SE conductors

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journeyman0217

Senior Member
Location
philadelphia,pa
hey everyone, was wondering what degree column you would use to figure out ampacity of SEU cable? looking at article 338 i see nothing stating how to size it. would you assume 75 degree column? ex: a 100 amp service for a single family dwelling would be #2 al correct? i made adjustment according to article 310.15 b 7....
 

journeyman0217

Senior Member
Location
philadelphia,pa
yes i see in article 338.10 b4 where it says 60 degree column when installed in thermal insulation and article 310.15b7 just says shall be rated not less than 83% of the service rating, but i can't find anywhere it saying what degree column to use when installed outside in a normal service location....??
 

augie47

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Staff member
Location
Tennessee
Occupation
State Electrical Inspector (Retired)
Art 338 dictates the ampacity of the cable itself. That ampacity varies depending on the Code cycle ('08-'11-'14) and the nature of the install ( in insulation or not in insulation in later Codes).
Once you have calculated your load, using the 83% rule where applicable and not using the 83% unless applicable, you select a conductor to carry that load.
For instance, if the 60° Table applies then #1/0 AL's ampacity is 100 amps.
If you were able to apply the 83% and, after applying it, you only need a 100 amp cable then 1/0 is sufficient.
However, say you were feeding a sub-panel or a HVAC unit and the load was 110 amps. The 83% does not apply and the 1/0 would be too small.
 

infinity

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Location
New Jersey
Occupation
Journeyman Electrician
yes i see in article 338.10 b4 where it says 60 degree column when installed in thermal insulation and article 310.15b7 just says shall be rated not less than 83% of the service rating, but i can't find anywhere it saying what degree column to use when installed outside in a normal service location....??

Like most conductors you would use it's 75° C ampacity for sizing. SE cable has a special condition that when in contact with thermal insulation it's ampacity is lowered to the 60° column in 310.15(B)(16) then apply the 83%.
 

Dennis Alwon

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Staff member
Location
Chapel Hill, NC
Occupation
Retired Electrical Contractor
Art. 338.10(B)(4)

(a) Interior Installations. In addition to the provisions of
this article, Type SE service-entrance cable used for interior
wiring shall comply with the installation requirements of Part
II of Article 334, excluding 334.80.

334.112 Insulation. The insulated power conductors shall
be one of the types listed in Table 310.104(A) that are
suitable for branch-circuit wiring or one that is identified
for use in these cables. Conductor insulation shall be rated
at 90°C (194°F).
 
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