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#85462 - 07/07/03 01:28 PM Engineering Supervision
mountainman Offline
Member

Registered: 01/29/02
Posts: 54
Loc: Richmond Va. U.S.A.
Article 310-15(b) of the 1996 NEC Engineering supervision, an engineer states that with his calculations he can use 4-4/0 conductors on a 4 wire wye circuit with a 225 ampere over currant protection. Would this override 310-15 Note #10(c). He has 4/0 copper in EMT in an electric room. And would you rquire the engineer to show his calculations? Thanks Joe

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#85463 - 07/07/03 02:10 PM Re: Engineering Supervision
Bjarney Offline
Moderator

Registered: 04/10/02
Posts: 2561
Loc: West-Southern Inner-Northeast ...
As the AHJ, an engineer has the responsibility to adequately demonstrate to you that the cable installation conforms to article 310. Paper calculations submitted to you containing a suitable explanation and his PE stamp may adequately support his position to your satisfaction.




[This message has been edited by Bjarney (edited 07-08-2003).]

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#85464 - 07/07/03 03:50 PM Re: Engineering Supervision
George Offline
Member

Registered: 02/23/02
Posts: 380
mountainman ---

If you are inspecting and is is not building according to the perscriptive code, you should ask for his calculations.

You need to have someone who can tell if the computations are correct or not.

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#85465 - 07/07/03 06:12 PM Re: Engineering Supervision
Ron Offline
Member

Registered: 03/13/02
Posts: 577
Loc: White Plains, NY
Absolutely have him/her show calculations and sign/seal them.
But, what am I missing? Table 310-16 shows 4/0 CU in the 75 degree column to have an ampacity of 230A. What is the issue with 225A CB serving a 230A conductor? Is it 100% rated breaker or something else? Maybe aluminum?

[This message has been edited by Ron (edited 07-07-2003).]
_________________________
Ron

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