3 Port Valve / Thermostat Fault

[andyman]

I seem to be having problems with the three port valve. When the hot water is calling for heat and the room stat has switched of the rads continue to get hot. When the cylinder stat is not calling for heat the room stat works fine. I have taken the top off the valve and it seems to work fine, any ideas.
Andyman

[sunbeam]

has it just started doing this?

how old is the valve?

sometimes the ball inside the valve gets swolen with age preventing it from motering over.

[andyman]

The valve was replaced last August, the problem started at Christmas. It got hot one day when we had a houseful, turned down the stat and we got hotter. Was ok then for a week or so and has given probs over the last week or so

[sunbeam]

so when the hot water is not calling for heat and the room stat is tuned down, the boiler turns off?

[andyman]

Correct. If i turn down the hot water stat or turn off hot water at the programmer the heating is fine.

[sunbeam]

I’d say It’s your valve, the ball isn’t blocking the central heating port off.

When it’s on heating only, the boiler the boiler room stat will turn off the boiler.