#2 Type SE (U and R)

[jbelectric777]

Hey guys, I just want some feedback on use permitted for aluminum type SEU and SER as service entrance, specifically its ampacity derating. I am pretty sure I am correct but non the less, here's the scenerio. I understand that note (8) allows the use of #2 type SEU and SER as 100 amp service conductor/s for single and two family dwellings only. I take that as it cannot be used as service entrance and have protection more than 100 for 1) R3 multi family 2) commercial occupancies. So in the case of a multi family apartment building each "dwelling" must have a 100 amp service BUT it cannot be using the number 2 AWG aluminum. It would have to be sized in accord with the table/s etc in 310-16 or be protected at the next common (code given) size, which would be 90amps. So if feeders were pulled in an R3 that were #2 Al they can only have 90 amp protection but at the same time the apartment service size would be in violation because it is a dwelling and the minimum size service is 100 amp. Who say yey and who say ney ? Thanks in advance, Jim

 

[Dennis Alwon]

I am thinking that the Table 310.15(B)(6) doesn't apply to the service for a multi family building but it may apply to each individual unit where the cable carries the entire load of the unit.

120/240-Volt, 3-Wire, Single-Phase Dwelling Services and Feeders. For individual dwelling units of one family, two-family, and multifamily dwellings, conductors, as listed in Table 310.15(B)(7), shall be permitted as 120/240-volt, 3-wire, single-phase service-entrance conductors, service-lateral conductors, and feeder conductors that serve as the main power feeder to each dwelling unit
and are installed in raceway or cable with or without an equipment grounding conductor.

Of course if it is 3 phase then this section will not apply

 

[inspector 102]

Just for clarification, this section states 3-wire services and feeders. Is this to mean that a 4-wire system such as would be installed after a main disconnect at the dwelling and feeds a sub-panel can not use this table for conductor size. Basically if there is an outside disconnect fed from the meter with #2 Al, then goes across the house to the load center in a basement, can the feeder still be #2 or should there be an increase in conductor size since it is a 4-wire feeder? Just asking.