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TheJay

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Can someone please tell me why there new thermostat isn't powering up? I copied the wiring from the old one, with the exception of the earth wire, which I have capped in a wago. Thank you.
[ElectriciansForums.net] Wiring a new smart thermostat
[ElectriciansForums.net] Wiring a new smart thermostat
[ElectriciansForums.net] Wiring a new smart thermostat
[ElectriciansForums.net] Wiring a new smart thermostat
[ElectriciansForums.net] Wiring a new smart thermostat
 
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Looks like you need a permanent live in terminal 4, a neutral in terminal 3 then 1&2 are the switch contacts for the heating system. Do you have a neutral at that stat? It looks like there may be but would need to test to be sure!
 
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your new stat requires a L to terminal 4 and neutral to terminal #3. the relay is 1& 2. depending on whether you want to switch 24V or 240V, you may not have enough conductors.
 
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Most stats are wired like that, it looks like you have enough cores there if the boiler control circuit is 230v! You will need to test to find which is live, neutral and switch live to fire the boiler, and make sure the control circuit is definitely 230v!
If you have a tester and know how to use it then I would proceed but with caution. If you don't then walk away now and call a pro before it potentially costs you an boiler PCB!
 
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TheJay said:
Can someone please tell me why there new thermostat isn't powering up? I copied the wiring from the old one, with the exception of the earth wire, which I have capped in a wago. Thank you.
Click to expand...
The swap is not just as simple as copying the existing wiring, the existing wiring looks like it is just a live and switched live and your new stat would need a neutral, copying the wiring it looks like you might have the live in the neutral connection
The live would also need a link to the switch contact
TheJay said:
There are four cables in coming through the wall on the thermostat end, how much help is that? How can I test?
Click to expand...
What test equipment do you have
Unless you are familiar with heating control wiring you may be better getting someone in
If you post your location there may be someone on here that is close to where you are
 
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You need to confirm that you have 230 / 240v across the brown and the black that has the wago fitted to it if it has then the brown should be connected to terminal 4 with a link connected to terminal 2, the black connects to terminal 3
 
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Yes, a multimeter can test for voltage on the right scale setting.

Wrong scale setting will

A word of caution however, that the spare wire may indeed be a neutral, or it may not be connected to anything at the other end.
Testing between your live and this mystery wire may give the impression the circuit is dead when it is not.

The other end of the cable may be in a wiring centre (joint box) rather than straight back to the boiler.
 
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littlespark said:
Yes, a multimeter can test for voltage on the right scale setting.

Wrong scale setting will

A word of caution however, that the spare wire may indeed be a neutral, or it may not be connected to anything at the other end.
Testing between your live and this mystery wire may give the impression the circuit is dead when it is not.

The other end of the cable may be in a wiring centre (joint box) rather than straight back to the boiler.
Click to expand...
Thank you. I was thinking of unscrewing the fused switch from the wall behind the boiler to see what wires are in there. Will all the wires be there or will some go straight to the fuse box?

Any recommended setting?
 
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TheJay said:
Thank you. I was thinking of unscrewing the fused switch from the wall behind the boiler to see what wires are in there. Will all the wires be there or will some go straight to the fuse box?

Any recommended setting?
Click to expand...
It would be unlikely to go to the switched spur, the thermostat could go to the heating controller, the wiring centre or direct to the boiler depends on what type of system you have
 
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To consolidate some of the above:
  • Terminal numbers on heating components are not standardised and there is no guarantee of correspondence or compatibility between one product and another. The schematic diagram and technical specs must be checked before use.
  • The original stat behaves like a switch. It does not require power to operate itself.
  • The smart stat also behaves like a switch but requires a continuous supply of 230V AC power for its electronics.
  • If the heating control circuit being switched operates at 230V then the existing cable with three cores plus earth may be adequate for the new stat.
  • The connections at the system wiring centre / boiler might need to be changed, so that the line feed is always live (rather than only being live when demanded by the programmer.) Whether this is possible will depend on the programmer and its wiring. The black core (at present unused) might need to be connected to neutral if it isn't already.
  • If the heating control circuit being switched operates at extra-low voltage, then the existing cable is not sufficient as there would be a need for two power cores and two control cores in addition to the earth.

Most of the information needed can be gleaned from studying the connections in the wiring centre or at least the other end of the stat cable which you need to find. Be prepared for it to be a spaghetti junction.
 
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