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 |