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Technical Articles on Underground Cable Ampacities

Aerial Cable Ampacities & the NEC Code

One would think that the limited number of alternative aerial cable applications are well covered by the Code Tables. While in some ways this is true, there are still some significant issues with the Code treatment of ampacity ratings for aerial systems, in particular for 0-2000 Volt systems.

 

Underground Ampacities & the NEC Code

The NEC Code is a very familiar document since it is the law of the land with regard to safe electrical installation practices.  However, the NEC's ampacities have always applied to only a very narrow range of defined underground installation configurations.  This article discusses the changes which have occurred over the years in the manner in which the NEC has addressed underground cable ampacities.

 

Neher-McGrath Calculations

The Neher-McGrath Calculations provide a method for calculating underground cable temperatures or ampacity ratings and are the analytical basis for virtually all standards which deal with underground cable ampacities.

NEC Six Duct Configuration Example

The object of this paper is to demonstrate with a fairly simple example problem the use of AmpCalc for Windows for an underground ductbank system. By using one of the standard NEC Code configurations, insight can also be gained into the manner in which the NEC assigns ampacity ratings to the cables in a ductbank.

 

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