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#97950 - 04/18/06 05:18 PM SER in Cable Tray
George Little Offline
Member

Registered: 01/18/04
Posts: 1492
Loc: Michigan USA
Trying to find some information on installing SER 3 cond. w/grd. in cable tray. As near as I can find out, it can be approved as long as the cable is listed and labeled TC and you don't stack them. If you install them in single layer and maintain spacing (1 cable diameter between them) the only derating applicable is ambient temperature adjustment. No spacing would cause a reduction to 95% of the ampacity on top of the temperature adjustment. Okay Cable Tray guru have your way with me
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2014 / 2011 NEC & Related Books and Study Guides
#97951 - 04/21/06 02:58 PM Re: SER in Cable Tray
HotLine1 Offline

Member

Registered: 04/03/02
Posts: 6804
Loc: Brick, NJ USA
George:
Looks like no one wants to touch this.
Sofar, I agree with what you said; I'll look thru '02 & '05 later tonite, time permitting.

John
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#97952 - 04/21/06 05:40 PM Re: SER in Cable Tray
Yoopersup Offline
Member

Registered: 03/04/03
Posts: 826
Loc: Michigan
George
Mc Graw_Hill"s National Electrical Code Handbook has a Very detailed explaination and several examples of what your asking.
Cable tray being a Support method can support just about any approved wiring method. As far as Derating theres several varaibles as to Derating including whether it's covered (Tray)or not.

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#97953 - 04/21/06 06:15 PM Re: SER in Cable Tray
George Little Offline
Member

Registered: 01/18/04
Posts: 1492
Loc: Michigan USA
I think that's why no one came back to me because I didn't really give very many details. So here's what I'm dealing with and this is what I've found:

1. Multi conductor cable ┬▒1.25" diameter.

2. Less than 2k volts.

3. Tray is ladder type 18" wide, uncovered.

4. SER cable Listed TC.

The question is- How many cables can I put in the tray and do I have to derate them in 86┬░ ambient?

I came up with 16 cables and since it's a ladder type tray no spacing is required nor is there any derating applicable.

Edited for spelling.

[This message has been edited by George Little (edited 04-21-2006).]
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#97954 - 04/21/06 07:19 PM Re: SER in Cable Tray
Yoopersup Offline
Member

Registered: 03/04/03
Posts: 826
Loc: Michigan
George
2005 NEC 392.9(A)1. If 4/0(all same size)or larger sum of all the cable diameters cannot exceed the cable tray width . 1.25x16=20inch.
329.9(A)2.If under 4/0 Cable fill area per table 392.9 Column #1. 1.25x16=20 table 329.9 Column #1 requires a 18 inch tray.
Ampacitys see 392.11(A)your cables would be side by side with no spaceing.


[This message has been edited by Yoopersup (edited 04-21-2006).]

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#97955 - 04/21/06 08:41 PM Re: SER in Cable Tray
George Little Offline
Member

Registered: 01/18/04
Posts: 1492
Loc: Michigan USA
Yooper- Here's what I came up with:

Conductors are <4/0 and the area of each cable is 1.23 sq. in. The allowable fill area per T392.9(A)(2) is 21 sq.in. so it looks like I could install 17 cables in the tray with no derating as long as they only had 3 current carrying conductors in each cable.

[This message has been edited by George Little (edited 04-21-2006).]
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#97956 - 04/22/06 04:23 AM Re: SER in Cable Tray
Yoopersup Offline
Member

Registered: 03/04/03
Posts: 826
Loc: Michigan
George
392.9(A)(1)
Where all of the cables are 4/0 or Larger ,the Sum of the diameters of ALL cables shall not exceed the Tray width, and the cables Shall be installed in a Single layer. 1.23x16=19.68 = 20 inch tray
The table your using is for Smaller then 4/0 thus does not apply.(392.9(A)2.
392.9(A)2 Where all the cables are SMALLER then 4/0.
392.9(A) 3 is for cables refers you to Col.#2 BUT thats for 4/0 and larger (AND)(Smaller cables.(Mixed).and only the smaller cables are to use the table. The 4/0 and over must still be placed sise by side.

Table 392.9 Column 2 Applicable For 392.(A)(3) ONLY.
2002 NEC is the same as 2005.

[This message has been edited by Yoopersup (edited 04-22-2006).]

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#97957 - 04/22/06 04:48 AM Re: SER in Cable Tray
George Little Offline
Member

Registered: 01/18/04
Posts: 1492
Loc: Michigan USA
Ernie - The conductors are smaller than 4/0 and the tray is ladder type uncovered so the applicable table is 392.9 column 1. The table shows an 18 inch wide tray can handle 21 sq. in. of cable. Each cable is 1.25'' diameter which is 1.23" when calculating the area. 17 X 1.23 = 20.91 = Green Sticker.
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#97958 - 04/22/06 10:42 AM Re: SER in Cable Tray
Yoopersup Offline
Member

Registered: 03/04/03
Posts: 826
Loc: Michigan
George
Yep if wires are all same size under 4/0 thats the table to use Per 392.9(A)2
Table 392.9 Column 1

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