How many 250 kcmil THHN fit in 5" Rigid?
20250 kcmil THHN/THWN-2 wires in 5" Rigid metal conduit (RMC, GRC)
20.212 sq in × 40 % = 8.0848 sq in allowed. ÷ 0.3970 sq in per wire = 20.36, so 20.
This pull in numbers
- 20 wires fill
- 39.3 % of 5" Rigid
- Limit for three or more
- 40 %
- For 21 or more
- 6" Rigid, up to 29
- Pipe to wire diameter
- 7.14 to 1
- In THW insulation
- 17 fit
- In XHHW-2 insulation
- 20 fit
Before you pull 20
- The ground counts. Every wire in the pipe counts toward fill, the green or bare ground and the neutrals too. 20 is the total, not the hots.
- Derating. If all 20 were current-carrying, each would be adjusted to 50 % of its ampacity (Table 310.15(C)(1)): a 250 kcmil THHN at 290 A in the 90 °C column becomes 145 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 5" conduit
| Conduit | Inside area | Most 250 kcmil THHN |
|---|---|---|
| Rigid metal conduit (RMC, GRC) | 20.212 | 20 |
| Rigid PVC conduit, Schedule 40 | 19.761 | 20 |
| Rigid PVC conduit, Schedule 80 | 17.855 | 18 |
250 kcmil THHN in other Rigid sizes
Other wire sizes in 5" Rigid
#6: 159#4: 98#3: 83#2: 70#1: 51#1/0: 43#2/0: 36#3/0: 30#4/0: 25250 kcmil: 20300 kcmil: 17350 kcmil: 15500 kcmil: 11