Main Mitre-AS Quick guide

INSTALLATION & SERVICE
INSTRUCTIONS
MITRE-AS
GAS FIRED -INSTANTANEOUS SINK WATER HEATER
G. C. APPLIANCE N° 51 476 33
THE GAS SAFETY (INSTALLATION AND USE) REGULATIONS 1984
In your own interest, and that of safety, it is the law that all gas appliances are installed by
competent persons, in accordance with the above regulations. Failure to install appliances
correctly could lead to prosecution.
Follow these instructions carefully and comply with conditions set out in the current edition of the
Building Regulations Local Water Authority Regulations and relevant Codes of Practice relating
to installation of Domestic Water Heating Appliances. (CP 342. and BS.5546).
LEAVE THESE INSTRUCTIONS BY THE METER

Page 1
Ventilation Page 2
Fixing Page 3
Water connection Page 3
Water spout connection Page 4
Gas connection Page 4
Commissioning appliance Page 4
Checking burner pressure Page 5
Servicing instructions Page 6
To remove case front Page 7
To remove spark igniter Page 7
To remove. thermocouple/pilot/spark electrode Page 7
To remove heating unit Page 8
To remove electro. mag. unit Page 9
To remove burner assembly and injectors Page 9
To remove slow ignition diaphragm Page 9
To remove water diaphragm Page 9
Short spare parts list Page
11
TECHNICAL DATA
DIMENSIONS HEIGHT WIDTH DEPTH
Overall mm (in) 483 (19) 216 (81/2) 210 (8 1/4) Not including
swivel spout
WEIGHT EMPTY
kg (1b)
7.25 (16)
Nominal heat input 11.6 KW : 39,580 Btu/h.
Nominal heat output 8.7 KW : 29,685 Btu/h.

NOMINAL BURNER PRESSURE
GAS GROUP GAS INLET PRESSURE NOMINAL BURNER
PRESSURE
INJECTOR
SIZE
N. G. mbar in. w.g. mbar in. w.g. mm dia
20- 85.7 2.3 1.25
THE MAXIMUM PERMITTED WATER PRESSURE THROUGH THIS APPLIANCE IS 10 BAR.
THE MINIMUM OPERATING HEAD THROUGH THIS APPLIANCE IS 10fT. (3 BAR).
ANY OTHER PRESSURE LOSSES INCURRED THROUGH THE ADDITION OF EXTERNAL
PIPES AND FIT-TINGS MUST BE TAKEN INTO ACCOUNT ON INSTALLATION.
THE NOMINAL WATER RATE IS 3.2 LITRES / MIN. (0.7 GALL/MIN.) AT A TEMPERATURE
RISE OF 40 °C (72 °F).
THE TEMPERATURE SELECTOR WILL GIVE A VARIATION IN TEMPERATURE RISE
BETWEEN 25 °C (45°F) AND 55 °C. (99°F).
VENTILATION AND AIR SUPPLY
This heater must be installed in accordance with B.S.5440 part 2.
This heater must not be installed in any room containing a fixed bath or shower and shall not be
used to heat water for a bath.
A clearance of 51 mm (2 in) must be left at both sides of the appliance when installed to facilitate
ease of servicing.
FLUELESS INSTALLATION
This appliance incorporates an Atmospheric Sensing Device that will shut down the appliance in
the event of the room being insufficiently ventilated.
Page 2
A minimum clearance of 450 mm (18 in.) must be observed between the top of the appliance
and the ceiling installed.
The room in which the appliance is fitted must be of greater volume than 6 m3 (215 ft. 3). In
addition rooms between 6 - 11 m3 (215 - 390 ft.3) must be provided with an air vent to the
outside atmosphere having minimum effective area of 35cm2. (5in 2) in addition to an openable
window.
For room greater than 11 m3 (390ft.3) an air vent is not required but the room must still contain
an openable window.
IMPORTANT
The heater is supplied ready for connecting the gas supply from the left hand side. If connection
of the gas supply from the right hand side is prefer-red the gas tap should be re-positioned
before fixing. See gas connection section page 4.
FIXING THE HEATER

Pull handles and knobs from front of appliance.
Remove the two fixing screws 1. Fig. 1 .
Carefully swing out bottom edge of case front to clear tap spindles. Disconnect wire lead from
rear of spark igniter and lift off case front. Deter-mine the correct position for the heater taking
into account instructions given under "VENTI-LATION AND AIR SUPPLY".
Place appliance in position on the wall and mark the wall for top fixing point.
Drill hole in wall using an 8mm. drill and insert plastic plug. Screw stud into plug down to the
depth of the threads. Remove any burrs from screw. Place appliance on the wall ensuring that
the stud engages into the fixing hole in rear of appliance. Using a spirit level ensure that the
appliance is vertical temporarily tighten the grub screw at the top rear of the appliance case.
Hold clips in position towards outside edge of slots as shown in Fig. 2 and mark wall. Slacken
grub screw and lift off appliance. Drill and plug wall to take clip securing screws. Place appliance
into position on wall, tighten grub screw and secure at bottom using the fixing clips.
WATER INLET CONNECTION
It is strongly recommended that the use of loose jumper washer type cocks be avoided.
Flush out all foreign matter from the supply pipe before connecting to the appliance.
Connect copper tail and sealing washer to water service cock 2. Fig. 3 and connect water supply
using 15 mm. copper pipe to B.S. 2871.
IMPORTANT. Remove the sealing washer from copper tail before making any soldered joints to
prevent damage from heat. Replace washer on completion.
WATER OUTLET SHORT SPOUT (WHERE APPLICABLE)
Connect short spout and sealing washer 4 Fig. 3 to water outlet 3 Fig. 3 .
IMPORTANT: Remove swivel spout if already fitted.
SWIVEL SPOUT CONNECTION (WHERE APPLICABLE)
Connect swivel spout and sealing washer 4. Fig. 3 to water outlet 3 Fig. 3 .

Fig. 1
Fig. 2
Page 3
MITRE - AS
WARNING

TO THE USER
PLEASE NOTE THIS APPLIANCE IS NOT SUITABLE FOR USE WITH SHOWERS.
Page 3A
IMPORTANT: Remove short spout if already fitted.
REMOTE HOT WATER OUTLET CONNECTION
Fig. 3
IMPORTANT: SEE SECTION ON VENTILA-TION AND AIR SUPPLY
The appliance is fitted with a remote hot water outlet. This outlet is for use when a hot water
supply is required in a room other than the room in which the appliance is fitted.
The remote hot water outlet is situated on the water section to the left rear of the spout
connection.
Remove nut and blanking washer and connect copper tail (available from the manufacturer part
number 30011). Connect pipework from appliance to remote tap or shower.

IMPORTANT: Remove the sealing washer from copper tail before making any soldered joints to
prevent damage from heat. Replace washer on completion.
IMPORTANT: The hot and cold taps on the appliance DO NOT control the remote outlet.
If the spout outlet is not to be used on the appliance blank off the outlet to guard against
accidental use of taps. The nut and blanking washer taken from the remote hot outlet should be
used for this purpose.
NOTE : The swivel spout or the remote outlet or both can be connected to the appliance as
required.
GAS CONNECTION
The supply may be connected from the opposite side of the appliance by repositioning the gas
tap after releasing the two fixing screws 6. Fig. 3 . The meter must be capable of passing 1.13 m
3/h (40 ft3/h) of natural gas CV. 1000 in addition to other requirements. The gas pressure
required at the appliance inlet connection is 20 mbar (8 in w.g.). A forward facing pressure test
point is located on the gas inlet body. Connect copper tail and sealing washer to gas inlet 5. Fig.
3and connect supply using 15 mm copper pipe to B.S. 2871.
IMPORTANT: Remove the sealing washer from copper tail before making any soldered joints to
prevent damage from heat. Replace washer on completion.
COMMISSIONING THE APPLIANCE
Turn on gas and water supply and check for soundness.
Remove screw and sealing washer and attach a pressure test gauge to burner pressure test
point 7. Fig. 3 .
Push spark electrode lead into rear of spark igniter and replace case front by locating lugs in the
top of the front panel into the mating slots in the appliance case. Push bottom of case front into
place and secure with two screws 1. Fig. 1. Re-fit all handles and knobs ensuring that the blue
marked knob is fitted to the right hand front spindle and the red marked knob is fitted to the left
hand front spindle.
Open gas tap fully, anti-clockwise, the tap is in the open position when the "FLAME" symbol on
the gas tap handle is visible.
Turn the burner control knob to the spark position marked
Repeatedly press and release the spark igniter button marked until the pilot is lit.
The pilot flame can be observed through the viewing window.
Once the pilot is lit wait 10 seconds and turn the burner control knob to the working position
marked
If the pilot goes out wait one minute and repeat the above operations.
Turn on the hot tap and check ignition of main burners.

Page 4
CHECKING BURNER PRESSURE
Allow burners to operate for one minute before checking the pressures shown below.
GAS GROUP GAS INLET PRESSURE NOMINAL BURNER
PRESSURE
INJECTOR
SIZE
N.G. mbar in. w.g. mbar in. w.g. mm dia
20 85.7 2.3 1.25
After checking, turn off hot water tap. Remove pressure test gauge and replace screw and
sealing washer.
IMPORTANT
Remove the protective vinyl film from the namebadge. Draw the attention of the user to the
warning label on the outer case. Hand the users instructions to the consumer.
Explain fully how to operate the appliance.
SERVICING INSTRUCTIONS
Operate the heater and check the following points.
Check List Action
Does the pilot flame ignite?
Does the pilot light go out after a
short period?
Check the spark igniter and spark
electrode and replace the units if
necessary.
Check for electrical shorting.
Check the spark gap, the gap should
be between 3 mm-4 mm. See Fig. 6 ..
This appliance is fitted with a "Heat
Sensor" positioned on the right hand
side of the heating unit.
Using a B.G.C. multimeter check for
continuity through the thermocouple
circuit (with the appliance cold). If a
fault is found it will be due to either a
faulty heat sensor or a faulty thermo-
couple.
To check the heat sensor remove it
from the cir- cuit and connect the two
leads together. Re-check the circuit, if
continuity is established then the heat
sensor is faulty and needs replacing. If
continuity is not established then the
thermo- couple is faulty.

Remove the deflector from the top of
the appliance and check the heat
exchanger. If the heat ex-changer
shows any signs of blockage remove
the heating unit and clean by brushing
or washing. If after checking the above,
the pilot flame will not ignite or the pilot
flame ignites and goes out after a short
period, turn off the appliance open the
doors and windows in the room and
well ventilate the room.
After ensuring that the room been well
ventilated light the pilot flame and
check that it remains lit. If not, replace
the atmosphere sensing device. See
the Short Parts List at the end of this
booklet.
Is pilot flame correct? Clean pilot assembly.
Page 5
Does thermo-electric flame safety device open
and close correctly?
This appliance is supplied with an
adaptor to enable the thermocouple
circuit to be tested using a B.G.C.
multimeter.
Check that the pilot strikes
thermocouple correctly. Replace
thermocouple and/or electric
magnetic valve if necessary.
Is burner pressure correct? Ensure gas inlet pressure is
sufficient.
Ensure main gas valve-is fully open.
Are there any water leaks? Check tightness of connections.
Replace sealing washers if
necessary.
Are there any gas leaks? Check tightness off connections.
Replace sealing washers if
necessary.
Does main burner extinguish quickly when hot
water tap is turned off?
Check that push rod in water section
moves freely. Lubricate if necessary.
Is heater noisy in operation? Check for flame "lift" on main burners
De-scale the heat exchanger if
necessary (See Section "TO
REMOVE HEATING UNIT").

1. TO REMOVE CASE FRONT
Pull handles and knobs from spindles at front of appliance. Remove two fixing screws 8. Fig. 4 .
Carefully pull out bottom edge of case front to clear tap spindles.
Disconnect wire lead (push fit) from rear of spark igniter.
Lift case front and remove.
Re-assemble in reverse order ensuring that the red marked knob is fitted to the left hand front
spindle and the blue marked knob is fitted to the right hand front spindle.
Fig. 4
2. TO REMOVE SPARK IGNITER
Remove case front, see Section 1 .
Pull retaining clip and washer from around the spark igniter behind case front. Pull spark igniter
forwards through case front.
Re-assemble in reverse order using a new "Push Fix" retaining clip (Part Number 30265).
3. TO REMOVE THE SPARK ELECTRODE, PILOT, THERMOCOUPLE, HEAT SENSOR,
PILOT REGULATOR AND ATMOSPHERE SENSING DEVICE.
IMPORTANT : Care must be taken when handling this assembly. The bi-metal strip MUST NOT
be touched by hand, skin contact may effect the operation of the control.
Page 6
IMPORTANT: The bi-metal sensor and its valve flap MUST NOT be mechanically opened or
adjusted in any way.
Turn off the gas. Remove the case front see section 1.
Release pilot supply fixing screw 9. Fig. 5 do not remove the screw from the pilot assembly, do
not lose the sealing washer.
Release the thermocouple nut 10. Fig. 5 .

Release the 'Heat Sensor' from the heating unit (centre screw).
Pull assembly carefully forward at the bottom and remove from the appliance by gently pulling
downwards to clear the burners.
Release screw 11. Fig. 6 and separate the unit.
The spark electrode and the thermocouple will now be free.
To clean the pilot jet, release union nut 12, fig. 6. and seperate unit. DO NOT lose the sealing
washer. DO NOT breakdown' the assembly beyond this point.
Clean by blowing through in the opposite direction to the gas flow. DO NOT clean by brushing or
poking through the orifice.
The pilot tube assembly, that incorporates the Atmosphere Sensing Device, may be cleaned by
rinsing in paraffin or metholated spirits or a similar volatile solvent. Care must be taken when
handling this unit, the bi-metal stip is extremely sensitive and easily damaged.
Re-assemble the top unit first, the electrode, pilot tube and thermocouple locate into their
respective sections in the metal plate, hook the remaining plate into position and secure with the
fixing screw 11. Fig. 6 . Check that all the components are correctly positioned.
Attach the regulator assembly to the pilot tube assembly 12. Fig. 6 ensure that the sealing
washer is in place, do not tighten the union nut.
With the electrode towards the back of the appliance push assembly into position between the
centre burners so that it locates behind the retaining strip.
Secure the assembly at 9. Fig. 5 ensure that the sealing washer is in place.
Tighten the union nut 12. Fig. 6 .
Re-connect the thermocouple at 10. Fig. 5 . TIGHTEN THERMOCOUPLE NO MORE THAN 1/4
TURN BEYOND HAND TIGHTNESS.
Re-connect the 'Heat Sensor' and ensure that the thermocouple leads are routed away from any
hot surfaces.
4. TO REMOVE HEATING UNIT
Turn off gas and water supply and drain unit by releasing drain screw and washer 14. Fig. 7 .
Remove case front see section 1 .

Fig. 5

Fig. 6
Page 7
Remove the complete pilot and sensing device assembly see section 3 .
Release two union nuts and washers 20. Fig. 5 . DO NOT lose sealing washers.
Release screw 21. Fig. 5 at front of flue deflector and remove retaining strip. Carefully pull
heating unit forwards out of the appliance. Brush or wash clean if necessary. If de-scaling is
necessary use a proprietary brand of de-scaling or a solution of 10 parts water to one part
hydrochloric acid. The water should preferably be hot. Add ACID to WATER not water to acid.
Fill heating body with solution and leave until solution stops bubbling. Flush thoroughly before
re-fitting.
Re-assemble in reverse order ensure sealing washers are fitted, and that the thermocouple
leads are routed away from hot surfaces.
WARNING

ACID/WATER SOLUTION MUST BE USED WITH EXTREME CAUTION. TAKE CARE NOT TO
SPLASH ONTO SKIN OR INTO EYES. WASH ANY AFFECTED AREAS WITH LARGE
AMOUNTS OF COLD WATER AND SEEK MEDICAL ADVICE.
5. TO REMOVE ELECTRO-MAG. UNIT
Remove case front see section 1 .
Release thermocouple nut 10. Fig. 5 .
Release securing nut 16. Fig. 5 and pull electro-mag. unit clear of assembly.
Replace in reverse order.
6. TO REMOVE BURNER ASSEMBLY AND INJECTORS
Turn off gas and water supply. Open a hot outlet to release pressure. Remove case front, see
section 1. Remove the complete pilot and sensing device assembly see section 3. Release
union nut 17. Fig. 5. Lift burner assembly vertically to fully expose spring and sealing washer.
Remove washer and spring assembly. Remove burner assembly.
Remove two fixing screws 18. Fig. 5 and pull burner assembly off manifold. To clean injectors
remove from manifold and blow through in op po-site direction to gas flow. Do not clean by
brushing or poking through orifice.
When re-fitting injectors re-seal the threads using an approved sealing compound, do not allow
sealing compound to block the injectors. When re-assembling the main valve spring and washer
ensure that the blind hole in the brass valve is correctly located on the push rod before re-fitting
the burner assembly.
Re-assemble the burner unit in reverse order ensuring that the location peg at the rear of the
unit engages in the positioning hole in the rear panel.
Fig. 7

Fig. 8
Fig. 9

Fig. 10
Page 8
7. TO REMOVE SLOW IGNITION DIAPHRAGM
Remove burner assembly see section 6 .
Remove four screws 23. Fig. 9 and lift off the cover.
Lift out diaphragm assembly, replace if necessary.
Re-assemble in reverse order ensuring that the brass weight is on the under side of the
diaphragm and locates in the gas chamber.
8. TO REMOVE WATER DIAPHRAGM
Turn off gas and water supply and drain unit by releasing drain screw and sealing washer 14.
Fig. 7 .
Remove case front see section 1 .
Disconnect water supply at rear of water diaphragm assembly.
Remove front retaining plate by releasing three fixing screws 19. Fig. 5 and easing free.
Remove burner assembly see section 6 . Remove union nuts 20. Fig. 5 . DO NOT lose sealing
washers. Remove two vertical screws 24. Fig. 10. Release two horizontal screws 25. Fig. 10 by
turning each four complete turns anti-clockwise and pull assembly forwards and out of
appliance. DO NOT lose rubber sealing washer from gas connection. Release two screws 26.
Fig. 11 by turning each four complete turns anti-clockwise. Separate water diaphragm assembly
from the Flame Safety Device. Separate water diaphragm assembly by releasing five screws 22
Fig. 7. DO NOT lose small by-pass tube when separating assembly.
When re-assembling ensure that the small by-pass tube is in position in the unthreaded hole in
the skirt of the water diaphragm assembly.

The diaphragm assembly must be fitted with the thrust washer and location boss on the top of
the diaphragm and the spring around the location boss on the top of the thrust washer. See Fig.
7.
Re-assemble in reverse order ensuring that the gas and water tap spindles face forwards. Re-fit
drain screw and washer.
Fig. 11
Page 9
SHORT SPARE PARTS LIST
Key No. G. C. PART
No.
Description No. Off Makers
Part No.
35 257694 Pilot regulator assembly 1 27691
32 Spark Electrode 1 38742
33 - Thermocouple 1 27783
12A 340453 Spark Igniter Assembly (Cosic P 1862-79) 1 30260
33B - Heat Sensor 1 27581
34 257622 Pilot burner/injector Assembly 1 27747
8285594 Hot Water Knob 1 31206
11 285597 Cold Water Knob 1 31207
9/10 285595 Temperature Selector/Burner Control Knob 2 22527
49 285622 Gas Tap Handle 1 20858

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