Please help! Boiler ch pump always on!

[123]

No because the burner comes on and the utility room where it is sited is tropical to say the least

So the pump and the burner are running?

Looks to me like you have a faulty zone valve as per post #6

 

[ruston]

If it is firing the boiler too , and it is only the utility room that is hot, do you have a hidden frost stat somewhere set wrong?

 

[Leesparkykent]

Do you have a manifold for the under floor heating with a separate pump?

 

[LeeD]

What cables do you have in the programmer. Where do they go? (Joint in airing cupboard most likely). Are you an electrician of any sort?

From the fuse spur it goes into a connector block, from here you have a link for the programmer live, you have the underfloor heating feed and a black labelled 1 to the boiler. In the second connector block there is a grey to the underfloor heating and black labelled 6 to the boiler. In the third connector block black labelled 5 to the boiler and a grey from a 3 core +cpc labelled SBJ. Neutrals all linked in a block too and lastly one twin and earth dead ended in there.

Im an electrician but always worked on streetlighting contracts as a cable jointer so this is not my forte!

There isn't an airing cupboard as it's a combi. Could it possibly be a faulty stat upstairs?

 

[LeeD]

Some boilers are known for having faulty overrun timers and make the pump run 24/7 !

it doesn't run 24/7 just on and off every few minutes or so and I can't even turn the heating off at the switch on the boiler

 

[LeeD]

Do you have a manifold for the under floor heating with a separate pump?

Yes and yes

 

[Leesparkykent]

If the boiler is occasionally firing briefly when the programmer is switched off and so is the thermostat for the underfloor heating I would say the boilers integral frost thermostat is playing up but without testing and not seeing it it's difficult to say obviously.