No central heating unless hot water system is heating

[pjpaul]

After some problems with a 3 way valve I have now discovered that the central heating only works (by this I mean the radiators get hot) when there is demand for hot water. To be exact the boiler only starts when the hot water is switched on and requires heating.
Any suggestions for solving this problem would be gratefully received.

 

[Agile]

Replace the three way valve or connect it correctly?

Tony

 

[swbjackson]

Sounds like a dodgy micro switch on the 3 port or a wiring fault. As agile suggests check wiring and/or swap valve. Depending on manufacturer/model you may be able to swap the head only to save draining down.

Mike

 

[pjpaul]

Thanks for advice. Also some further info. The system has a siemens rwb9 controller/programmer and a siemens ma-v322c 3 way valve. If the 3 way valve is manually opened, when only central heating timer is on, the radiators don't get hot. The boiler will only start up when hot water system is started.
Does this still suggest a valve problem?

 

[Agile]

Yes, valve or wiring!

 

[pjpaul]

ok thanks for advice. Will let you know the result when i get round to fixing it! Bit busy at the moment and as the house is warm its a low priority now i know what to do