I'm replacing an old mercury thermostat with a digital one.

The new unit has 7-8 connections (labeled w1,wh,r1,rh,y,c, etc.) and a bunch of instructions about how to connect similarly labeled existing wires.

But there are no instructions about how to connect an unlabelled two-wire thermostat. How do I connect the new thermostat?


2 Answers 2


Here's a good guide on thermostat wiring: http://wiki.xtronics.com/index.php/Thermostat_signals_and_wiring

Most likely, all you should need to do is connect one wire to either W for heating or Y for a cooling system, and the other to R (or Rh for heating or Rc for cooling).


Is it a line voltage thermostat? Do you have baseboard heaters or fan-forced heaters in the room? If yes, then you'll need a line voltage thermostat.

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