Radiators heating when only hot water is selected

[phil16c]

I have just replaced the digtal control box for our system as the radiators were heating when only the hot water was selected........to find that it hasn't helped. The system is still doing the same thing

Any ideas why this is happening???

It is a Baxi Bermuda SP gas fire with back boiler and has been working fine until recently.

[Rulland]

Hi,
The controller will select either hot water,heating or both dependent on your system-It very much sounds to me like the 3 way valve that gives heating/hot water or both has stuck.
In other words even though your asking for one or the other via the controller the valve isnt doing what it should and is seized in a mid position.
Regards.
Richard

[willmac]

Hi,
Problem is related to motorised valve normally mounted in airing cupboard near pump.Check room stat is working before condemming 3port valve