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37 SERVICING - continued
Remove the secondary heat exchanger front plate (6
screws) then slide out the secondary heat exchanger
baffles. Clean the fins with the brush provided and remove
all debris.
Reassemble in reverse order.
CXC 94/116 only.
Refit the distribution plate.
The secondary heat exchanger baffles (one to each bank
of tubes) must be fitted with their returns uppermost.
Before refitting the secondary heat exchanger front plate
and fan assembly check that the seals are intact. Replace
if necessary.
Do not refit the insulation and casing panels until a leakage
test has been carried out after recommissioning the boiler.
38 REPLACEMENT OF COMPONENTS - Refer to Frames 5, 40, 41 and 42
GENERAL
WARNING. ALWAYS turn OFF the gas supply at the gas
inlet cock and switch OFF and DISCONNECT the
electricity supply before working on the appliance.
39 GAS CONTROL VALVE
1. Disconnect the electrical connections to the faulty gas
valve.
2. Check that the gas inlet cock is OFF, unscrew the 4
screws on the gas valve inlet flange, the 4 screws on the
outlet flange and remove the valve.
3. If the valve has a brass restrictor fitted to its outlet,
remove by unscrewing and refit into the new valve. It is
imperative that the gas restrictor is fitted to the low-
rate valve.
4. Replace the gas control valve and re-assemble in
reverse order, ensuring that the arrow indicating the
direction of flow is in the correct position.
5. Ensure that new 'O' ring seals are correctly placed in
each flange connection.
6. Test for gas soundness.
7. Recommission the appliance and set the manifold
pressures as described in Frames 22 and 23 or 24.
Concord CXC -
Installation
SERVICING
TESTING AFTER SERVICING
After re-assembly restore the electricity and gas supplies.
Light the boiler (refer to the Lighting Instructions) and test for
leaks. Refer to Frame 19 'Testing for Gas Soundness'.
Check burner manifold pressures (Frame 22) and adjust if
necessary (Frames 23 or 24). Finally reset any external
controls to the desired position.
Check that there is no leakage of combustion products
around the fan, secondary heat exchanger and flue
connection, using a smoke match or smouldering taper.
If any leaks are evident, immediate steps must be taken to
rectify them.
To facilitate the replacement of components, remove
and replace the casing top and front panels, fan, NOx
duct and the burner front plate as necessary -
described under 'Servicing'.
40 MAIN BURNER
1. Remove the NOx duct and burner front plate, as
previously described in Frame 35.
2. On the CXC 48 and 70 remove the screws holding the
HT heat shield from the LH leg of the combustion
chamber. Raise slightly and withdraw the heat shield,
taking care not damage the leads.
3. Each burner can be removed by sliding back, to clear the
injector, and then lifting out. Disconnect the ignition leads
from the LH burner and the detection lead from the RH
burner.
4. Remove the 2 screws securing the electrode assembly
and heat shield to the LH burner bracket and the 2
screws securing the detection electrode bracket to the
RH burner.
5. Reassemble in reverse order.
IMPORTANT. Care must be taken to prevent damage to the
combustion chamber insulation when replacing burners.
27
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