How many #12 THHN fit in 1/2" PVC Sch 40?
812 AWG THHN/THWN-2 wires in 1/2" Rigid PVC conduit, Schedule 40
0.285 sq in × 40 % = 0.1140 sq in allowed. ÷ 0.0133 sq in per wire = 8.57, so 8.
This pull in numbers
- 8 wires fill
- 37.3 % of 1/2" PVC Sch 40
- Limit for three or more
- 40 %
- For 9 or more
- 3/4" PVC Sch 40, up to 15
- Pipe to wire diameter
- 4.63 to 1
- In THW insulation
- 6 fit
- In XHHW-2 insulation
- 6 fit
Before you pull 8
- The ground counts. Every wire in the pipe counts toward fill, the green or bare ground and the neutrals too. 8 is the total, not the hots.
- Derating. If all 8 were current-carrying, each would be adjusted to 70 % of its ampacity (Table 310.15(C)(1)): a #12 THHN at 30 A in the 90 °C column becomes 21 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 1/2" conduit
| Conduit | Inside area | Most #12 THHN |
|---|---|---|
| Electrical metallic tubing | 0.304 | 9 |
| Intermediate metal conduit | 0.342 | 10 |
| Rigid metal conduit (RMC, GRC) | 0.314 | 9 |
| Rigid PVC conduit, Schedule 40 | 0.285 | 8 |
| Rigid PVC conduit, Schedule 80 | 0.217 | 6 |
| Flexible metal conduit (FMC, Greenfield) | 0.317 | 9 |
| Liquidtight flexible metal conduit (LFMC) | 0.314 | 9 |
| Electrical nonmetallic tubing (smurf tube) | 0.285 | 8 |