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Thread: Reversing valve wiring issue

  1. #1
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    Reversing valve wiring issue

    Have a bosch condenser heat pump which the reverse terminal energizes for heat mode, the air handler however is made by trane which the terminal O is energized for cooling. Thought Rheem was the only one that was backwards but seems the new Bosch units are wired this way too. Whats the best way to approach the wiring issue?

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    Programmable t stat.

    Sent from my LM-G820 using Tapatalk

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    Quote Originally Posted by CEAS-AC-TECH View Post
    Programmable t stat.

    Sent from my LM-G820 using Tapatalk
    Nothing energizes in the air handler with an O or B terminal, the best way to approach it is match the AH and HP. Many issues may come with an unmatched HP and coil in the heat mode.

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    Quote Originally Posted by theoldscroll View Post
    Nothing energizes in the air handler with an O or B terminal, the best way to approach it is match the AH and HP. Many issues may come with an unmatched HP and coil in the heat mode.
    Agreed. I was saying he could use a programmable t stat and energize said out put to the units needs. Connected to the condenser of course.

    Thinking about it hey o.p. how long you been doing HVAC?

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    .
    Attached Images Attached Images  

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  7. #6
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    Quote Originally Posted by VTP99 View Post
    .
    Well if you want to get real technical

  8. #7
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    The O terminal on the air handler is just that a dead terminal, a place to land wire(s). The only power on that terminal is what is put on it through the wires. The answer to the question you are asking is in the thermostat. if you don't understand then you need more education to be working on this kind of equipment.

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  10. #8
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    Actually some Tranes will use the "O" to set the blower speed, if using an ECM. "O" will also be used to determine if the EEV is in cool mode or heat mode. Your answer depends on which Trane Air Handler you have.
    Philippians 4:13
    I can do all things in him that strengthen me.
    Apostle Paul inspired by GOD.

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  12. #9
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    Quote Originally Posted by Artietech View Post
    Actually some Tranes will use the "O" to set the blower speed, if using an ECM. "O" will also be used to determine if the EEV is in cool mode or heat mode. Your answer depends on which Trane Air Handler you have.
    That is mainly on the 2 stg scroll compressor units, air handler does not matter.

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    Quote Originally Posted by Artietech View Post
    Actually some Tranes will use the "O" to set the blower speed, if using an ECM. "O" will also be used to determine if the EEV is in cool mode or heat mode. Your answer depends on which Trane Air Handler you have.
    Thats what I have. Ecm with variable speed. So im guessing two options then. Set it to full speed or wire in a custom relay to energize/denergized the airhandler oppisite the condesner.

  14. #11
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    How about some model numbers ?

  15. #12
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    Quote Originally Posted by VTP99 View Post
    How about some model numbers ?
    Bosch bova36hdn1m20g
    Trane tem6a0b30h21saa

  16. #13
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    Assuming this is not a communicating system, why not just leave the existing T-stat that activates the RV in cool & put a simple SPST relay at the outdoor unit.
    I've done that plenty of times with Rheem/Ruud hp units. Before 410A we used to change tons of just outdoor HP's on the ocean front & leave the old AH.
    Gary
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  17. #14
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    Why not just put on a good thermostat that you can choose whether to energize the RV in heat or cool.

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  19. #15
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    Quote Originally Posted by BNME8EZ View Post
    Why not just put on a good thermostat that you can choose whether to energize the RV in heat or cool.
    Because a good thermostat can only energize heat or cool not both on two seperate terminals.

    Ah ecu needs energized for cooling
    Rv needs energized for heat

    Im going to try the relay idea. Just was a little gun shy but now that I know its been before i will try it out. Thanks for the help. Will let you know how it turns out

  20. #16
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    Quote Originally Posted by brainsboy View Post
    Because a good thermostat can only energize heat or cool not both on two seperate terminals.

    Ah ecu needs energized for cooling
    Rv needs energized for heat

    Im going to try the relay idea. Just was a little gun shy but now that I know its been before i will try it out. Thanks for the help. Will let you know how it turns out
    W
    T
    F
    ?

    A good T stat will decide when and how to energy!

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  22. #17
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    Quote Originally Posted by pecmsg View Post
    W
    T
    F
    ?

    A good T stat will decide when and how to energy!
    Wtf??? Did you even read the original post? Tell me how a good tstat will fix this? A good programmable tstat gives two choices energize in heat or cooling right?

  23. #18
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    Quote Originally Posted by brainsboy View Post
    Wtf??? Did you even read the original post? Tell me how a good tstat will fix this? A good programmable tstat gives two choices energize in heat or cooling right?
    WTF
    A good t-stat allowed you to decide if O or B is energized in cooling.

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  25. #19
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    Yes then what? The air handler needs energized for cooling but the condsenser needs non energized for cooling get it now???

    Ah for cooling needs O energized.. then for heat not energized
    Condenser for cooling O is not energized, heat is energized

    Rheem and bosch work backwards from everyone else.

  26. #20
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    Quote Originally Posted by brainsboy View Post
    Because a good thermostat can only energize heat or cool not both on two seperate terminals.

    Ah ecu needs energized for cooling
    Rv needs energized for heat

    Im going to try the relay idea. Just was a little gun shy but now that I know its been before i will try it out. Thanks for the help. Will let you know how it turns out
    You do realize that the air handler doesn’t care if the RV is energized or not.

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