Moderaters - Electricians- I need a Calc.


Old 01-25-05, 06:49 PM
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Moderaters - Electricians- I need a Calc.

I am installing a 600 amp three socket mini mod to supply three commercial rental units with a 200 amp panel each. I am also installing a 400 amp two socket mini mod on the same building for the same purpose......(total five commercial rental units. The inspector has told me to use 600 MCM (hot legs) and 500 MCM (neutral) on the two unit and two 350 MCM parrallel (hot legs) two 250MCM parallel (neutral) on the three unit...... HELP ME PLEASE. The 600 MCM is to big for the lugs....I have been told that I can rate the first meter at 100%...second meter at 50% and every meter after that at 25%. Is this true and where can I find this to help support my case......thanks

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Old 01-26-05, 05:09 AM
HandyRon's Avatar
Join Date: Dec 2001
Location: New York
Posts: 1,365
You cannot arbitrarily derate or apply a demand factor to the meter sockets. You need to perform a service calculation based on Article 220 in the NEC. How could a permit be issued without this calculation being presented to the AHJ (inspector)?
Without a whole lot more information, and detailed service calculations, fully sizing the service conductors, as recommended by the "inspector" is your only choice? How did you pick 600A and 400A services without calculations?
Old 01-26-05, 05:41 AM
Join Date: Nov 2002
Location: SC
Posts: 171
Agree the size of the service should be based on the calculation. Apears the inspector is sizing the service based on the rating of the meter socket mini mod. Question? Is there a 600A disconnecting means on the triple? A 400A disconnecting means on the double? Your total demand would be less if you could just use one service. How were you able to get 2 services on this building?
Can you get an underground service and let the utility co run the feed? Save you some cash.
Old 01-26-05, 04:23 PM
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There will be a total of 5 units in the building.....the power company wanted me to install one three tenant meter base and one two tenant meter base. The three tenant has a maximum rating of 600 amps and the two tenant has a maxium of 400 amps. Each meter socket will supply a panel with a rating of 200 amps. Each socket has a 200 amp disconnect. Having explained this to the inspectors supervisor, he agreed and I put 3/0 parralell in the three tenant and 350 MCM in the two tenant........

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