I have a glow worm ultimate boiler. The boiler is 12 years old and appears to be functioning perfectly. The problem i'm experiencing with the system is having changed 3 way valve. Heating and hot water is fine, but when calling hot water only the heating still comes on but radiators are very hot. The water is ok. could this be a problem caused by the boiler or is it with the external system wiring?

Leila, April 2013

A boiler is stupid - all it can do is heat water - it does not know what use will be made of the hot water - that is decided by the 3 way valve.

Your 3 way valve has just been changed.

I suspect a connection between the work done to change the valve and the fault condition you now notice.

Peccavi, April 2013