49
Response FF80
- Installation
YES but only
briefly
No pressure
or
wrong pressure
FAULT FINDING
EXIT
NO
Does the boiler light ?
Is there a spark at the ignition
electrodes during an ignition attempt ?
Go to Frame 85
Has the gas line been purged of air ?
Purge gas line
Can the correct burner pressure be
measured during an ignition attempt (i.e.
when PCB 37 LED2 goes OFF briefly) ?
Go to Frame 84
Is there power to PCB 37 ?
Go to Frame 83
NO
NO
Does the fan run correctly ?
NO
Is the 'low system pressure' neon lit ?
Go to Frame 82
NO
Go to Frame 87
YES
YES
NO
YES
NO
Does the boiler provide CH ?
Does the boiler provide HW ?
Go to Frame 81
Go to Frame 80
Does the boiler provide CH ?
YES
YES
YES
YES
YES
Go to Frame 86
NO
NO
The correct sequence of operation during ignition is as follows:-
1.
Mains to boiler with water pressure switch and overheat thermostat closed.
2. a.
Hot water tap turned on (HW and Fan lights come on) - the flow switch signals this to PCB 38, which starts the fan at full
speed and sends power to Ignition Control PCB 37 via the casing pressure switch.
or b.
Clock, heating switch and room thermostat call for heat (CH and Fan lights come on) - PCB 38 senses this, starts the fan at
full speed and sends power to the pump and Ignition Control PCB 37, via the casing pressure switch.
or c.
Both the above call for heat (HW and Fan lights come on) - HW takes priority, i.e. pump OFF, fan running at full speed,
power to PCB 37.
3.
If the casing pressure switch is closed and the fuse on PCB 37 is OK, the 'power' and 'lockout' LEDs PCB 37 illuminate.
4.
After 8 seconds pre-purge time 'lockout' LED 2 goes OFF, the spark starts and the gas valve opens.
5.
If a flame is detected the spark stops, 'lockout' LED stays OFF and the 'Burner on' neon lights - the fan speed and gas rate
then adjust as dictated by boiler water temperature.
6.
If a flame is not detected the spark stops, the gas valve closes, the fan continues to run and 'lockout' LED comes ON.
Foot Note:
Presence of Live supply on a terminal may be checked with a multimeter set to the appropriate AC range (apply the
other probe of the meter to mains neutral, e.g. on terminal N of the programmer terminal strip).
START THE BOILER FROM COLD
PCB = Printed Circuit Board
Correct
pressure
79 FAULT FINDING MAIN MENU
F
AUL
T FINDING
Note.
Switching the boiler on/off switch 'off'
when a frost thermostat is wired directly from
the mains may leave a live feed to the boiler.
