Apartment feeder size question

cdAtlanta

Member
Location
United States
I am working on a bid for a multifamily project, 208/120 V where each apartment is served by an SER cable (4-story wood construction bldg).

Plans call for the following SER sizes (ignoring voltage drop, using AL wiring): 110 Amps 2/0 cable, 125 Amps 3/0 cable and 150 Amps 4/0 cable.

Since the code eliminated the insulation requirement from article 338 for this size of service cable and since 310.15(B)(7) now allows the factor of 83% to be used for 208/120 I am thinking that this could be done using 2/0 for 150Amps, 1/0 for 125Amps and #1 for 110 Amps.

What am I missing? Thanks in advance
 

infinity

Moderator
Staff member
Location
New Jersey
Occupation
Journeyman Electrician
Are you under the 2017 NEC? Earlier versions did not allow the 83% for 208/120 volt systems.
 

cdAtlanta

Member
Location
United States
I am trying to find out if my code minimums are correct to have a conversation with the owner, i was surprised that the engineer was using wire so much larger. Do you guys agree with my approach or am i missing something?
 

Dennis Alwon

Moderator
Staff member
Location
Chapel Hill, NC
Occupation
Electrical Contractor
I wonder if the engineer didn't think you could use the 83% rule or maybe he was using the 60C column as it was in the 2014 nec.
 
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