Boiler not switching off when water and heating called

[rcssmb]

Hi
When I run the boiler to do heating and water at the same time it sometimes runs forever and to shut it down I need to switch it off at the fuse.

When used on their own the heating comes on and off when told to by the timer and thermostat and the water comes on and off when told to by the timer and tank thermostat.

It does do the water and heating at the same time as the valve switches to mid position. So everything work OK apart from it not shutting down. Even this fault is not consistent - ie it only does it sometimes. Every time I have had BG out it has behaved itself!

My question is really about which component is at fault - I am looking at getting a Heatmiser Neo thermostat and hot water controller but if its the boiler causing the problem I would rather fix it first.

Thanks

Boiler Potterton suprima 60
Contoller Potterton EP2002
Thermostat Potterton PRT100

 

[ianmcd]

Most likely your mid position valve that is faulty, you may be able to just change the actuator head depending on the make and model.

 

[rcssmb]

Thanks Ian

Even though when I switch water and heating both to off at the controller it still carries on until I switch off at fuse?

I am happy to do some diagnosis with a multimeter if only I knew where to measure...

 

[rcssmb]

Any tests I could do in the boiler wiring?

Untitled

• rcssmb
• 30 Mar 2014
• 1

Thanks!

 

[ianmcd]

its quite easy to tell if it is your external controls causing the fault, when you have turned off all the external controls see if there is still 240 v AC being supplied to the switched live at the boiler if there is then it is a matter of tracing it back to see where it is being supplied from, I have seen ep200 programmers sticking but an easy test of this is just remove the front off the programmer when your boiler is on without any demand, there are fault finding guides in the FAQs for testing your mid position valve

 

[ianmcd]

just seen your pic, the switched live is the black wire next to the blue

 

[rcssmb]

That is brilliant I will try and get it to misbehave and check - as it is intermittent it may be some time.

Thanks again