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Can you use a 240V breaker on a 600V system?

This is hypothetical, I am just curious. Please give this some thought.

I have a 600V, 5HP motor (3728.5 Watts) and a 600V panel I want to supply it from.

If I use a 20A, 600V breaker - the breaker will see ~6A on motor run. (P/V=I , 3728.5/600 = ~6A)

If I use a 20A, 240V breaker - the breaker mechanism will act as if ~15.5A is passing through. (P/V=I , 3728.5/240 = ~15.5)

For a 20A breaker, looks like 240V would work. What am I missing here? Does voltage have any affect?

11 Answers

  • Rita
    Lv 6
    2 months ago

    You can usually use a 600V rated breaker on 240V systems, but NEVER the other way around.

  • garry
    Lv 6
    2 months ago

    yes you can but you will need 3  of them , one for each line in . 3 phase has 3 lines .Just make sure you use slow blow fuses instead of instant blow fuses .

  • 2 months ago

    Your math setup is wrong. The 'v' variable is the voltage at source (600) and is not a factor in the voltage DROP across the breaker, which is either zero or infinity (closed vs open).

    The 240v rating on the breaker means that it is capable of opening and closing at that voltage at 20Amps, i.e., handling the instantaneous surge of power/heat at up to 240 volt at the contact points during the transition's high-resistance.

    When things go wrong at 600 volts, people die. 

    Have it be someone else.

  • 2 months ago

    absolutely, in fact go for a 120v breaker if you can, or even just use your finger as a breaker

  • 2 months ago

         Look up "arc fault" on Google and pay close attention to the stuff about the panel coming off the wall and filling your face with molten copper. You are in way over your head. Don't think about it.  Grampa B

  • ?
    Lv 7
    2 months ago

    CAN you: physically, maybe. SHOULD you: Oh, HELL no.

    It's a blatant disregard for code, for starters.  But it's just begging for trouble in any case:

    Voltage affects how long the gap must be for the breaker to break the circuit effectively.  If a 240v breaker opens on a 600v load, it may not be sufficient to quench the arc that forms as the circuit breaks and power continue into the circuit.

    Would anything go wrong: probably not.  But if it did the very safety device designed to prevent it getting worse would fail to arrest the fault, and possibly introduce a new one in a separate area.

  • 2 months ago

    you NEED the commercial gear that is rated for 600 volts or more.  nothing less will do -- the insulating qualities of lesser gear is insufficient to prevent instant arcing from hot to ground

  • 2 months ago

    If the breaker is rated at 240V, it will FRY INSTANTLY under 600V. If you don't know that, YOU are not qualified to READ the rating on a breaker.

    What you are missing is KINDERGARTEN level ability to THINK.

  • 2 months ago

    No. The 240V breaker is only rated for a 240V system. 

  • Anonymous
    2 months ago

    Not unless you want to start a fire.  What kind of question is this?

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