Live Brown goes to L
Neutral Black goes to N.
The Hot water ON wire, green/yellow, goes to the AUX NO terminal.
The CH ON grey wire goes to the CH NO terminal.
Then you need two short wire links, both connected at one end to L. At the other end of these links..one goes to CH COM and the other to AUX COM.
If you have trouble getting 3 wires innto the L terminal you could try linking L to CH COM and then linking CH COM with the 2nd wire to AUX COM. It doesn't matter as long as both COM terminals are made Live.
Some lightweight flex of the sort used in lighting pendants/table lamps etc will be easier to handle, something much lighter than the cables you already have in use on the old backplate.
For this sort of internal linking use, hidden away from inquisitive fingers, it doesn't need to be heavy duty stuff at all.
hi jackthorn thanks for your help yesterday tried that today the boiler would switch on but switch off again in a few seconds with no heat in radiators so have reverted back to old control again any ideas thx
Thanks I think it may be that I haven't removed the stat properly I only removed the stat head not the wiring so it would leave the connections open so stopping te valves from opening does that sound
Yes the existing thermostat wiring would have to be connected as if the old stat was permanently ON.
If you have a photo of it's wiring someone should be able to help and if you can identify where those thermostat wires connect to the rest of the system that would usually be the best place to bypass the old wiring.
thanks for reply put two photos on here one is the stat with the stat head removed the other is the junction box at the back of airing cupboard the wire from the stat I have marked with a black cross but i think it will be difficult to sort from photo without knowing where the other wires go is it poss to bridge the connections in the stat housing instead ?
To bypass the thermostat at the wallplate you would connect the yellow/green with brown sleeve to the Live brown lead. I would try that initially to make sure the new thermostat then works properly.
Then if you are certain the marked wire at the wiring centre goes to the thermostat it should be easy to work out which two terminals you have effectively connected together and replace the old wiring with a short link.
As far as I can tell from the photo, to decommission the old thermostat wiring at the wiring centre would mean removing it's blue wire from terminal 2 and it's other 2 wires from 4 and 5 then connecting a link between terminals 4 and 5.
hi Jackthorn very many thanks for your help all is working as it should just turned the old stat up as far as it would go 30 and it works fine just got to replace stat with a ordinary back box as the butcher who fitted the stat recently hacked at the arcatrive around the airing cupboard and bridge pos wires due a service so may talk nicely to BG engineer about sorting it in the box at back of airing cupboard for me once again many thanks to you and this forum