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Thread: Help explaining 208v system with compressor & capacitors

  1. #41
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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?
    Just to be clear depending on the transformer you can sometimes have a wild leg that will read substantially higher to ground. You do not want to use that for a 120V circuit because it is not 110-120V. As I understand they have been trying to eliminate those transformers but you still find one on occasion.

    Maybe this just muddied the water more

  2. #42
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    Quote Originally Posted by pecmsg View Post
    Now I'm confused!
    Yeah I should have clarified that the single phase could be coming from a 3 phase system and a transformer is used to get the single phase in residential.
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  3. #43
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    Quote Originally Posted by BNME8EZ View Post
    Just to be clear depending on the transformer you can sometimes have a wild leg that will read substantially higher to ground. You do not want to use that for a 120V circuit because it is not 110-120V. As I understand they have been trying to eliminate those transformers but you still find one on occasion.

    Maybe this just muddied the water more
    That's a whole other discussion!

  4. #44
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    Quote Originally Posted by pecmsg View Post
    That's a whole other discussion!
    I totally agree. The only reason I posted it was so if someone that didn't understand read your post that they wouldn't unknowingly tie into a wild leg for a 120V circuit.

  5. #45
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    Quote Originally Posted by BNME8EZ View Post
    I totally agree. The only reason I posted it was so if someone that didn't understand read your post that they wouldn't unknowingly tie into a wild leg for a 120V circuit.
    sought of like how we learned!

  6. #46
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    So, on a typical 3 phase system( no high leg). So, I can use L1 & L2 to power up a typical Single phase residential AC cond unit. So, why is that not called two phase? So, there is no single phase center tap xformer to produce a typical single phase power source for the typical single phase 208/230 vac res AC Cond Unit..???
    Last edited by TechmanTerry; 05-10-2021 at 09:13 AM.

  7. #47
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    Quote Originally Posted by BNME8EZ View Post
    I totally agree. The only reason I posted it was so if someone that didn't understand read your post that they wouldn't unknowingly tie into a wild leg for a 120V circuit.
    Yep
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  8. #48
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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!
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    Here is a cleaner schematic. This is what the #5 terminal does.
    I do a triple evac with nitro to remove non condensables.

  9. #49
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    Of course it would turn out sideways!
    I do a triple evac with nitro to remove non condensables.

  10. #50
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    Quote Originally Posted by BBeerme View Post
    Of course it would turn out sideways!
    Electrons know no direction

  11. #51
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    Well, I guess if they go in L1, gravity will take them to L2, LOL.


    Quote Originally Posted by pecmsg View Post
    Electrons know no direction
    I do a triple evac with nitro to remove non condensables.

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  13. #52
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    Quote Originally Posted by TechmanTerry View Post
    So, on a typical 3 phase system( no high leg). So, I can use L1 & L2 to power up a typical Single phase residential AC cond unit. So, why is that not called two phase? So, there is no single phase center tap xformer to produce a typical single phase power source for the typical single phase 208/230 vac res AC Cond Unit..???
    Terry that's a interesting question.
    If I'm understanding correctly your question is this.
    How does a residential 208/230 volt residential condensing unit work off of opposite phases on three phase as well as a residential single phase ( split phase ) service ?
    I gotta think about that and get back with you 🤔

    If you look at your home transformer you'll see only one line feeding the transformer. The primary side then has two wires coming off the secondary side. This transformer splits that single phase into two with a center tap for the neutral.
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  14. #53
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    Not sure if I'm following you guys, but if you draw it out, single phase has one sine wave, and three phase has three sine waves.
    I do a triple evac with nitro to remove non condensables.

  15. #54
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    Maybe this will help
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  16. #55
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    Quote Originally Posted by VTP99 View Post
    Terry that's a interesting question.
    If I'm understanding correctly your question is this.
    How does a residential 208/230 volt residential condensing unit work off of opposite phases on three phase as well as a residential single phase ( split phase ) service ?
    I gotta think about that and get back with you ��

    If you look at your home transformer you'll see only one line feeding the transformer. The primary side then has two wires coming off the secondary side. This transformer splits that single phase into two with a center tap for the neutral.
    I am more interested in "why" a regular 1 phase (2 hot legs w/ center tap,180* out of phase AC cond unit) is still called "single phase" when it is hooked up to a 3 phase power source and using 2 hot legs L1-L2/L1-L3/L2-L3.

  17. #56
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    Because the phases are out of phase from one another. Be it two opposite phases from 3 phases or 1 phase split from single phase .

  18. #57
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    Quote Originally Posted by VTP99 View Post
    Because the phases are out of phase from one another. Be it two opposite phases from 3 phases or 1 phase split from single phase .
    The 2 phases of a 3 phase power source are 120* out of phase w/ each other. 1 phase is 180* out of phase w/ each other

  19. #58
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    Now

    I need a drink!

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  21. #59
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    Quote Originally Posted by TechmanTerry View Post
    The 2 phases of a 3 phase power source are 120* out of phase w/ each other. 1 phase is 180* out of phase w/ each other
    That is correct but we still don't have a answer to your original question.
    Why do we call a single phase condensing unit connected to two opposite phases of a three phase system single phase ?

  22. #60
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    Quote Originally Posted by pecmsg View Post
    Now

    I need a drink!
    You are late,lol.

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