Overview

This article provides estimates for how many THHN insulated conductors will fit through a single CT as a function of the CT opening size, conductor gauge, and rated current of the CT. In practice you may not be able to fit as many conductors as listed because conductors are not perfectly straight. Also, the Total Current may exceed the Rated Current of the CT.

Information to compile this table came from the 2017 edition of the National Electric Code and from Southwire Corporation datasheets for THHN building wire products.

ACTL-0750 series

Conductor Count  Gauge Nominal O.D. Rated Amps at 75° C Total Current
1 250 0.678 in. 255 A 255 A
2 #2 0.378 in. 115 A 230 A
3 #3 0.346 in. 100 A 200 A
3 #4 0.318 in. 85 A 255A
4 #6 0.249 in. 65 A 260 A
5 #8 0.213 in. 50 A 250A
8 #10 0.161 in. 30 A 240A
12 #12 0.128 in. 20 A 240A
16 #14 0.109 in. 15 A 240A

ACTL-1250 series

Conductor Count Gauge Nominal O.D. Rated Amps at 75° C Total Current
1 750 kcmil 1.126 in 475 A 475 A
2 400 kcmil 0.821 in 335 A 670 A
3 3/0 AWG 0.568 in 200 A 600 A
4 2/0 AWG 0.518 175 A 700 A

See Also