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  1. #14
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    Single phase, is amps times volts equals watts.

    3 phase is amp times volts times 1.73 equals watts.
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  2. #15
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    Upstate SC
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    Quote Originally Posted by beenthere View Post
    Single phase, is amps times volts equals watts.

    3 phase is amp times volts times 1.73 equals watts.
    Yeah I edited after reading through it again to specify the difference between single phase and three phase

  3. #16
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    Thats where a lot of people make the mistake of thinking 3 phase A/C is cheaper to operate.
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  4. #17
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    i just thought that 13 seer would cost the same to operate using the same kw/hr rate regardless if single or 3 phase. i'm inclined to go with beenthere but would like to know for sure

  5. #18
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    SEER=Seasonal Energy Effificeny Ratio.

    Basically, a 13 SEER removes 13 BUs per watt of electric it consumes.
    (Not 100% true, but close enough for this explanation)

    So, if you have a sinle phase 13 SEER, and a 3 phase 13 SEER.
    They are both removing 13 BTUs per watt of electric they consume.
    So if they are both 2 tons/24,000BTUs.

    The 2 ton single phase would be consuming 1846 watts. At 240 volts that would be 7.69 amps.

    The 2 ton three phase would be consuming 1846 Watts. At 240 volts that would be 4.44 amps.

    If the thre phase was on a 480 volt service. It would still use 1846 Watts. Just its amp draw would be 2.22 amps.

    If the three phase service was a 208 volt service. It would still be 1846 Watts. With the amp draw being 5.13
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  6. #19
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    Talking

    thanks, u da man

  7. #20
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    Mar 2009
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    Spokane WA
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    Talking

    Dudes,

    3 Phase is cheaper to operate than single phase. 1/3 the power just bounces around the windings and is therefore 150% cheaper to run a 3 phase motor than a single phase motor at the same power range.

    You can google it if you want or you can read this article to see that the guys here that believe 3 phase is cheaper to operate are correct!

    Read this page to see exactly what we are talking about. Yes, watts are watts but, 1/3 of the power just bounces between the windings.
    http://www.windstuffnow.com/main/3_phase_basics.htm

    JJ. OUT!

  8. #21
    Join Date
    Jun 2003
    Location
    Chicago, IL
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    4,485
    Quote Originally Posted by Super Tech JJ View Post
    Dudes,

    3 Phase is cheaper to operate than single phase. 1/3 the power just bounces around the windings and is therefore 150% cheaper to run a 3 phase motor than a single phase motor at the same power range.

    You can google it if you want or you can read this article to see that the guys here that believe 3 phase is cheaper to operate are correct!

    JJ. OUT!
    A 3 phase motor may be cheaper to run than a single phase, but a 13 SEER air conditioner costs exactly the same to run no matter how many phases it has.

    Its like saying that two different cars get 13 MPG, but one uses half the gas of the other. Not possible. If it used half the gas it would get 26 MPG.


    also, single phase motors used in the HVAC world have nifty little efficiency boosting devices called run capacitors, which brings the efficiency much closer to that of a 3 phase motor.

    I need some more information about this magical A/C thats 150% cheaper to run. Seems like that means the utility would be PAYING ME to run it. Im gonna pack as many as possible into my garage, airflow clearances be damned. Then I'll just turn em on, sit back, and watch the money roll in

  9. #22
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    ROFL.

    You can't answer the OP's question correctly, by only looking at one factor.

    Get past the tunnel vision.
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  10. #23
    Join Date
    Mar 2009
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    174
    If you run a single phase unit an a 3 phase service and dont balance the 3rd phase with some other load , it will cost more to run due to your meter using your highest amp leg to spin the meter. Other wise it is the same.

  11. #24
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    Mar 2009
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    Spokane WA
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    Ok, read the page and dispute that.

    I hadn't considered that the motors would be downsized HP wise and therefore would still be using the same amount of wattage.

    That does make sense and there you get the 13 SEER. I do know what that means.

    I got stuck on the horse power thing. If you don't believe the percentage, then look it up.


  12. #25
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    There are other far better explanations of 3 phase then the one you found.

    That one is a little misleading.

    1/3 the power doesn't "just" bounce between the winding.

    But, the OP's question, was a system question, not a componet question.


    If your in the trade, apply for pro membership.

    Lots more info in the pro tech, and educational forums.
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  13. #26
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    Jun 2009
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    Upstate SC
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    Quote Originally Posted by Super Tech JJ View Post
    Ok, read the page and dispute that.

    I hadn't considered that the motors would be downsized HP wise and therefore would still be using the same amount of wattage.

    That does make sense and there you get the 13 SEER. I do know what that means.

    I got stuck on the horse power thing. If you don't believe the percentage, then look it up.

    You're funny

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