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Thread: Elevator motor OCPD question

  1. #1
    Join Date
    Apr 2012
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    Elevator motor OCPD question

    I'm trying to size branch circuit OCPD and conductors for an elevator motor. The only data that I have for the motor is 16 HP at 30.6 RPM, and the utility voltage 208/3 phase.

    For sizing the OCPD I need motor HP so my first thought what exactly is this info "16 HP at 30.6 RPM" even used for?

    How do I get the HP to use for sizing the OCPD?

    Does 30.6 RPM suggest a multi speed or low speed motor?

  2. #2
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    Williamsburg, VA
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    Quote Originally Posted by cppoly View Post
    I'm trying to size branch circuit OCPD and conductors for an elevator motor. The only data that I have for the motor is 16 HP at 30.6 RPM, and the utility voltage 208/3 phase.

    For sizing the OCPD I need motor HP so my first thought what exactly is this info "16 HP at 30.6 RPM" even used for?

    How do I get the HP to use for sizing the OCPD?

    Does 30.6 RPM suggest a multi speed or low speed motor?
    There's nothing from the mfg of the motor, drive unit, hydraulics unit, elevator mfg?

    30.6RPM seems to indicate to me a DC motor, reduction gearbox or most likely a VFD to achieve such a low, precise number, tho I admit I know about as much as elevator motors as I do biological invisibility cloaks for polka-dotted unicorns. A Google search of "16 HP at 30.6 RPM" yielding one result with that exact phrase: this thread.

    istm to be too easy to simply size the conductors and OCPD for a 16HP motor, keeping voltage drop at a low (3% or less) amount.
    Electricians do it until it Hertz!

  3. #3
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    Thanks. I will look further into it from the manufacturer.

    But, what are you supposed to do when you are given a HP that doesn't match up with the HP in the NEC tables? Just round UP? 16 --> 20 HP?

  4. #4
    Join Date
    Dec 2010
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    Quote Originally Posted by cppoly View Post
    Thanks. I will look further into it from the manufacturer.

    But, what are you supposed to do when you are given a HP that doesn't match up with the HP in the NEC tables? Just round UP? 16 --> 20 HP?
    I wouldn't round up. Maybe use the nameplate information?
    The more they overthink the plumbing, the easier it is to stop up the drain

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