Worcester W 125 FL Release note

6 720 606 003 (01.09) AL
W 125 FL
Flueless Singlepoint Water Heater
with Atmosphere - Sensing Device
INSTALLATION AND
SERVICING INSTRUCTIONS
G.C.Nº52-311-022
This appliance conforms to European Standard EN 26.
It is the law that all gas appliances are installed by competent persons.
The following instructions should be read carefully as the manufacturer cannot be held responsible for any
damage to property, persons or animals caused by incorrect installation or operation of the appliance.
Itisrecommendedthatthe appliance beserviced annually bya competent personor the localGas Region.
The Users Instructions should be handed to the user and the function and operation of the appliance
explained.
For your safety - if you smell gas:
1. Turn off the appliance
2. Open all windows and doors
3. Do not operate any electrical switches
4. Extinguish all naked flames
5. Contact the local Gas Region immediately

2
CONTENTS
7 Installation ......................................................... 6
8 Commissioning.................................................. 6
9 Inspection and Service ...................................... 7
10 Replacement of parts ........................................ 8
11 Spare parts ...................................................... 10
12 Fault Finding.....................................................11
1 InstallationRegulations...................................... 2
2 General information........................................... 2
3 Technical Data................................................... 5
4 Siting the appliance ........................................... 5
5 Air supply........................................................... 5
6 Gas supply ........................................................ 6
2.3 This applianceisnotsuitableforexternalinstallation.
2.4 The appliance is set to provide a maximum output
of 8.7 kW and a minimum output of 4.4 kW.
2.5 The appliance has a permanent pilot.
2.6 PRINCIPLEAPPLIANCE COMPONENTS
- Alow thermal capacity Gas to Water heat exchanger.
- Astainless steel main gas burner.
- A gas section.
- A water section.
- A thermoelectric safety valve.
2.7 GENERAL INSTALLATION
The appliance must be installed in the same room as the
water draw-off point.
The appliance must not be installed in a room where the
volume is less that 5m3.
The appliance must not be installed in a compartment or
roof-space or in a room which may be incorporated in a
protected shaft / stairway.
2.8 FLUE
This appliance is flueless, hence it is essential that the
correct installation requirements are satisfied. This
appliance is intended for intermittent use only, and must
not bepositioned inor adjacentto abedroom or anyroom
containing a bath or a shower.
2.9 SAFETY FEATURES
TheWorcesterW125is fittedwithanatmosphere-Sensing
Device which must not be altered in any way.
1.) If the air in the room in which the heater is situated
becomesdepleted of oxygen the pilotwill be extinguished
automatically.
2.) If the flue outlet is obscured or the heat exchanger
becomes blocked again the pilot will be extinguished
automatically.
1 Installation Regulations
1.1 GasSafety (InstallationandUse)Regulations1998.
Allgasappliancesmustbe installedbyacompetentperson
inaccordance withthe aboveregulations. Failureto install
appliances correctly could lead to prosecution.
1.2 Themanufacturers notes mustnot be taken,in any
way, as overriding statutory obligations.
1.3 The compliance with a British Standard does not,
ofitself,conferimmunityfromlegalobligations.In particular
the installation of this appliance must be in accordance
with the relevant requirements of the Gas Safety
(Installation and Use) Regulations 1998 (as amended),
localBuilding Regulations, Building Standards(Scotland)
(Consolidation),byelaws of thelocal Water Companyand
Health and Safety Document No. 635 (Electricity at Work
Regulations 1989). It should be in accordance with the
relevant recommendations of the following British
Standards:
BS 6798:1987 Specification for Installation of gas fired
hot water boilers of rated input not exceeding 60 kW.
BS 5546:1990 Installation of gas hot water supplies for
domestic purposes.
BS 5440:2:1989 Flues and ventilation for gas appliances
of rated input not exceeding 60 kW:Air Supply.
BS 6891:1988 Installation of low pressure gas pipework
installations up to 28 mm (R1).
1.4 To ensure that the installation will perform to the
highest standards, the system and components should
conformto anyother relevantBritish Standardsinaddition
to those mentioned in the instructions.
2 General Information
2.1 Thisappliance is availablefor use withnatural gas.
When installing the appliance for use with natural gas,
pleasecheck 10 digitnumber on carton toensure that the
correctappliance hasbeen specified.The10 digitnumber
for a natural gas appliance is 7 700 352 952.
2.2 This appliance is available for use with LPG.
When installing the appliance for use with LPG, please
check10 digit numberon cartonto ensure thatthe correct
appliance has been specified. The 10 digit number for an
LPG appliance is 7 700 452 908.
page page

3
Appliance water flow diagram.
Fig. 2
F869_086
14 Pilot gas pipe
17 Large poppet valve
18 Small poppet valve
19 Cross-ignition bolt
20 Main gas valve
22 Pilot gas button
23 Gas control slide
24 Piezoigniter
25 Water filter
26 Hot water tap
27 Cold water tap
29 Cold water pipe (inlet)
44 Pilot gas filter
47 Burner pressure test point
49 Burner injector
50 Main burner
51 Spark electrode
52 Thermocouple
53 Pilot burner
55 Heat exchanger
66 Throttle plate
76 Atmosphere sensing device
119 Temperature limiter
Natural Gas
L.P.G.
30 Hot water outlet
31 Volumetric water governor
32 Temperature selector
35 Gas inlet pipe
36 Sealing screw
37 Inlet gas pressure test point
38 Diaphragm
39 Venturi
40 Slow ignition valve
41 Electromagneticvalve
42 Gas filter
43 Pilot gas valve

4
Dimensions (in mm)
D770_046
6/2 Hot water tap
7 Temperature selector
8 Piezoignitor
9 Water valve assembly
11 Gas valve assembly
12 Heat exchanger
1 Flue gas deflector
2 Observationwindow
3 Front cover
4 Output slide control
5 Water outlet
6/1 Cold water tap
Fig. 3

5
3 Technical Data
Table 1 - GENERAL
Table 2 - PERFORMANCE
4 Sitting the appliance
4.1 The appliance may be installed in any room with
theexception of abedroom or any room containinga bath
or a shower.
4.2 Theappliance isnotsuitableforexternal 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 Technical Data – Table 1.
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 housing”.
4.6 The following clearances must be available for
installation and for servicing:
Above 300 mm
In front 600 mm
Below 150 mm
Right hand side 10 mm
Left hand side 10 mm
4.7 The appliance must NOT be installed in a room
having a volume of less than 5.0m3.
4.8 No combustible surface must be within 75 mm of
the casing. See BS 476:4.
5 Air supply
5.1 The appliance is a flueless appliance and requires
permanent ventilation in accordance with the following
details.
5.2 A permanent air vent shall be provided. This
permanent opening shall be direct to outside air and in
accordance with the following table.
The values given are the minimum required.
5
.0 to 10.0 m3
1
1.0 to 20.0 m3
A
bove 20.0 m3
100 50 nil Yes
Room Volume
Ventilation Requirements cm
2
Flueless Appliances Openable window or
equivalent reqd.
5.3 Where an extract fan is fitted additional air vents
shall be provided. As a general guide an extra 50 cm2of
air vent free area will be sufficient for most situations.
5.4 Refer to BS 6798 and BS 5440 part 2 for additional
information.
Natural Gas LPG
Minimum rated output (Pmin) 4.4 kW 4.4 kW
Maximum rated output (Pn) 8.7 kW 8.7 kW
Rated input (Qn) 10.4 kW 10.4 kW
Gas rate (maximum) 1.1 m3/h 0.8 kg/h
Number of injectors 8 8
Injector diameter (mm) 1.1 0.70
Pilot injector marking 111 70
Burner pressure 9 mbar 15 mbar
Height (mm) 438 438
Width (mm) 270 270
Depth (mm) 189 189
Dry weight 7.0 kg 7.0 kg
Maximum cold water supply inlet pressure 12 bar (180 p.s.i.)
Minimum cold water supply inlet pressure to operate the appliance 0.15 bar (1.5 p.s.i.)
Minimum cold water supply inlet pressure for maximum domestic hot water flow 0.6 bar (9 p.s.i.)
Domestic hot water delivery with temperature control knob fully anticlockwise 5 litres/minute at 25°C
temperature rise
Domestic hot water delivery with temperature control knob fully clockwise 2.5 litres/minute at 55°C
temperature rise

6
6 Gas supply
The appliance requires 1.1 m3/hr of gas. The gas meter
andsupplypipesmustbe capableofsupplyingthisquantity
ofgasin additionto thedemandfrom anyother appliances
being served. Refer to BS 6891 for further information.
Themeter governor should deliver adynamic pressure of
20 mbar (8 in w.g.) at the appliance.
The complete installation, including the gas meter, must
be tested for soundness and purged. Refer to BS 6891.
A gas service cock must be fitted before each appliance,
a gas service cock is supplied with every appliance.
Important: if the1.1m3/hr gasrateto theappliancecannot
be reached, the specified hot water conditions will not be
achieved.Thiscouldresultincustomer complaints.Always
ensure that the gas supply is adequate.
7 Installation
Theinstallationmustbecarried outbycompetent persons.
On delivery, check to make sure that the packaging has
notbeendamaged. Ifthereis evidenceofdamage, contact
your supplier immediately.
Check the 10 digit code number on the appliance carton
to ensure that the correct appliance for the gas supply
has been supplied.
Thecode number fora natural gasappliance is 7700 352
952. The code number for an LPG appliance is 7 700 452
908.
7.1 Appliance Installation
a) Unpack the appliance and take care to remove the
installationkitwhich ispackedon topofthe polystyrene
packing
The kit comprises of the following:
- One gas service cock with fibre washer
- One cold water isolating cock complete with fibre
washer
- Onewater dischargepipe completewithbrass swivel
union
- Two fixing screws and wall plugs.
b) Lay the appliance on its back and pull off the Hot and
Coldwater control Knobsand theTemperaturecontrol
knob. Unscrew the temperature control outer bezel to
releasethe casingfrom the appliance.Liftup thelower
front edge of the case and slide towards the top of the
heater to unhook the case from the back panel.
c) Offeruptheappliancetothewall andmarkthepositions
for the two fixing screws. Drill two holes and fit the wall
plugs and screws.
Hangthe appliance onthe fixinghooks and securethe
appliance back panel to the wall through one of the
twoholeslocatedatthelowerlefthandside ofthepanel.
d) Make up the gas supply to the upper connection on
the gas control assembly using the fibre washer
provided.Fitthe gasisolation cockasclose aspossible
to the appliance (see fig. 4, pos. 1).
e) Connect the appliance to the incoming cold water
supply via the fitting which includes the stop valve. A
fibre washer is provided (see fig. 4, pos. 2).
f) Fit the brass union for the water discharge pipe to the
water control valve outlet using the fibre washer
provided. Fit the chrome plated discharge pipe to the
unionand tightensufficiently toallow thepipe to swivel
(see fig. 4, pos. 3).
g) Turn on the water supply to the appliance. Open the
stop valve on the inlet fitting to the appliance and the
open the hot and cold water taps.
Allow water to flow to vent the system and close the
taps.
h) Iftheapplianceisnottobecommissioned straightaway,
re-fit the appliance casing and control knobs.
8 Comissioning
Before commissioning the appliance, the whole gas
installation must be purged and tested for gas soundness
in accordance with the current edition of BS 6891.
Important:Open alldoors andwindows. Extinguishnaked
lights and do not smoke while purging the gas line.
Proceed as follows.
a) Ensure that the gas service cock in the gas inlet pipe
is turned off.
b) Remove the appliance casing as described in section
7 above.
c) Loosen screwA and connect a pressure gauge to the
test point. See fig. 5.
Fig. 5
G661_016
Fig. 4
1
2
3
G081_240

7
d) Turn on the gas service cock.
e) Move the gas control slide to the ignition position. See
fig. 6.
Observe the pilot burner. Press in the central button of
the control slider and hold depressed while pushing
the Piezo igniter button two or three times. The pilot
should light. Wait approximately twenty seconds and
then release the centre button of the control slider.
Thepilot shouldremain alight.If thepilot doesnot light,
repeat the operation until a flame is established.
Note:On initial light up,or afterany prolonged shut down,
the pilot may take several attempts to establish due to
the presence of air in the gas supply system.
The pilot flame should envelope approximately 5 mm
of the thermocouple head.
f) Move the control slider fully to the right for maximum
output, see fig. 7. Fully open the hot water tap. The
main burner should light.
Fig. 6
G661_013
g) Checkthe dynamicinlet gaspressure. ForNaturalGas
the inlet pressure should be 20.0 mbar and for LPG
the pressure should be 28.0 mbar (Butane) or 37.0
mbar (Propane).
Ifthe pressure is not correctthen check thegas supply
to the appliance.
If the pressure is correct then turn off the hot water tap
and move the slider to the off position, see fig. 8.
Fig. 7
G661_012
Turn off the gas service cock. Remove the pressure
gauge and tighten screwA, see fig. 5.
h) Loosen screw D and connect the pressure gauge to
the test point, see fig. 9.
Fig. 8
G661_011
Re-light the appliance as described above. Turn the
temperature control to maximum.
i) Operate the appliance for at least two minutes, then
checkthat theburner pressureis asstatedinTechnical
Data –Table 1.
j) Turn off the hot water tap. Close the gas service cock.
Remove the pressure gauge and tighten screw D.
k) Re-fit the appliance casing and secure by re-fitting the
temperature control bezel.
Fit the temperature control knob and the hot and cold
water tap knobs.
l) Oncompletion of thecommissioning andtesting of the
system,the installershould handover the applianceto
the user with reference to the following.
1) Give the Users Operating Instructions leaflet to the
user.
2) Explainand demonstratethe lightingand shutdown
procedures.
3) Advise the user of the precautions necessary to
prevent damage to the system and to the building
in the event of the system remaining inoperative
during frost conditions.
4) Stress the importance of an annual service by a
competent person.
9. Inspection and Service
To ensure continuedefficientoperation ofthe appliance, it
is recommended that it is checked and serviced as
necessary at regular intervals.
Thefrequency ofservicing will dependupon theparticular
installation conditions and usage but in general once a
year should be adequate.
Itis the law that anyservice work must becarried out by a
competent person such as British Gas or other Corgi
registeredpersonnel.
Beforecommencing anyservice operationturn offthegas
supply at the main gas service cock
Carry out the service operation as follows.
9.1Remove the front casing by first removing the
temperaturecontrol knoband thetwo water tapknobs.
Unscrew the temperature control knob bezel and
remove to release the appliance casing.
Pull forward the lower front of the casing to clear the
tapspindles andliftup the casingto unhook it fromthe
appliance back plate.
9.2 Heat Exchanger
Inspect and clean the heat exchanger flueways as
necessary.
To remove the heat exchanger, isolate the appliance
fromincomingcold watersupply attheinlet cock.Open
the taps to release any remaining water pressure and
drain the appliance.
Undo the brass union nut on the pilot air supply pipe
and withdraw the pipe from the air inlet collector.
Disconnect the push on terminals from the overheat
thermostat at the top of the heat exchanger.
Pull out the retaining clips at the inlet and outlet
connections on the water control body, and spring out
thecopper inlet andoutlet pipes fromthe control body.
Fig. 9
G662_042

8
10 Replacement of Parts
The law requires that any service work must be carried
out by a competent person such as British Gas or other
Corgi registered personnel.
Beforecommencing anyservice operationturn offthegas
supply at the main gas service cock.
10.1 Pilot Burner / Injector
Remove the appliance casing as described in section
9.1 above.
Removethepilotassembly pipeasdescribed insection
9.3 above.
Removetheretainingclip,holding theignitionelectrode
and thermocouple to the body, from the side of pilot
burnerbodytorelease theelectrodeandthermocouple.
Fitthe newinjector and/orpilot burner in reverse order.
10.2 Ignition Electrode / Thermocouple
Followthe instructionsgiven abovein section10.1 and
replace the faulty components.
10.3 Main Burner
Remove the appliance casing and pilot assembly as
described in sections 9.1 and 9.3 above.
Remove the main burner as described in section 9.4.
Replace the burner in reverse order taking care that
the locating pin in the rear of the burner locates with
theslot in the rear frameand that the union joint ringis
correctlypositioned.
10.4 Piezo Spark Generator
Remove the front casing as described in section 9.1
above.
Pull forward the lower front of the casing to clear the
tapspindles andliftup the casingto unhook it fromthe
appliance back plate.
Unscrew the locking ring from the front of the Piezo
unit and withdraw the unit backwards through the
mounting plate. Pull off the two push on terminals and
discard the old unit.
Fit the new unit in reverse order taking care to locate
the unit on the small retaining peg. Also ensure that
theearthingwire issprung intothe holeinthe mounting
frame.
10.5 Heat Exchanger
Remove the heat exchanger as described in section
9.2 above.
Remove the overheat thermostat and pilot air inlet
collector and fit to the new heat exchanger.
Ensurethat two new‘O’ring seals are fittedto the inlet
and outlet pipes. Re-assemble in reverse order taking
care to locate the heat exchanger on the two support
hooks formed in the appliance back plate.
10.6 Water Control Assembly
a) Removethe front casing asdescribedin section9.1
above.
b) Isolate the appliance from incoming cold water
Take care not to damage the two ‘O’ring seals.
Unscrew the large heat exchanger retaining screw,
located at the rear of the combustion chamber just
above the burner blades, and lift clear the heat
exchanger assembly.
Inhard waterareas it maybe necessaryto descalethe
heat exchanger body. A proprietary brand of descaler
should be used. Fill the heat exchanger with this
solution and leave until the solution stops bubbling.
Drainandthoroughlywashouttheexchangerwithclean
water.
Warning: Acid/water solutions must be used with
extremecaution.Take care notto splash onto the skin
or into the eyes. Wash any affected areas with large
amounts of cold water and seek medical advice.
Reassemble in reverse order takingcare to locatethe
heat exchanger on the two support hooks formed in
the appliance back plate.
9.3PilotAssembly
Remove the appliance casing as described above.
Remove the pilot air supply pipe as described above.
Undo the union connection on the pilot gas pipe at the
pilotbody.
Undo the two screws securing the pilot body to the
burner front rail and withdraw outwards and upwards
away from the pilot gas pipe.
Note:take great care to retainthe pilot injector located
between the end of the pilot gas pipe and the inside of
the pilot body.
Inspect, clean and adjust as required.
Re-assemblein reverse ordertaking careto locatethe
pilot injector correctly.
9.4Main Burner
Remove the appliance casing and pilot assembly as
described in sections 9.1 and 9.3 above.
Slacken the pilot pipe union at the gas valve end and
swing the pilot pipe to the left.
Undothe brass unionnut holding theburner assembly
to the gas valve body.
To removetheassembly fromthe combustionchamber
it must be turned upside down. Proceed as follows.
Raise the front edge of the burner up into the
combustionchamber turning overaway from thefront.
Once the burner is upside down it can be withdrawn
fromunderthe combustionchamber,theunion passing
through cut-away in the front of combustion chamber.
Inspect and clean as required. Check the union joint
ring and replace if required.
Replace in reverse order taking care that the locating
pin in the rear of the burner locates with the slot in the
rear frame.
9.5 Final Inspection
Turn on the gas supply at the main gas service cock
and check for gas soundness in accordance with the
current edition of BS 6891 while the appliance is
running.
Re-commission the appliance as described in section
8.

9
supply at the inlet cock.
Open the taps to release any remaining water
pressure and drain the appliance.
c) Remove the water discharge pipe.
d) Undo the union connection on the water isolating
cock.
e) Pull out the retaining clips at the inlet and outlet
connections on the water control body, and spring
outthe copperinlet and outletpipes fromthe control
body.Takecarenot todamagethe two‘O’ringseals.
f) Pass a screwdriver through the hole in the centre of
the lower edge of the fascia panel and slacken the
firstofthetwo retainingscrews.Thesecondretaining
screw is located at 90 degrees on the right and is
accessed from the side.
g) With both screws slackened the water control
assembly can be withdrawn downwards away from
the gas valve body.
h) Replace in reverse order.
10.7 Gas Valve
a) Removetheburner asdescribedinsection9.4above
b) Removethe watercontrol assembly asdescribed in
10.6 above.
c) Undo the gas inlet union at the rear of the gas valve
d) Access the two gas valve retaining screws from the
left hand side and remove.
e) Withdraw the gas valve, complete with slider
controls, from the appliance.
f) Remove the Piezo igniter.
g) Removethecontrol fasciabytakingoutthefourfixing
screws and lifting clear complete with slider knob.
h) Prise out the slider bar and remove the two screws
retaining the control frame and lift clear.
i) Assemblethe Piezo igniter,slider bar, controlfascia
and pilot pipe to the new gas valve.
j) Re-assemble thegasvalve,burner andwatercontrol
assembly in reverse order.
10.8 Final Inspection
Turn on the gas supply at the main gas service cock
and check for gas soundness in accordance with the
current edition of BS 6891 while the appliance is
running.
Re-commissionthe applianceas describedin section
8.

10
11 Spare Parts
Fig. 10

11
Parts List
12 Fault Finding
Problem Cause Solution
Incorrect water temperature Incorrect gas rate Check the gas supply to appliance gas service cock
Open the gas service cock
Check the burner pressure
Check the inlet pressure
Water section sticking or faulty Clean or replace
Incorrect water flow rate Incoming supply valve closed Open supply valve
Low water pressure Check if water pressure is above 0.15 bar
Water section sticking or faulty Clean or replace
Noise Scale in heat exchanger Descale and service
High gas rate Check the burner pressure
Low water flow rate Check the water flow rate
Pilot flame will not stay alight No gas supply Connect gas supply
Gas service cock closed Open gas service cock
Air in gas line Purge the line
Pilot injector blocked Clean or replace the injector
No spark Clean or replace the electrode, piezo unit or cable
Main burner will not light Gas pressure low Check the inlet and burner pressure
Gas service cock partially closed Open the gas service cock
Low water rate Check the water rate
Water section diaphragm faulty Replace the diaphragm
Gas valve faulty Replace the gas valve
Buner extinguishes while in operation Oxygen deficiency sensor activated Ventilate the room and re-ignite the appliance some
minutes later. If it happens again, contact a Corgi
registered technician.
Description Propane Natural Gas
1Front Cover 8 705 411 730
2Temp. Control Knob
3Flue gas Deflector 8 705 505 249
4Heating Body 8 705 406 248
5Main Burner Assembly 8 708 120 239 8 708 120 352
6Main Burner Injector 8 708 202 130 8 708 202 157
7Gas Valve Assembly 8 707 011 786 8 707 011 100
8Slide Assembly & Guide plate
9Piezo-Igniter
10 Cross Ignition bolt --------------- 8 703 407 027
11 Magnetic Unit
12 Thermocouple
13 Temperature Limit Thermostat
14 Gas Inlet Washer
15 Pilot Burner 8 708 105 327 8 708 105 320
16 Pilot Injector 8 708 200 138 8 748 200 120
17 Pilot Tube
18 Spark Electrode 8 708 107 002
19 Ignition Lead 8 704 401 022
20 Pilot Air Collector 8 701 302 074 8 701 302 082
21 Pilot Air Inlet Pipe 8 700 705 527
22 Water Valve Assembly
23 Water Valve Cover 8 705 500 101
24 Cover Repair Kit 8 700 306 098
25 Diaphragm
26 Water Strainer
27 Valve spindle 8 708 500 277
28 Selector Screw
29 Venturi
8 700 507 001
8 707 002 630
8 700 503 050
8 702 000 219
8 708 205 275
8 708 500 233
8 700 103 014
8 701 000 105
8 707 201 015
8 707 202 039
8 748 108 023
8 707 206 132
8 700 707 334

Worcester Heat Systems Limited, Cotswold Way, Warndon, Worcester WR4 9SW.
Telephone: [phone]. Fax: [phone]
This booklet is accurate at the date of printing but will be superseded and should be disregarded if specifications and/or appearances are
changed in the interests of continued improvement.
All goods sold are subject to our official Conditions of Sale, a copy of which may be obtained on application
6 720 606 003 (01.09) AL