I believe it is AC 24v 60HZ
I have bypassed the thermostat totally during testing and the relay will pull in normally when current is run directly from the transformer to the coil on the relay. As soon as I try and connect in the thermostat or make the relay work through a switch it either won't pull in on the NO side or it chatters on the NC side.............I have an identical relay running the thermostats for another building and it seems to work fine? Could it be amperage related as there is no load on the circuit per say?
It is a very basic thermostat - Honeywell CT50 series.
I have no problem picking up another stat. Is there a contact rating I should be looking for?