I'm hearing conflicting information on how to solve problems on the number of CCCs allowed in a wireway. I've heard that it is an "approved method" to insert a divider in the wireway while still maintaining <30 CCCs and <20% fill for the subdivided section to be within Code compliance.
Is there documentation somewhere that this is an "approved method"? Some are saying that this is not an approved method. Which is it? It makes sense to me that a divider essentially makes two smaller wireways, so the code limitations apply equally to both sections of the subdivided wireway.
Is there an official NFPA interpretation? At least a couple city inspectors are approving this method.
I do not know of any formal interpertations on such. What type of wireway are you talking about? Are these UL approved "dividers"? One of the reasons we derate is because of heat. I do not think you are changing anything by adding dividers. All you are doing is making a couple of small "ovens" instead of one big one. But maybe I am not sure of your appication and situation.
Re: Field Question on Wirway Fill Rules#82571 11/29/0212:34 PM11/29/0212:34 PM
In Canada, this is the standard in which we base our decisions.
It's taken from the Canadian Electrical Code-2002.
I hope this insight helps.
Rule 12-2104 Conductors in Wireways
(1) Conductors used in wireways shall be the insulated types indicated in Table 19 as being suitable for use in raceways.
(2) Except as permitted in Subrule (4), wireways shall contain not more than 200 conductors and the aggregate cross-sectional area of the conductors and their insulation shall not exceed 20% of the interior cross-sectional area of the wireway.
Rationale and Intent for Rule 12-2104(2).
We intend that the maximum number of conductors in a wireway be 200, except for signal and control conductors, as indicated in Subrule (4). The sum of the cross-sectional areas of the conductors other than signal or control conductors is not to exceed 20% of the interior cross-sectional area of the wireway.
No conductor larger than 500 kcmil copper or 750 kcmil aluminum shall be installed in any wireway.
Intent for Rule 12-2104(3).
We intend that the size of a conductor that may be installed in a wireway not be larger than 500 kcmil copper or 750 kcmil aluminum.
Wireways containing only signal and control conductors shall be permitted to contain any number of conductors but the aggregate cross-sectional area of the conductors and their insulation shall not exceed 40% of the interior cross-sectional area of the wireway.
(5) The cross-sectional area for conductors in Subrules (2) and (4) shall be determined in accordance with Rule 12-1014(4).
Intent for Rule 12-2104(4).
We intend to allow the number of signal and control conductors in a wireway to exceed 200, provided the aggregate cross-sectional areas of the conductors will not exceed 40% of the cross-sectional area of the wireway.
Tony Moscioni Electrical Inspector Electrical Safety Authority
Re: Field Question on Wirway Fill Rules#82573 11/29/0202:19 PM11/29/0202:19 PM
Thanks for posting my question, Joe; and also to those providing insight.
The wireway in question is a UL approved 12"x12" B-Line that has small conductors (#6 to #1), and about 5 to 10% fill with 30 cables. B-Line makes UL approved dividers, so it would appear that placing more than 30 CCC in a large wireway is acceptable practice. Granted, dividing a wireway is most often done for separating power cables from Class II circuits.
I wonder how the somewhat arbitrary "no more than 30 current carrying conductors" limit was arrived at (regardless of wireway size), in light of the Canadian code limitation provided by Tony of up to 200 CCC! Thanks.