The home I just bought has a natural gas heating, with central AC, and a humidifier. The curent thermostat is a honeywell RTH5100, I just bought a honeywell TH811OU.

The wiring on the current model is:

RC jumped to R

RED - R
ORANGE - Y
BLACK - C
BLUE - W
GREEN - G
BROWN - W2

I tried wiring everything the same into the new one:

Red - R
Orange - Y
Black - C
Blue - W
Green - G

I don't have a W2 aux on the new one... and the only remaining jumpers are S1 and S2 which are for optional outdoor remote sensors.

THe problem is that when I put the new one on, the air conditioner does not work. I didn't try the heat though. The furnace fan works.

I had to put the old one back in to get the airconditioner to work again.


Anyone know how I can install the new thermostat? Thanks

What was wrong with the honeywell RTH5100 ?