Last night my radiators got scorching hot. When I turned the heating off from the control I could still hear the boiler going. In the end I had to turn it off from the switch. The water from the tap was not very hot though. Any idea what is wrong?

Jacqui, March 2010

Thanks for your help. I've now signed up for insurance with Directline.

Jacqui, March 2010

Call in a gas safe engineer - avoid british gas - have it fixed and serviced at the same time - I would guess above £200

Peccavi, March 2010

Thanks for the input. The boiler is a conventional boiler. Is it likely to be expensive to repair this or would a normal service be enough?

Jacqui, March 2010

I would assume a jammed valve too.

Stuck in the position to send water around the radiators a request from the programmer for hot water fires up the boiler and sends the heated water to the wrong place - the radiators - and not to the hot water tank.

Normal control to turn the boiler off should come from the thermostat on the outside of the hot water tank but the hot water tank is not getting warmed up - the tank stat remains closed, the boiler continues to burn and heated water continues to be sent to the rads which get very hot.

Very unlikely to be the timer/programmer or a wiring fault.

Peccavi, March 2010

Assuming this is not a combi boiler then i would guess that the three port valve has jammed in the heating position but not sure where it gets it power from if the programmer is not calling. Could just be a faulty programmer or incorrectly wired. Try turning down the room stat if you have one if this stops the boiler then i would say programmer fault. However there are various other scenarios it could be.

Stewiesnake, March 2010