How many #3 THHN fit in 1-1/2" Flex?
73 AWG THHN/THWN-2 wires in 1-1/2" Flexible metal conduit (FMC, Greenfield)
1.858 sq in × 40 % = 0.7432 sq in allowed. ÷ 0.0973 sq in per wire = 7.64, so 7.
This pull in numbers
- 7 wires fill
- 36.7 % of 1-1/2" Flex
- Limit for three or more
- 40 %
- For 8 or more
- 2" Flex, up to 13
- Pipe to wire diameter
- 4.37 to 1
- In THW insulation
- 6 fit
- In XHHW-2 insulation
- 7 fit
Before you pull 7
- The ground counts. Every wire in the pipe counts toward fill, the green or bare ground and the neutrals too. 7 is the total, not the hots.
- Derating. If all 7 were current-carrying, each would be adjusted to 70 % of its ampacity (Table 310.15(C)(1)): a #3 THHN at 115 A in the 90 °C column becomes 80.5 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.
#3 THHN in other 1-1/2" conduit
| Conduit | Inside area | Most #3 THHN |
|---|---|---|
| Electrical metallic tubing | 2.036 | 8 |
| Intermediate metal conduit | 2.225 | 9 |
| Rigid metal conduit (RMC, GRC) | 2.071 | 8 |
| Rigid PVC conduit, Schedule 40 | 1.986 | 8 |
| Rigid PVC conduit, Schedule 80 | 1.711 | 7 |
| Flexible metal conduit (FMC, Greenfield) | 1.858 | 7 |
| Liquidtight flexible metal conduit (LFMC) | 1.981 | 8 |
| Electrical nonmetallic tubing (smurf tube) | 1.986 | 8 |
#3 THHN in other Flex sizes
Other wire sizes in 1-1/2" Flex
#14: 76#12: 56#10: 35#8: 20#6: 14#4: 9#3: 7#2: 6#1: 4#1/0: 4#2/0: 3#3/0: 2#4/0: 1250 kcmil: 1300 kcmil: 1350 kcmil: 1500 kcmil: 1