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  1. #14
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    Sep 2002
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    Bypass all of the safety sensors .... see if that fixes the pulling in

  2. #15
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    Jul 2018
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    Thread Starter
    It just seems kind if weird, I isolated that contactor with it's own transformer and put the original coil wires on to a RIB relay. I think those RIB coils will pull in at around 10volts. And it did the exact same thing. While the contactor was chattering away I manual pushed it in and it held. very possible the relay could have been chattering also caused by a safty switch but a didn't see it and would think it would be less likely.

    Sent from my SM-G960U using Tapatalk

  3. #16
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    maroon lazyboy
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    Quote Originally Posted by Snapperhead View Post
    Bypass all of the safety sensors ....
    Hmmm

  4. #17
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    Jul 2018
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    Thread Starter
    I dont have a problem taking pressure switches a out of the circuit for troubleshooting.

    Sent from my SM-G960U using Tapatalk

  5. #18
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    Quote Originally Posted by Spitz View Post
    I dont have a problem taking pressure switches a out of the circuit for troubleshooting.

    Sent from my SM-G960U using Tapatalk
    Don’t run it long and don’t leave it that way.

  6. #19
    Join Date
    Nov 2006
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    While the contactor is trying to pull in, find the voltage drop in the circuit that is causing the loss of voltage. If you are using a stat call, it could be in the stat or the wiring. Start by disconnecting the stat wiring and make a jumper call in the unit.If you are not using a CTI board, put it in test mode.

    You will find a voltage drop. Somewhere.
    [Avatar photo from a Florida training accident. Everyone walked away.]
    2 Tim 3:16-17

    RSES CMS, HVAC Electrical Specialist
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  7. #20
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    Dec 2009
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    maroon lazyboy
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    I had a airflow pressure switch kick my tail once but it caused a cool fail not a chattering contactor.

  8. #21
    Join Date
    Nov 2011
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    East Side
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    This is a trane, is the output of the board a snubber circuit?

  9. #22
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    Nov 2006
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    It will have a snubber.
    [Avatar photo from a Florida training accident. Everyone walked away.]
    2 Tim 3:16-17

    RSES CMS, HVAC Electrical Specialist
    Member, IAEI

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  10. #23
    Join Date
    Jul 2018
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    Wisconsin
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    Thread Starter
    Does the snubber prevent arcing in the low voltage relay? Not overly familiar

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  11. #24
    Join Date
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    Quote Originally Posted by Spitz View Post
    Does the snubber prevent arcing in the low voltage relay? Not overly familiar

    Sent from my SM-G960U using Tapatalk
    Yes.

    If you think back to the Kettering (breaker point) ignition systems, the capacitor (called a "condenser" in old radio lingo) was used to extend the life of the point contacts by reducing arcing during the hundreds of thousands of operations, until the points were replaced at the next "tune up."

    One key point when working with the Trane snubber circuit is the fact that a high impedance multimeter will allow you to measure a voltage at the circuit outputs when no load (contactor) is connected to the leads because of the ability of the snubber to pass a trickle of current even when the outputs are de-energized, which is more than enough to power a meter with an 11 meg input impedance.

    A connected load like a contactor shunts that trickle current, so you will read zero volts across the de-energized coil terminals.
    [Avatar photo from a Florida training accident. Everyone walked away.]
    2 Tim 3:16-17

    RSES CMS, HVAC Electrical Specialist
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  12. #25
    Join Date
    Oct 2016
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    Clearwater, Florida
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    Sounds like a safety to me or some sort of loose/intermittent connection.

    Can you clip an alligator clip to the wires and run them to your meter and see what the voltage is as it's happening? Could be a voltage drop just big enough to cause it to drop.

    When does it happen? As soon as the comp starts or after a couple of minutes and pressure builds up?

  13. #26
    Join Date
    Jul 2018
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    Wisconsin
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    Thread Starter
    Talked to Trane tech support told me to run my 24v thru a relay which I had already done. He said the UPC may be at fault and has had this same call multiple times in the last few weeks. When I installed the relay I fed the N.O. contacts with it's own 50VA transformer, apparently a 50VA is not big enough to pull in the contactor. I put the 24v side directly to the coil and it would not pull in. Yes the OEM transformers are 75VA but they feed multiple contactors along with the damper actuators. I did wire the same transformer and contactor to 120v at my home and it pulled in no problem. I left the relay in place and ran a wire off the secondary to the relay contacts. The relay coil is energized by the original coil wires. If I get a call back they will be getting a contactor with a 208v coil and a new board.

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