60A sub panel fed with #6 SER feeder.

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csoc64

Senior Member
Location
northeast
Came across a sub panel today that is fed by a 60A breaker located in the main panel. Feeding this panel is a #6 SER conductor. Isn't this feeder undersized? From 310.15(B)(16), #6 AL is good for 50A at 75C (I am assuming terminations are 75C). Is this feeder allowed to be sized at 83%, or is that just for services? 2014 code applies here. Looks to me like #4 AL would bee the smallest size you could run for this application, so a #4 SER would be ok. Am I correct?
 

Dennis Alwon

Moderator
Staff member
Location
Chapel Hill, NC
Occupation
Retired Electrical Contractor
It is possible the wire is rated 75C-- look at 338.10(B)(4)

Even at 75C you are only good for 50 amps and that is a standard size overcurrent protective device (240.6)so you need a dp 50.
 

csoc64

Senior Member
Location
northeast
Agree. Just did 60 amp sub last month and used #4 SER. No insulation to factor in my run either.

Forgot about the insulation. In this case, the SER runs about 50 feet from the sub panel to the main panel, at least 40' is buried in an insulated wall. Do I need to de-rate further?
 

csoc64

Senior Member
Location
northeast
It is possible the wire is rated 75C-- look at 338.10(B)(4)

Even at 75C you are only good for 50 amps and that is a standard size overcurrent protective device (240.6)so you need a dp 50.

So if the SER is running through insulated walls, it is limited to 60C column; therefore limiting the OPD to 40A. Correct?
 
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