50 amp main breaker panel? No such animal

Discussion in 'Electrical Forum discussion & Blog' started by Homeownerinburb, Mar 26, 2014.

  1. Homeownerinburb

    Homeownerinburb New Member

    Messages:
    525
    Location:
    Los Angeles, CA USA
    Hey guys,

    I'm tasked with installing a sub panel in an out building. The customer does not need more than 50 amps out there, the largest tool he will be using is a 30 amp 240v welder.

    Here's the tricky part. I need a master breaker in the panel, of course. It is my understanding, and I could be wrong about this, that new code requires the master breaker be bolted down to the chassis of the panel in some manufacturer's UL approved arrangement.

    In other words, no back feeding of a 50 amp breaker just stuck onto the buss bars.

    It was not all that long ago that Murray had a 100 amp main breaker panel arrangement such that the main breaker was a conventional breaker plugged into a pair of blades that were bolted to the buss bars, and there was a simple clamp on the tail of the breaker that locked it down. That was the bomb. Just back out the screw, remove the 100 amp and replace with 50 amp, replace the clamp and screw.

    No longer.

    1) Am I correct, it is no longer permitted to just back feed a breaker?

    2) Does anyone know of a manufacturer that has what I need?
  2. Stuff

    Stuff Member

    Messages:
    53
    Location:
    Pennsylvania
  3. Homeownerinburb

    Homeownerinburb New Member

    Messages:
    525
    Location:
    Los Angeles, CA USA
    Possibly. I was chatting with an inspector and he did sort of hint at that.
  4. Speedy Petey

    Speedy Petey Licensed Electrical Contractor

    Messages:
    996
    Location:
    NY State, USA
    Not possibly, Stuff is correct.
    The 100A main breaker would only be a means of disconnect. This is done all the time for the exact reason.
  5. bluebinky

    bluebinky Member

    Messages:
    408
    Location:
    Santa Clara, CA
    Even the inspector out here "agreed" quickly on the difference between a disconnect and over current protection.
  6. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    22,262
    Location:
    New England
    The CB protects what's after it, and a 100A panel could (if it got it) support 100A, but obviously can't if the main panel's breaker is 50A. Sort of like a 20A circuit feeding a small electronics box with an internal 0.1A fuse...works fine, nothing burns up, at least it's not likely, and certainly not from overcurrent.
  7. Homeownerinburb

    Homeownerinburb New Member

    Messages:
    525
    Location:
    Los Angeles, CA USA
    Well. My mind is at rest.

    Happily, the inspectors in this town are pretty damned relaxed. Helpful. Friendly. Customer oriented.

    Beats the lot over in LA.
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