Saunier Duval THEMA C 23 User guide

1
Heating and hot water for the professionals
THIS IS A CAT II2H3+ APPLIANCE
01773 828100
IN WARRANTY
TECHNICAL HELPLINE
01773 828400
THEMA C 23
Installation and Servicing Instructions

2
INSTALLATION AND SERVICING INSTRUCTIONS
THEMA C 23
INSTALLATION SECTION
Introduction.................................................. Page 3
Dimensions ............................................................. 3
Technical data ...................................................... 4
Boiler schematic .................................................... 5
Fixing jig .................................................................. 6
Piping system installation...................................... 6
Heating system design ......................................... 7
Domestic hot water system design..................... 7
Boiler location ........................................................ 7
Boiler installation .................................................... 8
Electrical connection ........................................... 9
Commissioning ............................................... 9 - 10
Safety devices ..................................................... 11
Settings.................................................................. 11
Changing gas type ............................................. 12
SERVICING SECTION
Mandatory warning for CEE countries
Warning: This appliance is designed, approved and inspected to meet the requirements of the English
market. The identification plate located on the inside of the appliance certifies the origin where the
product was manufactured and the country for which it is intended.
If you see any exception to this rule, please contact your nearest Saunier Duval dealer.
Thank you in advance for your assistance.
Note!
The boiler serial number is marked on the label attached to the inside of the boiler. Refer to the
'Introduction' section page 3 for a description of the basic functions of the boiler. To safely oper-
ate the boiler, refer to the Users Instructions.
Routine cleaning and inspection ....Page 12 - 13
Replacement of parts ................................. 13 - 17
Boiler schematic .................................................... 5
Technical data ...................................................... 4
Schematic wiring diagram ................................ 18
Fault finding................................................... 18 - 20
Spare parts ........................................................... 20

3
INTRODUCTION
DIMENSIONS
The THEMA C 23 boiler is a wall mounted combina-
tion boiler providing central heating and instanta-
neous domestic hot water.
The boiler is of the II2H3+ category for use with
Natural Gas (G20) as distributed in the United King-
dom, or with Butane or Propane gas (G30/G31) with
the appropriate conversion kit.
Conversion kits:
Conversion Part No.
Natural Gas (G20) to G30/G31 XXXXX
Boilers burning LPG or similar gases MUST NOT be
fitted in basements or below ground level.
The boiler is an atmospheric type boiler. This means
that the air contained in the room where the boiler
is installed, is used for burner combustion. It is es-
sential, therefore, that installation of the boiler is in
strict compliance with rules and standards currently
in force for this type of boiler.
Both the central heating and domestic hot water
temperature are user adjustable from the boiler
control panel, see diagram1.
Electrical components have been tested to meet
the equivalent requirements of BEAB.
Domestic hot water demand always has priority
over heating demand.
The boiler is designed for use as part of a sealed
water central heating system with fully pumped
circulation. The pump, expansion vessel and asso-
ciated safety devices are all fitted within the boiler.
The installation must be carried out by a compe-
tent person in accordance with the relevant re-
quirements of The Building Regulations, The Water
Byelaws, The Building Standards (Scotland) Regu-
lations and any applicable local regulations.
Hab 268
Diagram 1
Hab 269
Diagram 2
The boiler is delivered in two separate packages:
- The boiler
- The fixing jig
Net weight: 36kg
Gross weight: 38kg
Ø 125
232
378
410
802

4
TECHNICAL DATA
Heating output adjustable from 8,7 kW to 23 kW (30,000 Btu/H to 80,000 Btu/H)
Efficiency 81 %
Maximum heating temperature 90°C
Heating adjustment 30 °C to 87 °C
Expansion vessel effective capacity 6,5 l
Expansion vessel charge pressure 0,5 bar
Maximum system capacity at 75°C 140 l
Safety valve, maximum service pressure 3 bar
Flue diameter 125 mm
Hot water output automatically variable from 8,7 kW to 23 kW (30,000 Btu/H to 80,000 Btu/H)
Operating threshold flow rate in domestic hot water mode 3 l/min
Maximum hot water temperature 65 °C
Specific flow rate (for 35°C temperature rise) 9,6 l/min
Minimum supply pressure 0,5 bar
Maximum supply pressure 10 bar
Maximum domestic hot water flow 12 l/min
Electrical supply 230 V
Maximum absorbed power 100 W
Natural Nas Butane Propane
(G20) G(30) G(31)
Burner injector 1,2 mm 0,70 mm 0,70 mm
Inlet pressure 20 mbar 28 mbar 37 mbar
Gas rate (maximum) 2,71 m3/h 2,02 kg/h 1,99 kg/h
Gas rate (minimum) 1,11 m3/h 0,83 kg/h 0,82kg/h
Pump:
The performance of the pump varies according to the pump bypass setting, see diagram 3.
Diagram 3
50
40
30
20
10
0 500 1000
1
2
3
5
4
Available pressure (kPa) between
heating flow and return
(10 kPa = 1 m WG)
1
2
3
4
5
Flow rate through heating system (I/h)
Bypass fully shut
Open 1/4 turn
Open 1/2 turn
Open 1 turn
Open 2 turns
Pom 052a
Heat output
(kW) 8,7 10 11 12 13 14 15 16 17 18 19 20 21 22 23
(Btu/h) 29704 34142 37557 40971 44385 47799 51214 54628 58042 61456 64871 68285 71699 75113 78528
Heat input
(kW) 11,6 13,1 14,2 15,3 16,4 17,5 18,7 19,9 21,1 22,2 23,4 24,6 25,6 26,8 27,9
(Btu/h) 39764 44631 48410 52326 56042 59742 63794 67819 71897 75872 79910 83836 87545 91412 95358
GAS
G 20 (mbar) 1,7 2,0 2,4 2,8 3,2 3,6 4,1 4,7 5,2 5,8 6,5 7,1 7,8 8,5 9,2
G 30 (mbar) 4,2 5,5 6,5 7,6 8,7 9,9 11,3 12,7 14,3 16,0 17,7 19,5 21,2 23,2 25,2
G 31 (mbar) 5,3 7,1 8,4 9,8 11,2 12,7 14,5 16,4 18,4 20,5 22,8 25,0 27,3 29,8 32,4

5
BOILER SCHEMATIC
1-On button
2-Off button
3-Piezo igniter
4-Central heating thermostat
5-Domestic hot water temperature adjuster
6-Temperature/pressure gauge
7-Non-return valve
8-Expansion vessel
9-Pump
10 - Automatic air vent
11 - Burner
12 - Heat exchanger bleed pipe
13 - Heat exchanger
14 - Gas valve
Diagram 4
16 - Overheat thermostat
17 - Ignition electrode
18 - Pilot
19 - High limit thermostat
21 - Loss of water switch
22 - Flue safety device
A- Heating return
B- Cold water inlet
C- Heating flow
D- Domestic hot water flow
E- Gas supply
AB CD E
23
13
12
11
10
9
8
6
21
7
22
19
18
17
14
15
3
2
1
5
4
16
Shy 127b

6
PIPING SYSTEM INSTALLATION
FIXING JIG
Diagram 5
From left to right, the fixing jig comprises:
A- Heating return with isolating valve (m).
B- Cold water inlet with isolating valve (p).
C- Heating flow with isolating valve (q), drain screw (r) and safety valve (s).
D- Domestic hot water out.
E- Gas service cock.
Filters and washers:
1- Fibre washer
2- Metal filter
3- Flow regulator
4- Plastic filter
5, 6 & 7- Black graphite washers
• Heating system connections - Pipe diam 22 mm
• Hot water system connections - Pipe diam 15 mm
• Gas connection - Pipe diam 22 mm
• Safety valve discharge - Pipe diam 15 mm
Water connection
Connect the water pipes to the fixing jig using the
copper tails supplied, see diagram 5.
Warning: To prevent damage to the isolating cocks,
do not solder joints or fittings with the copper tails
connected.
Connect the system pipework to the boiler observ-
ing the correct flow and return format as shown in
diagram 6.
Safety valve discharge
WARNING. It must not discharge above an en-
trance or window or any type of public access
area.
Connect the safety valve discharge pipe to the
boiler, the discharge must be extended using not
less than 15 m o.d. pipe, to discharge in a visible
position outside the building, facing downward
preferably over a drain. The pipe must have a con-
tinuous fall and be routed to a position so that any
discharge of water, possibly boiling or steam, can-
not create any danger to persons, damage to
property or external electrical components and
wiring. Tighten all pipe connection joints.
Gas connection
• The supply from the governed gas meter must
be of adequate size to provide a constant inlet
working pressure of 20 mbar (8 in w.g.).
To avoid low gas pressure problems, it is recom-
mended that the gas supply is connected using 22
mm pipe.
• On completion, the gas installation must be
tested using the pressure drop method and purged
in accordance with the current issue of BS6891.
Gas Safety (Installation and Use) Regulations
In your interests and that of gas safety, it is the law
that ALL gas appliances are installed and serviced
by a competent person in accordance with the
above regulations.
12
3
5
67
4
55 55
57,5 57,5
r
p
q
34
25
23
113
s
33
A
B
C
D
E
m
Pla 105c
Diagram 6
Flow
control valve Drain point
Filling point
Bypass
valve
Minimum 22 mm diameter
Tundish
(supplied)
Pressure
reducing
valve
(supplied)
Domestic
water
Heating
circuit
Return
Additional
expansion
vessel
(if required)
Boiler
Hot
Cold supply
Sch 173

7
HEATING SYSTEM DESIGN
• The THEMA C 23 boiler is compatible with any type
of installation.
• Heating surfaces may consist of radiators, convec-
tors or fan assisted convectors.
• Pipe sectional areas shall be determined in accord-
ance with normal practices, using the output/pres-
sure curve (diagram 3). The distribution system shall
be calculated in accordance with the output require-
ments of the actual system, not the maximum output
of the boiler. However, provision shall be made to
ensure sufficient flow so that the temperature differ-
ence between the flow and return pipes be less than
or equal to 20°C. The minimum flow is 450l/h.
• The piping system shall be routed so as to avoid
any air pockets and facilitate permanent venting of
the installation. Bleed fittings shall be provided at
every high point of the system and on all radiators.
• The total volume of water permitted for the heat-
ing system depends, amongst other things, on the
static head in the cold condition.
The expansion vessel on the boiler is pressurised at 1
bar (corresponding to a static head of 5 m w.g.) and
allows a maximum system volume of 140 litres for an
average temperature of 75°C and a maximum serv-
ice pressure of 3 bar. This pressure setting can be modi-
fied at commissioning stage if the static head differs.
An additional expansion vessel can be fitted to the
system if required, see diagram 6.
• Provision shall be made for a drain valve at the
lowest point of the system.
• Where thermostatic radiator valves are fitted, not
all radiators must be fitted with this type of valve, and
in particular, where the room thermostat is installed.
• In the case of an existing installation, it is ESSENTIAL
that the system is thoroughly flushed prior to installing
the new boiler using a product such as Fernox or Sen-
tinel. Contact the product manufacturers for specific
details.
Filling the system
Provision must be made for filling the system at low
level. The use of a WRC approved filling loop is strongly
recommended, connected as shown in diagram 6.
DOMESTIC HOT WATER SYSTEM DESIGN
• Copper tubing or plastic Hep2 O may be used
for the domestic hot water system. Unnecessary
pressure losses should be avoided.
• The boiler may operate with a minimum supply
pressure of 0,3 bar but under a reduced flow rate.
Optimum performance will be obtained from a
supply pressure of 1 bar.
• The flow restrictor must be fitted in the cold wa-
ter inlet during installation.
BOILER LOCATION
Clearances
The position of the boiler must be such that there is
adequate space for servicing.
The recommended clearances are:
5 mm either side of boiler
300 mm above boiler
250 mm below boiler
450 mm in front of boiler
Fixing jig
The fixing jig comprises three parts:
1) The connecting plate which allows the connec-
tion and soundness testing of all the pipework be-
fore the boiler is fitted and helps support the weight
of the boiler.
2) The hook which supports the weight of the boiler.
3) The template which ensures the hook and con-
necting plate are correctly fitted relative to one
another.
• Place template on wall in required position, mak-
ing allowances for the necessary clearances etc.
Note: It is permissible to install the boiler with re-
duced clearances at the bottom and sides of the
boiler PROVIDING that adequate consideration is
given for Servicing/Repairs at a later date. If any
doubt exists, contact the Saunier Duval Technical
Helpline 01773 828400.
• Mark the position of the holes for the hook and
connecting plate.
• Drill, plug and fix the connecting plate and hook
to the wall using suitable screws.
• Check that both the hook and connecting plate
are level.
If the boiler is not installed immediately, protect the
various couplings to prevent any ingress of foreign
materials e.g. plaster, paint etc.

8
ELECTRICAL CONNECTION
Warning. This boiler must be earthed
All system components must be of an approved
type.
Connection of the whole electrical system and any
heating system controls to the electrical supply must
be through a common isolator.
Isolation should preferably be by a double pole
switched fused spur box having a minimum con-
tact separation of 3 mm on each pole. The fused
spur box should be readily accessible and prefer-
ably adjacent to the boiler. It should be identified
as to its use.
A fused three pin plug and shuttered socket outlet
may be used instead of a fused spur box provided
that:
a) They are not used in a room containing a fixed
bath or shower.
b) Both the plug and socket comply with the cur-
rent issue of BS1363.
The mains electrical supply must be maintained at
all times in order to provide domestic hot water.
Do not interrupt the mains supply with a time switch
or programmer.
WARNING: ON NO ACCOUNT MUST ANY EXTERNAL
VOLTAGE BE APPLIED TO ANY OF THE TERMINALS ON
THE EXTERNAL CONTROLS CONNECTION PLUG.
Warning: This appliance must be wired in accord-
ance with these instructions. Any fault arising from
incorrect wiring cannot be put right under the terms
of the Saunier Duval guarantee.
External controls
The THEMA C boiler is designed to operate at maxi-
mum efficiency at all times and will benefit by be-
ing connected to a programmable electronic
room thermostat such as Saunier Duval part
number 40010. Please contact your supplier.
The boiler will work for heating without a room ther-
mostat and/or timeswitch being connected pro-
vided that the wire link fitted between the two ter-
minals of connector (E) is left in place, see diagram
10.
A 230V room thermostat can be used but do not
make any connection to the compensating resis-
tor.
ON NO ACCOUNT must any electrical voltage be
applied to any of the terminals of the external con-
trols plug.
Should any doubt exist about connecting external
controls, contact the Saunier Duval Technical
Helpline 01773 828400.
BOILER INSTALLATION
Statutory requirements
The installation of this boiler must be carried out by
a competent person in accordance with the rel-
evant requirements of the current issue of:
The Gas Safety (Installation and Use) Regulations
The Building Regulations
The local water company Byelaws
The Building Standards Regulations (Scotland)
The Health and Safety at Work Act
Sheet metal parts
WARNING. When installing or servicing this boiler,
care should be taken when handling the edges of
sheet metal parts to avoid the possibility of personal
injury.
Installing the boiler
Prior to starting work, the system must be thoroughly
flushed so as to eliminate any foreign bodies and
contaminants such as filings, solder particles, oil,
grease etc.
Note. Solvent products could cause damage to the
system.
• Engage boiler upper part onto the hanging
bracket, see diagram 8.
• Allow the boiler to seat down onto support plate,
see diagram 9.
• Fit filter and washers, strictly adhering to the se-
quential order and directions shown on diagram 5.
• Connect the various couplings between the
boiler and the connection plate.
Ins 020
Ins 021
➞
➞
Diagram. 8
Diagram. 9

9
ELECTRICAL CONNECTION
COMMISSIONING
The commissioning and first firing of the boiler must
only be done by a competent person.
Gas installation
It is recommended that any air is purged from the
supply at the gas inlet test point on the lower right
hand side of the gas valve, see diagram 11.
Filling the system
• Open shut off valves, see diagram 12 (slot of
screw corresponds to flow direction), and cap on
automatic air vent on top of pump.
• Bleed each radiator until a continuous jet of wa-
ter is obtained.
• Do not close automatic air vent cap on boiler.
• Open various hot water taps to bleed system.
• Make sure that pressure gauge reads between
1 and 2 bar. Re-pressurise system as necessary.
Important:
- If this procedure is not carried out properly, the boiler
will go into safety lock-out until all of the air has been
purged.
- When venting air from boiler, do not touch the
schrader valve on the expansion vessel, it is NOT a
vent.
- Before starting the boiler, turn the pump impellor to
make sure it is free to move.
• Unscrew black cap on front of pump.
• Using screwdriver, push in pump spindle and turn
pump impellor 3 to 4 times. DO NOT HIT SPINDLE. Re-
place black cap.
Diagram 11
Mec 005Ins 017a
Diagram 12
sch 229
sch 228
E
°C
For no external controls
leave wire link (E) in place
When fitting room thermostat,
remove wire link (E) and connect
voltage free thermostat as shown
Diagram 10
sch 227
The mains electrical cable is supplied with the
boiler. It is coiled and tucked inside the boiler
THEMA C 23
➜
➜ ➜
gas inlet
test point

10
COMMISSIONING
Starting the boiler
Before starting the boiler check that:
- The gas meter tap is open.
- The boiler gas service cock is open.
- The boiler is connected to the electrical supply.
First starting up
• Following the instructions given in the 'Controls
and Lighting' section, set boiler to run in central
heating mode.
• Set boiler thermostat for maximum temperature
and check that any external controls, if fitted, are
calling for heat.
• Allow the temperature to rise to the maximum
value, with all radiator valves open.
The temperature rise will cause release of the gases
contained in the water of central heating system.
- Gases driven towards the boiler will be automati-
cally released through the automatic air vents.
- Gases trapped at the highest point of the system
must be released by bleeding the radiators.
On reaching maximum temperature, the boiler
should be turned off and the system drained as
rapidly as possible whilst still hot.
• Refill system to a pressure of 1 bar and vent as
before.
• Restart boiler and operate until a maximum tem-
perature is reached. Shut down boiler and vent
heating system. If necessary, top up heating sys-
tem and make sure that a pressure of 1 bar
is indicated on the pressure gauge when system is
COLD.
Gas pressures
The main burner pressure should be checked dur-
ing commissioning to make sure the correct input
is obtained. Proceed as follows:
• Shut down boiler.
• Undo screw on burner pressure test point below
sealed combustion chamber, see diagram 14.
• Connect a suitable pressure gauge.
• Gain access to the rear of the control panel and
locate the range rating adjuster screw, see dia-
gram 13.
• Start boiler as described in 'Instruction for Use'.
• Set boiler thermostat to maximum and check
that any external controls are calling for heat.
• Check that the reading on the gauge matches
that given in 'Technical Data' for the type of gas
being used.
• Adjust the range rating adjuster screw as neces-
sary to obtain the desired input.
• Shut down boiler.
Reg 056
• Remove pressure gauge, tighten up test point
screws and check for gas soundness.
• Using a ball point pen, clearly indicate on the
data label the input the boiler is set to.
Note: This adjustment does not affect the domes-
tic hot water output.
If measured burner pressure differs greatly from the
given figure, check the gas inlet pressure as follows:
• Shut down boiler.
• Remove screw from inlet test point on the side of
the gas valve, see diagram 11.
• Connect a suitable pressure gauge.
• Start boiler as described in 'Instructions for Use'.
• Check that the inlet pressure reading matches
that given in 'Technical Data' for the type of gas
being used.
• Shut down boiler.
• Remove pressure gauge, tighten up test point
screws and check for gas soundness.
• If the gas pressure is incorrect, refer to the Fault
Finding section in 'Servicing Instructions'.
• If the inlet pressure is below that given, the gas
supply pipework/meter must be checked and any
fault corrected.
• In the case of an LPG installation, check the stor-
age tank or cylinder, regulator and pipework.
Des 044
Diagram 14
Diagram 13

11
SAFETYDEVICES
Flue safety device
If an obstruction, even
partial, of the flue oc-
curs, for any reason
whatsoever, the built in
flue safety device will
turn the boiler OFFand
the warning LED on the
Sec 055
In case of loss of water in
the system
CAUTION. The boiler is in-
stalled as part of a sealed
system which must only be
drained and filled by a
competent person.
If the pressure shown on
the pressure gauge, see
diagram 16, is less than 1 bar, the system must be
filled up immediately. Call your Installer/Service
Provider.
Overheat safety
In the event of a problem, the overheat safety
device cause safety shutdown of the boiler. If this
happens, call your Installer/Service Provider.
Frost protection
The THEMA C 23 boiler
has a built in frost pro-
tection device that pro-
tects the boiler from
freezing. If the boiler is to
be left and there is a risk
of frost, ensure that the
gas and electrical sup-
Diagram 17
plies are left connected and that the Summer/Win-
ter switch is in the 'Summer' position.
The frost protection device will light the boiler when
the temperature of the boiler water falls below 6°C.
When the temperature reaches 16°C, the boiler
stops.
Note: This device works irrespective of any room
thermostat setting and only protects the boiler.
Important notice: Under no circumstances must the
flue safety device be bypassed or removed. Any
repairs on the flue safety device must be carried
out by a qualified engineer using genuine replace-
ment parts only.
Air in the heating system
Persistent air in the heating system may indicate
leaks in the system or corrosion taking place. Call
your Installer/Service Provider.
Gas leak or fault
If a gas leak or fault exists or is suspected, turn the
boiler off and consult the local gas undertaking or
your Installer/Service Provider.
In case of power supply failure
The boiler no longer operates.
As soon as power supply is restored, the boiler will
be automatically restarted.
Important notice: A central heating system cannot
operate satisfactorily unless it is properly filled with
water and unless the air initially contained in the
piping systems has been properly bled off. If these
conditions are not satisfied, air noise will occur
within the system.
Sec 056
SETTINGS
Bypass
The built-in bypass must be adjusted according to
the requirements of the system. Refer to the flow
rate/pressure curve (diagram 3). The boiler is sup-
plied with the bypass open half a turn. It is adjusted
by turning the bypass screw, see diagram 18. Turn
the screw clockwise to close the bypass.
When using thermostatic radiator valves (TRV's), it
is advisable to fit a separate, adjustable bypass of
15 mm minimum diameter between the flow and
return connections of the heating circuit. Any by-
pass must be fitted before system controls.
Pump operation in heating mode
The PCB can be set to operate the pump in two
ways, see diagram 19.
Position D: Intermittent pump operation.
With the jumper set to position 'D', the pump will
operate during operation of the room thermostat.
Position C: Continuous pump operation.
With the jumper set to position 'C', the pump will
operate continuously.
Reg 013Reg 004
Diagram 15
boiler control panel will light. If this occurs, contact
your Installer/Service Provider.
Diagram 16
Diagram 18
Diagram 19

12
CHANGING GAS TYPE
Should it become necessary to change the gas type, a modification kit will be required.
This modification must only be carried out by a suitably qualified engineer.
Conversion: Natural Gas (G20) to G30/G31 Part No. XXXXX
Conversion: Natural Gas (G20) to G130 Part No. XXXXX
To ensure the continued efficient and safe opera-
tion of the boiler it is recommended that it is
checked and serviced at regular intervals. The fre-
quency of servicing will depend upon the particu-
lar installation conditions and usage, but in gen-
eral once a year should be enough.
It is the law that any servicing is carried out by a
competent person.
Service Check and Preparation.
• Operate boiler and check for any faults that
need to be put right.
• Isolate boiler from the gas and electrical supplies.
• On completion check all gas carrying parts for
soundness with leak detection fluid.
• Remove boiler casing as follows:
Upper front panel
• Hinge down control cover to gain access to con-
trol panel.
• Disengage the two 'quarter turn' fasteners by
turning the heads of the screws a quarter of a turn
towards the centre of the boiler.
• Carefully lower the panel down on its hinge until
it is horizontal.
• Turn both plastic catches to release upper front
panel.
• Remove upper front panel by pulling forward at
the bottom and lifting off.
Side panels
• From below boiler, unscrew and remove black
plastic screws securing side panels to the boiler.
• Prise out black plastic inserts and lift panel off
boiler.
Combustion chamber
• Loosen two wing nuts on combustion chamber
cover.
• Disengage retaining lugs from holes in either side
of combustion chamber and move rods away to
clear combustion chamber sides, see diagram 20.
• Unclip two toggle clips holding upper part of
combustion chamber in place.
• Holding both sides, pull chamber forward to re-
lease it from underside of heat exchanger and out
of boiler.
• Take care not to damage insulation material on
inside faces of combustion chamber.
Cleaning the burner
• Pull off lead to ignition electrode.
• Disconnect pilot pipe to pilot burner.
• Unclip pilot burner and remove.
• Remove pilot injector from pilot burner. Examine
and clean as necessary.
ROUTINE CLEANING AND INSPECTION
• Undo main gas supply nut from main burner.
• Unscrew and remove locking nut from both main
gas connection and burner pressure tapping point.
• Lift front edge of burner until tapping point and
gas supply connection are free. Remove burner
from boiler taking care to retain both fibre washers
and seal on gas supply for use on reassembly.
• Unscrew and remove two injector bar retaining
screws and separate injector bar from burner.
• Examine and clean injectors as necessary.
Note: Do not use a wire or sharp instrument on the
holes.
• Replace burner in reverse order to removal.
Heat exchanger
• After removal of burner, examine heat ex-
changer for any blockages or build up of deposits.
• Clean using soft brush or vacuum cleaner.
Important: Take care not to scratch, or otherwise
damage, painted surface of heat exchanger.
Reassembly of parts removed for servicing
• Replace all parts in reverse order to removal.
Flue system
• Inspect flue system to make sure all fittings are
secure.
• Carry out checks to make sure flue is operating
safely and efficiently.
Cold water inlet filter
• Drain down hot water circuit of boiler as follows:
• Close isolating valve on cold water inlet connec-
tion on fixing jig, see diagram 5.
• Open one or more hot water taps to drain boiler.
• Undo connecting nut from cold water inlet con-
nection to gain access to filter.
• Remove white filter from inlet connection.
Note: Connecting pipework is telescopic, it may be
necessary to slide sleeve back for easire access to
filter.
• Clean and inspect filter, replace if necessary.
Des 047
Diagram 20
Des 047

13
ROUTINE CLEANING AND INSPECTION
Operation of water valve
• With the Summer/Winter control in the 'Summer'
position, slowly open a convenient tap until boiler
lights.
• Measure water flow, it should not be greater than
3,5 litres/minute.
REPLACEMENT OF PARTS
To replace microswitch assembly
• Disconnect microswitch by pulling off plug.
• Unclip external controls connector from mount-
ing bracket.
• Undo two screws securing microswitch assembly
to reversing valve assembly, see diagram 21.
• Remove microswitch assembly from reversing
valve.
• Fit replacement microswitch assembly in reverse
order to removal.
• Reconnect plug and refit external controls con-
nection to bracket.
To replace main printed circuit board (PCB)
• With lower front panel down as described previ-
ously, undo and remove screws securing PCB cover
to lower front panel, see diagram 22.
• Hinge back PCB cover.
• Pull off connectors HT1, BT2 and BT5 on PCB.
• Remove PCB from housing.
• Fit replacement PCB in reverse order to removal.
• Refit connectors and cover in reverse order to
removal.
To replace pump
• Drain down heating circuit of boiler only as fol-
lows :
• Close isolating valves on flow and return connec-
tions on fixing jig, see diagram 5.
Note: These valves are closed when slots are at right
angles to direction of flow.
It is not necessary to drain entire heating circuit to
carry out this work.
• Drain boiler by attaching a plastic tube to drain
outlet and opening drain valve knob anticlockwise,
see diagram 5.
• Pull off pump connector and earth lead.
• Pull out retaining clip from telescopic pump out-
let connection and slide connection upwards to
release from pump.
• Undo and remove two fixing screws and remove
pump retaining bracket from front of pump.
• Grasp pump body, lift upward to disengage from
reversing valve and turn pump to right. Remove
pump by pulling forward and over reversing valve
assembly.
• Discard old pump inlet 'O' ring.
• Apply silicone grease to new 'O' ring supplied,
and fit onto inlet connection on replacement
pump.
• Fit replacement pump in reverse order to re-
moval.
Note: Apply silicone grease to pump outlet con-
nection 'O' ring before assembly.
• Refit pump electrical connection.
• Open isolating valves on flow and return con-
nections, refill, vent and pressurise boiler. Check for
leaks.
Hab 286
To replace temperature/pressure gauge
• Drain down heating circuit of boiler only as de-
scribed in 'To replace pump'.
• Undo and remove screw securing pressure
gauge capillary to front section, see diagram 23.
• Carefully pull capillary from front section.
• Pull off spring clip securing temperature gauge
phial to heating pipe.
• Undo and remove two screws securing tempera-
ture/pressure gauge to lower front panel and re-
move gauge.
• Fit replacement gauge in reverse order to re-
moval.
• Apply heat sink compound to temperature phial
prior to refitting onto heating pipe.
• Fit capillary of new gauge to front section using
new 'O' ring supplied.
• Open isolating valves on flow and return con-
nections, refill, vent and pressurise boiler. Check for
leaks.
• With both flow restrictor and filter in place, re-
connect pipe to inlet connection and tighten.
• Fully open isolating cock on cold water inlet con-
nection and check for leaks.
Diagram 22
Diagram 23
Cla 007 Sch 228
Diagram 21

14
To replace reversing valve assembly
• Remove pressure gauge capillary as described
previously.
• Remove pump as described previously.
• Remove microswitch assembly as described pre-
viously.
• Remove retaining clip from LHS pipe connection
on front section of valve and disengage pipe.
• Unscrew and disconnect heating flow (centre)
connection at fixing jig.
• Remove retaining clip from heating flow pipe
connection on right of front section.
• Remove flow pipe from boiler.
• Unscrew and disconnect heating return (left
hand) connection at fixing jig.
• Remove retaining clip from expansion vessel pipe
connection at rear of reversing valve assembly and
disengage pipe, pushing pipe back and out of re-
versing valve.
• Undo and remove large screw holding water
valve to back plate of reversing valve assembly,
see diagram 24.
• Push water valve back to disengage it from re-
versing valve.
• Unclip and remove loss of water pressure switch
from left of reversing valve assembly, see diagram
25.
• From below boiler, undo and remove three
screws holding reversing valve to bottom plate of
boiler. Remove complete reversing valve assem-
bly from boiler.
• Undo and remove heating return connecting
pipe and hose from rear of reversing valve assem-
bly. Fit hose to replacement reversing valve assem-
bly.
• Fit replacement reversing valve into boiler in re-
verse order to removal.
Note: Use new 'O' rings, retaining clip, filter and
washer provided.
• Unscrew and remove microswitch assembly from
top of replacement reversing valve assembly to
allow refitting of water valve.
Note: fit expansion vessel pipe and loss of water
switch to reversing valve assembly before pump,
to ensure that it is correctly located. Apply silicone
grease to all 'O' rings and hoses prior to assembly.
• Open isolating valves on flow and return con-
nections, refill, vent and pressurise boiler. Check for
leaks.
To replace reversing valve front section
• Remove temperature/pressure gauge as de-
scribed previously.
• Remove pipe connections from either side of
reversing valve front section, refer to previous sec-
tion.
• Move short selector lever on front of valve to left
hand position.
• From below boiler, undo and remove single screw
holding reversing valve front plate to bottom plate
of boiler.
• Undo and remove six screws holding front sec-
tion to rear section of reversing valve, see diagram
26.
• Remove front plate complete with pump bracket
and then front section from reversing valve, along
REPLACEMENT OF PARTS
with rubber sealing gasket.
• Assemble bypass valve provided and fit into hole
in underside of replacement front section. Fit 'U'
shaped retaining clip.
Note: Use bypass valve fitted to original front sec-
tion for guidance.
• Fit replacement front section, with gasket, to rear
section.
• Locate front plate and replace six fixing screws.
Take care to evenly tighten screws ensuring they
are not cross threaded.
• Refit pipe connections to either side of front sec-
tion using new 'O' rings provided. Apply silicone
grease to 'O' rings before fitting.
• Refit temperature/pressure gauge in reverse or-
der to removal.
• Ensure short selector lever on front of valve is set
to right hand position.
• Open isolating valves on flow and return con-
nections, refill, vent and pressurise boiler. Check for
leaks.
Diagram 25
Sec 059
Diagram 26
Cla 007
Des 054
Diagram 24

15
REPLACEMENT OF PARTS
To replace loss of water switch
• Drain down heating circuit of boiler only as de-
scribed in 'To replace pump'.
Note: It is not necessary to drain entire heating cir-
cuit to carry out this work.
• Pinch plastic cover to release retaing clips and
remove cover from switch. Pull plug lead from
switch terminals.
• Remove clip holding switch into left side of re-
versing valve assembly.
• Pull switch out of reversing valve assembly, see
diagram 27.
• Fit replacement switch in reverse order to re-
moval, using new 'O' ring provided and aplying sili-
cone grease to 'O' ring before fitting.
• Reconnect plug to switch terminals.
• Open isolating valves on flow and return con-
nections, refill, vent and pressurise boiler. Check for
leaks.
To replace water valve or diaphragm
• Drain down hot water circuit of boiler only as
described in 'Routine Cleaning and Inspection'.
• Remove microswitch assembly as described pre-
viously.
• Unscrew connecting nut from cold water inlet
connection, second from left on fixing jig. Keep fil-
ter and flow regulator.
• Remove clip holding connecting pipe in rear of
water valve. From below boiler, grip clip with long
nosed pliers and pull down.
Note: This connecting pipe is telescopic, it may be
necessary to slide back brass sleeve to facilitate
removal.
• Remove clip holding pipe to heat exchanger in
rear of water valve. From front of boiler, grip clip
with long nosed pliers and pull upwards.
• Unscrew and remove large screw holding water
valve to back plate of reversing valve assembly,
see diagram 24.
• Disengage water valve from reversing valve and
remove from boiler.
Note: When disengaging water valve from heat
exchanger pipe, check that non-return valve is not
held on end of pipe. If so, carefully separate pipe
from valve to ensure that small spring and plunger
do not fly out and are lost.
• To replace diaphragm, undo five screws and
separate main components of water valve.
• If white diaphragm cover is to be replaced, sepa-
rate original from water valve end casting and fit
replacement cover.
• Fit replacement diaphragm , making sure that
metal disc FACES diaphragm cover and beaded
edge of diaphragm is correctly fitted in correspond-
ing groove in both cover and plastic housing, see
diagram 28.
• Reassemble water valve, evenly tightening five
screws.
• Fit water valve actuating pin into hole in dia-
phragm cover, through nose end of valve and and
push in until flush, or slightly below, nose end of
valve.
Note: Apply silicone grease to pin before fitting.
• Refit water valve to boiler, locating nose end into
rear of reversing valve assembly, 'springing' heat
exchanger pipe to gain clearance as necessary.
Fit large water valve retaining screw but do not
tighten fully at this stage.
• Apply silicone grease to 'O' ring and fit onto end
of heat exchanger pipe. Fit pipe into water valve
by pulling it forward. Make sure that 'O' ring is cor-
rectly located.
• Whilst holding pipe in rear of water valve, fit re-
taining clip. This should easily clip over pipe and
should NOT have to be forced. If resistance is ex-
perienced, either pipe is not correctly fitted in rear
of water valve or clip is not being fitted properly
through slot between back plate and plastic hous-
ing of water valve. When clip is fitted, check con-
nection by pushing pipe back away from water
valve.
• Refit telescopic connecting pipe to inlet of wa-
ter valve after applying silicone grease to 'O' ring.
Fit retaining clip into groove on connecting pipe,
through slot between back plate and water valve
plastic housing. Check connection by pulling pipe.
Make sure that clip is not loose and likely to fall out
at a later date. If in doubt, fit a new clip.
• With both flow regulator and and plastic filter
washer in place, refit connecting nut to inlet con-
nection and tighten.
• Open isolating valve on cold water inlet connec-
tion and check for leaks.
• Replace microswitch assembly.
Diagram 27
Sec 059Des 058
Diagram 28

16
To replace push-button box
• Disconnect electrical connections from right
hand side of push-button box.
• Undo and remove screw securing push-button
box to bottom plate of boiler.
• Undo and remove screw securing push-button
box to front of gas valve.
• Remove push-button box by pulling forwards and
upwards, disengaging it from gas valve.
• Fit replacement push-button box in reverse or-
der to removal.
To replace thermocouple
• Ensure gas supply is off.
• Remove push-button box as described previ-
ously.
• Remove pilot burner as described in 'Routine
Cleaning and Inspection'.
• Disengage thermocouple from pilot burner as-
sembly and pull downwards through sealing grom-
met in base of combustion chamber..
• Unscrew thermocouple nut from solenoid at
back of gas valve.
• Fit replacement thermocouple in reverse order
to removal.
To replace thermocouple solenoid
• Ensure gas supply is off.
• Unscrew thermocouple nut from solenoid at
back of gas valve.
• Remove thermocouple interrupter connection
from solenoid.
• Unscrew and remove thermocouple solenoid
from back of gas valve casting.
• Fit replacement solenoid in reverse order to re-
moval.
To replace gas valve
• Ensure gas supply is off.
• Remove push-button box as described previ-
ously.
• Disconnect thermocouple from thermocouple
solenoid, as described previously.
• Disconnect electrical connections to gas valve
modulating coil.
• Undo two screws and remove pilot pipe retain-
ing plate and cork gasket from front of gas valve.
Carefully disengage pilot pipe from top of gas valve
by pulling upwards and out of 'O' ring seal.
• Undo gas supply nut from main burner.
• Remove three screws fastening triangular plate
to front of gas valve. Pull pipe forward to disengage
from gas valve and then down to disengage from
burner.
Note: Seal at burner must be kept for use on
reassembly.
• Undo gas union between gas valve and fixing
jig isolating valve.
• From below boiler, remove two screws securing
gas valve to bottom panel.
• Remove gas valve from boiler.
• Remove solenoid from rear of gas valve and fit
to replacement gas valve.
• Refit replacement gas valve in reverse order to
removal.
REPLACEMENT OF PARTS
Note: Use new 'O' ring provided between gas valve
and burner supply pipe.
• Refit push-button box and thermocouple.
• Refit electrical connections to replacement gas
valve.
To replace modulating coil
• Ensure gas supply is off.
• Disconnect two electrical leads from gas valve
modulating coil.
• Unscrew and remove two screws holding modu-
lating coil to gas valve and remove coil from gas
valve.
• Fit replacement modulating coil in reverse order
to removal.
• Reconnect electrical leads to replacement coil.
To replace safety valve
• Drain down entire heating system.
• From below boiler, disconnect heating flow pipe
from rear of fixing jig.
• Undo heating flow connection on front of fixing jig.
Remove clip from heating flow pipe connection on
right of front section of reversing valve. Pull pipe to-
wards right and out of reversing valve. Remove pipe
from boiler and keep.
• From below boiler, disconnect safety valve dis-
charge pipe.
• Working through boiler from the front using a long
screwdriver, undo and remove screw holding safety
valve assembly to fixing jig.
• Remove complete safety valve assembly from fix-
ing jig and remove from boiler.
• Fit replacement safety valve in reverse order to re-
moval.
Note: Apply silicone grease to 'O' ring before fixing
pipe into right hand side of reversing valve.
• Refill heating system and boiler, vent and pressu-
rise as described previously.
To replace heat exchanger
• Drain down both heating and hot water circuits of
boiler only as described previously.
Note: It is not necessary to drain entire heating sys-
tem to carry out this work.
• Remove combustion chamber cover as described
in 'Routine Cleaning and Inspection'.
• Remove two clips from heating connections to left
side of heat exchanger.
• Remove clip holding pump outlet connection into
pump and slide connection up pump outlet pipe.
Pull complete pipe down to disengage from heat ex-
changer.
• Remove retaining clip from LHS pipe connection
on front section of valve and disengage pipe.
• Disengage pipe downwards from heat exchanger.
• Unscrew and disconnect two hot water connec-
tions to right side of heat exchanger.
• Grasp both sides of heat exchanger and slide for-
wards and out of boiler.
• Fit replacement heat exchanger in reverse order
to removal.
Note: Use new sealing washers and 'O' rings provided.
• Open isolating valves on flow and return connec-
tions, refill, vent and pressurise boiler. Check for leaks.

17
To replace expansion vessel
1 Boiler in place
Note: The expansion vessel can be replaced with
the boiler in place provided that there is a mini-
mum clearance of 400mm on one side of the boiler
and that no vertical pipework passes between
boiler and wall on that side.
• Drain down the heating circuit of the boiler only
as described in 'To replace pump'.
Note: It is not necessary to drain entire heating sys-
tem to carry out this work.
• Remove pump from boiler as described previ-
ously.
• Unscrew pipe connection nut from expansion
vessel and disengage pipe from connection. Keep
sealing washer.
• Whilst supporting weight of vessel, push bottom
of vessel away from boiler, disengaging threaded
connection from hole in rear of boiler. Allow vessel
to drop out of its two upper retaining brackets.
• Remove vessel to side of boiler.
• Fit replacement expansion vessel in reverse or-
der to removal ensuring that sealing washer is fit-
ted to vessel pipe connection.
• Check that vessel charge pressure is 1bar. Cor-
rect if necessary.
• Open isolating valves on flow and return con-
nections, refill, vent and pressurise boiler. Check for
leaks.
2 Boiler removed from wall
• Drain down the heating circuit of the boiler only
as described in 'To replace pump'.
Note: It is not necessary to drain entire heating sys-
tem to carry out this work.
• Ensure that gas and electrical supplies to boiler
are turned off.
• Disconnect flue.
• Disconnect external controls connections, if fit-
ted.
• Unscrew and disconnect five connections be-
tween fixing jig and boiler.
• Disengage pipe connections. Lift boiler off hang-
ing bracket and place on a convenient working
surface.
• Remove expansion vessel from boiler as de-
scribed in previous section.
• Fit replacement vessel in reverse order to removal
and check charge pressure.
• Replace boiler on wall, tighten all connections,
gas connection first, ensuring that all sealing wash-
ers, filters and the cold water flow regulator are fit-
ted before tightening.
• Reconnect flue.
• Open isolating valves on flow and return con-
nections, refill, vent and pressurise boiler. Check for
leaks.
• Reconnect external controls connections, if fit-
ted
• Reconnect gas and electrical supplies to boiler.
• Check for gas soundness.
To replace overheat thermostat
• Locate overheat thermostat on right hand side
of heat exchanger.
REPLACEMENT OF PARTS
• Pull off electrical connections from thermostat.
• Unscrew and remove two screws holding thermo-
stat to heat exchanger.
• Fit replacement thermostat in reverse order to re-
moval.
• Refit electrical leads, the polarity is not important.
To replace high limit thermostat
• Locate high limit thermostat on heating flow pipe
on LHS of boiler.
• Pull off electrical connections from thermostat.
• Unclip high limit thermostat from flow pipe.
• Fit replacement thermostat in reverse order to re-
moval.
• Refit electrical leads, the polarity is not important.
To replace combustion chamber insulation
Front section
• Remove combustion chamber from boiler as de-
scribed in 'Routine Cleaning and Inspection'.
• Slide side panels out of combustion chamber sides.
• Lift front insulation panel free from retaining lugs
and away from cover.
• Fit replacement panels in reverse order to removal.
Rear panel
• Remove burner from boiler as described in 'Rou-
tine Cleaning and Inspection'.
• Remove clip from base of insulation panel.
• Pull bottom edge of insulation panel forward,
downward and out from behind heat exchanger.
• Fit replacement panel in reverse order to removal.
• Replace burner into boiler in reverse order to re-
moval.
To replace burner
• Remove burner from boiler as described in 'Rou-
tine Cleaning and Inspection'.
• Remove pilot burner as described previously.
• Unscrew and remove two screws holding burner
injector bar to burner and remove injector bar.
• Asemble replacement burner, supplied in parts, as
follows:
• Fit burner injectors to injector bar and tighten.
• Assemble burner elements (14) into front and rear
burner supports with securing pins and rods, using
original burner for guidance.
• Fit burner injector bar to burner.
• Fit pilot burner assembly to burner.
• Fit replacement burner to boiler in reverse order to
removal.
• Reconnect ignition lead.
To replace burner injectors
• Remove burner as described previously.
• Remove pilot burner as described previously.
• Unscrew and remove two screws holding burner
injector bar to burner and remove injector bar.
• Unscrew and remove burner injectors from burner
bar.
• Fit replacement injectors to injector bar and tighten.
Note: make sure that injector size, marked on each
injector, is the same as that given in 'Technical Data'.
• Reassemble burner and replace into boiler in re-
verse order to removal.

18
SCHEMATIC WIRING DIAGRAM
Diagram 29
Sch 238
FAULT FINDING
Before fault finding, check :
Inlet gas pressure = 20 mbar
Electrical supply = 240V - 50 Hz
Central heating system is pressurised at 1 - 1,5 bar
Overheat thermostat on RHS of heat exchanger has
not tripped. Reset if necessary.
Flue safety device on draught diverter has not
tripped. Reset if necessary.
Carry out electrical system checks i.e. earth continu-
ity, resistance to earth, short circuit and polarity with
a suitable meter.
Note: These must be repeated after any servicing or
fault finding. Ensure that all external controls are cor-
rectly wired and calling for heat.
The fault finding charts will enable the majority of faults
to be diagnosed. To use the charts effectively, it is
necessary to determine exactly which aspects of the
boiler are working correctly and which are not.
For example:
If the domestic hot water works correctly but the heat-
ing doesn’t, refer to chart No. 1.
If heating works correctly but the hot water doesn’t,
refer to chart No. 3.
IMPORTANT: Always adopt a logical, step by step pro-
cedure starting at the beginning of the appropriate
fault finding chart.
WARNING. Always isolate the boiler from the electri-
cal supply before carrying out any electrical replace-
ment work.
Always check for gas soundness after any service
work.
1.11
1.07 2.04
2.01
N
J1
1.09
1.10
L
T
T°
K16
K11
K5
AQ
Bdis.
1.12
P
1.04
2.02
2.03
2.05
2.10
2.11
EV1
2.6
2.8
2.9
2.12
4.1
4.3
4.2
4.5
14 12
11 21
22
5.3 5.4 5.5 5.2
X24
T
T°
K4
3.09
3.05
3.01
TRA
b3
b1
SW1
P2
5.015.12
CTN
3.02
3.03
3.08
3.06
SW3
P
TA
Ra
R1
Bdis = Push-button box
P=Pump
P2 = Domestic temperature adjuster
K11 = Flue safety device
SW3 = Microswitch
K4 = Overheat thermostat
K5 = Loss of water switch
EV1 = Gas valve
J1 = Romm thermostat connection
TA = Room thermostat
X24 = Thermocouple and solenoid
CTN = Domestic thermistor
TRA = Transformer
K16 = High limit thermostat
AQ = Boiler thermostat
SW1 = Summer/winter switch

19
CHART 1
Turn boiler thermostat to max.
Does burner fire?
Does pump run?
Is short selector lever on
front of reversing valve in
right hand position?
NO CENTRAL HEATING
Refer to chart no. 2
Does burner fire when
a hot tap is opened? Refer to chart no. 3
External controls
(if fitted)
Short out external controls
connection on top of
reversing valve. Does
burner fire?
Rectify wiring/operation
faults on external controls
Is boiler thermostat operating
correctly i.e. two stage operation
of burner by rotating knob? Replace boiler thermostat
Replace main PCB
NO
NO
YES
YES
YES
YES
NO
NO
YES
NO
FAULT FINDING
Thermistor values
Temperature (oC) 0 5 10 15 20 25 30 35 40 45 50
Nominal resistance Ωfor NTC 32565 25345 19875 15700 12500 10000 8060 6535 5330 4370 3605
Temperature (oC) 55 60 65 70 75 80 85 90 95 100
Nominal resistanceΩfor NTC 2989 2490 2085 1755 1480 1260 1070 920 785 680
PUMP NOT RUNNING
CHART 2
Is there 240v at pump?
Is there 240v between
terminals 1.04 and 1.09 of
PCB?
Replace PCB
YESNO NO
NO
Is pump jammed?
Free pump Replace pump motor
YES
Correct
NO

20
FAULT FINDING
Open hot tap fully.
Does burner fire
With selector switch in CH position
and central heating temperature
adjuster turned to maximum, does
burner fire for CH?
Is there at least 3 litres/min
water flow at tap?
Check operation of water valve
diaphragm. Does reversing valve
mechanism move when hot tap is
opened?
Is there continuity across DHW
microswitch and PCB connec-
tions 3.03 and 3.08?
Remove leads from hot water
thermistor. Check its resistance in
accordance with thermistor value
table. Is thermistor ok?
Refer to chart no. 1
Check mains water
supply/water filter
Replace diaphragm
Replace DHW microswitch
Replace DHW thermistor
Replace PCB
NO
NO
NO
NO
NO
NO
YES
YES
YES
YES
YES
CHART 3
NO HOT WATER
SPARE PARTS
When ordering spare parts, quote the part number and description, stating the appliance model number
and serial number from the data badge.
Short parts list
No. Description Part No.
1 Pump 51236
2 Piezo unit 57066
3 PCB 57126
4 Water valve diaphragm kit 52519
5 Microswitch assembly 51590
6 Temperature/pressure gauge 57264
No. Description Part No.
7 Boiler thermostat 57269
8 Hot water thermistor 57042
9 Overheat thermostat 51511
10 Thermocouple 51144
11 Thermocouple solenoid 51160
108197 B 01/98