Central heating shuts down unexpectedly

Martyn4526 · 20 Nov 2012

Over the past two weeks my central heating has developed an intermittent fault. For no apparent reason the heating cycle stops even though all the requirements to provide heat are satisfied i.e. power from room thermostat OK, timer in it’s timed ON cycle and all terminals from the timer live/non-live as they should be. But if I turn the main power switch off then on again the boiler starts up again as normal.
Has anyone any suggestions as to what the problem might be please.

narkeybee · 20 Nov 2012

Hi Martyn, the guys on here are a great help, but you will need to provide a lot more inof, type of boiler, is it combi, etc, my guess to your problem would be a 3 way port needs looking at ,but I am only going by having a similar problem.
the FAQ's are a good starting point.
NB

hazetimesfive · 20 Nov 2012

what is your day job martyn

Martyn4526 · 20 Nov 2012

Hi narkeybee thanks for your response. Mine is a 'Y' plan system with:-
Glow worm Micron Boiler 50FF
Honeywell T6060 room thermostat
Danfoss 4033 time programmer
Honeywell 4073a distribution valve
I am having the occasional problem with the 4073a valve which keeps the radiators hot all the time but I think that is down to the ball and I am waiting for a replacement ball and plate to be delivered but I think that is a separate problem since, under those circumstances, the boiler and pump keep working as they should. With the problem that I posted originally there is no response from the boiler at all which makes me think it could be a component on the boiler PCB breaking down.
When the boiler fails to light there are no error codes from the LEDs.

And Hazetimesfive, I am now retired but before that I was a freelance Automotive Design Engineer.

hazetimesfive · 20 Nov 2012

sounds fancy, wossat then

Armo74 · 20 Nov 2012

If your radiators are heating when only hot water is on then your valve is stuck in mid-position

Have you tried removing the actuator and try to manually move the valve spindle?

Martyn4526 · 20 Nov 2012

Hi Armo74.
The actuator moves OK when the power is switched on and off. I have removed the actuator and the spindle is free. As it only happens occasionally I suspect that the ball is not seating properly, that's why I will be fitting a replacement. Ive worked on that valve before in the past. I think I'll sort that one out OK eventually. It's the boiler problem that concerns me more at the moment, thanks.

hazetimesfive....I used to design vehicle supension, brakes and steering systems. I really enjoyed my work but I also enjoy every minute of being retired. Don't know how I found time to go to work.

hazetimesfive · 20 Nov 2012

i hope you aren't responsible for my dodgy van

Agile · 21 Nov 2012

Martyn4526 said:
Hi

hazetimesfive....I used to design vehicle supension, brakes and steering systems. I really enjoyed my work but I also enjoy every minute of being retired.

For which makes/models?

I might have some questions!

MANDATE · 21 Nov 2012

Martyn, there's a bit more to the actuator than you may think.

Beside moving the valve to the CH only position the boiler has to receive power and it can't do this via the cylinder stat which it does when there is a HW involvement.

If the valve is moving to CH only and boiler not firing it is most likely due to faulty micro switch No 2, if this is not making contact then there will be no power on the valves orange wire.
You may find when you replace the actuator head your problem will be resolved

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Central heating shuts down unexpectedly

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