New Thermostat For American Standard

Supmac

Help!
The color code that my HVAC contractor used for wiring my furnace thermostat does not follow any standard code.
To make matters worse both ends the furnace and thermostat are just marked 1-5. Does anyone know
how to decipher the wires so that I can install a new setback thermostat.

Thanks

Supmac

Bestheating

Guess I haven't run into your situation. A standard rule of thumb, is as follows:

To thermostat:
R=Red wire
W=White wire
G=Green wire
Y=Yellow wire - sometimes blue is used in this case if there is no yellow.

From A/C unit there will be typically two wires that go to the unit:
Y=same as Y or Blue from thermostat
C= common on board
Quite often these wires are just red and white two strand wire.

Send me an e-mail if this works or not.
Bestheating@msn.com
Larry

Supmac

This is a large commercial unit and the color
scheme on the wires is strange ( including some tan and blue)
I will get the exact colors and there order when I go back in to work
tomorrow. Is there a way to use a volt meter and test voltage at the thermostat
as I cycle from heat to cool to fan?