central heating Help and information on all topics relating to your central heating, air conditioning and ventilation issues.

[johnemi]

when I programme the controller for hot water only, the radiators heat up at the same time.This happens even if the room stat is not calling for heat and even if the setting for CH is in the off position on the controller.
Could this be a faulty control box or faulty motorised valve.Both are about 15 years old.Is replacing either a D.I.Y.proposition

[GeckoGas]

Sounds like your motorised valve....

It's a DIY job if you are competant at electrics (5 wires), plumbing (Draining & filling a system) and the valve is reasonably accessible.