My old Honeywell rotary thermostat (mercury switch) is a 2-wire system and I want to replace it with a programmable thermostat (Honeywell RTH6300B). Problem is when I pulled off the faceplate, both wires were the same color and there is no letter coding on the wallplate where the wires are connected. My system is gas-fired hot water baseboard, heat only, no air conditioning. Any suggestions? Answer to similar questions on this website seemed to indicate that I could connect one wire to the W terminal and the other wire to the R terminal.