I have purchased a RiteTemp 8082C Programmable Thermostat with remote control to replace my old mercury swtich type thermostat. While preparing to install the new one, I noticed in the instructions that all of the connections map correctly to my existing setup except one. The instructions say that a 'C' connection is required for the remote control to work. I don't have that connection on the existing thermostat and I don't see one on the transformer at the unit (Trane XE60 - Gas furnace with AC coil). The transformer has RGWY connected to matching points on the existing thermostat. There is a 'B' connection on the transformer that does not connect to the thermostat. Apparently the 'C' connection is supposed to be a 24V common side tap on the transformer. The only 24V tap on the transformer I have seems to be R. Do I need to replace the existing transformer to obtain the 'C' tap, use a 2nd transformer, or I am just out of luck?

Thanks

B = C. The old thermostats only switch one terminal of the transformer to heat, cool, or fan. To complete the circuit, a wire, usually blue, B, runs to the other side of each coil from the other terminal of the transformer. If the cable that runs to the thermostat includes a blue wire, connect it to the B terminal at the furnace, and the C terminal on the thermostat.

Labman,

Thank you very much for the quick response. I'll give that a try.