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Here's a cable that may use B.310.1, which is probably overkill for most
of our work:
http://www.amercable.com/doc/catalogs/VFDCables.pdf
MC cable requires you to use Table 310.16 for your 600V wires, with a
few caveats (330.80)
That being said, not sure what "raceway in free air" means. Maybe
they're trying to draw a distinction between that and underground ducts
(e.g. Table B.310.5)
Here's the 330.80 section:
***
330.80 Ampacity.
The ampacity of Type MC cable shall be determined in accordance with
310.15 or 310.60 for 14 AWG and larger conductors and in accordance with
Table 402.5 for 18 AWG and 16 AWG conductors. The installation shall not
exceed the temperature ratings of terminations and equipment.
(A) Type MC Cable Installed in Cable Tray. The ampacities for Type MC
cable installed in cable tray shall be determined in accordance with
392.11 and 392.13.
(B) Single Type MC Conductors Grouped Together. Where single Type MC
conductors are grouped together in a triangular or square configuration
and installed on a messenger or exposed with a maintained free airspace
of not less than 2.15 times one conductor diameter (2.15 × O.D.) of the
largest conductor contained within the configuration and adjacent
conductor configurations or cables, the ampacity of the conductors shall
not exceed the allowable ampacities in the following tables:
(1) Table 310.20 for conductors rated 0 through 2000 volts
(2) Table 310.67 and Table 310.68 for conductors rated over 2000 volts
***
-------- Original Message --------
Subject: [RE-wrenches] NEC Art 310 Ampacity
From: Peter Parrish <peter.parr...@calsolareng.com>
To: 'RE-wrenches' <re-wrenches@lists.re-wrenches.org>
Date: 2009/8/5 16:45
When we do ampacity calculations, we always use Table 310.16 in Section
310.15 for wire in raceway (EMT, PVC, FMC, LNFC, LMFC), and MC cable. Of
course we use Table 310.15(B)(2)(a) in a raceway or cable with more than
three conductors.
A colleague asked me about the applicability of table B.310.1. It would seem
to apply to 2-3 conductors within an overall covering (multi-conductor
cable) in raceway in free air. Would MC apply? But what in the world is a
"cable, in raceway, in free air"? I'm usually pretty good in parsing this
stuff, but this stumps me.
- Peter
Peter T. Parrish, President
California Solar Engineering, Inc.
820 Cynthia Ave., Los Angeles, CA 90065
CA Lic. 854779, NABCEP Cert. 031806-26
peter.parr...@calsolareng.com
Ph 323-258-8883, Mobile 323-839-6108, Fax 323-258-8885
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