FAULT FINDING
& DIAGRAMS
INSTALLATION & SERVICING INSTRUCTIONS FOR WORCESTER BOSCH
40
FAULT FINDING
FAULT FINDING
8-716-106-256a (08.05)
BOILER LOCKOUT:
Indicated by the illumination of the 'Lockout' indicator
on the burner control box.
To reset, wait 2 minutes then press the lockout
indicator/reset button.
PROBLEM CAUSE REMEDY
LOCKOUT:
Pulsation on start CF - Flue draught incorrect CF - Check flue draught
Combustion settings incorrect Set up as in installation instructions
Faulty nozzle Replace nozzle
Intermittent lockout Bad electrical connection Check control box/electrical connections
Intermittent flame detection fault See flame detection fault
Downdraught Extend flue or fit an anti- downdraught
cowl (CF only)
Burner motor fails to
operate
Faulty motor or electrical supply
to motor
Check for 230V at motor plug during
startup period
Control box fault Replace control box
Flame detection
fault
Photocell filmed over (dirty) Clean
Photocell faulty Replace
Control box faulty Replace
Air adjustment fault Incorrect CO
²
Set up as in installation instructions
No oil from nozzle No oil at pump Check and refill oil tank/bleed oil line
Check and clean filters & valves from oil
tank to boiler
Air in pump Bleed pump
Nozzle blocked Replace nozzle
Faulty pump or drive Replace
Faulty mechanical shut off valve Clean or replace
Ignition failure Electrode settings incorrect Set up as in installation instructions
Faulty ignition transformer Replace
Open circuit ignition Check and replace electrodes or high
tension leads if necessary
Faulty control box or electrical
connections not properly made
Correct electrical control box
connections or replace control box
BURNER FAILS
TO START
No power to boiler Check electrical / control circuit
Faulty boiler thermostat Check by temporarily linking out high
limit and control thermostats
Faulty control box Replace
HIGH SMOKE
NUMBER
Air intake/flue blocked Check & clear air intake/flue
Incorrect combustion settings Set up as in installation instructions
Oil pressure incorrect Adjust to correct pressure
Incorrect components used on
combustion head
Check with installation instructions
Faulty nozzle Replace nozzle
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