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Thread: Compressor with built in breaker?

  1. #1
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    Compressor with built in breaker?

    A local garage has a problem with a single pole 40 amp breaker tripping on an air compressor. This breaker is part of the compressor but only disconnects one leg. Behind this compressor is the disconnect. I want to bypass this breaker but I want to make sure I am not bypassing something that I should not. I don't even know why this breaker is installed as part of the compressor assembly.
    Should I be able to bypass this without an issue?
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    Rick. Shelby county TN. 2002 code cycle.

  2. #2
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    Sounds like it may be a motor overload protection device if it only opens one pole. Does the motor have overload protection other than this device?

  3. #3
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    Are we to guess that it's a 1ph 240v motor?
    The suggestion that the device that your are refering to as a breaker may actually be some sort of overload device to protect the motor and as such I would strongly suggest that you contact the compressor manufacturer about it and not try being a hero and end up frying the motor.
    I'm sure all of have been guilty of 20-20 hind sight which contributes to our continuing education. That's why this forum is helpful. I know that I've learned a lot from it when you say to your self "I didn't even think of that" or " I didn't know that."

  4. #4
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    It may be an overload protection device. If the manufact is still in business, you could call them to confirm.
    Reward the hard worker and drop the buddy buddy slacks!!!

  5. #5
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    it is a 1ph 230/v 7hp
    33.8 amps
    Fused at 50 amps at the panel. #8 conductors.

    Customer is going to look into getting a new motor.
    Rick. Shelby county TN. 2002 code cycle.

  6. #6
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    Quote Originally Posted by aftershock View Post
    it is a 1ph 230/v 7hp
    33.8 amps
    Fused at 50 amps at the panel. #8 conductors.

    Customer is going to look into getting a new motor.
    Those little terminals (spade connectors) carried 33.8 amps???
    Cheers and Stay Safe,

    Marky the Sparky

  7. #7
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    may not be an electrical problem, the compressor might be trying to start under too much head pressure and the "breaker" is doing what it is designed for. just a thought......

  8. #8
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    Quote Originally Posted by aftershock View Post
    it is a 1ph 230/v 7hp
    33.8 amps
    Fused at 50 amps at the panel. #8 conductors.

    Customer is going to look into getting a new motor.
    Without finding out what is wrong first?

    Can I sell him parts?

    If there is mechanical problem with driven load new motor will likely do same thing.

  9. #9
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    Quote Originally Posted by aftershock View Post
    it is a 1ph 230/v 7hp
    33.8 amps
    Fused at 50 amps at the panel. #8 conductors.

    Customer is going to look into getting a new motor.
    I know it's late I can't get past the thought of 1ph 230V , could it be that the #8 wire is just toast?

    Did you swap the wires, did you megger the wires? I do like MNBiker's suggestion to.
    If your even thirsty, your two quarts low.

  10. #10
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    Quote Originally Posted by cadpoint View Post
    I know it's late I can't get past the thought of 1ph 230V , could it be that the #8 wire is just toast?

    Did you swap the wires, did you megger the wires? I do like MNBiker's suggestion to.
    I think you missed the part in the OP that the breaker that is tripping is part of the compressor not the 50 amp two pole that protects the conductors feeding the compressor.

    The problem with these small OEM breakers is they are made to Carry allot of current in a small package and they do fail or at least weaken the more times they have been tripped, My thought would also be to make sure the unloading valve in the pressure switch is opening when the pressure switch shuts the compressor off, I would only for testing purpose bypass it if it wont hold at all, if you can manually trip the pressure switch after it runs for a little to see if you hear the valve open and hear the air sound, also monitor the amp readings as it builds up pressure and note at what pressure the motor gets to the FLA if it does at the set point it good to go but if it reaches it way before then see if the pressure switch was cranked up.

    Which another quit common problem is many of these shop owners or workers will run up the pressure above the compressors design rating, I had one a few week ago who had cranked his up to 195# on a compressor that was only design for 150# max I had to tell him that it was not design to run that high, after installing a new motor I was watching the amps which started going over the FLA at 160#, so we put a smaller pulley on the motor because he had a sand blaster that needed 180# and now it runs up to 190# with no problems but just takes a little longer getting there.

    I have by passed these built in over loads but only after installing a manual motor starter and protecting the motor at the FLA, as far as these stab on connections I have seen them used on heater loads with over 40 amps on them and while they are made better then most female connectors you can by at a big box store you can get better grades that are much harder to slide on, and have a much tighter connection.

    Oh and another problem is many shop owners will control the compressor by turning off the breaker feeding it at the end of the night, which can be fine if the air system leaks down before they turn it back on the next day, but turning off the breaker or any switch will not release the head pressure and if they try to start the compressor back up it will start under a high head pressure, while some compressors have a oil pressure controlled dump valve to release the head pressure which will dump the head pressure anytime the compressor stops turning most smaller ones use the pressure switch to dump the head pressure, if the compressor doesn't reach the set point the head pressure never gets dumped, like I said in another thread sometimes we have to educate these owners or motors can get expensive.
    Wayne A. From: N.W.Indiana
    Be Fair, Be Safe
    Just don't be fairly safe

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