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Thread: alternating relay for duel motor starters

  1. #1
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    alternating relay for duel motor starters

    I was called to fix a motor on a duel motor compressor. One motor hwd failed and could no longer be run in the settup . I had to bypass all aux sw. And relay which shifts the primary starting motor from the left or rt..
    The compressor tank has two motors mounted on top with two pressure sw'sand an alternating starter relay btwn the two... Ideal each motor is made to be the primary one time after the next... This was very difficult to rewire.
    Is there any good references out on the market which will help with wiring motor controls and starter combimation... Here is a pic....
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  2. #2
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    This one is the simplest I found. And KISS is always best when it comes to controls.

    http://midwest-control.com/images/St...20Diagrams.jpg
    Some people are like slinkies. They serve absolutely no useful purpose. But still put a smile on your face when pushed down a flight of stairs.

  3. #3
    Join Date
    Jan 2012
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    Philly Pa burbs
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    Quote Originally Posted by Angel Electric View Post
    I was called to fix a motor on a duel motor compressor. One motor hwd failed and could no longer be run in the settup . I had to bypass all aux sw. And relay which shifts the primary starting motor from the left or rt..
    The compressor tank has two motors mounted on top with two pressure sw'sand an alternating starter relay btwn the two... Ideal each motor is made to be the primary one time after the next... This was very difficult to rewire.
    Is there any good references out on the market which will help with wiring motor controls and starter combimation... Here is a pic....

    Something you want to keep in mind about that control is, during times of high air demand both compressors will run. it does a little more than just alternate
    Proverbs 31;10


  4. #4
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    that is correct

    Thank you both for your input....
    I was able to rewire, but only after an extensive period of time...
    The real issue for me was becoming familiar with the centrer control relay and its incorporation of controlling one or the other of the two compressors, yet allowing both compressors to funtion, when air use is extreme... Seemed as though between the to motor starter, the center relay and the twopressure switches,I was dealing with a series parallel wiring application...I hoping there is a book or website which walks a student thru the various options for all the different motor controling applications?

  5. #5
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    Feb 2003
    Location
    Huntsville Alabama
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    That's why I posted the diagram for alternating and duplexing.

    I used to do a lot of sewage lift stations and you would be surprised at how complicated some of the designers would make the factory panels.

    Did one in South Alabama that not only alternated and duplexed but utilized 4 motors that alternated in sets
    and duplexed in pairs.
    Some people are like slinkies. They serve absolutely no useful purpose. But still put a smile on your face when pushed down a flight of stairs.

  6. #6
    Join Date
    Jan 2012
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    Philly Pa burbs
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    Quote Originally Posted by Angel Electric View Post
    Thank you both for your input....
    I was able to rewire, but only after an extensive period of time...
    The real issue for me was becoming familiar with the centrer control relay and its incorporation of controlling one or the other of the two compressors, yet allowing both compressors to funtion, when air use is extreme... Seemed as though between the to motor starter, the center relay and the twopressure switches,I was dealing with a series parallel wiring application...I hoping there is a book or website which walks a student thru the various options for all the different motor controling applications?

    Probably American Electrician's Handbook. You can probably find a used copy for about 30 bucks online. Older editions are fine for working on most of what you find out in the field.
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    Proverbs 31;10


  7. #7
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    Try $1.14 plus shipping. And believe me, It is a "must have"

    http://www.textbookx.com/detail.php?...nge&price=1.14
    Proverbs 31;10


  8. #8
    Join Date
    Apr 2008
    Location
    OBX, NC.
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    58

    thanx again...

    I used to have that book but somebody else must hv known its value at that time...Cause it disapeared from desk in job trailer... The diagram was helpful........

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