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  1. #1
    Join Date
    Aug 2011
    Location
    Northern VA
    Posts
    38

    How to determine motor starter for small rotary compressor?

    Hey guys,

    I claimed a small rotary compressor off ebay, never been installed. Problem is, I did not get any of the starting gear with it and the manufacturer's site is not helpful.

    The compressor is:
    Rechi Precision
    Model 39R131F R-22
    115V 60Hz single phase
    23 LRA
    5240 BTU , 620W input power
    http://www.rechi.com/en/webProductsE...=getCompressor

    A run capacitor is specified, but no starting gear information. Can I just use one of those hard start kits with it? Do these type of compressors typically use a potential relay and start capacitor, PTC, or something else?

    Also, when determining HP size of the motor to aid in determining a proper starter kit, is that just the input power, as in 620W/735 = ~ .84 hp?

    Thanks in advance.

  2. #2
    Join Date
    May 2004
    Location
    SE Pennsylvania
    Posts
    928
    Never seen a low HP rotary with a start cap and relay and at 620 W that appears to be .84 HP. They only list a 15 uf 270 vac capacitor which appears to be a run cap, but I would contact rep.

  3. #3
    Join Date
    Dec 2004
    Location
    Chicago area
    Posts
    1,439
    A hard start kit can be installed on any motor. As for the style using potential relays, you need to know the correct back emf for the potential relay to work.

    Regardless, that's is not switch gear. The switch gear is the motor starter, and for that a simple contactor, and and an adjustable ESP type overload would do just fine.

  4. #4
    Join Date
    Aug 2011
    Location
    Northern VA
    Posts
    38
    After some poking around, it appears this compressor is a permanent split phase with a run cap between the start and run windings and no separate starting gear, but I will see if i can get a wiring diagram from the manufacturer. Hopefully they can give me the spec for the overload switch as well.

    Weird thing is, they specify a 15uF capacitor, but forum posts I've read reported it doesn't start it and they had to use a 25uF.

    Thanks for the info.

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