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.
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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