Replace Condo's 2 wire mechanical thermostat with digital thermostat
Rh- Power (24v) heating
Rc- Power(24v) cooling
C- Power (24v) common
Problem- A 2 wire stat is very much like an automatic light switch. One wire is power, when the normaly open switch closes, it sends that power to a valve or relay, and the light(ex) would come on.
The problem is that they are not normaly connected to W and Y. One normaly goes to Rh or Rc, the other goes W or Y. If you have a 2 wire stat (existing) it wouldnt have a Y on it. Are you positive ther wasnt a 3rd wire, and that the connections you described are accurate?
So there is no confusion, on a 2 wire stat, you would have only R and W.
It would be very unusual for a 2 wire stat to operate both heating and cooling. The heating "switch closes as it get colder, the cooling "switch closes as it gets warmer, a 2 wire stat, cannot do both.
If you are describing that R,W and Y are all connected together, you have no "control", and your thermostat is nothing more than a wall decoration.
Last edited by 8 Ball; 05-23-2008 at 06:57 AM.