red tag service conductor size

[kingroad77]

I'm totaly confused. when sizing single family service feeder wire I used NEC 310.15(b)(6) and it tells me for 200A all I need to use is 4/0 AL type ser cable. The red tag is telling me that I must derate the cable. I don't see in the 2008NEC that I need to do any derating. I'm in Florida if that helps.

 

[Hameedulla-Ekhlas]

NEC states for derating when it is more than three cable in the same race way. If it is only one cable then you dont need to apply the derating factor. If it is more then three than you have.

 

[charlie b]

The word "derate" only applies to conductors in specific situations, such as when there are more than 3 current-carrying conductors in the same raceway, or when the ambient temperature exceeds 30C. I don't see that word applying to your situation. From what you have described, a 4/0 aluminum service should have been accepted. I suggest calling the inspector and asking for a code reference or an explanation.

 

[charlie b]

Perhaps I need to withdraw my earlier response. You said you used SER. That type is not listed among the acceptable types at the top of Table 310.15(B)(6). Is it possible that that is the source of the red tag?

 

[kingroad77]

ser cable

ser cable

4/0-4/0-4/0-2/0 has type SE aluminum in one jacket. I use it all over Orange Co. Florida. This is in a city.That dose it's own inspection.

 

[iwire]

You said you used SER. That type is not listed among the acceptable types at the top of Table 310.15(B)(6).

It is SE, the 'proper way to type it would be "SE-U" or "SE-R". SE-U is flat two wire +grd cable SE-R is a round multi-conductor cable.

I think the issue might be 334.80 and where the the SE-R is run.

 

[raider1]

I think the issue might be 334.80 and where the the SE-R is run.

Agreed, it could also be that there are more than 1 feeder from the main panel so the change in the definition of a "main power feeder" might also be the source of the "red tag".

Chris

 

[Dennis Alwon]

I agree that se cable is allowed to use table 310.15(B)(6) however you called it a feeder and not service conductors. Which is it? Does it carry the full load of the service? Now the inspector may be talking about article 338.10 (B)(4). He may also be thinking that T 310.15(B)(6) does not apply because of 338.10(B)(4).

 

[rodneee]

i don't know how to cite code references but if i understand the original post i would say the red tag was due to using 4/0 ser instead of 4/0 seu.

 

[augie47]

The OP could calrify for us, but I read his post to say the SER was not derated which is most probably the inspectors take on 338.10(B)(4) (assumimng it was an interior installation).
The same installation would be rejected here.

 

[charlie b]

Sorry, Gus, but I don't understand that. If we are talking about a service or a main power feeder, then the discussion of interior feeders in 338.10(B)(4) does not apply. If we are not, then 310.15(B)(6) would not apply.

In addition, the connection between "derating" and 338.10(B)(4) is that you are led to 334, and specifically to 334.80, and the discussion of derating there is all about multiple current carrying conductors in the same raceway. As I said earlier, that would not apply to this installation.

Finally, you can't use the word "derating" in the context of table 310.15(B)(6). You don't have an ampacity value to start with, so you can't get a derated ampacity value to end up with.

So what would you be looking for, what is the reason for rejecting this install, and what would the electrician have to change, in order to pass inspection?

 

[augie47]

Charlie, the term "derated" was probably misused by me here. I read the OP to say the inspector turned down an SER installed as a 200 amp feeder.
From many discussions here, I know there is controversy on the enforcement of 338.10 (334.80) vs 215.2, but in the jurisdictions in my area, 338.10 is interpreted so as to not allow 4/0 SER as a 200 amp feeder on interior installations due to the 60 ? rating.
I was trying to indicate that the same logic might be the reason for his rejection.

 

[charlie b]

The way I read 338.10(B)(4), the phrase "interior wiring" pertains to stuff after the building's main disconnecting means. It should not apply to a wire, just because some portion of the wire is located within the building's outer skin. A service conductor that starts at a utility transformer on an outside pole, and that penetrates the house, landing just inside the wall on a main breaker panel, is not "interior wiring." That phrase is all about branch circuits serving receptacles and lights, and it's about feeders to sub-panels.

Also, the word "ampacity" does not appear in Table 310.15(B)(6). Nor is a temperature adjustment described anywhere nearby. It does not say, for example, that the ampacity of a 4/0 AL SE cable, when its "conditions of use" include its use as the main power feeder and include its use within certain ambient temperature limits, is 200 amps. All is says is this size conductor can be used for a main power feeder with a calculated load of 200.

 

[augie47]

The way I read 338.10(B)(4), the phrase "interior wiring" pertains to stuff after the building's main disconnecting means. It should not apply to a wire, just because some portion of the wire is located within the building's outer skin. A service conductor that starts at a utility transformer on an outside pole, and that penetrates the house, landing just inside the wall on a main breaker panel, is not "interior wiring." That phrase is all about branch circuits serving receptacles and lights, and it's about feeders to sub-panels.

I agree.
From the fact that the OP stated SER, I assumed , an interior feeder

Also, the word "ampacity" does not appear in Table 310.15(B)(6). Nor is a temperature adjustment described anywhere nearby. It does not say, for example, that the ampacity of a 4/0 AL SE cable, when its "conditions of use" include its use as the main power feeder and include its use within certain ambient temperature limits, is 200 amps. All is says is this size conductor can be used for a main power feeder with a calculated load of 200.

I agree to a point. I will leave it up to those that wish to to search previous threads on the subject. Suffice to say, there is a school of though amongst some inspectors that, despite the lack of the "ampacity" term in 310.15(B)(6), that 4/0 AL SER can not be used on as a 200 amp interior feeder due to the wording of 338.10.
I happen to be one of those who looks at it this way, you appear not to, and I won't persue that as it has been beat to death in previosu discussions.
I as simply pointing out to the OP that his inspector may be one of the inspectors who reads it that way.