How many #12 THHN fit in 3/4" IMC?
1712 AWG THHN/THWN-2 wires in 3/4" Intermediate metal conduit
0.586 sq in × 40 % = 0.2344 sq in allowed. ÷ 0.0133 sq in per wire = 17.62, so 17.
This pull in numbers
- 17 wires fill
- 38.6 % of 3/4" IMC
- Limit for three or more
- 40 %
- For 18 or more
- 1" IMC, up to 29
- Pipe to wire diameter
- 6.65 to 1
- In THW insulation
- 13 fit
- In XHHW-2 insulation
- 13 fit
Before you pull 17
- The ground counts. Every wire in the pipe counts toward fill, the green or bare ground and the neutrals too. 17 is the total, not the hots.
- Derating. If all 17 were current-carrying, each would be adjusted to 50 % of its ampacity (Table 310.15(C)(1)): a #12 THHN at 30 A in the 90 °C column becomes 15 A. Grounds don't count as current-carrying. How derating works
- Bends. A full pipe pulls hard. Keep to 360° of bends between pull points, less for a tight fill.
#12 THHN in other 3/4" conduit
| Conduit | Inside area | Most #12 THHN |
|---|---|---|
| Electrical metallic tubing | 0.533 | 16 |
| Intermediate metal conduit | 0.586 | 17 |
| Rigid metal conduit (RMC, GRC) | 0.549 | 16 |
| Rigid PVC conduit, Schedule 40 | 0.508 | 15 |
| Rigid PVC conduit, Schedule 80 | 0.409 | 12 |
| Flexible metal conduit (FMC, Greenfield) | 0.533 | 16 |
| Liquidtight flexible metal conduit (LFMC) | 0.541 | 16 |
| Electrical nonmetallic tubing (smurf tube) | 0.508 | 15 |