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O & B TERMINALS

Paul S_3Paul S_3 Posts: 1,257Member
what are the o & b terminals on a tstat.....and how are they wired for a heat pump???
ASM Mechanical Company
Located in Staten Island NY
Servicing all 5 boroughs of NYC.
347-692-4777
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ASMHVACNYC.COM
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Comments

  • JStarJStar Posts: 2,751Member
    edited March 2010
    Depends...

    ...on the exact system, and the way the t-stat is set up, but typically O/B will energize the reversing valve for cooling. You'd wire this terminal on the t-stat to the air handler and condenser.
  • sasmansasman Posts: 29Member
    O/B

    it does depend on what t-stat ypu are using



    if O?B it's for reversing valve, engage in  heat or cool



    if the O  and B are in different locations, you really have to be careful what you hook to



     those terminals..........
  • Empire_2Empire_2 Posts: 2,343Member
    edited April 2010
    Look at the manual.

    In the North East where we use "Fail safe heat",  where we energise the RV on a call for cooling "O" is generally energised on a call for cooling.  "B" is actually energised as soon as you flip the heat/cool switch to heat, where as the "O" will energise when the call is made.  "B" in this case can be used to energise a Isolation relay to separate the cooling circuit,...Y so that is will not back feed and energise thru the stat thus energising Y(Cool) G fan and "O".  In a nut shell "B" allows the separation of the 2 Modes at the condenser.

    I know that doesn't make sense, let me look for the Wiring diagram to clear it up.  Don't forget it can do anything you want it to do, as long as we all think it through.  Think about it in HP mode and in heat, W1 calls for hp condenser....What is to stop that w1 circuit from back feeding right back through Y1 at the stat, which is also interconnected to G......and O??? Now were calling for cooling again..  What's really weird once you find and understand a wiring diagram you like,................Lennox, Heil, Carrier...etc.  every manufacturer is different.  Go figure.........I scratch my head sometimes.



    Feed back please



    Peace



    Mike T.
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