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  1. #1
    Join Date
    Mar 2009
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    carrier heat pump

    I was working on Carrier 5 ton heat pump today M#50TJ006-501GA. So customer complained that unit would get stuck in heating mode even if thermostat is not calling for heating. So I go out there find thermostat blank. Found L-2 leg on contactor burned. Fixed burned wire, turn the unit on. First tested in cooling mode, but heating mode comes on. This unit has Venstar T-2800 thermostat, checked pins back of thermostat set up for heat pump b energized in heating. As far as I could remember Carrier reversing valve supposed to be energized in cooling. So I switched it to O and opposite is happening, when calling for cooling unit runs in heating, when call for heating unit runs in cooling. So I checked at W terminal at unit when thermostat set for B I have no power at terminal strip but reversing valve has 24V but when set for O opposite happening. So looking all the wiring everything is landed correctly on heating relay and there another little coil relay I cant remember now, schematic diagram was kind worn off. So I put thermostat back to B and everything starts to work fine. Till I go down and turned thermostat off, unit was in heating mode but it would get stuck in heating mode but thermostat is not calling for it. In cooling mode it would turn off with no problem. So my questions is what hell do I got going on here. It doesn't make sense at all.

  2. #2
    Join Date
    Dec 2002
    Location
    SouthEast NC ICW & Piedmont Foothills
    Posts
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    Is this a GEMINI unit?
    It`s better to be silent and thought the fool; than speak and remove all doubt.

  3. #3
    Join Date
    Mar 2009
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    Thread Starter
    Not sure if itís a Gemini?

  4. #4
    Join Date
    Sep 2007
    Location
    edmonds wa
    Posts
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    I remember those using y1,y2,w1,w2 for unit connections wire like a conventional unit. Google that model number and check carrier start up guide.
    UA Local 32 retired as of Jan 2020

  5. #5
    Join Date
    Mar 2009
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    Thread Starter
    It shows the unit without economizer the one I have it said when T-stat calls for cooling, terminals G and Y1 energized . The indoor fan contractor C1, reversing valve and compressor contractor are energized and indoor fan motor and outdoor fan motors runs. It doesnít say anything about W-2 which I would think it would control the reversing valve. So I am not sure how is the reversing valve controlled on my unit. But on bigger units 8-12 ton it specifically said upon request for heating terminal W-1 will be energized with 24 V. The IFC, OFC are energized. The reversing valve switch position and indoor fan, outdoor fan and compressor are energized. So bigger units reversing valve gets energized in heating. Itís kind of confusing, so did someone programmed this thermostat wrong for bigger size unit, I tried the other way but it didnít work. I did grab a thermostat from some other unit but I donít know what size, I couldnít go on other roof and it was landed B on thermostat. Thatís why maybe that thermostat didnít work either. I have to call Carrier on Monday to figure this out.

  6. #6
    Join Date
    Sep 2007
    Location
    edmonds wa
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    Take a pic and post unit wiring diagram on the low volt side. I bet you have the terminals i said before.
    UA Local 32 retired as of Jan 2020

  7. #7
    Join Date
    Jan 2010
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    I'm not seeing that model as a heat pump
    Attached Images Attached Images  

  8. #8
    Join Date
    Mar 2009
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    Thread Starter
    Itís a 50TJQ

  9. #9
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    Mar 2009
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    Thread Starter
    I canít post pic for some reason but it does have W-1 terminal.

  10. #10
    Join Date
    Jan 2010
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    Quote Originally Posted by drage93 View Post
    M#50TJ006-501GA.
    Ok then one letter makes a difference
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  11. #11
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    Mar 2009
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    Thread Starter
    Thatís is it but it doesnít explained detailed sequence of operation. If you looked at schematic W-1 orange wire controls heating relay coil so I assume when W-1 has 24 v it switches power all n/c contacts to N/O contact on heating relay so that would mean if reversing valve was n/c it would make reversing valve de-energized. So the way it is wired right now at unit itís reversing valve energized in heating mode so it has 24 v at W-1 terminal. But I donít know how to explain unit running after thermostat shuts off.

  12. #12
    Join Date
    Sep 2007
    Location
    edmonds wa
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    I would use a meter and see if any call is coming up to the unit. Sounds like it has been wired wrong. You can always use jumpers right at the unit to verify operation, take all the wires off from the stat first. r to g is fan on ,w1 to r with the fan still jumped will be heat, w2 with fan on should get elec heat. That does not mean the wiring on the low voltage has not been adjusted, but by using the jumper test should prove operation.
    UA Local 32 retired as of Jan 2020

  13. #13
    Join Date
    Jan 2010
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    W1 to Heat Relay , relay closes contact for violet wire to defrost board. Violet sends power to board and compressor contactor.
    Upon a defrost mode those two normally open contacts on board close energising the reverse valve and electric heat strips to temper indoor air. It also disables the outdoor fan.
    It energizes the reversing coil in cool mode.
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