Potterton combi 80 air flow switch

[Bmt]

Hi there
I was wondering what is the purpose of air flow switch and could failure of this be the reason for the fan running constantly for 5 minutes after demand for hot water or central heating is finished.
Recently I have replaced the mod. PCB and the DHW flow switch and microswitch.
I have had this problem for quite a while now and I am sure the boiler fan did not run on this long when first installed.
It is not causing any adverse conditions I just would like it stop as soon as possible after demand is over. I dont mind replacing it but not if it is not going to make any difference
Thanks

 

[Agile]

Well, we do mind you replacing it!

DIYers should not be opening the combustion chamber or doing any work on the gas/combustion or safety devices.

In any case its not likely to be that.

More likely to be the PCB.

Was it really a genuine new PCB from an authorised dealer?

Who set up the gas adjustments?

Tony

 

[TCCHeating]

The air pressure switch is a safety device. It is used to check the fan is running at the correct speed before ignition.

Some boilers keep the fan funning after the burner has shut down for cooling purposes. Maybe yours is one of those. I'm sure if you could call potterton to confirm if this is the case with this model.

If the boiler is working fine, i would live with it.