Derate SER for insulation

[GerryB]

I have read previous posts and want to post this question for a specific scenario. Meter main outside, #2 alum ser comes in the house and through an outside wall 25', then pops out to the panel. That 25' will be encased in foam insulation. So 338.10(B)(4) brings that cable down to 75 amps on the 60 degree table in T310.15(B)(16). Is that correct?
The second scenario is similar, same cable goes up the wall 8' and into floor joists for 40' or so to panel. Previous posts seem to indicate this is also at 60 degrees and no exception (10' 10%) applies. Also correct?
Solution: if the above are correct would ser with XHHW-2 (if they make it) solve the violation? Thanks in advance for any replies.

 

[jumper]

If the SER in encased in insulation yes the final ampacity will be the 60C column. SER with XHHW-2 can use the 90C column for derating and correction factors, but the final ampacity would still be the 60C column if installed in insulation.

 

[GerryB]

I have read previous posts and want to post this question for a specific scenario. Meter main outside, #2 alum ser comes in the house and through an outside wall 25', then pops out to the panel. That 25' will be encased in foam insulation. So 338.10(B)(4) brings that cable down to 75 amps on the 60 degree table in T310.15(B)(16). Is that correct?
The second scenario is similar, same cable goes up the wall 8' and into floor joists for 40' or so to panel. Previous posts seem to indicate this is also at 60 degrees and no exception (10' 10%) applies. Also correct?
Solution: if the above are correct would ser with XHHW-2 (if they make it) solve the violation? Thanks in advance for any replies.

To partial answer myself I think the ser is already xhhw-2

 

[jumper]

To partial answer myself I think the ser is already xhhw-2

I believe you are correct, but even if you did not have insulation you would be limited to the 75C column at best for final ampacity because of terminal ratings, 110.14(C).

 

[curt swartz]

The temperature limit for SER and NM cables is for the cable assembly not the individual conductors. SER cable already has 90C conductors that are XHHW or THHN/THWN depending on the cable manufacture. NM also has 90C conductors but is limited to 60C. At lease the CMP realized this change was nonsense and only requires the 60C to be used for cables #10 and smaller in the 2017 NEC.

 

[GerryB]

The temperature limit for SER and NM cables is for the cable assembly not the individual conductors. SER cable already has 90C conductors that are XHHW or THHN/THWN depending on the cable manufacture. NM also has 90C conductors but is limited to 60C. At lease the CMP realized this change was nonsense and only requires the 60C to be used for cables #10 and smaller in the 2017 NEC.

Thanks both for your answers. I just looked up 338.10(B)(4) in the 2017 and that is a nice change. We are on 2014 here in CT.

 

[Carultch]

To partial answer myself I think the ser is already xhhw-2

Some SE cable is XHHW-2, some SE cable is THWN-2. Some manufacturers specify both on the same datasheet, because it is subject to the factory inventory when the lot is manufactured.

 

[MasterTheNEC]

Greetings,

I am sure you are also aware that in the 2017 NEC that reduction in regards to being "in" thermal insulation was reduced to only smaller sizes of Type SE Cables. While you are going to always be limited to the terminal ratings and the overall product ratings themselves, the 2017 NEC did change and stated the following " Type SE cable with ungrounded conductor sizes 10 AWG and smaller, where installed in thermal insulation, the ampacity shall be in accordance with 60C (140F)conductor temperature ratings."

Disregard as I see someone already stated it.....My Bad and I can't seem to delete it, only edit it.