30
Mexico Super CF 3/100, 3/125, 3/140 -
Installation
NO
NO
Is there a spark at the ignition electrode ?
Is there gas at the pilot burner when the gas valve
knob is pressed ?
50 PILOT WILL NOT LIGHT
51 PILOT WILL NOT STAY LIT WHEN THE GAS CONTROL VALVE KNOB IS RELEASED
Have you confirmed that the system controls
are 'Calling for Heat' ?
Note.
After any faults have been corrected, return all thermostatic and other controls to the previously noted settings
NO
Is there a supply voltage between the gas control valve
terminals ? Expect 230 V +10% -6%
YES
YES
NO
Set any CH and HW controls to the 'Continuous'
position. Is there a supply voltage between CH and N,
also between HW and N? Expect 230 V +10% -6%
YES
Is there a supply voltage at the input to the control box?
FAULT FINDING
YES
YES
NO
NO
YES
52 PILOT LIT BUT NO MAINS GAS
Check the supply voltage, e.g., by using a multimeter,
set on the 300V AC range, between the L and N
terminals. Expect 230V +10% -6%. If no supply, check
the fuse in the plug or other supply point.
Check that the gap between the electrode and the pilot
burner is 3-4 mm. Refer to Frame 44.
Check that the HT lead and electrode are undamaged and
the connections are NOT close to earthed metalwork.
Check the piezo unit is operative - by holding an earthed
screwdriver approx. 3mm from the HT output terminal
(with the ignition lead removed) and by operating the
button.
Is there a spark across the gap ?
NO
Faulty piezo
unit - replace
Allow time to purge any air
present.
Check that the gas control knob is
being pressed fully in, that there is
gas pressure at the boiler inlet and
that the pilot jet is not blocked
NO
NO
Replace the
gas control
valve
If no supply, check controls. Reference may be made
to the British Gas Multimeter Instruction Book
Check the settings of the room thermostat and cylinder
thermostat. Check the control system. Reference may
be made to the British Gas Multimeter Instruction Book
Does the main burner light ?
Replace the gas
control valve
Check the boiler thermostat. Reference may be
made to the British Gas Multimeter Instruction Book.
Check the TTB downdraught thermostat. Is there
downdraught in the flue ?
Before attempting any electrical fault finding ALWAYS carry
out preliminary electrical system checks, i.e. earth continuity,
polarity and resistance to earth using a suitable meter.
Detailed instructions on the cleaning and adjustment or
replacement of faulty components are contained in the
'Servicing' section of this publication.
Check that there is no blockage
in the pilot line or pilot injector.
YES
Does the pilot light when a
match is applied ?
NO
Replace the gas control valve
NO
Check the thermocouple output (6-10 mV closed circuit). Replace
thermocouple if output is outside the stated range. Reference may
be made to the British Gas Multimeter Instruction book
Does the pilot now stay alight ?
YES
YES
Is the pilot flame correctly set to maximum ?
Does the overheat thermostat (if fitted) require resetting ?
Does the pilot now stay alight ?
YES
NO
Is the connection between the thermocouple and
the gas control valve clean and tight ?
NO
Clean the contacts and reconnect securely
NO
Replace the overheat thermostat
F
AUL
T FINDING
Summary of Contents for CF3/100
Page 1: ......
