I'm replacing standard heating controls for a Drayton Wiser Heat Hub 3 channel.
I have a Vaillant Ecotec 810 boiler, unvented hot water tank, Honeywell C27 programmer, manual stat downstairs hallway for all house heating(1), and a separate digital stat for conservatory heating (2).
Have managed to get hot water and main heating working fine through the wiser but stuck on (2) heat channel.
It appears the C27 is only two channel and I can't work out where (2) is going.
The backplate for the C27 has 3 live wires connected to L so was assuming (2) had been wired on to L to get round the limitation of the C27. Removing one of the live wires at a time produces following results;
Live 1 removed - boiler doesn't power on / heat hub doesn't power on
Live 2 removed - boiler doesn't power on / heat hub powers on
Live 3 removed - boiler powers on, hot water symbol on boiler, but doesn't get call from hub to fire up, and no heat symbol on boiler / hub powers on
Not sure what to check next.
Have attached pic of the backplate wiring (3 and 4 have been moved to 2 and 3 for the Wiser now).
Thanks for reading.