplied with the programmer kit.
10.9 Atime switch or programmer can be fitted externally to the
appliance.
10.10 SAFETY CHECK. After installation or in the event of an
electrical fault the electrical system shall be checked for short
circuits,
fuse failure , incorrect polarity of connections, earth
continuity and resistance
to earth.
(All components shown viewed from front of appliance.)
A
TO
CASVAI.Vl
IIAII AIIO
OOIIESTlC
HOT WATER
TltEAIIOST AT
COLOUR CODE
br - brown bl - blue gy - green and yellow bk-black or-orange
r-red w- wh i te y- yellow g- grey v- vi olet pk - pi nk
10
...,

Fig. 8. Wiring Diagram -Components outside control panel
(All components shown viewed from front of appliance.)
r------------- ------- ---- -------l
,r------------ ------- -----~ I
/ ' I
/ ' I
r i 1
l I I
I
I
I
I
I
I
I
I
I
I
I COLOUR CODE
~ br-brown bl-blue gy-green and yellow bk-black or-orange
J- r-red w-white y-yellow g -g rey v-violet pk-pink
I ·- ·- ·- ·. -:::: ·.=;!
I · - . -- · .--- · - · -·- . L.-- ·-
- ~ - - ----- · -- L-. ----
'T ·- ·- ·
I I
I I
I I
I I
I ~
I
I
Pump
Overrun
Thermostat
-----1
_____ _J I
_ . ...J...-1... .
-= ·. -::::. ·. ::=: .- - Tj ·
II
I I
I I
I I
I I
/) I
-----// I
I
I
I
------------- ---- ------- -i
Diverter Valve Micro-Switch
br
gy~--..
bl
11
Main Valve
Modureg
Regulator
Gas Valve
Domestic Hot
I
I
I
I
I
I
I
I
I
I
I
- ...J...
Water '-...!...
1
Thermostat 1 ~
Domestic Hot
Water Sensor

-
N
/ N
' lli POWER ON r=;_[. DEMAND
I ~ INDICATOR I Q3D INDICATOR
bla ck black
L r--- -------------------- - ------------------.,
' I X11 i PIN1 1 X111PI N1 1 ~ONVtRIOARD I
I I Xl i PIN " I
~-----C,.._,H FROST THERMOSTAT IIF FITTED ! RELAY RY1 I
~ FUSE f1 _r:::::::] XI /PIN 11
l2A X4 1 PIN ~ ~ - U - ~4 1 PIN 11 TRANSFORMER fl®Ot------------,
UIPI NJI ~
;~~~M ! Ill ~or.~=---,.._,-----TE-ST~:r---t ELECTRONICS
: THERMOSTAT WATEROIVERTERVAlVE ~II 1 -
XIO X4 nl MtCRO SW1TCH L----..J FUSE F2
- I PI N11 i PIN 11 X4 1 PIN1 1 T315mA
r
CH gr ev T- - T u ye11ow CH grey
brown I I !PIN11 Xl i PI N"
XIO I PI NJl I O+IW Of'TlONAll!Nit ' i OHW Xl ! PIN Jl
h l
~
- w lie XII I PIN 11 Xl I PIN 11 white ' I _/ CH r
OPERATING SWITCH '- -! a ed ElECTRONICS
l OR PROGRAMMER ! I .• D+IW Xl i PI NSl
. W4TER OMRTER V4LVE I
L-- - - · - · - -->-·-- - -~~-_j
XS ! PI NJl C£NTR4l H£4TING SENSOR -
red
XS I PIN 11 .--a DOMES11C HOT WATI:R SENSOR -
brown T Tl:MI'ERATURE CONTROt.I'OTI:NTIOMETtR - ~
L brown GAS
PUMP OVERRUN THERMOSTAT Oflnge I VALVES.__,. N
XI I PIN 11 I .......__
L ---------------------- ~ ~ PI~ I -- ---- - ----- -- _____ _j
btOWI'l
Fig . 9. Functional flow diagram. PUMP 0 -:
' )
Fig. 10. Room thermostat
connections.
Remove link .
1 2 3 4 5
Terminal X4 on
main driver board .
Honeywell room thermostat
T60608 (or similar .)
Fig. 11 . Frost thermostat
connections.
Terminal X4 on
main driver board.
Honeywell frost thermostat
T 41 60A (or similar .)

'
11 . Installation
11 .1 The appliance is supplied suitable for fitting to a sealed
system. If
it is to be fitted to an open vent system refer to Sec ·
tion 11 .2 following and Section 8.
The flue must be installed as specified in BS 5440 Part 1.
Note READ THIS SECTION FULLY BEFORE COMMENCING
INSTALLATION
11 .2 GENERAL FlmNG.
Check that the appliance carton contains :· Appliance
Installers Instruction Pack Appliance Mounting Plate
Users Information Pack Installer Hardware Pack
Check that the position chosen for the appliance is in accor·
dance w it h the instruct ions given in Sections 4 and 5.
The distance from the bottom of the mounti ng plate to the top
of the appliance casing is 1 06 mm .
Hold the appliance mounti ng plate to the wall . Check that the
plate is horizontal. See Fig. 12 .
Sealed System:
Unscrew and discard the !lUtomatic air vent cap. See Fig 13 .
Open Vent System:
Remove and discard the automatic a ir vent. Fit the preformed
pipe (optional extra) . Connect the feed and expansion tank. See
Fig 14 .
Connect the flue pipe to the appliance and seal the gap between
the pipe and the spigot. The flue must be supported so that its
weight is not put upon the appliance. Connect and make good
the flue system and terminal as specified in BS 5440:1.
11 .3 FINAL INSTALLATION
Check that all the water connections and the gas connection
have been tightened.
If a facia mounted programmer is to be fitted, unscrew the
upper two screws holding the facia panel in place and carefully
lower the facia . See Fig . 15 .
Unplug the Operating Switch from the terminal X1 0 on the main
driver board.
See Fig . 7. Unscrew the four screws hold i ng the
switch plate and remove the complete Operating Switch assem·
bly . Fit the programmer and tighten the four screws. Plug the
Fig. 12. Appliance mounting plate and flue position.
- App li ance cas i ng
REAR FLUE POSmON
Mark the position of the fixing holes and the position of the flue
hole centre line onto the wall .
Drill the fixing holes 60 mm deep for No . 12 size plugs and fix
the appliance mounting plate, and check that it is horizontal
before tighten ing the screws.
The gas and water pipes ca n be l ed towards the appliance at
this stage. See Fig 3. It is recommended that temporary connec·
tions be made to thoroughly flush the central heati ng syst em .
Al so flush the prima ry cold water supply pipe before the appli ·
ance is fitted to the wall .
Prepare the opening in the wall or ceiling for the flue pipe . Hang
the appliance onto the wall . Drill (at a slight rising angle) thro ugh
the two appliance fi xing holes at the bottom of the casi ng . Plug
and fix the casing bottom. Connect the gas, water and pressure
relief valve connections to t he appliance.A 15 mm shut-off valve
(supplied with the Installer Pack) must be fitted to the cold water
supply connection. See Fig 3.
Remove the cab inet front panel. Refer to Section 14 .3 (a) .
13
265mm nom .
SIDE FLUE POSmON
programmer into terminal X10 on the main driver board.
Lower the control box as described in Section 14 . 3(d).
Connect the mains electrical supply to the appliance and con ·
nect any room and/ or frost thermostats. The electrical leads to
the room and frost thermostats must pass through the appropri·
ate holes in the control panel and be fixed with the cable clamps
provided.
See Fig . 16 . Refit the control box and facia panel.
Test the gas supply pipework up to the appliance for soundness
as indicated
in BS 6891 .
Refer to Section 12 for a full description of the filling, venting
and, with a sealed system, the pressurising of the system.
If the appliance is not to be commissioned immediately, replace
the cabinet front panel. Check that the gas supply, the electrical
supply and the water connections are
all turned off .
If the premises are to be left unoccupied during frosty condi·
tions, then commission the appliance as described in Section 12
and leave it under the control of the frost thermostat or leave
operating continuously with the room thermostat set at 6°C.
If the unoccupation is to be of a long duration then drain the
appliance and system and commission the appliance upon
re ·
occupation.

Fig. 13. Automatic air vent .
Unscrew and discard the cap
Automatic air vent
( Sealed systems only I
llllllllll Jnlllll
Feed and vent connection _:::_l ~~r
I Open vent water system only ) -
Gas to Water heat exchange r
Fig. 14. Pipe connection for open vent
systems.
To Gas to Water heat exchanger
14
Fig . 15. Appliance casing and control
equipment fixings.
r
f \
I I
Inner casing co ver Cabilet side panel
fixing screws (2)
~\ .
) 0
~
'I!:
Control box fixing screws (2)
Upper fac 1a panel fixi ng screws (2)
~
I
--·
__ _ ::301
-me
-·
Low er facia pane l fixing screws (2)

Fi g. 16. Electrical cable exits from control box.
12. Commissioning
TO
GAS VALVE
IWIAIIO
OOIIEST1C
HOTWATtR
Th"Ef!IIOSTAT
12.1 The appliance is despatched with the controls set to pro-
vide a max i mum ou t put for domestic hot water of 24 kW
(82, 000 B tu/h) and satisfy a central heating load of 16.1 kW
(54,900 Btu / h ).
Domestic Hot Water System. Check that the mains water sup·
ply has been fully flushed out at installation.
Central Heating System. Check that the central heating system
has been
fully flushed out at installation.
Gas Service .
The complete system, in clud,ing the meter, must be
inspected and tested
for soundness and purged as indicated in
BS 6891 .
12.2 APPLIANCE AND CENTRAL H EATIN G SYSTEM
PREPARATION
Remo ve the cabinet front pane l.
Check that the electrical supply and the gas service to the appli·
ance are off. See F ig 3. ·
Check
that all the water connections throughout the system are
tight.
Open the system valves at the appliance. See Fig 3. Open all the
radiator valves,
fill the system and vent each radiator in tum.
On sealed systems the automatic air vent, (fixed to the flow man-
ifold) will vent the appliance. Check that the air vent cap has
been removed.See Figs 13.
Check that the pressure relief valve operates by turning the knob
anti-clockwise until
it releases. Water should be expelled from
the discharge pipe. See
Fig . 17. Lower the control box to gain
access. Refer to Section 14.3( d) .
S
EALE DS YSTEMS O NLY
Set the Expansi on V es se l Pre ssure
The charge pressure of the expansion vessel as despatched is 0.5
bar, which is equivalent to a static head of 5 metres (17 ft) . The
charge eressure must not be less than the static head at the
point of connection. See Fig . 4. A Schraider type tyre valve is
fitted to the expansion vessel to allow the charge pressure to be
increased if necessary.
Set
the S ystem Pres sure
Fill the system until the pressure gauge shows 2.5 bar (37
lblins ')and check for water soundness. Release water from the
system using the relief valve test knob until the System Design
15
MA ll DIIVER BOARD
TO
WA TIII
OMIDIIl
VAI.Vf
IIICJIO.IWITCM
Pressure is obtained, up to a maximum of1.5 bar.
System Design Pressure
in bar = Static Head of the System in
bar+ 0.3
Note: 1 bar is equivalent to 10.2 metres (33 .5 ft) of water.
Set the movable pointer on the pressure gauge to coincide with
the indicating pointer giving a permanent record of the set
system pressure.
If the pressure indicated on the pressure gauge is greater than
2.5 bar when operating at the maximum central heating tern·
perature, an extra expansion vessel must be fitted to the system
as close as possible to the appliance central heating return con·
nection.
The
appliance (as despatched) can accommo~ate a system
volume of about 104litres. Refer to B~ 7074 Part 1. If the system
volume is in excess of that accommodated by the expansion
vessei fitted to the appliance then an extra vessel must be fitted
as close as possible to the central heating return connection of
~he appliance.
Any extra vessel fitted must be pressurised to the same figure as
the integral vessel. If the expansion vessel fails then the speci·
fied replacement must be fitted.
12.3 PROGRAMMER
Any programmer fitted on the appliance should be set up at this
stage following the instructions sent with the programmer. The
Fig. 17. Pressure relief valve.
Pressure relief valve di scharge pipe

plug- in programmer will retain the setting for up to four weeks
following an interruption
in the electricity supply.
12.4 APPLIANCE OPERATION
Check
that the gas supply to the appliance is off. Switch the elec·
tricity supply on at the mains. Put the Operating Switch to Heat·
ing and Water. Leave the system to operate in a cold state for
about 20 minutes, venting as necessary to remove air from the
system.
Set the Operating Switch to
OFF. Switch off the electrical supply
to the appliance.
1\.lrn on the gas supply. Check for gas sound·
ness around the gas valve.
Light the pilot by pressing in the grey button on the gas valve
and operating the red spark igniter button. When the pilot has
lit continue to hold the grey button in for a further 20 seconds
and then release
it slowly.
If the pilot does not stay alight, twist the gas valve button anti·
clockwise. Wa it for 3 minutes and repeat the operation until the
pilot
has lit. Continue to hold the gas valve button for 30
seconds then release it slowly.
Tes t for gas soundness at the joint between the pilot pipe and
the burner with leak detection
flu id .
Observe the pilot flame. It should be about 18·20 mm long and
envelope the thermocoup
le tip. If not. refer to Section 14.4. See
Fig . 23.
Loosen
the burner pressure test point screw and connect a
pressu
re gauge. See Fig . 18.
Domestic Hot Water.
Set the Operating Switch (or Programmer) to WATER and fully
open a hot water tap.
The boiler should light at a burner pressure of 2·3 mb (0 .8·1.2 in .
wg.) rising immediately to 14 and 14.5
mbar (5 .6 and 5.8 in .
wg.).
If the burner pressure is low, check that the supply pres·
sure at the gas valve inlet with the appliance operating is at
least 19 mbar (7 .6 in. wg) .
Note: The burner pressure
is factory set and if (after checking
that the supply pressure is sufficient) the correct pressure is not
obtained then Wo rcester Heat Systems Service Department
should be contacted.
With the main burner alight test the integral gas supplies and
joints
for soundness using leak detection fluid .
Gradually close the hot tap and check
that the burner pressure
drops.
Fully open the tap and check that the burner pressure
rises. After 10
minutes operation check for spillage at the
diverter outlet as described in BS 5440: 1. Fully close the tap and
check
that the burner goes off . The pump will continue running
until the appliance has cooled to a preset temperature.
Set the Operating Switch (or Programmer) to OFF .
Central Heating
Check that all the radiator valves are open. Set the room thermo·
stat and the Central Heating Temperature Control to maximum.
On sealed systems check that the system is pressurised and set
to the required pressure as indicated on the gauge.
Set the Operat ing Switch ( or Programmer) to HEATING &
WATER .
The burner
will light.
The appliance
will modulate its output from 9.2 kW (31 ,400
Btu / h) to the set output of 16.1 kW (5 4,900 Btu / h) over a peri·
od of about two minutes.
Check the system to ensure that all the radiators are heating up
evenly.
Shut down all but one of the radiators and observe the burner
pressure
fall . Open all of the radiator valves and check that the
burner pressure rises.
If a greater heat output up to a maximum of 24 kW (82,000
Btu/h) is required, then the burner pressure must be adjusted at
the potentiometer located at the rear of the control box. Adjust
the potentiometer to give a burner pressure of 14.S mbar.
This
16
figure can only be achieved if the burner pressures are correctly
set
in the domestic hot water mode.
Balance the system so
that the required temperature difference
across the central heating
flow and return pipes is obtained. See
lable 3.
Adjust the central heating by-pass valve until the same tempera-
ture difference is obtained. See Fig 19. This should be carried out
with only a single radiator operating. If thermostatic radiator
valves are fitted then one radiator should be left uncontrolled.
The bypass valve should never be
fully closed.
Set the room thermostat to minimum and check that the burner
goes out. Reset the room thermostat to maximum and the burn·
er will relight and follow the normal operating procedure.
Set the Operating Switch (or Programmer) to OFF .
1\.lrn off the gas service cock and the electrical supply to the
appliance. After about 60 seconds the flame failure device can
be heard to operate. Check
for its correct operation by turning
the gas back on
at the gas cock and attempting to light the pilot
w
it hout depressing the gas valve button. If the pilot can be lit in
this way, turn off the gas supply and contact Worcester Heat
Systems.
Disconnect the pressure gauge and re-tighten the test point
screw.
Test for gas soundness at the screw.
Drain the system while the appliance
is still hot.
Refill , vent and, with a sealed system. re -pressurise as described
in Section 12.2.
Domestic Hot Water
and Central Heating
Light the pilot as described
in the preceding notes.
Set the Operat ing Switch (or Programmer) to HEATING &
WATER. If a programmer is fitted, set the domestic hot water to
Continuous or 24Hrs
and the central heating to ON . The burner
will light and heat will pass into the system. 1\.lrn on a hot water
tap and check that
fully heated hot water is discharged from the
tap .
Close the tap and the burner will go off . The appliance will then
return to the central heating mode and automatically
ba lance
with the system requ
ir ements.
Se t the Operating Switch (or Programmer) to OFF and the burner
will go out.
12 . 5 COMPLETION OF COMMISSIONING
Disconnect the pressure gauge and tighten the test point.screw.
Restart the appliance and check
for gas soundness around the
test point screw.
Refit the cabinet front panel.
If the appliance is being passed over to the user immediately,
refer to Section 13 -Instructions to the User
and set the controls
to the user's requirements.
If the appliance is to be left inoperative, check that the Operating
Switch
is set to OFF . 1\.lrn off the gas service cock and switch off
the electricity supply.
If there is any possibility of the appliance and system being left
inoperative during frosty conditions, drain
the appliance and
system. For short inoperative periods leave the boiler under the
control of a frost thermostat
or operating continuously under
the control of a room thermostat set
at 6°C.
13. Instructions To The User
13 .1 Tell the user how to operate the appliance and hand over
the Users Instructions leaflet.
13 .2 Tell the user what to do if the the heating system is not to
be used
in frosty weather.
13.3
Tell the user the sealed system set pressure if applicable.
13.4 Tell the user of the importance of regular servicing. Worces·
ter Heat Systems Ltd offer a comprehensive maintenance con·
tract.

Fig. 18. Gas valve.
Note
E lec trocal co nnect rons- Marn valve -----.._
! brown · blue • green/yellow)
axrmum pressure ad1ur:er -----....
Mrnrm um pressure adjuster
Turn the nuts ctockwrse
to rnc rease and a rlli - clockwrse
to decrease the pressure
~
odureg c ap
Mod u reg •~gul ator he ad
Fig. 19. Central heating by-pass adjuster.
13.5 Se t the system controls to the user's requirements.
13.6
If an external programmer has been fitted wh ich has a pro·
grammable domes ti c ho t water facility then it is suggested that
t
his be set to Continuous or the equivalent.
14 . Inspection and Servicing
14 .1 To ensure continued efficient operation of the appli·
ance it must be checked and serviced as necessary at regular
intervals. The frequency of servicing will
depend upon the
particular installation conditions and usage, but once per
year should generally be adequate . The extent of the service
required by
the appliance is determined by the operating
condition of the appliance when tested by fully qualified
engineers.
Any service work
must be carried out by competent engi·
neers such as British Gas or Corgi registered personnel.
14 . 2 PRE- SERVICE INSPECTION
Check that the flue terminal is clear.
Check that the ventilation and combustion air openings are
clear. See Section 6 - Air Supply.
17
::r-'=-___;;~-:::----- Pi lo t pi pe connect i on
ECO lead comection
Check the system and remake any joints or fittings which show
signs
of leakage.
Refill, vent and, with a sealed system, re·pressurise as described
in Section 12. 2.
Operate the appliance and the system taking note of any faults.
Warning
Disconnect the electrical supply at the mains and turn off the
gas supply
at the gas service cock on the appliance before
servicing.
See Fig . 3.
After completing the service always test
for gas soundness as
indicated in BS 6891 .
14. 3 DISMANTLE THE APPUANCE
To carry out a full and comprehensive service of the appliance
remove the following parts to gain access to the components
which need to be checked or serviced.
(a) Cabinet Panels. Remove the front panel by lifting off the
supports. Lower the control box as described in Section 14. 3(d) .
Pull off the lead from the spark generator. Unscrew the screw
fixing each of the cabinet side panels and remove the panels.
See Fig . 15.
(b) Inner Casing Cover. Remove the cabinet front panel. Un·
screw the two screws securing the cover to the casing and
remove. See Fig 15.
(c) Facia Panel. Check that the electricity supply to the appli·
ance is turned off . Remove the cabinet front panel. Unscrew the
two screws and lower the facia assembly. See
Fig . 15.
(d) Control Box . Remove the cabinet front panel. Unscrew the
two screws
as shown in Fig . 15. Support the assembly and allow
it to hinge down into the servicing position.
(e) Diverter. It is not necessary, nor possible to remove the
diverter assembly when servicing the appliance.
(f) Combustion Chamber Cover. Remove the the inner casing
cover. Unscrew
the four screws securing the cover and pull
downwards to remove the cover.
See Fig 20.
(g) Main Burner Assembly. Remove the combustion chamber
cover. Unscrew the pilot
fixing screws. Unscrew the two screws
and remove the burner assembly by lifting the front of the
burner and pulling forward. See Fig . 22.
(h) Flue Clean· OUt Cover. Unscrew the four screws and remove
the cover.
(i) Thermostat Cover. Unscrew the two screws and move the
cover to oneside (electrical leads still attached). See
Fig . 20.
14. 4 SERVICE OF COMPONENTS
Clean the Main Burner. Brush the blade tops and mixing tube
with a soft non-metallic brush and check that all the flame ports
are clear. Inspect the injector
and clean with a soft brush .
Replace the injector
if it appears damaged. Do not use a wire

Fig. 20. Appliance components and fixings (upper assembly).
Combust i on chamber cover fixing screws (4)
Combust i on chamber cover
Diverter baffle
Access cover
Fig. 21 . Pilot burner assembly.
2mm
Thermocouple
0
18

brush or anything likely to cause damage.
The burner
is fitted with a lint filter which can be removed by
unscrewing the nut
at the end of the burner and removing the
endcap. Brush or wash
in soapy water and carefully refit. Check
that the endcap is fitted correctly before tightening the nut.
Clean the Pilot Burner Assembly . Brush with a soft brush.
Remove the pilot injector and clean by rinsing it
in warm water.
Replace the thermocouple
if it appears damaged. Replace the
spark electrode if it appears damaged . Fit the electrode lead
before replacing the electrode.
Clean the Gas to Water Heat Exchanger. Cover the main burner
manifold with a cloth. Clean
the heat exchanger using a soft
brush.
Remove the deposits from the bottom of the combustion
Fig. 22. Main burner fixings.
Ma in burner fix i ng screws (2)
chamber. Do not distort any of the blades.
Combustion Chamber Insulation. Examine and replace any
pads
that are damaged. See Section 15.7.
Controls. Remove any dust or deposits using a soft non·metallic
brush. lake care not to mishandle any component connections.
Reassemble the appliance in the reverse order.
Check that ALL components are in place and correctly fixed.
Leave the cabinet front panel to be fitted after checking the oper·
ation of the appliance.
14. 5
TEST THE APPUANCE
On completion of the serv ice and reassembly of the appliance,
check
for gas soundness and the correct operation of the appli·
ance as described in Section 12 -Commissioning.
Refit the cabinet fron t panel and reset the controls to the users
requ
ir ements.
15. Replacement of Parts
15 .1 WARNING.
Switch off the electricity and gas supplies before replacing any
components.
After the replacement of any components, check
for
gas soundness where relevant and carry out functional
checks as described in Section 12 -Commissioning
15.2 COMPONENT ACCESS
To replace components it is necessary to remove one or more
sections of the cabinet and cover plates within the appliance as
described
in Section 14.3. The facia panel and control box may
also need to be lowered as described
in Section 14.3
15.3 DRAINING THE APPLIANCE
Check that the electricity supply to the appliance
is turned off .
19
Before removing any component holding water it is important
that as much water as possible is removed from the appliance.
(a) Appliance. 1\un off the central heating flow and return
valves at the appliance. See Fig 3. Fit a tube to the drain tap on
the Water to Water heat exchanger and open the tap about one
turn. See
Fig 26. Close the drain tap when the flow has stopped.
Extra water can be removed by operating the relief valve knob.
Some water will remain in the expansion vessel, pump,
diverter valve and Gas to Water heat exchanger and extra
care
must be taken when removing these components .
(b) Domestic Hot Water Circuit. lllrn off the mains cold supply
valve at the appliance using a flat-bladed screwdriver and open
the lowest hot water tap. See
Fig 3. A quantity of water will
Fig. 23. Pilot burner settings.
remain in the Water to Water heat exchanger and the diverter
valve
and extra care must be taken when removing these
components.
15 .4 COMPONENT REPLACEMENT
1. Automatic Air Vent. (Sealed system installation only.)See Fig
13.
Remove the cabinet front panel
and left- hand side panel as
described in Section 14. 3(a) .
Dra in the appliance as described in Section 15 .3(a) .
Unscrew the assembly.Take care not to distort the pipework.
Fit the replacement assembly.
Open
the valves and fill and re· pressurise the system as
described in Section 12.2.
2. Overheat Thermostat
See Fig 20.
Check that the electricity supply to the appliance is turned off .
Remove the cabinet front panel, the right-hand side panel and
the thermostat cover as described
in Section 14. 3(a) and (i) .
Unscrew the two screws to release the thermostat head. Release
the thermostat connections at the gas valve. See F
ig .8.
Fit the replacement thermostat in reverse order ensur in g that
some heat sink compound is on the mounting plate.
3. Gas
to Water Heat Exchanger. See Figs 13, 24 and 25.
Check that the electricity supply to the appliance is turned off .
Remove the combustion chamber cover as described
in Section
14.3tn.
Drain the appliance as described in Section 15. 3(a) .
Remove the screw securing the control box at the left-hand side
and
lift off the left-hand side panel.
Remove the pump overrun thermostat, overheat
thermostat ,
and main burner as described
in Sections 14. 3(g), 15. .4 .6 and
15.4.
2.

Remove the side panels of the combustion chamber by carefully
removing the insulation and removing the four screws. See Fig .
25 .
Unscrew t he flow pi pe at the hea t exchanger and at the bottom
left of the inner casing and remove the pipe .
Unscrew the return connection at the bottom left of the inner
casing and manoeuvre the heat exchanger from the casing.
Transfer the return pi pe to the new heat exchanger.
Fit the replacement heat exchanger in the reverse order ensuring
all the fibre washers are in place and a layer of heat sink com ·
pound is on each thermostat pad. Align the return pipe and
tighten the connection.
Refit the combustion chamber side
plates and insulation pads.
Re -assemble the appliance in t he reverse order.
Open the valves and fill and re ·pressurise the system as described
in Section 12 .2.
4. Pump Overrun Thermostat. See Figs 8 and 20 .
Check that the electric i ty supply to t he appliance is turned off .
Remove the cabinet front panel, right·hand side panel and
thermostat
cover as described in Section 14 . 3(a) and (i) .
Unscrew and loosen the access cover on the baffle. See Fig . 20 .
Use a long screwdriver, from above,to loosen the rear M4 screw
securi
ng the thermostat to its mounting place on the Gas to
Water heat exchanger. Remove the front screw and thermostat.
Carefully remove the three wires from their connections and
make note
of their positions.
Fit the leads to the new thermostat.
Fit the replacement thermostat ensuri ng a layer of heat sink
compound is between t he faces .
5. Combustion Chamber Insulation. See Fig 25 .
Check that the elec t ric i ty supply to t he appliance is turned off .
Remove the combustion chamber cover as described in Sect i on
14 .3( f). Remove the fibr e insulation pads from the combusti on
chamber si de , rear.and fron t.
F it the replacement pad s in the reverse order tak i ng care not to
damage them.
6. Main Burner. See Fig . 22 .
Check that the electricity supply to the appliance is turned off .
Remove the burner assembly as descri bed in Sect i on 14 . 3(g) .
Fit the replacement burner
in t he reverse order taking care not
to bend the pilo t bracket on the main burner.
7. Thermocouple. See Figs. 21 , 26 .
Remove the inner casi ng cover as descri bed in 14. 3(b) .
Unscrew the two screws and remove t he pilot burner from the
main burner.
Unscrew the ther mocouple at t he pi lot burner and t he gas valve
and remove .
Fit t he replacement thermocouple in t he reverse order and ref it
the
pilot burner.
8. Pilot Burner.
See Fi gs . 21 and 23 .
Remove the inner casing cover as described in 14 . 3(b) .
Unscrew the two screws and remove the pilot burner from the
ma in burner. Undo the pilot pipe . Unscrew and remove the ther·
mocouple .
Remove the spark electrode cable and pull out the electrode.
Fit the replacement burner in the reverse order ensuring that the
pilot injector is in place . F it the electrode lead before replacing
the electrode. Check the pilot burner settings as shown in Fig .
23 .
9.
Main Burner Injector. See Fig . 22
Remove f he main burner as described in Section 15 . 4.6 .
Unscrew the brass injector at the back of the combustion cham·
ber .
Fi t the replacement injector in the reverse order.
1
0. Spark Electrode. See Figs . 21 and 23
Check that the electricity supply to the appliance is turned off .
20
Remove the pilot burner assembly as described in Sections
14 .3(b)and 15 .7.
Pull the spark electrode out of the clip .
Fit the replacement electrode in the reverse order, check i ng that
the spark gap
is 4 to 5 mm. Fit the electrode lead before replac ·
ing the electrode.
11. Pilot Burner Injector. See
Fig 21
Remove the inner casing cover and pilot burner assembly as
described
in Sections 14 . 3(b) and 15.4 .8. Remove the injector (a
push fit inside the pilot assembly) .
Fit the replacement injector in the reverse order.
12 . Spark Electrode Lead. See Fig . 21
Check that the electricity supply to the appliance is turned off .
Remove the inner casing cover as described in Section 14 . 3(b) .
Carefully pull the lead from the spark electrode and from the
spark
generator.
Fit the replacement lead in the reverse order. Loosen the pilot
assembly
to refit the lead to the electrode.
13. Piezo Spark Generator.
See Fig. 26
Remove the cab i net front panel as desc ri bed in Section 14 . 3(a ).
Pull off the electrode lead . Unscrew the two screws and remove
the generator.
Fit the replacement generator in the reverse order.
14 . Gas Valve. See Fig . 18 .
Check that the electricity and gas supplies to the appliance are
turned
off .
Hang the control box assembly in the servici
ng positi on as
described
in Section 14 .3( d) .
Disconnect the pilot pipe. Unscrew and remove the black plastic
plugs.
Carefully pull off the two yellow wires from their term i·
nals. Disconnect the thermocouple and the overheat thermostat
lead at the valve . Remove the eight screws securing the valve to
the pipework and
remove the valve from the appliance.
Fit the replacement gas valve in the reverse order ensuring the
sealing washers are correctly fitted.
ll.lrn on the gas supply and check for soundness.
To replace the Modureg head only.
Pull off the electrical connections. Unscrew the two screws
securing the
Modureg head to the main body and remove .
Fit the new Modureg head (Honeywell3061) in the reverse order
ensuring that the gasket
is in the correct position.
To setthe burner pressure. See Fig. 18.
The minimum and maximum burner pressures must be set after
a
new gas control has been fitted .
Follow the procedure described in Section 12 .4 - Appliance
Operation.
Fig. 24. Gas to Water heat exchanger
connections.
Bo i ler ret u rn
i
Bo i le r fl ow co n nector screws