Wiring Programmable Thermostat

aaronasprey · May 16, 2020

Hi Guys.

I have a Worcester Greenstar 30i boiler and when we moved in we had our old Thermostat removed and a Nest installed, I have now removed the Nest ready to put the old thermostat back on (Honeywell CM907) but don't know where the wires are meant to go.

I think I've done the boiler bit right.

And just a note that the Black and Grey wires that come from the boiler (L and LR) are connected by a terminal block and the Black Wire is changed to a Brown Wire and the Grey stays as Grey.

I've attached some pictures, and what went into my nest.

I hope this post makes sense and hope someone can help as I can't get my heating to turn off lol!

oz-plumber · May 17, 2020

Terminals on CM-907 - A & B.
You've lost the screw out of B so pinch the one from the C terminal.

The thermostat is powered by batteries.
This thermostat only switches the signal wire back to the boiler - 240v or 24v compatible.

aaronasprey · May 17, 2020

oz-plumber said:
Terminals on CM-907 - A & B.
You've lost the screw out of B so pinch the one from the C terminal.

The thermostat is powered by batteries.
This thermostat only switches the signal wire back to the boiler - 240v or 24v compatible.

Which colour goes in which?

Does the boiler bit look right?
[automerge]1589705617[/automerge]

aaronasprey said:
Which colour goes in which?

Does the boiler bit look right?

I'm assuming the brown to A for Live and B must be the grey wire?

We also have a black wire coming through the wall that's pushed back out the way. And idea what that one would be for?

ShaunCorbs · May 17, 2020

Have you messed with the wiring as your pictures don’t make sense ?

oz-plumber · May 17, 2020

Colours don't matter. It only a switch.
Doesn't matter which live wire goes to each terminal

aaronasprey · May 17, 2020

ShaunCorbs said:
Have you messed with the wiring as your pictures don’t make sense ?

No its how it was wired up when we moved in, there is a fused socket to turn the boiler on and off and in the socket the L and LR wires are attached via terminal blocks, the grey one has a grey wire attached and the black has a brown which are what are fed to the thermostat in the picture you can see attached to the nest.

ShaunCorbs · May 17, 2020

aaronasprey said:
No its how it was wired up when we moved in, there is a fused socket to turn the boiler on and off and in the socket the L and LR wires are attached via terminal blocks, the grey one has a grey wire attached and the black has a brown which are what are fed to the thermostat in the picture you can see attached to the nest.

so the nest has never worked as it’s linked out hence the white wire

aaronasprey · May 17, 2020

The nest worked perfectly, I've put the white wire in since removing the nest as I remembered it being there, have I put it in the wrong place?

ShaunCorbs · May 17, 2020

Yes want moving over one terminal In the yellow block

nest end

brown to a
Grey to c

leave the boiler end black and grey where they are in the pic

aaronasprey · May 17, 2020

ShaunCorbs said:
Yes want moving over one terminal In the yellow block

nest end

brown to a
Grey to c

leave the boiler end black and grey where they are in the pic

Thanks mate I'll give it a try when I'm home 🤞
[automerge]1589739950[/automerge]

aaronasprey said:
Thanks mate I'll give it a try when I'm home 🤞

Cheers mate! Moved the white link over one on the yellow block and on the thermostat I tried A and C which didn't work.

Tried A and B as someone said above the connections for the honeywell are A and B and it is working! Finally have it working again.

Wiring Programmable Thermostat

aaronasprey

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oz-plumber

aaronasprey

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ShaunCorbs

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aaronasprey

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