Combi boiler stat not turning off heating

[Matt0029]

If the stat is not shutting off a combi boiler (analogue stat Honeywell) even though the stat is clicking when turned up above the room temperature. What are the likely causes. Unless it's never been wired right from the start up. Thanks.

 

[Matt0029]

Is a pro combi 100he.

 

[Matt0029]

I'll check the wiring etc the stat may not even be wired in. I guess.

 

[SJB060685]

Get your multimeter out and test to see if it's actually cutting the feed. Stats can still click despite having failed.

 

[Matt0029]

I just wondered if the stat can still be the fault if it is clicking when turned above and below room temperature? This is the stat?

 

[ShaunCorbs]

I could be stuck but haven’t seen many esp the 6360s need to test

 

[SJB060685]

As Shaun and I say get your multimeter out , simple enough mate.

 

[Deleted member 120897]

Check to make sure there’s not a link in the boiler end - either a 24v one, or linked the stat out.

 

[Matt0029]

Thanks yes I will check there is no link on the boiler.

 

[Matt0029]

As Shaun and I say get your multimeter out , simple enough mate.

Just going to download the instructions. But to test would I be looking to see if I get 240v between live and switch live?

 

[Deleted member 120897]

Without trying to be condescending, do you know how to test the stat?

 

[Deleted member 120897]

Just going to download the instructions. But to test would I be looking to see if I get 240v between live and switch live?

No mate, testing that you’ll probably get 120vac.

Test Neutral to live in (should be terminal 1) - 240vac
Test Neutral to Switch live - on demand - 240vac
Test Neutral to switch live - on satisfied (or stat at lowest) - should be 0 Vac

 

[Matt0029]

Thanks so testing neutral to live in. With a reading of 240vac between the ports. Shows I am getting 240vac to the stat.

 

[SJB060685]

If you test between live and switch live with the stat contacts closed, you would get a reading of 0 volts as there's no difference in potential between the two. As above you need to test between live and neutral and switch live and neutral.

 

[Matt0029]

Does testing neutral to switch live on demand with a reading of 240ac show that switch live is sending power to the boiler. Making a circuit when there is a call for heat?

 

[Deleted member 120897]

Thanks so testing neutral to live in. With a reading of 240vac between the ports. Shows I am getting 240vac to the stat.

Yes correct, but doesn’t prove it works properly, hence the additional testing and don’t forget the link.

 

[Deleted member 120897]

Does testing neutral to switch live on demand with a reading of 240ac show that switch live is sending power to the boiler. Making a circuit when there is a call for heat?

Yes

 

[ShaunCorbs]

Test terminal 3 to earth or neutral with stat off should be no voltage

If there is 240v check 1 if that’s got 240v aswell stats dead

 

[Matt0029]

Yes correct, but doesn’t prove it works properly, hence the additional testing and don’t forget the link.

Thanks yes I will make sure it's wired in to the boiler.

 

[Matt0029]

Thanks just trying to find the wiring diagram. I think Live is 1. Neutral 3. Switch live 2. ?

 

[Deleted member 120897]

Thanks just trying to find the wiring diagram. I think Live is 1. Neutral 3. Switch live 2. ?

No:

1 should be live in
3 should be switched
2 should be Neutral

Wiring diagram usually on the reverse of stat cover.

 

[Matt0029]

Thank you

 

[Matt0029]

No:

1 should be live in
3 should be switched
2 should be Neutral

Wiring diagram usually on the reverse of stat cover.

Thanks what Shaun said to test makes more sense now!

 

[Matt0029]

Test terminal 3 to earth or neutral with stat off should be no voltage

If there is 240v check 1 if that’s got 240v aswell stats dead

To to check I'm on the right track. Testing 3 (switched) to earth or neutral with the stat off. A reading of 0v. Shows that no volts are passing though the circuit i.e no call for heat at the boiler?

 

[ShaunCorbs]

Correct but I have seen them wired backwards eg 3 live 1 switch

 

[Deleted member 120897]

Correct but I have seen them wired backwards eg 3 live 1 switch

Yep, me too. Had one recently, set to a mid point, so in winter it’s fine. The way it was wired max was off and low (5 degrees) on the VRT30 was off.

 

[Matt0029]

Correct but I have seen them wired backwards eg 3 live 1 switch

Thank you!

 

[Matt0029]

Correct but I have seen them wired backwards eg 3 live 1 switch

Thanks of wired backwards at the stat it would still work? I know if get the wires wrong when swapping a boiler at the boiler side the stat comes on when turned down and off when turned up.

 

[Matt0029]

Test terminal 3 to earth or neutral with stat off should be no voltage

If there is 240v check 1 if that’s got 240v aswell stats dead

If that stat was dead, would that cause it not to knock off the heating. As is happening. Thanks

 

[ShaunCorbs]

Yes they can stick eg on all the time

 

[Matt0029]

Yes they can stick eg on all the time

Thanks even though it is making the clicking sound when going above/below cut of temperature?

 

[Deleted member 120897]

Thanks even though it is making the clicking sound when going above/below cut of temperature?

Yes. I’ve had some fail brand new out of the box.

 

[Matt0029]

The stats wires for some reason had been pulled out of the boiler not sure why. How old would be a pro combi he100 be around 10 years old?

 

[Matt0029]

Pro combi is a vokera?