Replacing a thermostat (which wires where?)

dancelikeamonkey

Hi all, I want to replace an old wall mounted thermostat with a better quality one and was hoping someone could confirm my wiring plans before I go ahead.

This is the existing wiring:


And this is the new wiring diagram:


Am I correct that the blue wire goes to the "N", yellow goes to "A1" and red goes to "L"? There doesn't seem to be anywhere to attach the earth wire. Can that just have one of those blocks attached to it and left hanging loose?

Thanks in advance for your help.

Owain_Moneysaver

Could you show us the back of the old thermostat please? Or make/model.

Also make/model of new stat please.

Your existing thermostat is quite likely a mains switching one, your new thermostat says "volt free switching" and might not be suitable for mains use.

Probably the connections are:

Red - L
Blue - N
Strap L to A1 with a short piece of red insulated wire
Yellow to A2

Earth to a piece of 'choc block' terminal strip.

dancelikeamonkey

Hi, thanks for the quick reply. It's a Heatmiser PRT which said it was "230v" on the advert and says Volt free and 230VAC on the back of the unit. This is the new one:

This is the old one:

Looking at the manual, it also includes a digram for 240V switching:

The only difference I can see is that is that there seems to be a link between Live and A1, but I don't have a wire for that on the existing setup. Any idea?

gas4you

You will need a permanent live to go to the L of the new stat.

The one you have now, Red, will be switched from the programmer heating side.

So what you will need is to make the Red a permanent live and go to L on the new stat, Blue to N and Yellow to A2 with a link between L & A1.

I would respectfully suggest that if you are having to ask on here, you should get a sparky in or a heating engineer who does his own electrics.