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#207389 - 10/24/12 01:10 AM Sizing Power Cable
wewire2 Offline
Member

Registered: 11/14/02
Posts: 246
Loc: California
In sizing a 200 amp 120/240V power cord and using NEC table 400.5 under the 75 degree E2 column it shows that 1/0 type "W" cable is sufficient for 207 amps. Since compliance with 110.14 (C) is based on Table 310.16 does that mean
the ampacities listed in 310.16 override the ampacities listed in table 440.5?

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2014 / 2011 NEC & Related Books and Study Guides
#207390 - 10/24/12 08:05 AM Re: Sizing Power Cable [Re: wewire2]
HotLine1 Offline

Member

Registered: 04/03/02
Posts: 6785
Loc: Brick, NJ USA
In plain english....the temp rating of the termination points cannot be exceeded. If you have 75 deg. terminations, then 400.5 rules, IMHO.

A read of 110.14(C) in 2011 & 2008 will direct you to details regarding conductors over 100 amps (110.14 (C)(1)etc.
_________________________
John

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#207393 - 10/24/12 11:58 AM Re: Sizing Power Cable [Re: HotLine1]
wewire2 Offline
Member

Registered: 11/14/02
Posts: 246
Loc: California
Thanks Hotline. The commentary at the bottom of 2008 NEC Handbook page 483 (step 3, Termination analysis) is still confusing for me because it verifies the compliance of the application example using Table 310.16.
In my example (120/240V 200 amp power cord) with no applicable derating factors and using the 75 degree column in Table 400.5, using table 310.16 for verification as the commentary suggests would not result in compliance for 1/0 conductors.

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#207400 - 10/24/12 06:41 PM Re: Sizing Power Cable [Re: wewire2]
HotLine1 Offline

Member

Registered: 04/03/02
Posts: 6785
Loc: Brick, NJ USA
Following your path above, you are 100% correct that 1/0 Cu is insufficient via 310.16 for verification. I'll have to wait 'till tommorrow to read the Handbook comm., as both '08 & '11 are in my office, and I can't find the '11 Handbook on DVD.

BTW, I still stand on my previous comment.
_________________________
John

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#207415 - 10/27/12 02:25 PM Re: Sizing Power Cable [Re: wewire2]
wewire2 Offline
Member

Registered: 11/14/02
Posts: 246
Loc: California
If you get a chance, please read the commentary after 110.14 (2)on pages 48 and 49 of the 200 NEC Handbook let me know how that affects your stance. Still trying to make 100% sense of this....Thank you.

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#207416 - 10/27/12 06:51 PM Re: Sizing Power Cable [Re: wewire2]
wewire2 Offline
Member

Registered: 11/14/02
Posts: 246
Loc: California
2008 Handbook.

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#207419 - 10/28/12 12:09 AM Re: Sizing Power Cable [Re: wewire2]
gfretwell Offline

Member

Registered: 07/20/04
Posts: 9012
Loc: Estero,Fl,usa
Did you see note 3 in 400.5(B)?
I think that puts you into the F column with a 120/240 cable (3 cc conductors)
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#207421 - 10/28/12 12:38 PM Re: Sizing Power Cable [Re: wewire2]
wewire2 Offline
Member

Registered: 11/14/02
Posts: 246
Loc: California
Hi Greg. I was going with note 2 in 400.5(B) since the neutral per 400.5(B)is not required to meet the requirements
of a CCC. Even the F column ampacities in table 400.5(B)( 2/0 = 208 amps)would not fly using table 310.16 for the termination requirements. The commentary after 110.14(2) pretty much says to not use tables other than 310.16 for termination verification which seems to mean that is does override table 400.5.

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#207425 - 10/28/12 10:57 PM Re: Sizing Power Cable [Re: wewire2]
gfretwell Offline

Member

Registered: 07/20/04
Posts: 9012
Loc: Estero,Fl,usa
There is an example that puts you in 3/0 in the handbook but it is talking about >30c.

I have to admit I have never been in this article and it is pretty confusing the way they word it. I am not 100% sure why you wouldn't have to just use 310.16.

It does sound like they are talking about a line cord for a listed piece of equipment and just giving the NRTL some wiggle room

400.5
Quote:
...These tables shall be used in conjunction with applicable end-use product standards to ensure selection of the proper size and type...
_________________________
Greg Fretwell

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#207426 - 10/29/12 12:17 AM Re: Sizing Power Cable [Re: wewire2]
wewire2 Offline
Member

Registered: 11/14/02
Posts: 246
Loc: California
Cool! I was worried it was a no-brainer and I was missing the boat.
The quote from 400.5(A) you posted is also confusing because the wording "in conjunction" seems ambiguous. I'm guessing they mean the lowest rating between the NEC and NRTL shall prevail.

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