conduit fill

[dennis ryland]

Does the NEC have any requirements regarding the size of wires that can be pulled into the same conduit? For example 2-350kcm with 2-#10, provided the there are no over fill issues, I know there are some design criterias within certian companies that do not allow this but I dont know if there are any code requirements.

 

[don_resqcapt19]

Re: conduit fill

Dennis,
This in not covered in the code rules. The code only covers the total wire fill area and not the relative sizes of the conductor. If your run has much length and a couple of 90s it is very likely that the #10s will not survive the pulling process. This will happen when the #10's end up on the outside radius of the second or third 90 in the run. They will have be a little longer than the 350's and may break because they are not strong enough to pull this required extra length through the pipe.
Don