How Does a Thermostat Activate Heating?

[fawk3s]

Please read this page:
http://home.howstuffworks.com/home-thermostat3.htm

And now tell me, or better draw, how is the circuitry connected when the heat is turned on, following those pictures. It started to interest me and now that I can't solve it, its just driving me crazy!

 

[schip666!]

I'm too lazy to figure out how to draw and post a schematic... But basically a thermostat is a switch, so the wiring is just like you would see for a light bulb or doorbell. The heater is the doorbell -- probably a relay or solenoid that turns on the real system -- and the thermostat is the push button. There is some kind of power supply, a 12v or 24v transformer, in the heater that supplies the juice for the switch and relay.

All the heaters I've ever dealt with (in older houses) just want a simple switch connection to the thermostat -- two wires that you connect together to make hot come out. Newer AC units may have some fancier computer controller that makes everything more complicated so you have to hire the guy to fix the switch...I dunno...

 

[fawk3s]

No, I actually understand how the device works and I can clearly see how the circuitry for the cooling system works (exactly what path does the electricity flow) and I think its beautiful. But when I tried to draw the path for the electricity when the switch was turned on "Heat" (just like the red path is drawn on the web page there for the "Cool"), I just can't figure it out. I do have a couple of ideas, but they seem to contradict the picture where you can see the wires on the top layer. (No wire connects to the socket where I want the electricity to flow.) Plus, my path wouldn't have the "Auto" fan option, since I couldn't find any paths there when "Heat" is turned on. (Or isn't heating supposed to have the fan option?)

So I am kinda puzzled about that. If anyone has any clues, please help !

 

[schip666!]

Oh, I think I see... Those photos and description are about as clear as mud...

I think when the switch "ball" is in the heat position, the top-right (unlabeled) terminal and RH are connected together. What that means is a bit of a mystery. A schematic diagram and a larger, square-on photo of the circuit board would be of great help.

Maybe you can find an actual thermostat like that one and trace out the circuit. Having a cordial relationship with your local hardware store staff would possibly be a benefit in this endeavor.