Page 1 of 2 12 LastLast
Results 1 to 20 of 29

Thread: Contactor wont pull it

  1. #1
    Join Date
    Jul 2018
    Location
    Wisconsin
    Posts
    1,103
    Post Likes

    Contactor wont pull it

    Trane YCH480 1996 vintage. Replaced failed compressor #1. Along with contactor. All is well. Two days later no cooling, find 24v transformer tripped. Check for shorted wires none found, reset breaker on transformer. Contactor chatters and wont pull in and then the breaker trips. While its chattering I can push it in and it holds drawing 1.1amps. While its attempting to pull it's at about 15v. When it pulls in I get 27v. Replaced new contactor with another new one. Both were Trane OEM. Installed a new transformer and a RIB relay to so the contactor gets it's own transformer. Same thing.... IMO it a fairly larger contactor for 24v 75Amps. I'm thinking about getting a contactor with a 208v coil and running it thru a relay. Disabled that compressor for the weekend. What gives?

    Sent from my SM-G960U using Tapatalk

  2. #2
    Join Date
    Jul 2011
    Location
    DFW, TX.
    Posts
    1,747
    Post Likes
    make sure the incoming voltage to your transformer is on the correct tab for the voltage being supplied. If not it will cause the chattering your experiencing.

    Sent from my LG-G710 using Tapatalk

  3. #3
    Join Date
    Jul 2018
    Location
    Wisconsin
    Posts
    1,103
    Post Likes
    Thread Starter
    Yes it's running around 205v and it's on the 208v tap. I have a solid 27v

    Sent from my SM-G960U using Tapatalk

  4. #4
    Join Date
    Jul 2018
    Location
    Wisconsin
    Posts
    1,103
    Post Likes
    Thread Starter
    Tried to dig my old contactor out of there dumpster but no luck.

    Sent from my SM-G960U using Tapatalk

  5. #5
    Join Date
    Sep 2002
    Location
    Virginia
    Posts
    7,453
    Post Likes
    I've seen this a couple times , and both times ended up being High pressure switch\LPS was junk

    Another time had a walkin cooler sounded like the contactor was sending out morse code messages , ended up being the thermostat was bad

  6. Likes CEAS-AC-TECH, icy78 liked this post.
  7. #6
    Join Date
    May 2018
    Location
    VA/DC
    Posts
    344
    Post Likes
    that is a 50va transformer? sounds like its not big enough. going by your spec sheet it needs 32 va to hold it, which is the 1.1 amps. but needs much much more to pull it in. what was the original transformer size.

    you could put a rib relay and a 208 v coil. it would fix it. take the current contactor coil leads and put them to the rib coils. then 208v coil on the contactor

  8. #7
    Join Date
    Jul 2018
    Location
    Wisconsin
    Posts
    1,103
    Post Likes
    Thread Starter
    Quote Originally Posted by Cool breeze 38 View Post
    that is a 50va transformer? sounds like its not big enough. going by your spec sheet it needs 32 va to hold it, which is the 1.1 amps. but needs much much more to pull it in. what was the original transformer size.

    you could put a rib relay and a 208 v coil. it would fix it. take the current contactor coil leads and put them to the rib coils. then 208v coil on the contactor
    That's the plan. Original is a 75 it runs the actuators and the other contactors.

    Sent from my SM-G960U using Tapatalk

  9. #8
    Join Date
    May 2018
    Location
    VA/DC
    Posts
    344
    Post Likes
    i bet if you check the amps when it pulls in they are well past a 100 va transformer.



    Quote Originally Posted by Spitz View Post
    That's the plan. Original is a 75 it runs the actuators and the other contactors.

    Sent from my SM-G960U using Tapatalk

  10. #9
    Join Date
    Nov 2011
    Location
    CO
    Posts
    7,916
    Post Likes
    if it worked fine for 25 years, as designed, I would be looking at the path from Y1 to the contactor coil. I have also had pressure switches pass voltage but not enough current, due to burnt internal contacts. all of the times it has happened to me have been on units with issues that caused the switches to cycle a lot.

  11. #10
    Join Date
    Jul 2018
    Location
    Wisconsin
    Posts
    1,103
    Post Likes
    Thread Starter
    Quote Originally Posted by 71CHOPS View Post
    if it worked fine for 25 years, as designed, I would be looking at the path from Y1 to the contactor coil. I have also had pressure switches pass voltage but not enough current, due to burnt internal contacts. all of the times it has happened to me have been on units with issues that caused the switches to cycle a lot.
    That's what we were originally thinking but the breaker on the transformer had never tripped before the new contactor went in.

    Sent from my SM-G960U using Tapatalk

  12. #11
    Join Date
    Aug 2002
    Location
    Southold, NY
    Posts
    29,493
    Post Likes
    Follow the low voltage and test each and every safety switch, one or more are not making good contact under load.

  13. Likes Spitz liked this post.
  14. #12
    Join Date
    Jul 2018
    Location
    Wisconsin
    Posts
    1,103
    Post Likes
    Thread Starter
    Makes sense maybe the new contactor coil draws a little more. I should have just replaced those junk encapsulated switches during the compressor replacement. Maybe put in a real switch.

    Sent from my SM-G960U using Tapatalk

  15. #13
    Join Date
    Aug 2002
    Location
    Southold, NY
    Posts
    29,493
    Post Likes
    A contactor coil is like a motor high amperage until its pulled in. This is what's causing the chattering that high amperage across bad contacts drops the voltage, the coil releases and immediately re-energizes.

    Pull the load side of the contactor to prevent pitting the points as you trouble shoot!

  16. #14
    Join Date
    Sep 2002
    Location
    Virginia
    Posts
    7,453
    Post Likes
    Bypass all of the safety sensors .... see if that fixes the pulling in

  17. #15
    Join Date
    Jul 2018
    Location
    Wisconsin
    Posts
    1,103
    Post Likes
    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

  18. #16
    Join Date
    Dec 2009
    Location
    maroon lazyboy
    Posts
    2,723
    Post Likes
    Quote Originally Posted by Snapperhead View Post
    Bypass all of the safety sensors ....
    Hmmm

  19. #17
    Join Date
    Jul 2018
    Location
    Wisconsin
    Posts
    1,103
    Post Likes
    Thread Starter
    I dont have a problem taking pressure switches a out of the circuit for troubleshooting.

    Sent from my SM-G960U using Tapatalk

  20. #18
    Join Date
    Dec 2009
    Location
    maroon lazyboy
    Posts
    2,723
    Post Likes
    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.

  21. #19
    Join Date
    Nov 2006
    Location
    Southeastern Pa
    Posts
    32,269
    Post Likes
    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
    Member, IAEI

    AOP Forum Rules:







  22. #20
    Join Date
    Dec 2009
    Location
    maroon lazyboy
    Posts
    2,723
    Post Likes
    I had a airflow pressure switch kick my tail once but it caused a cool fail not a chattering contactor.

Page 1 of 2 12 LastLast

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •