Heating only when hot water required

[sumner]

A strange problem in the house I am currently living in. The radiators in the house only get hot when hot water is required (eg. when someone has had a shower and the cylinder is refilling.)

I believe the system is a gravity fed hot water system with pumped central heating. From research i have identified the main components of the system. We have an indirect hot water cylinder, a Grasslin 7 day control module, Landis & Gyr 3 port motorised valve and a pump. Oh, and of course a boiler in the kitchen.

I think what has happened is the motorised valve is somehow not working and sticking in AB (both hot water and heating) mode. Then when the hot water is required the pump turns on and pumps water around the radiators too. But then when the hot water is to temperature the system shuts off and the radiators cool down. I have manually activated the valve and then the heating runs... but only for a while.

Does it sound about right that the motorised vavle is the problem here or is it somewhere else in the control circuitry?

Thanks

 

[breezer]

I am not a plumber or heating engineer but i would say that yes the three way valve has gone.