Help - Boiler cuts out when I run a bath?

[trevvyj]

I have a combi boiler.
When I run a Bath the boiler cust out!
The heating works fine.
If i run the bath hot tap very slow it is ok but if i run the bath tap faster the whole boiler just cuts off and i need to reset it.
Can anyone advise the cause of this please?

[gucciman]

when you say cuts out do you mean when you run a bath the water keeps going hot, cold, hot cold or is the boiler actually going to lock-out so you have to re-set the boiler either by the re-set button, turning the power on or off or pressing a over-heat stat reset button ??

[trevvyj]

The whole boler just switches off. I have to turn it off and on again.
The Central heating is fine - the shower seems fine as do the kitchen taps - the problem only seems to be when i run a bath. An engineer fitted a new thermostat but it made no difference - he said he would be back next week!!!
When i turn the water temp knob on the boiler down half way i can run a bath very very slowly and boiler stays on - but if i run the bath normally or the temp knob is at full the boiler just shuts down.

[Steviegb]

Which make and model is it because different combi`s work in different ways

[gucciman]

can only think that it has to be an overheating problem then as the burner runs at a higher pressure when heating the water rather than the radiators. is probably ok when the kitchen or hand basin tap is used because they only tend to be run for a short while compared to a bath.
would be useful to know what make and model of boiler it is as you say the thermostats been changed but most of the modern combi's have the thermostat as part of the circuit board.
could also still try changing the hot water thermister, apart from that could be poor water circulation caused by either the pump not running as it should or the heat exchangers being sludged up.

[Velvetee]

Mine was doing that, but I can't remember what the engineer said the problem was, but of course, it wasn't covered by the British Gas insurance.

[Ice.Maiden]

My parents had similar trouble not so long ago, and it DID turn out to be a case of over-heating. Hope you soon get it fixed V, or you'll be lugging the kettle over to your shower!

[trevvyj]

the boiler is a Britony Combi SE.
I have found out that it was the Thermister? not the thermostat that the engineer replaced. Apparently he is coming back to flush the boiler? to de-sludge it ?
Is this likely to be the cause? I have found now that if i turn the mains stopcock down so water runs rather slow and turn the temp adj knob on the boiler down half way then it doesnt cut off when the water runs - only thing is that the water pressure throughout is rubbish! Also after running the hot water for a few minutes - when i turn the tap off I get a bit of heat through my radiators - which arent even on? Heeeelp.