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    ellen saracino's Avatar
    ellen saracino Posts: 1, Reputation: 1
    New Member

    Aug 26, 2005, 04:41 PM
    Wiring a 2nd zone
    Central a/c is all set up on my finished basement as a 2nd zone. In the upstairs hall closet, I can see a large round pipe running down from the attic to the basement. Ceiling ductwork and vents in the basement are all connected to it. There is a programmable thermostat in the basement as well. The only thing missing is the wiring running from the fan in the attic to this thermostat. There are only 2 wires connected to the thermostat, and they run from the boiler for heat. My question is how do I go about doing the wiring to get the system up and running in the basement? Thanks.
    labman's Avatar
    labman Posts: 10,580, Reputation: 551
    Uber Member

    Aug 26, 2005, 07:59 PM
    Usually there is a 24 volt AC transformer in the furnace with the secondary winding connected to a red wire running to the thermostat and a blue wire, common, to the gas valve, A/C relay, and fan relay. From the thermostat there will be white wire to the gas valve, yellow to the A/C, and green to the fan. The thermostat is wired to switch the power from the red to the white, yellow, and green as needed with the blue completing the circuit. Most thermostats and furnaces have the contacts labeled R, B or C, W, Y, and G for the corresponding wire colors. It may be wired to have the A/C control wires return to the furnace and its controls and then a second wire goes to the A/C unit. Internal wiring may replace the green wire if the thermostat does not give you the option of fan only or continuous fan. Digital or programmable thermostats may need the blue wire connected to them.

    With multiple zones you must also have dampers in the air ducts activated by the thermostats to direct the cooled air to the proper zone or zones. The ''Y'' wire from each thermostat must be connected to the proper damper. I have worked with a zoned hot water heating system, but never a zoned A/C. I am not sure how the dampers would be wired up. Maybe if you give me more details, I can help you figure it out.

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