In article ,
xena wrote:
This leaves nothing going to the 3 (Call for heat), which I guess is why
the thermostat isn't working!

I'm guessing that one of the following is the case: 1) the green/yellow
wire may actually be the 3 (Call for heat) 2) the green/yellow is
actually neutral, and the blue is the 3 (call for heat) but I need to
know how to check this without fusing the system! Also this would
leave no earth - is this likely?

Using an earth as a 'live' is all too common a bodge where plumbers get
involved in wiring. And some DIY types too, who should know better.

You've got a couple of options.

Do the job properly, and replace the cable with a Triple and Earth. The
earth is probably not needed, but you do need three properly insulated and
identified wires for this type of stat to operate correctly.

Wire the stat without the accelerator coil. Then you'll only need two
wires. But it won't be as accurate.

Replace the stat with a programmable one. These are battery operated and
only need two wires. They'll soon save their cost in reduced fuel bills.

Either way, it looks like you'll have to delve inside the connections at
the boiler end to sort out this bodged wiring.

--
*If all the world is a stage, where is the audience sitting?

Dave Plowman London SW
To e-mail, change noise into sound.