HIVE - UT1 programmer and ES1 Thermostat wiring issues

I have a British Gas installed Worcester 28i boiler with a UT1 programmer and ES1 Thermostat and trying to replace the UT1 and ES1 with Hive.

ES1
The wiring for the ES1 is 4 wires Brown, Blue, Black and Green/Yellow. the black and yellow/green wires have red sleeves near the end. (All 4 wires connect directly to the programmer.)
Thermostat backplate




UT1
The wiring for UT1 is N-Blue, L- Brown plus loop to 1 , and Green/Yellow, only this wire has a red sleeve near the end and is live.
Programmer backplate - The white taped wires shown are the 4 from the thermostat


If I wire the back panel according to the wiring for Hive and remove the thermostat wiring then the boiler wont work. I can only get it to work if the thermostat is in the on position. My problem is the Heating On wire. I know that when the thermostat is on the black wire is connecting to the programmer and then notifying the boiler to switch on but cant see a switch wire connected to the programmer if I remove the thermostat


My problem is that if I remove the thermostat then I have no CH switch wire.
Im loath to connect the green/yellow wire as the switch wire for fear of damaging the main board on the boiler but that seems to be the only option.












Many thanks for taking time to read this convoluted post

I am afraid what you have here is a bodge! Someone has run out of cores and used the earth (g/y) as a switch wire. Earths appear to have been dispensed with. Although I could tell you which wires to connect together, I suggest you get a local spark to pop in and check the install to ensure it’s safe.

Cheers Andy, it was installed by a British Gas engineer in 2004. I strongly suspect the earth wire is being used as a switch as its live when there's power to the boiler. Ill get a mate whos an electrician to check it.
If the y/g is the switch wire then all I need to do is remove the 4 wires from the thermostat and put the y/g switch wire into No 3 but like you say better get it checked.

Chris Eldwood said:

If the y/g is the switch wire then all I need to do is remove the 4 wires from the thermostat and put the y/g switch wire into No 3

Click to expand...

No, all you need to do is install a cable with the the correct number of cores.

Thanks Davesparks, that's a better solution than mine. I've contacted British Gas this morning in case this cowboy has done the same elsewhere. I may even get a free rewire from them.