Raceway Fill Calculator corrections and Latest News from electrician.com

Raceway Fill Calculator Problem

The cross sectional areas for No. 14, 12, 10, and 8 THHW, THW, and THW-2 have areas in the 2002 and 2005 Code Chapter 9, Table 5 that are not the same as in the 1999 Code. Starting in 2002 these insulations were moved to the TW slot in Table 5, but this was not done in Appendix C, Table C. Table C is still the same as the 1999 NEC for these insulations.

The raceway fill calculator recalculates Table C using the 1999 areas and still duplicates Table C in the 2005 NEC for conductors of all the same size and insulation (at least so far as anyone knows.) There appears to be an error in the NEC and until it is corrected I am not going to change the calculator until this problem is resolved (maybe in 2008).
Temporary fix

If you are installing Nos. 14, 12, 10, and 8 for THW, THW-2, or THHW insulations and want to use the 2005 areas from Table 5 substitute TW for the insulation type in place of THHW, THW-2, or THW for sizes 14, 12, 10 and 8. This will overcome the problem for the time being and allow you to place more conductors in a raceway for these insulations and sizes, but will not duplicate Table C in Appendix C where all wires are of the same size and insulation.

Here is a breakdown of the differences for THHW, THW, and THW-2:
(areas from Table 5 and all areas in sq inches)

Wire size	1999 NEC	2005 NEC areas
No 14	0.0209	0.0139
No 12	0.0260	0.0181
No 10	0.0333	0.0243
No 8	0.0556	0.0437

I had a call today from an engineer about the Neher McGrath Excel Calculator at electrician.com. He was working on an underground 4160 volt duct bank. I explained that the calculator was only for above ground 600 volt wiring in conduits and was only for teaching electricians about Neher Mcgrath. I suggested several sources for him one being the Calcware program for Neher McGrath that sells for about $2,000. Complete Neher McGrath calculations for underground Duct banks are far beyond the normal tasks performed by electricians and most engineers. Appendix B of the NEC has some tables for Neher McGrath Calculations.

I received an email asking for a cable tray fill calculator. It has been my experience that calculating cable tray fill is not a normal task for electricians, and such a calculator would only be used by very few, and I doubt that they would rely on a web page calculator for such an expensive installation. I know I wouldn't. Cable tray installations in industrial establishments are usually done under engineering supervision. Of course electrician tests can have at least one very difficult tray fill problem, and the electrician test course has one such example.

I have also seen a bitter mistake made when 4 each per phase paralleled 500 Kcmil 480 volt single conductor cables were installed with all the A phases, then all the B phases, then all the C phases in flat configuration. The code clearly states for very good reason that paralleled single conductor cables in cable trays shall be bundled in groups of A, B, and C Phase and the neutral if there is one. I actually had the experience of finding such an installation where the cables were not bundled in 1978 on Alaska's North Slope. The adjacent A and B phase and Adjacent B and C phase cables had such low inductive reactances that in a run of only 20 feet they carried about 90 per cent of the current while the outside cables for A and C phase carried about 10 per cent of the current.

Now about the alaskavirtualtour site...
I added a link to electrician.com for this site. It is a hobby of mine to develop various multimedia productions about Alaska and I place them at my domain alaskavirtualtour.com That is a long name but all the short ones were taken.