How many 250 kcmil THHN fit in 6" Rigid?
29250 kcmil THHN/THWN-2 wires in 6" Rigid metal conduit (RMC, GRC)
29.158 sq in × 40 % = 11.6632 sq in allowed. ÷ 0.3970 sq in per wire = 29.38, so 29.
This pull in numbers
- 29 wires fill
- 39.5 % of 6" Rigid
- Limit for three or more
- 40 %
- For 30 or more
- no bigger Rigid
- Pipe to wire diameter
- 8.57 to 1
- In THW insulation
- 25 fit
- In XHHW-2 insulation
- 30 fit
Before you pull 29
- The ground counts. Every wire in the pipe counts toward fill, the green or bare ground and the neutrals too. 29 is the total, not the hots.
- Derating. If all 29 were current-carrying, each would be adjusted to 45 % of its ampacity (Table 310.15(C)(1)): a 250 kcmil THHN at 290 A in the 90 °C column becomes 130.5 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.
250 kcmil THHN in other 6" conduit
| Conduit | Inside area | Most 250 kcmil THHN |
|---|---|---|
| Rigid metal conduit (RMC, GRC) | 29.158 | 29 |
| Rigid PVC conduit, Schedule 40 | 28.567 | 28 |
| Rigid PVC conduit, Schedule 80 | 25.598 | 25 |
250 kcmil THHN in other Rigid sizes
Other wire sizes in 6" Rigid
#4: 141#3: 120#2: 100#1: 74#1/0: 63#2/0: 52#3/0: 43#4/0: 36250 kcmil: 29300 kcmil: 25350 kcmil: 22500 kcmil: 16