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Thread: multi stage Fan Control on Airconditioner ! (CT-80)

  1. #1
    Junior Member

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    multi stage Fan Control on Airconditioner ! (CT-80)

    hello .. quick thing,

    i have a Airconditioner which is NOT compatible to any Thermostat .. however i managed to get it workign anyway with a few relays.

    the only problem is that the fan speed can not be controlled, somehow the CT-80 has only ON/OFF option for a fan ..
    which is like back in 1980 ..

    is it possible with a CT-80 to use the AUX connections for multi stage controls ? or any other connections ?
    its not really a question if this is technically possible (it is), its more a question on operating the thermostat so it actually does make some sense ...

    any ideas ?

  2. #2

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    As you already know the CT-80 is not setup to control a multi speed fan. The Aux is for heat. You could install some additional relay that are connected to G, Y and W to determine what speed to run the fan.

  3. #3
    Junior Member

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    yeah exactly that was my idea ..

    but i not sure how the ct-80 would then control it.

    right now i set it up like this:

    Y goes to a relay which is between the original wire go to the compressor switch.
    G goes to a relay i put between the Fan and the Power

    so the thermostat can controll the Compressor but the Airconditioners own electronics decide to start it or not.
    same for the fan and fan speeds.

    the next step would be the have the CT-80 control the fan Speeds as well

    how about use Y1 for Full speed fan .. and set the CT-80 for 2 stage cooling ?
    this would put the fan into full power if the temperature difference is greater .. right ?

    just need to come up with some relay logic to make sure the stage 1 is off if y1 is active .. but thats not really complicated to accomplish.

  4. #4
    Junior Member

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    another "problem" i need to solve is.

    the airconditioner can not be turned completly off .. as it has a waterpump, which sucks up the condensation water.
    but the manual override is just a push button (not a physical switch) ...

    all my aproaches to carrier where pretty much hopeless to get this sorted out

  5. #5

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    The drawing below is how I was thinking that your could wire in the the fan speeds with 3 additional relays. With this set up you would have a different fan speed for each mode.

    Click image for larger version. 

Name:	CT-80 3 speed.jpg 
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  6. #6
    Junior Member

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    wow great work .. yes i had something semilar in mind .. but with 1 less relay where the first one disables the secound one to make sure i never trigger 2 speeds .. but that what you made works just the same way .. and you have 3 speeds (my design only had 2)

    but how do i trigger the "W" pin to turn on on the CT-80 ? (i understand aux and heat are the same) ..

    the manual is very little to no helpt at all in this matters ..

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