National Electrical Installation Standards

Standards as High as Your Own

Friday, February 23, 2018


Article 501, 501.15 C 6 states that the conductor or optical fill, the cross section area of seal shall not exceed 25% of the cross section area of a ridged conduit of same trade size?? is this for pouring in chico into EYS, don't understand this, conduit fill vs. seal off fill when its the same conduit?????

Mike Garcia



Hey Mike thanks for your question, that is a lot of question marks. Yes, the 25 % fill limit stated in 501.15(C)(6) is because of the preparation and sealing necessary for hazardous (classified) locations. If standard sealing fittings are used they are limited to 25% even though the same size conduit can usually be filled to 40%. Either special sealing fittings with a 40% fill limit or larger ones with reducing fittings must be used if you want the 40% fill.

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