My potterton prima F60 boiler keeps firing when programming unit indicates both hot water and central heating are off. The only way to stop it from heating is to switch it off at the main switch. As soon as switched on again it fires and heats both HW and CH. Can anyone help with this type of fault?

SG, March 2008

Although, it could be a motorized valve that is stuck, sending permanent live to the boiler...

T, March 2008

could be fault with programmer. somewhere its getting power demanding heat. my guess would be programmer as generally that is the supplier of electricity to the rest of the system.

iain, March 2008