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440 volt run capacitors

Replaced a 377 volt run capacitor on a heat pump with a new one and system started up and runs fine.  Got back to shop and parts guy called and said that he gave me a capacitor rated at 440 volts.  Is there any problem running the 440v or should it be replaced with one rated at 377?


  • Empire_2
    Empire_2 Member Posts: 2,343
    370 vs 440vac cap:

    As a general rule equipment designed for use of the 370 vac cap requires the use of same.  In a bind for only a short time should the 440 be used.  It packs more of a punch and can harm psc motors designed for 370 caps.  If ya get a chance, read some on start caps used in refrigeration.  These come in many sizes and you will get an idea of how and where they can be used.  I know you have a run cap, but it's to shed some light as to why motors are rated for certain caps, be it compressors, psc motors, etc...

    Mike T.
  • Techman
    Techman Member Posts: 2,144
    edited July 2012
    cap vs. cap vs. vac

    I'm going to twist things just a little.A given compressor will create or produce or make or generate only a certain amount of "double voltage which is additive stuff".
  • zepfan
    zepfan Member Posts: 383
    not a problem

    there is not a problem at all with using a 440volt capacitor in place of one that was rated at 370v.i stock only 440 volt capacitors on my truck,and still service units that i installed 440volt capacitors on fifteen years ago.the same way you can use a 600 volt fuse on all voltages up to and inlcuding 600 volts,you can use a 440 volt capacitor to replace capacitors that have a voltage rating of up to 440volts.
  • SWEI
    SWEI Member Posts: 7,356

    The capacitance value (read in µF) needs to match the old one.

    The voltage rating is a maximum limit for the cap, so using higher voltage cap is fine, but lower is not.  Remember that an AC cap has to handle peak voltage and not just RMS.
  • zacmobile
    zacmobile Member Posts: 211

    We had a bad run of run caps on our geo units, they came supplied with 370V ones and were almost guaranteed to blow within 6 months. Then the manufacturer started supplying them with 440V ones and have had zero problems for about two years now.
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