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#80521 - 04/25/02 05:29 AM Conduit Fill Lighting circuits?
Reel-Break Offline
Member

Registered: 04/04/02
Posts: 179
Loc: nc
Yesterday we went to a plant where some conductors melted in the conduit.There was several problems all the circuits were over loaded #12`s 20+ amps about 19 8' floresant on each cir.They have 1 1/4 conduit with 36 # 12 conductors all over loaded and the conduit is very hot.The question I have how best to explain to the electrical poeple How to size the number of circuits in a pipe.The code table c8 says they can have 45 in the pipe but I tried explaining that with the ciruits over loaded and the heat generated the fill and current carrying capasity of the wires would be less.I don`t think I did a good job with them understanding so please help us out with some examples and code articals thanks guys.We ran another 1 1/4 conduit over and that reduced the heat and we split the circuits droping the current to each circuit.

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#80522 - 04/25/02 08:59 AM Re: Conduit Fill Lighting circuits?
Redsy Offline
Member

Registered: 03/28/01
Posts: 2138
Loc: Bucks County PA
See table 310.15(B)(2)(a) for adjustment factors.
36 conductors require an ampacity adjustment that results in only 40% of the Table 310.16 values.
In your case (using the 90c column for derating purposes) .4 x 30 amps = 12 amps for #12 copper.

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#80523 - 04/28/02 05:29 PM Re: Conduit Fill Lighting circuits?
Glenn Offline
Member

Registered: 01/17/01
Posts: 78
Is that 36 ungrounded conductors plus neutrals ?

Many plants have 3Ø 4W so the neutrals would be current carrying also on circuits with ballasts.

If so, could be 35 percent derate.
30A * 0.35 = 10.5 Ampacity.

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