How many #8 THHN fit in 2" Rigid?
378 AWG THHN/THWN-2 wires in 2" Rigid metal conduit (RMC, GRC)
3.408 sq in × 40 % = 1.3632 sq in allowed. ÷ 0.0366 sq in per wire = 37.25, so 37.
This pull in numbers
- 37 wires fill
- 39.7 % of 2" Rigid
- Limit for three or more
- 40 %
- For 38 or more
- 2-1/2" Rigid, up to 53
- Pipe to wire diameter
- 9.64 to 1
- In THW insulation
- 31 fit
- In XHHW-2 insulation
- 31 fit
Before you pull 37
- The ground counts. Every wire in the pipe counts toward fill, the green or bare ground and the neutrals too. 37 is the total, not the hots.
- Derating. If all 37 were current-carrying, each would be adjusted to 40 % of its ampacity (Table 310.15(C)(1)): a #8 THHN at 55 A in the 90 °C column becomes 22 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.
#8 THHN in other 2" conduit
| Conduit | Inside area | Most #8 THHN |
|---|---|---|
| Electrical metallic tubing | 3.356 | 36 |
| Intermediate metal conduit | 3.630 | 39 |
| Rigid metal conduit (RMC, GRC) | 3.408 | 37 |
| Rigid PVC conduit, Schedule 40 | 3.291 | 36 |
| Rigid PVC conduit, Schedule 80 | 2.874 | 31 |
| Flexible metal conduit (FMC, Greenfield) | 3.269 | 35 |
| Liquidtight flexible metal conduit (LFMC) | 3.246 | 35 |
| Electrical nonmetallic tubing (smurf tube) | 3.291 | 36 |
#8 THHN in other Rigid sizes
Other wire sizes in 2" Rigid
#14: 140#12: 102#10: 64#8: 37#6: 27#4: 16#3: 14#2: 11#1: 8#1/0: 7#2/0: 6#3/0: 5#4/0: 4250 kcmil: 3300 kcmil: 3350 kcmil: 2500 kcmil: 1