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  1. #1
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    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?

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  2. #2
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    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
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    Yes it's running around 205v and it's on the 208v tap. I have a solid 27v

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  4. #4
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    Tried to dig my old contactor out of there dumpster but no luck.

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  5. #5
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    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

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  7. #6
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    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
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    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.

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  9. #8
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    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
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    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
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    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.

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  12. #11
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    Follow the low voltage and test each and every safety switch, one or more are not making good contact under load.

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  14. #12
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    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.

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  15. #13
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    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!

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