Thanks Madcodger - I think that makes sense.
" if you don't have the system built so that the TRVs can tell the boiler to turn on somehow, then you'll need to have a central thermostat set so that it turns on the boiler when any of the TRVs might need heat (i.e., it would need to have a higher setpoint than any TRV)."
Yes, I thought that I'd use a smart relay to control the on-off, using logic based on time (ie its evening, lets turn the heating on - like my 7 day programmer) AND if one or more TRV's were reading not at set temp.
That was my thoughts so far.... I'm sure I've not thought it through well enough yet.
