Changing ch room thermostat

[shamilt1]

On your old wiring, the blue goes on to N = Neutral (you need that)
The red goes on L (live) and you need a bit of wire to link L to A1 too
Yellow goes to A2
That's it.

Okay. I've wired it up as you stated but I'm getting nothing but a blank display? Any ideas?

 

[EFLImpudence]

Perhaps, because it was not required before, the Blue is not connected to Neutral at the other end.

 

[shamilt1]

Perhaps, because it was not required before, the Blue is not connected to Neutral at the other end.

I'll give it a go. Hope I don't break the thing wiring it up wrong!

 

[Taylortwocities]

It should't have broken it. But you'll ned to open up the heating wiring centre and find the other end of the wire to the thermostat.
A picture of what is in there will be useful.

 

[shamilt1]

It should't have broken it. But you'll ned to open up the heating wiring centre and find the other end of the wire to the thermostat.
A picture of what is in there will be useful.

'Heating wiring centre'? I will if I know what that is! I have a combi boiler and there is a switch next to it that turns its power off. Do you mean look in there? Also, seeing as I wired it the way you suggested and it didn't work, do you think I could have a faulty unit? Cheers, Steve.

 

[Echo the husky]

The cable could well be wired back to the boiler wall switch if it is a combi boiler. Ensure you switch the supply to that switch off at the fuse box/consumer unit before opening the switch. The thermostat is likely to be fine, especially as you have wired it correctly (I frequently fit these). As the blue wire was taped up in your old thermostat it will likely be taped up in the same way at the other end of the cable.

If you do find the blue wire taped up in behind the switch, it simply needs connecting to the neutral out/load terminal of the switch.

 

[Iggifer]

The cable could well be wired back to the boiler wall switch if it is a combi boiler. Ensure you switch the supply to that switch off at the fuse box/consumer unit before opening the switch. The thermostat is likely to be fine, especially as you have wired it correctly (I frequently fit these). As the blue wire was taped up in your old thermostat it will likely be taped up in the same way at the other end of the cable.

If you do find the blue wire taped up in behind the switch, it simply needs connecting to the neutral out/load terminal of the switch.

Surely a thermostat cable actually goes all the way back to the boiler? Not to the supply for the boiler.

It's more likely that he will need to remove the cover for wiring portion of the boiler, and will find the blue taped up in there.

 

[EFLImpudence]

Yes, boiler or wiring centre, it's not likely to go to the switch.

 

[shamilt1]

Okay. I opened up the switch. The yellow and red join up to two black wires that go to the boiler. The blue connects to the blue that goes to the boiler also. So I need to follow the white cable back to the boiler now and look for a disconnected blue wire....is that correct?

 

[EFLImpudence]

Oops.

 

[Echo the husky]

Oops.

XD I've wired many central heating systems in the last 12 years c:

Looking at the photo the thermostat cables blue wire is already wired as it should be.

There are 2 possibilities that I can think of right now.
1. The 2 black cables could need swapping. One black could be live from the boiler the other switched live back from the thermostat.

Do you have a multimeter that can prove one of the black wires is actually live at 240V AC? If 1 is I would expect it to be the one joined to the yellow wire. If that is the case, swap the 2 black wires over and all should be well.

If not, can you supply a photo of the terminals where the 5 core flex connects to the boiler?

2. The 2 black wires are not mains controls at all and are extra low voltage and are shorted together to switch on the boiler.

If this is the case you will likely need a different thermostat, most likely a battery powered version of the one you have.

Echo

 

[Taylortwocities]

Good thinking Freddo. I'll bet too that the black wires need to be swopped over.

Or swop the red and yellow wires at the thermostat end!

If that does not work, then some work with a multimeter is needed!

 

[shamilt1]

Good thinking Freddo. I'll bet too that the black wires need to be swopped over.

Or swop the red and yellow wires at the thermostat end!

If that does not work, then some work with a multimeter is needed!

I will give this a go. If it doesn't work then I think I will send it back and get a different one- one that doesn't need the Neutral wire connecting to it. If that's the case I will be back on for suggestions of a replacement that is also a modern looking bit of kit!

 

[shamilt1]

Good thinking Freddo. I'll bet too that the black wires need to be swopped over.

Or swop the red and yellow wires at the thermostat end!

If that does not work, then some work with a multimeter is needed!

Okay. I tried this and still nothing. I'm starting to get a little out of my depth now we are talking multimeters and checking terminals at the boiler. I think at this stage the best solution for me is to send the thermostat back ( good old Amazon) and get a different one- one that doesn't require the neutral wire. I want one that looks nice and modern like the one I'm sending back. Any suggestions guys?

 

[shamilt1]

Okay, I've seen this one- a Salus ST620. Looks pretty modern and has a two wire connection.
Hopefully this will be a bit more straightforward!