MDU Loadcenter MB vs Disconnecting Means

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jwatts

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Multi Unit Apt bldg has both 125a and 100a load centers. It is cheaper to purchase a 24cct 125a MB panel than a 24cct 100a, as well as simplifies the installation if all panels are the same. If I installed a 100a breaker at the corresponding meter stacks, which are in the electric closets on each floor, and fed the tenant load centers with 100amp wiring (#1 alum), is this compliant? I tend to think the 100amp breakers at the meter stacks are the OCP, and sized accordingly for the wiring.....and the 125a MB in the loadcenter would be considered a disconnecting means.
 
jwatts said:
Multi Unit Apt bldg has both 125a and 100a load centers. It is cheaper to purchase a 24cct 125a MB panel than a 24cct 100a, as well as simplifies the installation if all panels are the same. If I installed a 100a breaker at the corresponding meter stacks, which are in the electric closets on each floor, and fed the tenant load centers with 100amp wiring (#1 alum), is this compliant? I tend to think the 100amp breakers at the meter stacks are the OCP, and sized accordingly for the wiring.....and the 125a MB in the loadcenter would be considered a disconnecting means.
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I agree with Don's view, but I wonder why you are using MB load centers as opposed to MLO. Is this a local requirement to have a main breaker?
 
inspector is concerned that the 100amp breaker at the meter stack will trip in lieu of the 125amp main breaker at the load center should a fault occur.....and the meter stacks are located in locked electrical closets, which would require maintenance to be contacted to open the room. I can't find anything code related that would prohibit my proposed installation.
 
jwatts said:
inspector is concerned that the 100amp breaker at the meter stack will trip in lieu of the 125amp main breaker at the load center should a fault occur.....and the meter stacks are located in locked electrical closets, which would require maintenance to be contacted to open the room. I can't find anything code related that would prohibit my proposed installation.
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I forgot about that rule. The inspector may have valid point. Look at 240.24(B).
 
don_resqcapt19 said:
I forgot about that rule. The inspector may have valid point. Look at 240.24(B).
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True, but since this is a multiple-occupancy building, wouldn't the exception in (2008 NEC) 240.24(B)(1)(1) take affect? I have done many apartment buildings and Condo's that have meter stacks in a centralized electrical room and have never had an inspector say anything about 24024(B).
 
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