I want to upgrade from a battery powered Honeywell thermostat to an ecobee3 lite. This is for heat only.
My current Honeywell has two wires: Red and White. Missing is the C cable. There are enough wires in the cable in the wall they are just not connected.
The transformer on the boiler has the following terminals:
Currently the red cable from the thermostat is connected to G. The white cable from the thermostat is connected to Y.
Question: Where do I connect my 'c-cable' ? Is this a question of just connecting that one cable or would the entire transformer need to somehow re-wired ?