I have an old thermostat which needs replacing. It does not have batteries. I am replacing with a Honeywell programmable battery model.

I have the following wires:
Red
Green
Blue
Yellow
White
Black

On the old thermostat, the blue was plugged in at a different location from the others. It is a Trane forced air gas furnace with air conditioning.

Did you happen to make note of which wires went to which terminals on the old thermostat? It is pretty much up to the guy who wires it as to which wires go where. Usually they follow the following:

W- White - Heat
Y - Yellow - Cooling
G - Green - Fan
R - Red - High Side of Transformer

Blue can be any of the following: Common (common of transformer, IE other side of power), O (to put into cool mode), B (to put into heat mode) or several others depending on what you have.

Some thermostats are "power stealing" thermostats and do not require batteries, or use R and C from the transformer. It is a good idea to shut the system off while swapping out the thermostat so you don't short anything out if it does in fact have a common wired up to it.

Other thermostats have batteries and the option to wire a common to it. Read the instructions that come with it, and you can always open up the unit with the power off and see which wires are connected at the other end. BE CAREFUL if you decide to do so!!

Hope this helps.

Quote:

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Originally Posted by dewey066

Did you happen to make note of which wires went to which terminals on the old thermostat? It is pretty much up to the guy who wires it as to which wires go where. Usually they follow the following:

W- White - Heat
Y - Yellow - Cooling
G - Green - Fan
R - Red - High Side of Transformer

Blue can be any of the following: Common (common of transformer, IE other side of power), O (to put into cool mode), B (to put into heat mode) or several others depending on what you have.

Some thermostats are "power stealing" thermostats and do not require batteries, or use R and C from the transformer. It is a good idea to shut the system off while swapping out the thermostat so you don't short anything out if it does in fact have a common wired up to it.

Other thermostats have batteries and the option to wire a common to it. Read the instructions that come with it, and you can always open up the unit with the power off and see which wires are connected at the other end. BE CAREFUL if you decide to do so!!!

Hope this helps.

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Do you have multiple thermostats going to this one furnace, is it zoned? What model thermostat did you buy? With certain damper panels there are master and slave thermostats and some thermostats will not work.