Solving the Conduit Fill Conundrum

When asked if we could build a Custom Fixture Whip in 3/8” Steel Flex with 3-12 AWG wires and 2-16 AWG wires, I wondered if this amount of wire would fit inside our 3/8” Steel Flex—even with an External Connector. So I consulted my 2014 NEC code book, and coincidentally, this very topic arose during a recent continuing education credits course I took.

According to my calculation, the total cross-sectional area of the five conductors exceeded the allowable 40% fill rate of the 3/8” conduit. I concluded that we would have to use 1/2” Steel Flex.

As a result of this inquiry, I thought it might be valuable to share this table—Maximum Number of Insulated Conductors in 3/8-inch Flexible Metal Conduit.

If you’ve got questions, we’re here to help figure out the answers. Call Tim Nelson, EPCO Inside Sales Supervisor and Master Electrician – 800.336.1976 or Email – sales@engproducts.com.