No Control Over Central Heating

[logan 1]

Sat here watching telly and the missus says its ruddy hot in here, so I check the room stat which is making all the right noises, its clicking off but the boiler is still belting it out.
Next I turn off the heating and hot water at the programmer but the boiler is still active.
Finally I turn off at the main isolating switch which has the desired effect.
I'm no expert when it comes to electrics but I recon something weird is going on when neither the programmer or the room stat fails to stop the power supply
Any ideas guys

 

[Riley]

something is obviously stuck making a switch to turn the boiler on. Likely be a two or three port valve in your airing cupboard

 

[logan 1]

Thanks for your reply Riley but the way I see it no components should be active if the central heating and hot water are both programmed OFF.

 

[Riley]

A heating system is just a series of switches if a switch is stuck on further down the line it can still give the impression to the system that prior switches are made too

 

[Vee]

You’ve asked the question. Listen to the experienced engineer who gives you a correct reply. Heating works in mysterious ways.

 

[jtsplumbing]

Also possible that the programmer is faulty and sending power to system.

 

[Vee]

As he says a series of switches.

 

[Murdoch]

Contributing as a spark - as others have said it could be a switch in the heating set up, a faulty programmer or a DIY self inflicted issue

 

[logan 1]

The system was installed by professionals Murdoch so what makes you say it could be a DIY self inflicted issue?

 

[Murdoch]

The system was installed by professionals Murdoch so what makes you say it could be a DIY self inflicted issue?

Picture hook nail through cable - connecting PL to SL - seen it happen!

 

[Frog67]

It its a Y plan system even with the programmer off there's still power going to the wiring center. Sounds to me like the micro switch in the 3 port valve could be stuck in the closed position.
A knowledge of electrics and a mulimeter is the best bet

 

[Harvest Fields]

Sat here watching telly and the missus says its ruddy hot in here, so I check the room stat which is making all the right noises, its clicking off but the boiler is still belting it out.
Next I turn off the heating and hot water at the programmer but the boiler is still active.
Finally I turn off at the main isolating switch which has the desired effect.
I'm no expert when it comes to electrics but I recon something weird is going on when neither the programmer or the room stat fails to stop the power supply
Any ideas guys

When you. Changed the zone valve in may last year did you change just the hot water valve or the heating one as well?

 

[logan 1]

Yes you're right Frog I've got a sparks checking things out for me tomorrow.
I'm leaning more towards a zone valve being the culprit now but we shall see.

 

[logan 1]

Okay so I've had a sparks check out the programmer and room stat which are both okay which points to the motorized valve playing up.
I don't know if he freed the valve up by operating it manually but the system is now working fine.
However I think I'll buy a new valve as a standby.
I need to replace a V4073A 1002 the last numeral is either a 5 or S can't make it out.
Can this be replaced with a V4073A 1039 which seems to be the currant model but I'm not sure if the wiring is compatible.
Your advise would be appreciated, oh, and before you chirp in Murdoch it wont be me fitting it.

 

[Vee]

That should be fine. Even the older Honeywell would be a five wire. And yes he has probably freed the spindle whilst diagnosing.

 

[logan 1]

Thanks for your help Vee its surprising how out of touch you get when you've been off your tools for a few years
I've still got tallow, plumbers black, wiping cloth, putty rag and string in by tool kit, I am joking of course, but I remember those days like they were yesterday.
However I also remember how some sparks used to get confused when they discovered they had too many or not enough wires when changing a 3 port valve.
Thanks again for your help.