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  1. #1

    Confused Reverse Logic Relay

    I need to connect a Honeywell whole house dehumidifier to a Carrier air conditioner. The Carrier thermostat puts 24v on when the dehumidifier is NOT needed. The dehumidifier has a wire pair that when connected it TURNS on. Carrier calls this reverse logic. I call it &*$@($%@. I believe I can get the units to communicate with a normally closed relay that opens when voltage is applied. I went to the local HVAC parts dealers and they had no idea of what I was talking about. I know it is just a communication problem because I am a scientist and not an engineer.

    I looked through the forum and it seems like there are so great folks here. Can anyone advise me on this installation? A part number or reference would be fantastic.

    Thank you,

    Mike

  2. #2
    Join Date
    Apr 2009
    Location
    Mobile, AL.
    Posts
    88
    Install a dpst relay and use the common and normally closed contact.

  3. #3
    Thank you for the response. Not sure what a DPST relay is but I will google it.

    Mike

  4. #4
    Join Date
    Apr 2009
    Location
    Mobile, AL.
    Posts
    88
    I am sorry, I meant to type spdt. That is a single pole double throw relay. I just bought some from an electronics distributor last week.
    What that means is there is a common input that is switched from one output (the normally closed) to another (the normally open) when the 24 vac is applied to the coil. This "reverses" the output. You feed the 24 vac from the power to the common and it is switched to the normally closed terminal until you power the coil. Then it is fed to thr normally open terminal.

  5. #5
    THanks for the come back. I was really getting confused looking at the DPST wiring diagram.

    Mike

  6. #6
    Join Date
    Jul 2013
    Location
    Ma
    Posts
    21

  7. #7
    Join Date
    Jan 2006
    Location
    Near Atlanta, GA.
    Posts
    14,531
    Moved to AOP Residential.

    Only approved Pro Members may give advice.

  8. #8
    Join Date
    Nov 2006
    Location
    Southeastern Pa
    Posts
    18,574
    A reminder to members:

    we don't provide DIY information.
    [Avatar photo from a Florida training accident. Everyone walked away.]
    2 Tim 3:16-17

    RSES CMS, HVAC Electrical Specialist

    AOP Forum Rules:







  9. #9
    Thanks all. I actually found one that will fit perfectly next to my furnace circuit board. Not sure why you would not provided info to me. I own 3 companies that install security alarms, home automation and computer support. Sorry for the trouble.

    Links to direct purchase sites are not permitted.
    Last edited by beenthere; 08-18-2013 at 02:20 PM.

  10. #10
    Join Date
    Nov 2006
    Location
    Southeastern Pa
    Posts
    18,574
    Quote Originally Posted by InVision Inc View Post
    Thanks all. I actually found one that will fit perfectly next to my furnace circuit board. Not sure why you would not provided info to me. I own 3 companies that install security alarms, home automation and computer support. Sorry for the trouble.

    Removed link
    Probably because you did not show enough respect to read the site rules.

    If you had, you would have found that with 15 posts you could become a Pro member, and then post technical questions in the closed Pro areas, where any number of us would be happy to give you all of the guidance you need.

    Even if you are a guy who likes to crow about owning three companies...
    Last edited by jpsmith1cm; 08-18-2013 at 09:22 PM.
    [Avatar photo from a Florida training accident. Everyone walked away.]
    2 Tim 3:16-17

    RSES CMS, HVAC Electrical Specialist

    AOP Forum Rules:







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