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Thread: Help explaining 208v system with compressor & capacitors

  1. #21
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    Quote Originally Posted by flangatang7 View Post
    EDIT: For those looking for more information see below.

    Thank you!


    COMPRESSOR WHILST RUNNING
    these 3 don't tell you much except they are energized (hot)
    Ground to #5 on Potential Relay = 120v
    Ground to #1 on Potential Relay = 120v
    Ground to # 2 on Potential Relay = 120v

    Start Capacitor
    Ground to either terminal = 120v
    L1 (Common) to either terminal = 208v This tells you the terminals are powered through L2

    Run Capacitor
    Ground to either terminal = 208v
    L1 (Common) to either terminal 250v yep..... 250v

    L1 (Common) to Start winding = 250v

    L1 (Common) to Run winding = 208v Shows common is powered by L1, run is powered by L2

    L2 to Run winding = 0V
    proof of above, R and L2 are the same potential


    You should really take a class on electrical theory or read up on it, or get a senior tech to help you understand what you are looking at. It will also keep you safer!

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  3. #22
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    Both windings are both powered by L1 & L2.

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  5. #23
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    Thread Starter
    Quote Originally Posted by BNME8EZ View Post
    proof of above, R and L2 are the same potential


    You should really take a class on electrical theory or read up on it, or get a senior tech to help you understand what you are looking at. It will also keep you safer!

    100% electrical has never been my strong point coming from Australia where we don't use 208v it's a little harder. I am trying and taking time out to learn though. Will see if I can find some classes.
    Can you explain to me what #5 does on the potential relay? All I can say for certain is it has 120v coming in from L1.

    Thanks for your response!

  6. #24
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    Quote Originally Posted by flangatang7 View Post
    100% electrical has never been my strong point coming from Australia where we don't use 208v it's a little harder. I am trying and taking time out to learn though. Will see if I can find some classes.
    Can you explain to me what #5 does on the potential relay? All I can say for certain is it has 120v coming in from L1.

    Thanks for your response!
    Terminal 5 is one end of the relay coil, it is the same power leg as C terminal on the compressor.

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  8. #25
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    If you took that relay apart , you would be like .... oh .... so thats how it works

    Its just a magnetic coil , and a set of points

    The magnetic coil kicks the points open , and that drops out the Start Cap

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  10. #26
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    Quote Originally Posted by Snapperhead View Post
    If you took that relay apart , you would be like .... oh .... so thats how it works

    Its just a magnetic coil , and a set of points

    The magnetic coil kicks the points open , and that drops out the Start Cap
    Yep!

    Is it fair to say that the contact on terminal 1 opens once compressor reaches 75% running capacity?

  11. #27
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    The voltage is generated in the start winding. If the pick up voltage of your relay is higher than what you measure it won't pick up. if you take 80% of it you are close to the proper pu voltage. I have used potential relays on farm motors to replace the switches in the end caps.

  12. #28
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    Would that be the centrifugal switches ?

  13. #29
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    Quote Originally Posted by Snapperhead View Post
    I have gotten bad motors straight out the box ....

    Maybe you finally got yours
    I have got several over the last couple years.

    Sent from the Okie state usin Tapatalk

  14. #30
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    Quote Originally Posted by flangatang7 View Post
    100% electrical has never been my strong point coming from Australia where we don't use 208v it's a little harder. I am trying and taking time out to learn though. Will see if I can find some classes.
    Can you explain to me what #5 does on the potential relay? All I can say for certain is it has 120v coming in from L1.

    Thanks for your response!
    Is 208v in canada a twin phase circuit?

  15. #31
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    Quote Originally Posted by MadeInAustralia View Post
    Is 208v in canada a twin phase circuit?
    Here in the States we use the term single phase or 3 phase. 208 / 230 can be both. (I know gets confusing) 3 phase does not get start components.

  16. #32
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    A little reading material

    Hope it helps
    Attached Images Attached Images

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  18. #33
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    So you call a circuit with active and neutral 1ph

    and also call a circuit between two phases of a three phase supply 1ph as well?

  19. #34
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    YES

  20. #35
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    Quote Originally Posted by MadeInAustralia View Post
    So you call a circuit with active and neutral 1ph

    and also call a circuit between two phases of a three phase supply 1ph as well?
    Our 115 Volt can use any of the 3 phases with a Neutral. Phase to Phase is 208 / 230 Single phase

    I believe you use 230 volt for standard power supply. Each leg to ground shows 110 volts?

  21. #36
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    .
    Attached Images Attached Images  

  22. #37
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    Quote Originally Posted by VTP99 View Post
    .
    Now I'm confused!

  23. #38
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    Quote Originally Posted by pecmsg View Post
    Our 115 Volt can use any of the 3 phases with a Neutral. Phase to Phase is 208 / 230 Single phase

    I believe you use 230 volt for standard power supply. Each leg to ground shows 110 volts?
    415v 3ph standard supply, 230 any phase to neutral.

  24. #39
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    Quote Originally Posted by MadeInAustralia View Post
    415v 3ph standard supply, 230 any phase to neutral.
    OK that's the difference.

  25. #40
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    maneurope made a 415v phase to phase sump heater back in the day.

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