Glow worm Combi Boiler CH won't turn off

[redbike]

Hi,

I have a Glow Worm Energysaver Combi Boiler providing HW and CH. Just recently, the boiler is ignoring the lack of demand from the CH room thermostat and is providing CH all the time the boiler is switched on. I suspected the 3-way valve which has a Honeywell actuator (VC8010 6 SEC, 6 VA Valve 24 VAC).

If I remove the actuator, I can physically push the shaft into the 3-way valve although it is really very stiff. The valve then slowly returns back to its original out position. When I put the actuator back on and watch it when I switch the boiler power on, the actuator lever is initially moved to the left but then returns to the center position. I can't physically move that grey actuator lever by hand without risk of snapping it and I'm assuming this is a bad thing?

I am happy that the wirless CH room thermostat is correctly working. When I trigger the CH to come on, or go off, via the room unit, the receiver unit turns green but the 3-way valve lever stays in the central position whether I'm turning the CH off or on. If I turn the wireless receiver unit off, it also makes no difference to the 3-way valve lever/position.

I know the actuator can physically move the 3-way valve all the way to the left but it then stays in the mid-position which I'm assuming is for CH.

Can someone give me some advice on where the problem lies please?

Thanks

David

 

[picasso]

Could be the frost protection (faulty thermistor) coming on but you really need someone to check it out, doubt you will sort it out over the tinternet.

 

[redbike]

Thanks for that. I was hoping someone might have ruled out the 3 way valve and actuator as potential causes, based on my description of the problem.
Is it possible to narrow it down to a faulty thermistor or could it still be the valve and/or actuator?