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Replacing dial thermostat with digital programmable one - can I do this myself?

(5 Posts)
TheGMF Sun 23-Nov-14 14:32:26

I want to replace my old analogue thermostat with my shiny new Honeywell CM907. I thought it would a be a simple job that I could do myself but now I'm not so sure. I have three wires in the old thermostat and I only need two in the new one, as the earth (striped) is not needed. I understand the earth wire needs to be 'made safe' but I'm not sure how to do this.

Should I even be attempting this myself or is it a job for an electrician?


BaffledSomeMore Sun 23-Nov-14 16:02:34

DH has done a few. But he can't remember them having earths.
I think if you get the green and yellow insulating tape and wrap it securely then that's ok.

PigletJohn Sun 23-Nov-14 16:31:03

don't use tape, as it unravels in time. It is vitally important that the earthwire cannot touch any of the other terminals. it must not go into terminal A, B or C.

In the backbox, you may see a parking terminal with a screw to hold the earth wire. If not, you can either buy a plastic "chocolate block" connector and cut off one of the blocks (you will understand this when you see it) and secure the wire inside that, or slide G&Y sheathing over the wire so that it is longer than the exposed end, then bend the wire back on itself like a hairpin.

You must turn off the electrical supply to the boiler and test for dead, because the terminals in your picture carry mains voltage.

PigletJohn Sun 23-Nov-14 16:33:34


G&Y sheathing but your local hardware shop will sell you a little packet of half a metre or so for the same price.

BaffledSomeMore Sun 23-Nov-14 18:37:08

I stand corrected. DH did say he'd use a choc block but I wasn't sure I could correctly get it across what that was on my phone.

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