Hi all! I'm sort of an electronic and computer nerd. I'm trying to figure out how the furnace thermostat actually works. I know the color codes, Rc & Rh are red (24vac), W is white (heating call), Y is yellow (cooling call), and G is green (fan). My question is, if I take the red (24vac) and connect it directly to, say G (fan), will the fan start? Same for Y and W, would they start also. I'm designing my own zoned system and need to know how to set up my relays. Don't worry, nobody is responsible for anything I may do wrong!

Thanks!

I believe you are correct Tom.
Here is a diagram (http://www.qsl.net/ve3lny/images/ATMega164%20Thermostat%20Schematic%282L%29.jpg) that seems to indicate what you are describing. There also might be some useful info on that website (http://www.qsl.net/ve3lny/thermostat.html).

Best of luck!
WallyH

, if I take the red (24vac) and connect it directly to, say G (fan), will the fan start?(yes)

Same for Y and W, would they start also. (yes/yes)

But only one at a time,as you move the red wire to each wire

Sounds like you have a good handle on this. The red wire is the 24v wire. The thermostat simply lets the 24v go to w, y, g depending on what the stat is calling for.