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#82569 - 11/28/02 09:55 AM Field Question on Wirway Fill Rules  
Joe Tedesco  Offline
Member
Joined: Oct 2000
Posts: 2,749
Boston, Massachusetts USA
Quote
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.


Joe Tedesco, NEC Consultant

2017 / 2014 NEC & Related Books and Study Guides

#82570 - 11/28/02 10:06 PM Re: Field Question on Wirway Fill Rules  
spyder  Offline
Member
Joined: Oct 2002
Posts: 210
Massachusetts
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.


#82571 - 11/29/02 01:34 PM Re: Field Question on Wirway Fill Rules  
George  Offline
Member
Joined: Feb 2002
Posts: 375
Consider a 6" conduit. Run 3 2" conduits inside of it. Fill each with wires so that no derating is required.

Consider a second 6" conduit. Put the same number of wires inside. Derating is required.

Conduit fill is based on number of CCCs. It should be based on the amount of heat produced (resistance of the wires) and the size of the conduit.


#82572 - 11/29/02 03:06 PM Re: Field Question on Wirway Fill Rules  
Tony Moscioni  Offline
Moderator
Joined: May 2001
Posts: 144
CANADA
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.

Rule 12-2104(3)

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.


Rule 12-2104(4)

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


#82573 - 11/29/02 03:19 PM Re: Field Question on Wirway Fill Rules  
sparky  Offline
Member
Joined: Oct 2000
Posts: 5,306
the captive heat of any group of CCC's vs. the volume of area they occupy is apparently a generic call via the NEC.

that derating is required in a wireway were there is more room and less CCC's in the panel below, or above should be fodder for debate.

also note wireways vs. JB's here....

that we are not let to wander from this doctrine is fine with me, that there is no rationale available to validate this makes me wonder if we are a trade with amnesia.

[This message has been edited by sparky (edited 11-29-2002).]


#82574 - 12/02/02 08:07 AM Re: Field Question on Wirway Fill Rules  
sparky  Offline
Member
Joined: Oct 2000
Posts: 5,306
perhpas the NEC & the CEC should do lunch??


#82575 - 12/02/02 04:53 PM Re: Field Question on Wirway Fill Rules  
sjsmith2  Offline
Junior Member
Joined: Dec 2002
Posts: 1
Hillsboro, OR, USA
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.


Stephen J. Smith
Intel Electrical Proj Engr


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