Baxi solo control wiring

[andrewoit]

Hi, moved in this summer but now winter has hit we are having trouble with the DHW/CH controls, Ive done a small amount of fault finding,
HW stat does call/power off at temp
Remote CH stat bats changed and does call/power off signal at temp.
The CH stat has a timer built in plus we have a separate HW timer, looking at the wiring (2010 Baxi solo boiler). My madness stats as even if the CH is calling for heat, if the DHW is on timed or off the boiler wont do heat. boiler is only feed by perm N, earth and Switched live from DHW timer, SL from CH looks to link straight to 3 port M valve. any advise welcome ie should I link the Sl from the CH with the Sl from the DHw timer-boiler?

 

[stem]

As I understand it when the radiators are set to be 'on' they don't heat up unless the DHW is 'on' and calling for heat at the same time.

If so, it most likely is the 3 port valve that has failed. Inside the valve is a small microswitch that switches the boiler 'on' when the central heating only is required. When DHW is required, the boiler is controlled by the hot water cylinder thermostat so will operate OK. This is a very common problem.

If you are able to use a multimeter, you can carry out some tests to see, but you need to be fairly skilled to do it. Depending on the type of valve you have, you may be able to change the actuator which contains a small motor and said microswitch.

If it has been working OK then the wiring will be fine. If you make the link you suggest, then when DHW is 'on' the heating will come on also and vice versa.