Check out some similar questions!

PamG · Jan 3, 2007, 09:45 AM

Hi,
We installed a new Honeywell Deluxe 5-2 Programmable Thermostat (RTH6300B) last week. We have a Carrier Furnace that is 15 years old, I believe.

We've noticed that the temperature of our house doesn't seem to be reaching the temperature it's set for but have been so busy and out so much that we haven't had time to look into it.

It is set to be at 17 degrees Celsius during the night and then to go to 21 degrees at 6:30 AM. At 9:30 this morning, we noticed the temperature in our house was 16 degrees. When we turned up the manual temperature, the furnace heat did not come on. We're starting to wonder if the electric baseboard heat in our addition is the only thing heating the whole house.

We installed the thermostat ourselves. The previous thermostat was probably original to the house (built in the 50s). There are only two wires: for heat and for the fan. They are called G and W. The G is white and the heat is black. We think fan is G and W is heat. We have the G attached to G and W attached to W. We even tried switching them around this morning but it didn't make a difference.

It's cold in Manitoba in January so I'm hoping we can get some advice! If we have to call a furnace installer, the $100 service call will make our new thermostat much more costly than we'd planned.

Thanks,
Pam

Peter Kwan · Jan 3, 2007, 12:07 PM

I think your old thermostat act just like a switch, when the temperature in the house fall below the setting, it will turn on to give a short circuit, and will turn off (disconnect) when the temperature is above the set point.

To test your system, if you have a volt meter, if you measure the voltage across the two wires, you should have 24-27 VAC. If that is the case, shorting the 2 wire, your furnace should turn on.

If the above test is correct, to solve your problem, one of your wire should connect to R terminal and the other to W terminal on your thermostat.

Let me know if this help.

PamG · Jan 3, 2007, 12:14 PM

Thanks Peter,

My husband solved the problem by tracing the wires from the thermostat back into the furnace and finding where they were connected. It turns out the white was connected to W and the black was connected to R. I think the main confusion about the whole situation was the fact that when disconnecting the original thermostat, the white was connected to a screw labelled G.

Everything seems to be working fine now.

Cheers.