How many #10 THHN fit in 1/2" ENT?
510 AWG THHN/THWN-2 wires in 1/2" Electrical nonmetallic tubing (smurf tube)
0.285 sq in × 40 % = 0.1140 sq in allowed. ÷ 0.0211 sq in per wire = 5.40, so 5.
This pull in numbers
- 5 wires fill
- 37.0 % of 1/2" ENT
- Limit for three or more
- 40 %
- For 6 or more
- 3/4" ENT, up to 9
- Pipe to wire diameter
- 3.67 to 1
- In THW insulation
- 4 fit
- In XHHW-2 insulation
- 4 fit
Before you pull 5
- The ground counts. Every wire in the pipe counts toward fill, the green or bare ground and the neutrals too. 5 is the total, not the hots.
- Derating. If all 5 were current-carrying, each would be adjusted to 80 % of its ampacity (Table 310.15(C)(1)): a #10 THHN at 40 A in the 90 °C column becomes 32 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.
#10 THHN in other 1/2" conduit
| Conduit | Inside area | Most #10 THHN |
|---|---|---|
| Electrical metallic tubing | 0.304 | 5 |
| Intermediate metal conduit | 0.342 | 6 |
| Rigid metal conduit (RMC, GRC) | 0.314 | 6 |
| Rigid PVC conduit, Schedule 40 | 0.285 | 5 |
| Rigid PVC conduit, Schedule 80 | 0.217 | 4 |
| Flexible metal conduit (FMC, Greenfield) | 0.317 | 6 |
| Liquidtight flexible metal conduit (LFMC) | 0.314 | 6 |
| Electrical nonmetallic tubing (smurf tube) | 0.285 | 5 |