Boiler cutting out

Patrick2010

Recently our boiler has started cutting out after 30 minutes or so. I'm suspecting its because the water isn't moving around the system but I haven't been able to check the pump is working ok. I've tried opening the centre screw in the pump so I can see if the pump is moving but the water just keeps coming out so I can only open the screw a turn or so. Any ideas what can the problem be?
Should mention that our living room rad does heat up quite well until the boiler cuts out so I know the water is getting that far.
Pump and valves were replaced about 6 months ago.

sullzz

Oil or gas ? Is the boiler inside or outside , do you have to reset the boiler when it cuts out?

JohnnieK

Wouldn't suspect the pump if it cut's out after 30mins. If there was no circulation it would cut out fairly lively.

As Sullzz said a few more details are needed. Make and model of boiler oil or gas and so on.

Patrick2010

Thanks guys, its a Potterton Netaheat gas boiler. Once the boiler trips I can reset it once it cools down for a while. Just noticed one of the taps in the hot press seems to be dripping slightly, not sure what its controlling.
It was put on when we had an extension added and the boiler was moved to the kitchen. I opened up the valves in the hot press but maybe that was wrong?
Also noticed the pressure in the hot water tap upstairs is low, downstairs hot taps are ok.
I know I should get a plumber but I've spent 500 this winter between 2 plumbers, one charged 300 to fix a leak coming from the pump area by replacing the pump, then paid another 200 to another who replaced the pump valves and pipes around the pump.

sullzz

Patrick2010 wrote: »

Thanks guys, its a Potterton Netaheat gas boiler. Once the boiler trips I can reset it once it cools down for a while. Just noticed one of the taps in the hot press seems to be dripping slightly, not sure what its controlling.
It was put on when we had an extension added and the boiler was moved to the kitchen. I opened up the valves in the hot press but maybe that was wrong?
Also noticed the pressure in the hot water tap upstairs is low, downstairs hot taps are ok.
I know I should get a plumber but I've spent 500 this winter between 2 plumbers, one charged 300 to fix a leak coming from the pump area by replacing the pump, then paid another 200 to another who replaced the pump valves and pipes around the pump.

I could be wrong but i think this boiler has a pump over run thermostat , this could be faulty , one of the other lads might correct me on this , but i think it has one .either way its not something you can investigate , you need to get an rig in to have a look

DGOBS

Could be pump overrun, but would more tend to cut out on overheat once the boiler is finished it's use for the evening and turned off, residual heat then causing the overheat to trip (pump should keep running if under demand so shouldn't overheat in this manner)
Possibly the boiler stat is faulty, do the rads get very hot before it cuts out?

Bottom line, you really need to have a qualified person out to have a look

cram1971

I had the exact same problem on a Vokera gas boiler a few times it has always been a faulty thermisitor which is a sensor on the flow and return heating pipes inside the boiler. I get a error code on the LED panel on the front of the boiler. In my case is it a 15 euro fix

DGOBS

A netaheat does not have a thermistor it uses liquid expansion valves, so less of the gas DIY might be a good idea, after all it is illegal!

cram1971

DGOBS wrote: »

A netaheat does not have a thermistor it uses liquid expansion valves, so less of the gas DIY might be a good idea, after all it is illegal!

With all due respect who the heck are you to tell me "less of the gas DIY might be a good idea" I was simply offering my experience to the OP I was not giving instructions on how to repair their boiler. Secondly if one of the valves has become faulty it could possibly cause the same probably. I absolutely agree get a qualified professional in to repair the boiler.

Sorry for bringing the thread OT

OP I hope you got sorted with this weather.

DGOBS

You said you changed the thermistor in your boiler, DIY? Hence the comment

As a gas installer, we are constantly attempting to give advise here, but at the same time discourage the 'have a go hero' as we have seen and know what can happen.

No offence intended. But it is illegal to tamper with these appliances, and for good reason.

Patrick2010

DGOBS wrote: »

Could be pump overrun, but would more tend to cut out on overheat once the boiler is finished it's use for the evening and turned off, residual heat then causing the overheat to trip (pump should keep running if under demand so shouldn't overheat in this manner)
Possibly the boiler stat is faulty, do the rads get very hot before it cuts out?

Bottom line, you really need to have a qualified person out to have a look

Rads aren't heating at all. The pipe coming from the pump is cold while the pipe leading from the boiler is quite hot but only at the boiler it gets noticeably cooler further along.

DGOBS

Check pump, water pressure and isolation valves for DHW & CH arent all closed

Patrick2010

Pump is working ok, valves either side of it are both open, are they the valves you mean?. Both pump and valves were replaced only 6 months ago. Theres a few taps in the hot press I was turning but they're all open now, is it possible theres an air lock somewhere?. I've bled all the rads. Curious thing is the bathroom hot water tap has quite low pressure but the other hot taps downstairs are fine.