Boiler firing up continuously

b56c

No heating/hot water 2 weekends ago. Fan and pcb eventually replaced and everything back to normal. Tonight I notice how hot the house feels - thought someone had changed settings but no they’re as they should be. Switched water and heating to Always Off at controls but still fires up. Turned thermostat down and have now switched all radiators off. What do you think is the problem? Will the action I’ve taken help at all? Looking at appointments’ system and engineer can’t get out till 3 January!!! so I need to be able to try to regulate system in roundabout way so I’m not spending a fortune.

Mr.Generous

Some combi's fire up to have hot water on standby unless in eco mode? If the power to the boiler is off it won't fire until engineer can attend, I suspect controls are at fault / wired wrongly.

b56c

Mr.Generous wrote: »

Some combi's fire up to have hot water on standby unless in eco mode? If the power to the boiler is off it won't fire until engineer can attend, I suspect controls are at fault / wired wrongly.

This is old-style not combi - only fires up when scheduled to. I’d set the heating and water to Off from the controls but it was still firing. I’ve now opened up a door on side of boiler and turned it off from there. Hopefully that will prevent it firing now.

Alex1983

One of the zone valves or mid pos valve has failed and keeping the boiler on all the time. Only thing you can do temporarily is turn the fuse spur to the boiler off and back on when you want heating or hot water.

b56c

Alex1983 wrote: »

One of the zone valves or mid pos valve has failed and keeping the boiler on all the time. Only thing you can do temporarily is turn the fuse spur to the boiler off and back on when you want heating or hot water.

The knob inside the hinged door which I’ve switched to the off position seems to have knocked things off for now. Can I just turn that back to Max tomorrow when I want heating on? Safe to do that?

Alex1983

Yes that will also do it but I would imagine the pump will be continuously running.

b56c

Am managing with manual off/on until the engineer arrives. Was going to be 3rd Jan but after naming and shaming on Twitter they messaged me and have found a slot on 26 Dec.

Thanks for your input everyone.

robatwork

What make/model of boiler is it? Sounds like possibly a dud replacement PCB in a potterton.

b56c

robatwork wrote: »

What make/model of boiler is it? Sounds like possibly a dud replacement PCB in a potterton.

Potterton Suprima. Fan and PCB were replaced less than 2 weeks ago and all was well until Friday night.

a&akay

If it's a zone valve seized open, it will fire up your boiler as it's a switch in the boiler's control line that's always on. If you have a ZV, turn off the power to the boiler. If the lever on the valve has no resistance then it's likely seized on. A good dose of WD40 freed off mine and still OK 3 years later.

robatwork

b56c wrote: »

Potterton Suprima. Fan and PCB were replaced less than 2 weeks ago and all was well until Friday night.

Good guess huh? I had 2 of these and 3 replacement PCBs. It may well be a dud PCB again