How many #6 THHN fit in 3" PVC Sch 40?
576 AWG THHN/THWN-2 wires in 3" Rigid PVC conduit, Schedule 40
7.268 sq in × 40 % = 2.9072 sq in allowed. ÷ 0.0507 sq in per wire = 57.34, so 57.
This pull in numbers
- 57 wires fill
- 39.8 % of 3" PVC Sch 40
- Limit for three or more
- 40 %
- For 58 or more
- 3-1/2" PVC Sch 40, up to 77
- Pipe to wire diameter
- 11.98 to 1
- In THW insulation
- 40 fit
- In XHHW-2 insulation
- 49 fit
Before you pull 57
- The ground counts. Every wire in the pipe counts toward fill, the green or bare ground and the neutrals too. 57 is the total, not the hots.
- Derating. If all 57 were current-carrying, each would be adjusted to 35 % of its ampacity (Table 310.15(C)(1)): a #6 THHN at 75 A in the 90 °C column becomes 26.3 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.
#6 THHN in other 3" conduit
| Conduit | Inside area | Most #6 THHN |
|---|---|---|
| Electrical metallic tubing | 8.846 | 69 |
| Intermediate metal conduit | 7.922 | 62 |
| Rigid metal conduit (RMC, GRC) | 7.499 | 59 |
| Rigid PVC conduit, Schedule 40 | 7.268 | 57 |
| Rigid PVC conduit, Schedule 80 | 6.442 | 51 |
| Flexible metal conduit (FMC, Greenfield) | 7.069 | 55 |
| Liquidtight flexible metal conduit (LFMC) | 7.475 | 59 |
#6 THHN in other PVC Sch 40 sizes
Other wire sizes in 3" PVC Sch 40
#10: 137#8: 79#6: 57#4: 35#3: 30#2: 25#1: 18#1/0: 15#2/0: 13#3/0: 11#4/0: 9250 kcmil: 7300 kcmil: 6350 kcmil: 5500 kcmil: 4