Wildfowler12 Posted April 9, 2014 Report Share Posted April 9, 2014 (edited) Evening all, in the infinite wisdom of PW I'm hoping someone who knows better than me can offer some boiler advice. Here goes... I've noticed an intermittent fault with my boiler - a Potterton Prima B. Occasionally it won't fire up for central heating. My timer is set to come on at 17:00, but some nights (around once a month) it just won't fire up at all. The thermostat appears to be working, clicks on and off when increasing/decreasing temp, and the boiler control display is showing that it's calling for heat, but the boiler won't fire up. Even if I press the advance button, or switch it to constant. Usually when this happens we sit in front of the fire (like tonight), then when we wake the next day, it's working again (the boiler comes on 05:30 for an hour), radiators hot, and it may be a few weeks before we see the problem again. Interestingly the hot water part functions fine. Always fires up when the control panel tells it to. And even when the boiler won't fire for heat, press the advance button for water, and it fires up fine! Obviously I'll be getting a plumber / heating engineer out in due course. But usually PW can offer answers to these sorts of things, so figured I'd give it a shot. Any help would be appreciated. Thanks I should add, obviously I've turned the thermostat right up, to make sure it's not failing to come on due to the ambient temp being above the requested temp. Edited April 9, 2014 by Wildfowler12 Quote Link to comment Share on other sites More sharing options...
vmaxphil Posted April 10, 2014 Report Share Posted April 10, 2014 micro switch in the 3 way valve Quote Link to comment Share on other sites More sharing options...
kingo15 Posted April 10, 2014 Report Share Posted April 10, 2014 Could be the motor in the valve starting to play up or the end switch? Quote Link to comment Share on other sites More sharing options...
LondonLuke Posted April 10, 2014 Report Share Posted April 10, 2014 Motorised valve head failed I would think. See if you can locate a valve that looks like the below and when it happens try and manually move the spring set switch on the side. It's possible you may have two of these if you have an S Plan system. In most cases it will just be the head of the valve that fails so if you are reasonably competent you could change it yourself - PM me if taking this on as quite a good shortcut to this. Perhaps possible the pump is on the way out so check this next time goes too. http://m.screwfix.com/pr-gallery.htm?id=30424#imggal1 Quote Link to comment Share on other sites More sharing options...
Wildfowler12 Posted April 10, 2014 Author Report Share Posted April 10, 2014 Many thanks Quote Link to comment Share on other sites More sharing options...
Yellow Bear Posted April 10, 2014 Report Share Posted April 10, 2014 Could be the motor in the valve starting to play up or the end switch? +1 - not a boiler problem. Quote Link to comment Share on other sites More sharing options...
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