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  1. #1
    Join Date
    Jun 2009
    Posts
    7

    Hmm Contactor not pulling in

    I've been working on a Carrier RTU Model 50hjq014. First time found the contactor not pulling even though had correct voltage at contactor. Just touched contactor and it pulls in. I replaced contactor and it worked fine for about a month. Called back out same problem. Checked for loose wiring, bad ground (contactor 120v coil), pressure switches. Couldn't find anything wrong, but went ahead and tried another contactor. Works for about a month then same problem happens. Tried even replacing current sensing switches. And it happened again. Any suggestions would be appreciated, maybe Im missing some kind of stat or switch that is on the unit.

  2. #2
    Join Date
    Jun 2009
    Location
    Ancaster,Ontario
    Posts
    27
    does this unit have an economizer?

  3. #3
    Join Date
    Jun 2009
    Posts
    7
    No this unit does not have an economizer.

  4. #4
    Join Date
    Jun 2009
    Location
    Ancaster,Ontario
    Posts
    27
    how did the contacts look on the replaced contactors?

  5. #5
    Join Date
    Jun 2009
    Posts
    7
    contacts looked good. no pitting or burning. looked pretty much new.

  6. #6
    Join Date
    May 2007
    Location
    Dry as a bone Tucson
    Posts
    4,544

    120 volt coil ?

    Quote Originally Posted by moseamo View Post
    I've been working on a Carrier RTU Model 50hjq014. First time found the contactor not pulling even though had correct voltage at contactor. Just touched contactor and it pulls in. I replaced contactor and it worked fine for about a month. Called back out same problem. Checked for loose wiring, bad ground (contactor 120v coil), pressure switches. Couldn't find anything wrong, but went ahead and tried another contactor. Works for about a month then same problem happens. Tried even replacing current sensing switches. And it happened again. Any suggestions would be appreciated, maybe Im missing some kind of stat or switch that is on the unit.
    ? are you sure that the coil is supposed to be 120 volt?
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  7. #7
    Join Date
    Jun 2009
    Location
    massachusetts
    Posts
    22
    Maybe your contactor should be 240v, did you ever check original that you took out

  8. #8
    Join Date
    Sep 2008
    Location
    Da' Mitten
    Posts
    71
    I've seen something similar with units that have a delay on make timer on them to prevent short cycling when the stat is being fiddled with..
    The timer works properly most of the time, but every so often it passes correct voltage but not enough current to pull in the coil on the contactor. When this happens you see correct voltage and the contactor still does nothing.

    Does the replaced contactor work properly when 120 is applied to the coil after replacement? If so it would indicate the problem is not the contactor but the board or the stat.

  9. #9
    Join Date
    Dec 2007
    Posts
    28
    IS YOUR CONTACTER CHATTERING? CHECK THE VA RATING ON YOUR TRANSFORMER SEE WHAT YOUR PULLING. IF YOUR USING WHAT EVER CONTACTOR YOU HAVE ON YOUR TRUCK IF YOU GO TO BIG YOUR TRANSFORMER MIGHT NOT BE ABLE TO PULL IT IN. TRY BUMPING UP THE SIZE OF YOUR TRANSFORMER.

  10. #10
    Join Date
    Jun 2009
    Posts
    7
    Quote Originally Posted by Bill Bednarick View Post
    I've seen something similar with units that have a delay on make timer on them to prevent short cycling when the stat is being fiddled with..
    The timer works properly most of the time, but every so often it passes correct voltage but not enough current to pull in the coil on the contactor. When this happens you see correct voltage and the contactor still does nothing.

    Does the replaced contactor work properly when 120 is applied to the coil after replacement? If so it would indicate the problem is not the contactor but the board or the stat.
    Yes new contactor works fine for about a month. Next time it happens Ill try checking how much current the coil is pulling. Never thought of that.

  11. #11
    Join Date
    Jun 2009
    Posts
    7
    Quote Originally Posted by stenly View Post
    Maybe your contactor should be 240v, did you ever check original that you took out
    Yes the original was 120v.

  12. #12
    Join Date
    Jan 2005
    Posts
    605
    Quote Originally Posted by moseamo View Post
    Yes the original was 120v.
    How many people have been there before you?
    Replacing, like for like, doesn't mean it's correct.

  13. #13
    Join Date
    Mar 2009
    Location
    Several Miles from Sane
    Posts
    1,472
    Quote Originally Posted by REFERJMAN View Post
    IS YOUR CONTACTER CHATTERING? CHECK THE VA RATING ON YOUR TRANSFORMER SEE WHAT YOUR PULLING. IF YOUR USING WHAT EVER CONTACTOR YOU HAVE ON YOUR TRUCK IF YOU GO TO BIG YOUR TRANSFORMER MIGHT NOT BE ABLE TO PULL IT IN. TRY BUMPING UP THE SIZE OF YOUR TRANSFORMER.
    referjman, turn off the capslock, it's like you're yelling !

    Check the inrush and holding VA requiremenrs for the contactor, had 1 recently that worked fine when I was there but 4 hours later it wouldn't pull in. The holding current was 22VA but the inrush was 75VA. Transformer was, you guessed it 75VA. That was on 24VAC circuit but I have also seen it happen on 120 control circuits. If you can find out what Original Make/Model was, that may solve your problem. Also check to see if you have a pilot relay that controls the contactor, that deserves a look also.
    If sense were so common everyone would have it !

    All opinions expressed are my own. Any advice provided is based on personal experience, generally accepted fact or publicly available information. As such, it is worth exactly what you paid for it, not a penny more not a penny less !!

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