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#74523 - 01/26/07 05:53 AM Ampacity
Rowdy Rudy Offline
Junior Member

Registered: 10/30/06
Posts: 6
Had lunch yesterday with a contractor who had just returned from 2 years in Korea building military facilities. Some things surprising , such as #14 rated @ 30A., #12 @ 40A. & #10 @ 54A. These ratings are based on AWG.
Rowdy

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#74524 - 01/26/07 06:58 AM Re: Ampacity
renosteinke Offline
Cat Servant
Member

Registered: 01/22/05
Posts: 5305
Loc: Blue Collar Country
I can't speak for Korea, but the USA is almost unique in it's particular wiring practices. As such, one really has to "leave the USA behind" when leaving the borders.

The ampacity tables are, simply put, our best judgment call. One can always make a case for a higher, or lower, number. It's not at all surprising that different places have slight differences in opinion.

Code issues are not the only places where countries differ. Local construction methods, and lifestyle, have a great effect.

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#74525 - 01/26/07 10:50 AM Re: Ampacity
e57 Offline
Member

Registered: 05/27/03
Posts: 2837
Loc: S.F.,CA USA
Military and Federal facilities are not under the NEC for the most part, but only guided by industry standards - depending on contract. (This one not being 'standard' for this country....) You also don't mention the insulation - they might be using silicone - which has a much higher temp rating.
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#74526 - 01/26/07 11:11 AM Re: Ampacity
SolarPowered Offline
Member

Registered: 07/05/04
Posts: 615
Loc: Palo Alto, CA, USA
Right out of our own NEC, #14 THHN is rated at 25A, #12 @ 30A, and #10 @ 40A. It is only the hyperconservative limits of 240.4(D) that make our normal limits so much lower.

Even these restrictions do not entirely prevent fires from overloaded branch circuits. But they do manage to do a pretty good job of it.

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#74527 - 01/26/07 03:07 PM Re: Ampacity
ShockMe77 Offline
Member

Registered: 06/11/05
Posts: 823
Loc: Rahway, New Jersey
I thought #14 AWG was only rated at 25 amps for derating purposes. That rating is in the 90┬║ column. My understandng is that #14 is good for 20 amps but in only in applications described in 240.4 (G).

[This message has been edited by ShockMe77 (edited 01-26-2007).]

[This message has been edited by ShockMe77 (edited 01-26-2007).]

[This message has been edited by ShockMe77 (edited 01-26-2007).]

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#74528 - 01/26/07 03:11 PM Re: Ampacity
Texas_Ranger Offline
Member

Registered: 12/17/01
Posts: 2343
Loc: Vienna, Austria
30A for #14 sounds real heavy!
2.5mm2 is larger than #14 and has an absolute maximum rating of 26A in free air, 25 degrees Celsius ambient temp. So considering #14 is smaller AND Korea most likely has a higher ambient temperature... scary!

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#74529 - 01/27/07 05:08 AM Re: Ampacity
pauluk Offline
Member

Registered: 08/11/01
Posts: 7693
Loc: Norfolk, England
 Quote:
2.5mm2 is larger than #14 and has an absolute maximum rating of 26A in free air, 25 degrees Celsius ambient temp.


2.5 is rated 30A absolute max. here, free air, 2-core cable, same ambient/conductor temperatures. Clipped direct to a surface it's still 27A.

Which just goes to show how little agreement there is!

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#74530 - 01/27/07 05:10 AM Re: Ampacity
Texas_Ranger Offline
Member

Registered: 12/17/01
Posts: 2343
Loc: Vienna, Austria
 Quote:
Which just goes to show how little agreement there is!

Definitely!
By the way, in general purpose installs said 2.5mm2 is usually protected by a 16A breaker or fuse... so there's another difference between max. rating and real life.

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#74531 - 01/27/07 07:54 AM Re: Ampacity
SteveFehr Offline
Member

Registered: 03/19/05
Posts: 1192
Loc: Chesapeake, VA
 Quote:
Military and Federal facilities are not under the NEC for the most part, but only guided by industry standards - depending on contract. (This one not being 'standard' for this country....) You also don't mention the insulation - they might be using silicone - which has a much higher temp rating.
The US military has adopted the NEC for facilities in lieu of older MIL-SPECs and other codes that are just easier to use existing industry standards for. Anything built on a US base *should* be conforming to NEC and a number of other MIL-HDBKs that often exceed NEC requirements. We have much wider authority for deviation then in the civilian sector, though, as a single entity is generally responsible for funding, building and approving a project and isn't always as heavy-handed as a city inspector when it comes to failing things for non-compliance!

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#74532 - 01/29/07 06:11 PM Re: Ampacity
OreElect Offline
Member

Registered: 03/05/04
Posts: 96
Loc: Salem,Oregon.USA
I think in Mexico its ok to use #14 for a 200 amp service as long as you use white pipe.

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