Central heating electrical issue

[HughF]

Ok, I've narrowed the fault down to this:

Something in the airing cupboard/ wiring center is backfeeding the room stat via the switched live (new Honeywell stat, neon is on permanently) and is also keeping the call for heat to the boiler active.

It's not a short in the 3 core that's in the wall to the room stat, I've buzzed that out.

Should I suspect the 3 way valve motor?

 

[brightspark]

frost stat in system ??if the live and switchwire in thermostat are parted does the boiler still fire up and heating come on

 

[Kayos]

3 port valve, the capacitor that holds it in mid position can fail and cause all kinds of issues

I’ve had 315v at the room stat

 

[HughF]

frost stat in system ??if the live and switchwire in thermostat are parted does the boiler still fire up and heating come on

No frost stat..... Disconnect the switched live out from the stat, boiler still fires

 

[HughF]

3 port valve, the capacitor that holds it in mid position can fail and cause all kinds of issues

I’ve had 315v at the room stat

Cheers, I'll check this out.

 

[brightspark]

its not calling on the water side is it

 

[HughF]

its not calling on the water side is it

Programmer water side is set to off pretty much all year round, we use the immersion come summer time.

 

[HughF]

It's not a major issue because:

This house needs a lot of heat input anyway

I can turn the loop temperature down on the old baxi bermuda

 

[voipio]

Suspect the three way valve, but not necessarily the motor. I came across one once, where the plasterer had dropped a dollop of their finest on top of the valve cover, preventing the lever from moving. Clearing the plaster away solved the problem.

The valve itself may have got stuck. Removing the valve cover and giving the valve spindle a twist will test this.

Less likely, the switch contacts have welded together.

 

[Kayos]

3 port valves rest in hot water so don’t need electricity to just heat the cylinder

Very common is for them to seize up in summer so they don’t work once people want the rads on, or they stick in mud position and the rads heat up with the water

Most of the calls are people thinking its the programmer, to be fair I had a run on them last year and swapped 2, compared to about 22 3 port valves

 

[HughF]

Trying to figure out what could cause the 3 way valve to be back feeding the room stat and also keeping the boiler on:



From looking at that, it would be an internal short between grey and white, but from memory, my programmer doesn't have a hot-water off output connected.

 

[Kayos]

Trying to figure out what could cause the 3 way valve to be back feeding the room stat and also keeping the boiler on:

View attachment 158284

From looking at that, it would be an internal short between grey and white, but from memory, my programmer doesn't have a hot-water off output connected.

Trust me, it doesn’t make sense but 99% of the time it’s the valve

If you don’t have hw off then you can only have hw or hw and ch together but not just ch

It may have a hw off from the cylinder stat

 

[HughF]

Trust me, it doesn’t make sense but 99% of the time it’s the valve

If you don’t have hw off then you can only have hw or hw and ch together but not just ch

It may have a hw off from the cylinder stat

Yep, CH gives CH & HW

I'll buy a valve from Screwfix, guess I need to drain the system down and refill?

 

[Kayos]

Yep, CH gives CH & HW

I'll buy a valve from Screwfix, guess I need to drain the system down and refill?

You may have valves to isolate including the pump ones, but if it’s upstairs I usually just empty the top of the system

I have had issues with the Flomasta valves in the past, the newer ones seem better or Danfoss, I don’t think Honeywell are worth the premium these days

You should be able to reuse the old nuts and olives, I just smear a bit of paste on them, check first as most valves have a fine thread but not all

 

[HughF]

You may have valves to isolate including the pump ones, but if it’s upstairs I usually just empty the top of the system

I have had issues with the Flomasta valves in the past, the newer ones seem better or Danfoss, I don’t think Honeywell are worth the premium these days

You should be able to reuse the old nuts and olives, I just smear a bit of paste on them, check first as most valves have a fine thread but not all

Pump has isolators, 3 way doesn't..... Cheers for the advice.

 

[HughF]

Three port actuator was completely shot and was all rattling, new one fitted....

Then the tank stat satisfied connection was faulty duff so back to Screwfix for a new tank stat.

Everything is now fully operational. When tank stat cuts out the valve switches to ch only. Thanks for everyone's help.