Only have two wires. Red and white. Relay at boiler has two existing wires hooked to indicators T and T. Which connection would I use in this system to add the c or constant. Following are locations I have L1 L2 C1 C2 Zc zr b1 b2 and the two T's
the new thermostat Calls for a common and I can get power to it but what I have to do removes the white which I think turns the heat on when system calls for it.