Heating not come on until UFH on

[trevorbayliss]

Our heating didn't come on this afternoon. Boiler working fine with HW. I thought it might be the Honeywell stat talking to the boiler issue. Pressure all ok as a combi.

Manually put the UFH on for the kitchen and boiler started up and UFH came on, but the rads also started to come on.

I think I have an issue with the motorised gate valves. got 2 of then on the flow and return.

Do these need replacing or can they be greased or cleaned to work again ?

 

[Exedon]

Sounds like a failed microswitch on radiator motorised valve.
If your competent with mains voltages and have a multimeter check if you have a live supply on orange wire from heating motorised valve when it's motored open.