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Thread: Max Breaker

  1. #1
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    Max Breaker

    After roughing in a new house and before final, we customarily get what is called a "service release". This is just an inspection with a few circuits connected to allow the POCO to connect power. This is mostly for HVAC to be turned on to acclimate the house for flooring, painting, etc.
    When I was preparing the panel for the service release I asked the HVAC installer what size breaker he needed for his unit as it was not on site when I left. He told me a 30A breaker and that's what I put in.

    Now I'm back doing trim-out and I just thought I would look at the unit to see what the nameplate said. The "Max Breaker" size was 40A. I know the 30A is legal but I don't want to be called back for nuisance tripping. However, this unit has been running for a couple of months and no reported tripping. Since this house is quite a distance for me to drive, do you think I should swap the breaker out for a 40A?
    If you aim at nothing, you will hit it every time!

  2. #2
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    A 40 now is cheaper than latter.

    I only had a couple that wouldn't start on smaller then max OCPD, and they ended up with hard start kits anyway.
    Tom
    TBLO

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    What is the minimum ckt ampicity? My guess is if it's been running for months your probably good, but as time goes by frequent over heating would likely cause that breaker to trip

    Sent from my SM-G965U using Tapatalk

  4. #4
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    Quote Originally Posted by nickelec View Post
    What is the minimum ckt ampicity? My guess is if it's been running for months your probably good, but as time goes by frequent over heating would likely cause that breaker to trip

    Sent from my SM-G965U using Tapatalk
    MCA was a little over 23A. It was 23.xx, I can't recall exactly.
    If you aim at nothing, you will hit it every time!

  5. #5
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    Your probably fine I would be able to sleep at night

    Sent from my SM-G965U using Tapatalk

  6. #6
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    If it will hold the starting surge it will likely be fine. If you are running on some temp service and then later switch to permanent service, there is a chance there is less overall circuit impedance in your permanent service and that could lead to higher starting surge from that arrangement - increasing the chance it trips upon starting.
    I live for today, I'm just a day behind.

  7. #7
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    I would leave the 30 amp CB. It should never trip under normal conditions.
    Rob

    Moderator

    All responses based on the 2014 NEC unless otherwise noted

  8. #8
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    Quote Originally Posted by infinity View Post
    I would leave the 30 amp CB. It should never trip under normal conditions.
    NEC allows a 35 amp breaker for 10 HP 480 V three phase motor.

    Many manufacturer selection charts suggest a 25 amp breaker.

    I've seen many connected to a 15 amp breaker and they never trip upon starting, but that don't mean all will hold on a 15 amp breaker either. All depends on starting surge current, which will remain pretty consistent until you make some change to the supply circuit.

    Had a big feed mixer motor at cattle feed yard several years ago - maybe 25 or 30 HP 230 volts. It ran for years on a 100 amp breaker no troubles. Then we happened to replace the supply line to that area with larger conductor - 100 amp breaker would randomly trip at startup - new supply conductors with less resistance meant starting surge increased enough to get into the instantaneous trip range on that breaker. Unfortunately it was a QO breaker and they don't make a 125 amp three pole so it took more than simple swap of a breaker to resolve this issue.
    I live for today, I'm just a day behind.

  9. #9
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    Quote Originally Posted by Little Bill View Post
    I know the 30A is legal but I don't want to be called back for nuisance tripping. However, this unit has been running for a couple of months and no reported tripping. Since this house is quite a distance for me to drive, do you think I should swap the breaker out for a 40A?
    What's the downside to swapping it out ? you purchase a new 40 amp breaker but you still have the 30 amp breaker that you remove and those get used all over the place. It's not like it goes to waste.
    The 95% of people that you can't trust give the other 5% a bad name.

  10. #10
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    Leave the 30 and if the customer has a call back or something else for you then change it out. I would not make the extra trip unless you were in the area.
    They say I shot a man named Gray and took his wife to Italy
    She inherited a million bucks and when she died it came to me
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