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Can I put a 60-amp breaker in a 60-amp panel?

Discussion in 'Charging and Infrastructure' started by Phil Kulak, Oct 3, 2017.

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  1. Phil Kulak

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    This sounds a bit silly, but I have a 60-amp sub panel in my garage, currently with a 50-amp breaker for the EVSE and a couple 15s for lights and such. I'd like to replace the 50 with a 60 for the HPWC, and I don't see why that would be an issue, but does anyone know if it's against code in the US? I know it's fine for breaker amps to sum higher than the panel, but this seems different...
     
  2. RandyS

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    Hi Phil,
    EV Charging load is considered a continuous load with respect to the National Electrical Code. Because of that, a continuously loaded circuit can only be loaded up to a maximum of 80% of the rating of the breaker. So that's one issue.

    When you say you have a 60 amp subpanel in the garage, what is the limiting factor? Is it the bus in the panel? The size of wire that is feeding the panel?

    My first inclination is your panel is probably too small to load it up as much as you're talking about....But we probably need more information....
     
  3. garsh

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    Note: I know very little about electrical codes, and slightly more about household electrical work, so ask a professional if you want a good answer. That said, even professionals don't really know all the codes. Here are a number of people - including some professionals - discussing this very issue:
    https://www.garagejournal.com/forum/archive/index.php/t-34198.html

    The consensus seems to be that the breakers are sized to protect the wires, and that there are no NEC codes about sizing breakers in this situation. Some electricians, however, say that any breaker should be sized at most 80% of its disconnect breaker, which would imply that you should leave it at 50 amps.

    I assume that you plan to limit the HPWC to 48 amps even if you install a 60 amp breaker for it. That will keep the continuous load to under 80% of both the EVSE circuit breaker as well as the main breaker. The problem is that if you turn on *any* additional continuous load in the garage, you will immediately be over 80% of the main breaker's rating. You'd be in an interesting situation where the 60 amp feeder breaker could trip, while all of the individual breakers are happy and stay connected.

    Check the sub panel in your garage. The sub-panel itself may indicate a maximum breaker size. If there's no writing available on the sub-panel itself, share the make & model and we can try to help you look up specifications for it. If the panel can handle the load, and you don't think you'll run other continuous loads concurrently with the HPWC, then I think you would be OK.
     
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    • Phil Kulak

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      That's a good point about going over the 80% for the panel so easily. All I have is a single LED bulb... but still, that's continuous. :D

      I may wait for final confirmation that the 3 will charge at 48 amps, then just have an electrician come over. I've been angry at myself for years for making it a 60 amp panel instead of 120... maybe this is the excuse to fix that.

      Thanks for the advice, guys!
       

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