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  1. #14
    Join Date
    Jan 2008
    Location
    LEHIGH VALLEY, PA
    Posts
    697
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    Yes me to lost a recovery machine to a wild leg , on a compressor change out , make sure to check in future the voltage of phase to ground before using my cheater cord.

  2. #15
    Join Date
    Sep 2002
    Posts
    27,218
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    What is the two-phase power used for these days?

    PHM
    -------



    Quote Originally Posted by timebuilder View Post
    2 phase power requires four power conductors and a grounding conductor.

    It is still produced from the generated 3 phase for Center City Philadelphia using Scott-T transformer arrays, for feeders that run mostly along Walnut Street.

    So if those rooftop units were 2 phase, each one would have four conductors and a ground going to it.
    PHM
    --------
    The conventional view serves to protect us from the painful job of thinking.

  3. #16
    Join Date
    Nov 2006
    Location
    Southeastern Pa
    Posts
    32,126
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    Quote Originally Posted by Poodle Head Mikey View Post
    What is the two-phase power used for these days?

    PHM
    -------
    There are two answers.

    The first answer is that newly remodeled stores with new panels will get their own Scott-T transformer to produce a three phase source to run RTU's and such.

    The other use is to power an existing 2-phase power panel, where each phase pair is a 240 volt feed that can power 240 volt loads. There are very likely some old elevators that run on the 2-phase.

    Mostly, the feeds power a transformer. I think all of the motor-generator sets are gone, but I could be wrong.

    This is done to avoid having to pay for a new 3-phase conductor set to be brought in from the street. With permits and excavation costs, that be well in excess of $10 - 15k, and most of the corporates that rent store spaces along Walnut will do anything to avoid a complete service replacement. On top of that figure, there are metering cabinets and CT transformers that can raise the cost to $20k.
    [Avatar photo from a Florida training accident. Everyone walked away.]
    2 Tim 3:16-17

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