How many #4 THHN fit in 2-1/2" Rigid?
234 AWG THHN/THWN-2 wires in 2-1/2" Rigid metal conduit (RMC, GRC)
4.866 sq in × 40 % = 1.9464 sq in allowed. ÷ 0.0824 sq in per wire = 23.62, so 23.
This pull in numbers
- 23 wires fill
- 38.9 % of 2-1/2" Rigid
- Limit for three or more
- 40 %
- For 24 or more
- 3" Rigid, up to 36
- Pipe to wire diameter
- 7.68 to 1
- In THW insulation
- 20 fit
- In XHHW-2 insulation
- 24 fit
Before you pull 23
- The ground counts. Every wire in the pipe counts toward fill, the green or bare ground and the neutrals too. 23 is the total, not the hots.
- Derating. If all 23 were current-carrying, each would be adjusted to 45 % of its ampacity (Table 310.15(C)(1)): a #4 THHN at 95 A in the 90 °C column becomes 42.8 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.
#4 THHN in other 2-1/2" conduit
| Conduit | Inside area | Most #4 THHN |
|---|---|---|
| Electrical metallic tubing | 5.858 | 28 |
| Intermediate metal conduit | 5.135 | 25 |
| Rigid metal conduit (RMC, GRC) | 4.866 | 23 |
| Rigid PVC conduit, Schedule 40 | 4.695 | 22 |
| Rigid PVC conduit, Schedule 80 | 4.119 | 20 |
| Flexible metal conduit (FMC, Greenfield) | 4.909 | 24 |
| Liquidtight flexible metal conduit (LFMC) | 4.881 | 23 |
#4 THHN in other Rigid sizes
Other wire sizes in 2-1/2" Rigid
#14: 200#12: 146#10: 92#8: 53#6: 38#4: 23#3: 20#2: 17#1: 12#1/0: 10#2/0: 8#3/0: 7#4/0: 6250 kcmil: 5300 kcmil: 4350 kcmil: 3500 kcmil: 2