SE cable in insulation

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teco

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An installation of 4/0 AL SE cable from the back of the meter into the basement, runs about 4 feet before entering the 200A panel. The builder had foam insulation installed along the sill plate area, filling the bay from the sill to the 1st floor joist, where the cable is. My question is does the exception 310.15(A)2 apply here or is adjustment required? Thanks.
 
The exception would not apply if you did not meet the 10%/10' part of the rule.

You need a conductor with a rating of 83% of 200 amps {310.15(B)(7)} which is 166 amps. Since you're in thermal insulation your SE cable must be sized at 60° C which according to Table 310.15(B)(16) is 150 amps for #4/0 Aluminum.
 
infinity said:
The exception would not apply if you did not meet the 10%/10' part of the rule.

You need a conductor with a rating of 83% of 200 amps {310.15(B)(7)} which is 166 amps. Since you're in thermal insulation your SE cable must be sized at 60° C which according to Table 310.15(B)(16) is 150 amps for #4/0 Aluminum.
Click to expand...

Thanks Rob,

I'm confused with this exception language, no surprise. Being that this whole run is under 10' long, doesn't this meet the under 10' portion requirement the exception? Either 10' or 10%? Thx.
 
Take a look at this graphic from Mike Holt:

808ecmCBfig3.jpg
 
infinity said:
Take a look at this graphic from Mike Holt:

808ecmCBfig3.jpg
Click to expand...

So the entire circuit has an allowable ampacity of 30 amp because the lower portion is under 10 feet? or am I missing something? I thought that fit into my situation. I am assuming the meter and through the wall being the transition point.
 
The graphic shows that you can ignore derating because the portion of the circuit that's subject to the lower ampacity falls under the 10%/10' rule.

How long is the overall length of your SE cable and how much is embedded in the insulating material?
 
infinity said:
The graphic shows that you can ignore derating because the portion of the circuit that's subject to the lower ampacity falls under the 10%/10' rule.

How long is the overall length of your SE cable and how much is embedded in the insulating material?
Click to expand...

Ok, I thought it was 10 feet or under and the 10% was for circuits longer than 10 feet. The cable is overall eight feet long with about 1/2, four feet in the foam insulation.
 
teco said:
Ok, I thought it was 10 feet or under and the 10% was for circuits longer than 10 feet. The cable is overall eight feet long with about 1/2, four feet in the foam insulation.
Click to expand...

Unfortunately with a 8'/4' ratio your stuck with the lower ampacity and cannot apply the exception.
 
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