How many #4 THHN fit in 2" IMC?
174 AWG THHN/THWN-2 wires in 2" Intermediate metal conduit
3.630 sq in × 40 % = 1.4520 sq in allowed. ÷ 0.0824 sq in per wire = 17.62, so 17.
This pull in numbers
- 17 wires fill
- 38.6 % of 2" IMC
- Limit for three or more
- 40 %
- For 18 or more
- 2-1/2" IMC, up to 25
- Pipe to wire diameter
- 6.64 to 1
- In THW insulation
- 15 fit
- In XHHW-2 insulation
- 18 fit
Before you pull 17
- The ground counts. Every wire in the pipe counts toward fill, the green or bare ground and the neutrals too. 17 is the total, not the hots.
- Derating. If all 17 were current-carrying, each would be adjusted to 50 % of its ampacity (Table 310.15(C)(1)): a #4 THHN at 95 A in the 90 °C column becomes 47.5 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.
#4 THHN in other 2" conduit
| Conduit | Inside area | Most #4 THHN |
|---|---|---|
| Electrical metallic tubing | 3.356 | 16 |
| Intermediate metal conduit | 3.630 | 17 |
| Rigid metal conduit (RMC, GRC) | 3.408 | 16 |
| Rigid PVC conduit, Schedule 40 | 3.291 | 16 |
| Rigid PVC conduit, Schedule 80 | 2.874 | 14 |
| Flexible metal conduit (FMC, Greenfield) | 3.269 | 16 |
| Liquidtight flexible metal conduit (LFMC) | 3.246 | 15 |
| Electrical nonmetallic tubing (smurf tube) | 3.291 | 16 |
#4 THHN in other IMC sizes
Other wire sizes in 2" IMC
#14: 149#12: 109#10: 69#8: 39#6: 28#4: 17#3: 15#2: 12#1: 9#1/0: 8#2/0: 6#3/0: 5#4/0: 4250 kcmil: 3300 kcmil: 3350 kcmil: 2500 kcmil: 1