Potterton Prima F Fan switch

[armstrongracer]

Hi,

I changed out the flue fan on a Potterton Prima F boiler. Thought it would be a plug & play job as fan was the same part number as original. New fan was obviously a later version of the original and on a stand-alone test the bearings appeared freer and it appeared to spin up faster than the original. When I try to run it installed, there is an issue. The pressure switch clicks in very early as the fan is winding up then clicks off again. The boiler keeps cycling like that but never fires up. If I blow slightly down the clear pipe the pilot light fires up and the boiler runs perfectly. If I squeeze the red pipe (high pressure) the boiler fires up and runs fine too. The manual diagnoses this as a faulty pressure switch, but it's not, the switch works perfectly. That is the issue. When I look at the application guide for the Honeywell pressure switch it looks like the switch mechanism compares high and low pressure and is looking for the correct pressure profile on start up. Once running switch is just looking for pressure to be a minimum level, which is why it works fine once the boiler is fired up. Has anyone come across this problem before and found a fix?

 

[flameport]

This forum does not provide advice on gas repairs.

 

[ianmcd]

yep most pros on here know what you have done, but as already advised we are not allowed to give you gas advice, what you are doing is very dangerous, get someone qualified in and stop messing with something so dangerous