Hi all, Really struggling wiring up some thermostats. I have a combi boiler. The thermostat I removed was wired in as below; A grey wire and exposed earth wire weren't connected. Here's the instructions. Now I tried connecting as the instructions say, the thermostat powers on etc but it does not kick the central heating on! Found a user who connected as my picture below, doing it that way for me provides no power to the thermostat and it doesn't turn on or do anything! Can anyone advise? What am I doing wrong? The only way the unit powers up is with brown in 1 and black in 2.
You’ll definitely need 3 wires maybe 4. It depends on what voltage the boiler is switching. Your grey wire may also not be connected at the other end. You need to trace this cable and check it.
You are assuming that brown is live, grey is neutral and black is trigger for the boiler and that the boiler is 240v switching. How have you made sure you know that? *Edit - Mike's on the case ignore me.
How can I establish this for sure? I have a voltmeter. I'm just about to access the boiler wires to confirm hopefully.
Boiler side first to see where they all go and if it's 240v switching, then work from there. You can now, however, measure the voltage between black and brown with the wires out of the unit but still trace where everything is going. I'll leave this for Mike to pick up on.
If you can trace the cable then it can be installed just by identifying the wires. It’s probably just a matter of connecting the extra wire to a neutral but needs confirmed.
The white cable that enters the boiler and the grey cable from the stat. Do these cables meet at a switch next to the boiler?
The grey and black on the boiler are connected to the cable at your stat somewhere. You need to find this.
This earlier picture looked correct. If you disconnect the brown and black one of the wires should be 230v. This would be the live.
We know that the brown and black are common and switched live. They turned the boiler on and off with the old stat. What we don’t know is what one was the common. With the old stat it didn’t matter what wire was in what terminal but it does now. It should be simple to wire from what you’ve exposed. You only need the 3 wires then a link from live-1 on the new stat.
I'm officially stuck then. Only ever get any power if black and brown are in 3+4. Tried to measure volatge but not sure my multimeter is correct. Brown is constant 24.5v, black is 0 and grey is constantly going up or down. Worth noting I've got 2 stats an both give same results.