Table 310.60(C)(77) and similar tables

[mshields]

These tables for conductor ampacity of MV cable installed underground, have in their descriptive paragraph the indication that so long as the duct bank is like that of those shown in figure 310.60, the values in the table that follows apply.

Does this mean that so long as you stick to one of these configurations, one need not concern themselves with a Neher McGrath calculation?

 

[ramsy]

Try sending a private message to king PB.

MV cable manufactures may void warranty with idiot tables, and the NEC 90.1(C) explicity excludes itself as a design specification.

 

[jusme123]

http://www.csemag.com/single-articl...formula/c01c5623e458ee6f79087c4798d121a3.html

 

[Julius Right]

According to NEC art. 90.5 Mandatory Rules, Permissive Rules, and Explanatory Material. it is stated:
Permissive rules of this Code are those that identify actions that are allowed but not required, are normally used to describe options or alternative methods, and are characterized by the use of the terms SHALL BE PERMITTED or shall not be required.
310.60 Conductors Rated 2001 to 35,000 Volts.
(A) Ampacities of Conductors Rated 2001 to 35,000
Volts. Ampacities for solid dielectric-insulated conductors
shall be permitted to be determined by tables or under engineering supervision, as provided in 310.60(B) and (D).

Informational Note No. 1: For ampacities calculated in
accordance with 310.60(A), reference IEEE 835-1994 (IPCEA
Pub. No. P-46-426), Standard Power Cable Ampacity
Tables, and the references therein for availability of all factors and constants.
The reference IEEE 835_1994 describes the cable for which the ampacity is indicated. NEC does not.
However if your cable does not match any cable type from the list you may calculate the ampacity according to the methodology attached here based-generally-on Neher and McGrath theory. You also may change the number, the diameter, the distance between ducts and so on.

 

[ron]

These tables for conductor ampacity of MV cable installed underground, have in their descriptive paragraph the indication that so long as the duct bank is like that of those shown in figure 310.60, the values in the table that follows apply.

Does this mean that so long as you stick to one of these configurations, one need not concern themselves with a Neher McGrath calculation?

Yes

Config and other aspects of the detail and table characteristics, such as rho values, depth etc need to be followed as part of the deal

 

[mshields]

great input

great input

thank you all