100A resi sub-feed

Status
Not open for further replies.
M

mjmike

Senior Member
Just not seeing it so maybe somebody can chime in. For a residential 100A sub-feed from a 200A main panel in the same residence, you go to the box stores and even destributers, they say you can use 2/2/2/4 SER (or SE) al cable. I can't understand how they are saying this. You can't use table 310.15(B)(6) (08 code) because it is not the main dwelling unit feed. Just don't understand how they are saying this, anybody know?

The only way I see to properly do this installation is with 3-#3 thhn/thwn and 1-#8 gnd in 1 1/4" EMT copper or 3-#1 thhn/thwn and 1-#6 gnd in 1 1/4 EMT if using aluminum. (based on 75 degree C table 310.16).

There isin't a 3-conductor+G sheathed copper cable and if you use a SE alum cable, I think you have to use the 60 degree C column of table 310.16.

Am I missing something?
 
augie47

augie47

Moderator
Staff member
Location
Tennessee
Occupation
State Electrical Inspector (Retired)
You are not mssing anything.

Fairly common here to use a 1/0 AL SER.
 
M

mjmike

Senior Member
thanks augie47. 1/0 al ser, this would meet the 60 degree column of table 310.16 and would probably be cheaper than copper in conduit. Is this because my recolection that if using SER, you must use the 60 degree column? I thouhgt I had read that in the code someplace before.
 
augie47

augie47

Moderator
Staff member
Location
Tennessee
Occupation
State Electrical Inspector (Retired)
It appears that 338.10 is addressed very differently from jurisdiction to jurisdiction.
In regard to "whole house" service and feeders, it has been discussed and cussed in numerous threads which you can review on the Forum.
In regard to sub-panel feeders and branch circuits, the 60? rating is not enforced uniformly. A change in the '11 Code has, IMO, added fuel to the fire.
 
Status
Not open for further replies.
Top