Thermostat replacement

absolutebeginner · Apr 18, 2008

Hi,

I need to fit a replacement thermostat and I'll confess now... I'm not an electrician

The new thermostat has a neutral, live & switched live connection (please see attachment 'wire.jpg') for the wiring diagram.

The old thermostat has 4 wired connections: red, blue, yellow and green/yellow (please see attachment 'thermo.jpg' for the current thermostat)

What I need to know is which colour wires I need to connect to the new thermo plate as per the wiring diagram, and which wires I need to cover as they won't be used.

Any help gratefully received.

Thanks,

Andy

Sparky83 · Apr 18, 2008

Obviously you should really test them to be sure but when i worked for British Gas doing heating wiring installations normally the old systems were pretty much as you would expect - Red = live, Blue = Neutral, Green/yellow = CPC, Yellow = Switch live. I would imagine thats how they have been done.

rumrunner · Apr 18, 2008

hi.
you only need the neutral if the new stat has an excelerator heater,test the old one in the off position all wires disconnected and look for a resistance between two of the terminals,it should be the ones the red and blue are connected to,if so blue is the neutral ,you can check this by testing it to earth with the power on ,you should have nothing there,check the live the same way ,you should have a supply there ,. if the new stat only has 2 terminals just use live and switch wire ,if it has more make sure you dont get live and neutral accross the switch ,thats all you nead to look out for
hope this helps