How many #10 THHN fit in 1-1/4" Flex?
2410 AWG THHN/THWN-2 wires in 1-1/4" Flexible metal conduit (FMC, Greenfield)
1.277 sq in × 40 % = 0.5108 sq in allowed. ÷ 0.0211 sq in per wire = 24.21, so 24.
This pull in numbers
- 24 wires fill
- 39.7 % of 1-1/4" Flex
- Limit for three or more
- 40 %
- For 25 or more
- 1-1/2" Flex, up to 35
- Pipe to wire diameter
- 7.77 to 1
- In THW insulation
- 21 fit
- In XHHW-2 insulation
- 21 fit
Before you pull 24
- The ground counts. Every wire in the pipe counts toward fill, the green or bare ground and the neutrals too. 24 is the total, not the hots.
- Derating. If all 24 were current-carrying, each would be adjusted to 45 % of its ampacity (Table 310.15(C)(1)): a #10 THHN at 40 A in the 90 °C column becomes 18 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 1-1/4" conduit
| Conduit | Inside area | Most #10 THHN |
|---|---|---|
| Electrical metallic tubing | 1.496 | 28 |
| Intermediate metal conduit | 1.647 | 31 |
| Rigid metal conduit (RMC, GRC) | 1.526 | 29 |
| Rigid PVC conduit, Schedule 40 | 1.453 | 27 |
| Rigid PVC conduit, Schedule 80 | 1.237 | 23 |
| Flexible metal conduit (FMC, Greenfield) | 1.277 | 24 |
| Liquidtight flexible metal conduit (LFMC) | 1.528 | 29 |
| Electrical nonmetallic tubing (smurf tube) | 1.453 | 27 |
#10 THHN in other Flex sizes
Other wire sizes in 1-1/4" Flex
#14: 52#12: 38#10: 24#8: 14#6: 10#4: 6#3: 5#2: 4#1: 3#1/0: 2#2/0: 1#3/0: 1#4/0: 1250 kcmil: 1300 kcmil: 1350 kcmil: 1