I replaced thermostat (mercury) for carrier furnace model 58GS050-3 with ritetemp 8022c.
The wiring from old one are W, R & B (on thermostat) and I noticed that the R wire also connect to C on thermostat board. My old thermostat was energy saver Carrier brand and my furnace has heater only (No AC). Anyone can show me how to wire on my new thermostat, thank you

I replaced thermostat (mercury) for carrier furnace model 58GS050-3 with ritetemp 8022c.
the wiring from old one are W, R & B (on thermostat) and I noticed that the R wire also connect to C on thermostat board. My old thermostat was energy saver Carrier brand and my furnace has heater only (No AC). Anyone can show me how to wire on my new thermostat, thank you
Addition information that my old furnace has 3 wires which connect to R, W and C. I was wondering what is the C Connection on furnace, it is represent for heat or common?

Usually there is a 24 volt AC transformer in the furnace with the secondary winding connected to a red wire running to the thermostat and a blue wire, common, to the gas valve, A/C relay, and fan relay. From the thermostat there will be white wire to the gas valve. The thermostat is wired to switch the power from the red to the white with the blue completing the circuit. Most thermostats and furnaces have the contacts labeled R, B or C, W, Y, and G for the corresponding wire colors.

Check to see if you still have power. Connecting the red to the com may have blown a fuse or burned out the transformer.