This goes out to anyone who might be able to help out. I purchased a Honeywell
RTH230B to replace the old mercury thermostat. I have a gas furnace w/ A/C
I have a 5 wire system with the following color code. Green for the fan, Yellow is on Remote A/C, White is on the W1 (Thermostat), Red also on (Thermostat), and Brown on Remote A/C. My question is I have wired the new thermostat as follows and I have no A/C operation and the fan will not come on when placed in the on position. The red is in the Rh slot, Brown is in Rc position, White is in the W position, Yellow is in Y position, and Green is in the G position. I hope I wired this correctly, but if not does anyone know the correct wiring? Furnace worked all winter, but now it's summer and I need the A/C to work. Any advise would be very helpful.

Is this a Heat Pump system/ why is there two remote ac units? If you do have a Heat Pump, this thermostat will not work.

On the new stat:
Rh = heating control feed or power In
W = Heating relay or control feed Out
Rc = Cooling control feed or power In
Y = Cooling control feed or power Out
G = Fan control

The only reason this stat handles five wires is to allow for two separate 24 volt control sources , one for heat and one for cooling. If there is only one control power source, then Rh and Rc get jumped.

Hope this helps

Can I control an exhaust fan using a thermostat with 110 volts is are 24 volts needed?
Glenn

If you plan to use the exhaust fan for warm or hot air, then you can use a line voltage (120 Volt Rated) cooling thermostat, the switch closes on temperature rise.

24 Volt system also needs a transformer and a relay, along with a Low Voltage stat.

Here is one that is for a finished space:
http://www.grainger.com/Grainger/wwg/itemDetailsRender.shtml?ItemId=1613553304

Here is one for an unfinished space:
http://www.grainger.com/Grainger/wwg/itemDetailsRender.shtml?ItemId=1611760764