NEC Article 392.22 (A) Sizing and things

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MasterSpark

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Question for the all knowing and knowledgeable board!

If I have a Multi-Conductor Cable to be installed in a ladder tray, it falls under 392.22 (A)(1).

A) if the multi-conductor cable is a (4/C-500 kcmil w/ #2 gnd), what subsection does that fall under? I am talking about all those conductors under one jacket, not separate or individual phase and ground conductors.

Logically this is a subsection (a) calculation. However as I strictly read the code, this should fall under subsection (c) because not all the cables installed are 4/0 and larger. But falling under subsection (c) clearly doesn't work because I cannot count the #2 separate (its part of the same cable)? I could interrupt that to mean this specific cable is not permitted in Tray, but the manufacture sells it as TC rated. Any ideas on interpretation of where that cable belongs?

B) The actual wording in the code says cables "smaller" or "larger" then "4/0", however note of table 392.22(A) gives an actual measurement. It states that the sd term is the "sum of the diameters of all cables 107.2 mm [or 4.2 inches] and larger", which is huge and certainly exceeds 4/0! That is larger then most 4/C-1000 kcmil w/ gnd cable... so what are they trying to tell me!

(help? and many thanks! :))
 
Have I stumped the Forum?

Or have I been lumped in with the group of untouchables labeled: "over their head" and thus treated with the "Do nothing, ignore the post and move on" response? :)
 
David,

Thank you. I tend to concur, it's just I am creating a VBA enabled Excel spreadsheet right now to automatically size raceway (conduits, tray, wireway, etc). Being programming based, I need to be fairly specific in generating the rules to select the correct methodology. That means pulling apart the data fields to make sure the cable data is correctly analyzed by the program.

Individual conductors would clearly be a 392.22(A)(1)(c) calculation, but lump them under a single jacket and the code doesn't cleanly fit the situation. (And requires some assumptions, at least in my opinion).



If I may ask, what are your thoughts on the second part of the question... regarding the 107.2 mm number they provide in note b of Table 392.22(A)?
 
MasterSpark said:
B) The actual wording in the code says cables "smaller" or "larger" then "4/0", however note of table 392.22(A) gives an actual measurement. It states that the sd term is the "sum of the diameters of all cables 107.2 mm [or 4.2 inches] and larger", which is huge and certainly exceeds 4/0! That is larger then most 4/C-1000 kcmil w/ gnd cable... so what are they trying to tell me!
Click to expand...

The note is written poorly. It should say the sum of the diameters of all cables 107.22 mm²...


107.22 mm² is the same conductor area as 4/0AWG
 
david luchini said:
The note is written poorly. It should say the sum of the diameters of all cables 107.22 mm²...


107.22 mm² is the same conductor area as 4/0AWG
Click to expand...

David,

Thank you again for the response and sorry for the delay in getting back to you. 107.22 mm2 is the conversion of 211000 cmils to mm2. (I had come to that conclusions years ago as well but forgot! :slaphead: Thanks for the reminder.)

But with that said and just to confirm, the code wants me to treat ANY multi-conductor cable larger then 211000 cmil (or 107.22 mm2 or .167 in2) under 392.22(A)(1)(a) [or (c) depending on the criteria].

If I have a multi-conductor cable, 37-Conductor #12, the individual wire gauge is smaller then 4/0 but that doesn't matter. The overall area is larger then an individual 4/0 would be, and it would treated as a "larger then 4/0" cable, correct?
 
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