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Geocritter's avatar
Geocritter
Explorer
Jun 11, 2013

Another question about roof-top AC's

A few days ago I posted a question about my roof-top AC acting oddly. The response that made the most sense was that it was a thermostat problem. Okay, a simple fix until I looked up a thermostat for my 19 year old AC. It seems I have to purchase some type of new controller that goes on the AC (kaching!), a new thermostat (kaching!), a wiring kit (small kaching), and finally pay $46 shipping (painful kaching) for a total cost of around $340. As frustrated angry thoughts raced through my mind it dawned on me, when push comes to shove this is nothing more than an AC system probably not much different than my home system, especially if you isolate out the furnace part of the system. Why not simply disconnect the current (and complicated) Duo-therm thermostat and go to Home Depot or Lowes and purchase an inexpensive generic AC thermostat and wire that into the system. My question is has anyone taken this approach?
Steve
Class A
  • Golden_HVAC's avatar
    Golden_HVAC
    Explorer
    Jun 11, 2013
    I agree that $46 shipping is a painful kaching!

    Yes you "Should" be able to use a battery powered thermostat. The Honeywell 6000 series comes to mind. It runs on 2 AA batteries. Yet remember that if the battery is dead, the furnace will not work. So keep a extra pair around, or remember to rob the TV remote control when you need to.

    Normally there is a yellow wire that energizes the cooling relay.

    White is normally the furnace relay.

    Another wire or two is used to power the fan on low speed and high speed. You connect the wire you selected to run the A/C fan on the G terminal. You can not run both speeds (it will melt the fan wiring) so I would select high fan speed and hook up that wire to the G terminal, the other fan wire do not connect. The furnace fan runs on it's own.

    If you have a heat pump, it will have difficult wiring on it. Good luck! Yet you do not "Have" to run the heat pump, just wire it for cooling, and use the furnace by energizing the white wire with the W terminal.

    The thermostat should have a
    W - White wire (typically)
    Y - Yellow wire cooling
    G - A/C fan wire
    C - common wire used in a 24 VAC (home) system only
    R- input wire to the thermostat. In MY RV, the wire is red.

    Have fun camping.

    Fred.

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