Fault Finding - IDEAL Concord CX40 Installation & Service Manual

Before attempting any electrical fault finding ALWAYS carry
out the preliminary electrical system checks as detailed in the
Instructions for the British Gas Multimeter or other similar
commercially available meter.
The preliminary electrical system checks are the FIRST
electrical checks to be carried out during a fault finding
procedure.
On completion of any service/fault finding task which has
required the breaking and remaking of electrical connections
47 PILOT WILL NOT LIGHT
Is there a spark at the ignition electrode ?
Is there gas at the pilot burner when the gas
valve button is pressed ?
Does the pilot burner light when a match is
applied ?
Adjust the pilot to the correct size (flame
enveloping approximately 13mm of the
thermocouple tip). Confirm satisfactory
ignition using the piezo unit
48 PILOT WILL NOT STAY LIT WHEN THE GAS VALVE BUTTON IS RELEASED
Is the connection between the thermocouple,
the limit thermostat leads and the gas valve
clean and tight ?
Is the pilot flame of the correct length?
The flame should envelop approximately
13mm of the thermocouple tip
Is the overheat thermostat calling for heat ?
Check the thermocouple output
(8 - 15 mV, closed circuit) using a suitable
multimeter or replace the thermocouple
Does the pilot now stay alight ?
30

FAULT FINDING

YES
YES
YES
YES
YES
YES
the following checks MUST be repeated:
a Earth continuity
b Polarity
c Resistance to earth
Detailed instructions on the replacement of faulty components
are contained in the 'Servicing' section of these Installation &
Servicing Instructions.
NO
Check that the gap between the electrode and
pilot burner is 3-4 mm. Refer to Frame 15.
Ensure that the H/T lead is undamaged and that
the connections are not close to earthed
metalwork. Check that the piezo unit is
YES
operative, by holding an earthed screwdriver
approximately 3mm from the H/T output
terminal (with the ignition lead removed) and
operating the button.
Is there a spark across the gap ?
NO
Faulty piezo unit - replace
Allow time to purge any air present by
increasing the pilot gas rate via the adjusting
screw. Check that the button on the gas valve is
being pressed fully in.
Ensure that there is gas pressure at the boiler
inlet. Check that the pilot jet is not blocked.
NO
Clean the contacts and reconnect securely.
NO
Adjust the pilot gas rate
NO
Push in and release the manual reset button
on the thermostat body.
NO
Replace the gas valve
NO
Concord CX
- Installation