How many #12 THHN fit in 1/2" Flex?
912 AWG THHN/THWN-2 wires in 1/2" Flexible metal conduit (FMC, Greenfield)
0.317 sq in × 40 % = 0.1268 sq in allowed. ÷ 0.0133 sq in per wire = 9.53, so 9.
This pull in numbers
- 9 wires fill
- 37.8 % of 1/2" Flex
- Limit for three or more
- 40 %
- For 10 or more
- 3/4" Flex, up to 16
- Pipe to wire diameter
- 4.88 to 1
- In THW insulation
- 7 fit
- In XHHW-2 insulation
- 7 fit
Before you pull 9
- The ground counts. Every wire in the pipe counts toward fill, the green or bare ground and the neutrals too. 9 is the total, not the hots.
- Derating. If all 9 were current-carrying, each would be adjusted to 70 % of its ampacity (Table 310.15(C)(1)): a #12 THHN at 30 A in the 90 °C column becomes 21 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.
#12 THHN in other 1/2" conduit
| Conduit | Inside area | Most #12 THHN |
|---|---|---|
| Electrical metallic tubing | 0.304 | 9 |
| Intermediate metal conduit | 0.342 | 10 |
| Rigid metal conduit (RMC, GRC) | 0.314 | 9 |
| Rigid PVC conduit, Schedule 40 | 0.285 | 8 |
| Rigid PVC conduit, Schedule 80 | 0.217 | 6 |
| Flexible metal conduit (FMC, Greenfield) | 0.317 | 9 |
| Liquidtight flexible metal conduit (LFMC) | 0.314 | 9 |
| Electrical nonmetallic tubing (smurf tube) | 0.285 | 8 |