17
16
MAIN BURNER NOT CYCLING
(
ROOM TEMPERATURE TOO HIGH)
REPLACE
MULTIFUNCTIONAL
CONTROL
N
Y
REPLACE
ELECTRONICS
MODULE
DISCONNECT
YELLOW WIRE AT
MULTIFUNCTIONAL
CONTROL
N
DOES
BURNER
GO
OUT?
DISCONNECT
THERMISTA-STAT
REPLACE
THERMISTA-STAT
Y
DOES
BURNER
GO OUT?
N
CHECK FOR VOLTAGE AT
FAN LIVE TO EARTH
REPLACE
ELECTRONICS
MODULE
Y
N
IS
FUSE
OK ?
REPLACE FUSE
N
Y
CHECK FOR
VOLTAGE
AT FAN LIVE TO
NEUTRAL
MAIN BURNER ON, BUT FAN NOT RUNNING
Y
REPLACE FAN
DOES
FAN
START?
N
BRIDGE OUT
AIRFLOW SENSOR
Y
REPLACE
AIRFLOW SENSOR
REPLACE
TRANSFORMER
Remedy
Check for gas at inlet pressure test point
on the multifunctional control
Purge gas suply pip in accordance with BS
6891
Clear pilot orifice or replace pilot injector
Check igniter, lead and electrode.
Check that the mains gas pressure is 20
mbar and reduce if necessary.
Check that connection is secure.
Replace multifunctional control
Replace thermocouple
Check connections from electrical panel to
fan.
Check connections
Check for correct settings
Replace, taking care not to damage impeller
Replace
Check gas rate and burner pressure
setting.
Adjust fan speed or gas rate accordingly
Check that filter and air path is clear
Open additional outlets
Carry out spillage test and retify
Replace TTB
Check gas rate and burner pressure
settings
Check for correct settings
Check for correct settings
Check burner pressure settings
Replace fan assembly
Adjust fan speed
Consult diagnostics chart and follow
recommended procedure.
Check mains supply
Check that the time control and room
thermostat are operating correctly
Replace fuse and check for short circuits
Check connections
Check with test meter/replace if necessary
Replace
Short cicuit switch & replace if necessary
Fit temporary loop in heater thermostat socket.
If heater ignites check external circuit.
Possible Cause
1) No gas to the heater
2) Gas supply not purged
3) Pilot orifice restricted
4) Piezo system faulty.
5) Excessive gas supply pressure
1) Connection between thermocouple and
mutifunctional control not secure
2) Faulty power unit multifunctional
control
3) Faulty thermocouple
1) No voltage to fan
2) Loose electrical connection on fan
delay control
3) Fan delay control set incorrectly
4) Faulty fan assembly
5) Faulty fan delay control
1) Gas rate or burner pressure setting
high
2) Temp rise excessive
3) Air filter or return air path restricted.
4) Excessive number of oulets closed
5) Spillage of flue gases.
6) Spillage monitoring device (TTB) faulty.
1) Gas rate or burner pressure setting too
low
2) Fan delay control set incorretly
1) Fan delay control set incorrectly
1) Gas pressure too high
2) Noisy fan motor
3) Fan speed setting too high
1) Fault related to Modairflow Control
system.(See relevant pages)
1) Mains electrical suply not connected
to heater.
2) No demand for heat
3) 3A fuse failed
4) Loose connection to rom thermostat,
limit switch, Multifunctional Control
lead, Time Control or transformer
5) Transformer open circuit
6) Multifunctional Control faulty
7) Limit switch Faulty
8) Room thermostat/external wiring faulty
or room thermostat faulty
Symptom
A) Pilot will not light
B ) Pilot lights but goes out on releasing
START button during initial light-up,
or after normal operation.
C ) Main burner lights but the fan fails to
run after approx. 3 mins.
D ) Main burner operating intermittently
E) Main burner operating with
intermittent fan operation
F) Fan runs for excessive periods or
intermittently after main burner shuts
down
G) Noisy operation
MODAIRFLOW MODELS
H) Incorrect operation of fan and main
burner
NON-MODAIRFLOW MODELS
I) Pilot alight but main burner not igniting
