Ignition sequence of combi with pressure switch

[ant101]

Could somebody please explain the ignition sequence. (eg common, normally open, normally closed wires).
Also what would happen if the fan was to fail and the air pressure switch/micro switch? was stuck down.

Thanks

 

[gas_man_gaz]

what fault ya got? n what boiler?

 

[ant101]

No problem,Im a student. Just intersted

 

[Rob]

No problem,Im a student. Just intersted

Books, boiler courses and experience.

 

[ant101]

Im on a course,
Plenty of books,
Experience.. not much, but its helpful to hear answers from people in the know

 

[Rob]

General boiler workings and sequences are in plenty of books etc.

You'd be better off with a specific problem on a certain boiler for more info.

In order to your OP. The fan wont be sent power from the pcb if the APS is still in the N/O position. Most have 3 wires Common, NO and NC. It checks it is in the NC before powering fan.

rob

 

[ant101]

cheers rob

 

[gas4you]

Im on a course,
Plenty of books,
Experience.. not much, but its helpful to hear answers from people in the know

Sounds like son of Dr Drivel

 

[Agile]

Sounds like son of Dr Drivel

Dr Drivel tells us what he thinks we should think, all gleaned from reading manufacturers brochures.

This fellow asks us!

Tony

 

[chilli985]

ignition sequence of a direct burner ignition for fan flued combi boiler

* demand for heat
*demand reaches PCB via interlocks
*Air pressure switch proves in normally closed position
*Fan runs
*Air pressure switch moves to normally open position
*Spark generator on
*Low fire gas solenoid opens
*Burner ignnites at low fire
*Flame proved by flame rec
*High fire gas solenoid opens
*Burner operates at high gas rate
*Flame constantly monitored by flame rec

i had to learn this for a british gas exam