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  1. #1
    Join Date
    Jul 2008
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    Control 2-stage heating via Thermostat or Furnace

    I have a Carrier Variable speed 2-stage furnace (58UHV) with a Carrier Thermidistat control that does support 2-stage heating. I just noticed that it's wired for only single-stage heating and I've been reading up on this to figure out why. It seems that in this configuration, the adaptive algorithm built into the furnace is handling the 2-stage heating. My question is, which is the more efficient method for handling the 2-stage heating: the adaptive algorithm or using the thermostat control?

    Unfortunately, I only have an 8-wire bundle going to the thermostat and all the wires are being used. It was suggested that I could use one of the external temp sensor wires and just do without the temp readings, but I'm not so sure about that. The other option would be to run another wire (possible, but not easy). Would it be worth going through the trouble of doing this to control the 2-stage heating using the thermostat?


  2. #2
    Join Date
    May 2000
    Indianapolis, IN, USA
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    Either way won't affect efficiency, 2 stage stat helps comfort by allowing long run cycles on gentle low in bitter weather. The timer method allows a max of 16 minutes on low and some cycles could decide not even to use low. While the algorithm is better than fixed timer, still can't beat control based on need.

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