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Thread: 3 Phase or Single Phase

  1. #11
    Join Date
    Dec 2007
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    NE Nebraska
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    36,308
    Quote Originally Posted by petersonra View Post
    Is that typically true with 240 V single phase motors?

    I would bet by the time you add it all up it will be really hard to make an economic case for it.

    you would need to get a larger 480V 3 phase service for one thing. In this case something like 800 Amps. And often such services come with demand meters and they can be a real expensive proposition.

    Having said that demand meters are pretty much coming to everyone, and not to long down the road.
    Though it can vary from place to place, what I have seen around here is demand metering doesn't really kick in until you get over certain kVA level regardless of whether you are supplied with single or three phase and voltage doesn't really matter. Which makes sense if you are demanding 100 kVA it is still 100 kVA regardless of what voltage it is or number of phases. About 100 kVA and up seems to be where those demand charges start to kick in. Now it is somewhat rare, but not impossible to see single phase service that large.
    I live for today, I'm just a day behind.

  2. #12
    Join Date
    Aug 2004
    Location
    Northern illinois
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    16,538
    He might be looking at upwards of 500 KVA in total. that's a pretty substantial service I think just about every place that would be on a demand meter of some sort.
    Bob

  3. #13
    Join Date
    Dec 2007
    Location
    NE Nebraska
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    36,308
    Quote Originally Posted by petersonra View Post
    He might be looking at upwards of 500 KVA in total. that's a pretty substantial service I think just about every place that would be on a demand meter of some sort.
    I agree.

    And don't forget when you have demand metering and charges - you often also pay a minimum demand charge whether you use that minimum amount of energy or not. That is partly because of the higher kVA infrastructure they supplied for you - they invested some $$ on it and might expect to earn some revenue from usage, but if you seldom or never utilize that capacity it doesn't pay back for them very well, and at least a part of the reason for minimum demand charges. Though those higher capacity users may have that minimum demand charge - they often have lower energy rate then other customers, or even a tiered rate that changes at certain levels of usage.
    I live for today, I'm just a day behind.

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