How can I cure the cold start problem on my Potterton Prima 40F boiler?
Hi, I have a Potterton Prima 40F, a fan driven, balanced flue boiler that will not start in cold weather. The flue is through a north facing wall, and whenever there is a cold spell with a high pressure system causing northerly winds the boiler will not fire up. The problem appears to be caused by the pressure switch sensing too high a pressure during startup and causing the startup process to terminate before ignition. The boiler keeps attempting to start but then cuts out again (i.e. fan keeps starting up but then stops again after a couple of seconds, although on the first attempt it runs for quite a bit longer before stopping). I suspected the pressure switch and replaced that, but it was still the same, and I have also checked for blockages in the flue and everything else I can think of. I can get the boiler to start up by pulling off the red pipe to the pressure switch, in which case the fan continues running without cutting out, but ignition does not start until I very steadily
