How Many 350 MCM Wires Fit in RMC Conduit?
Complete NEC-compliant fill chart for 350 MCM THHN wires in Rigid Metal Conduit (RMC) conduit. Maximum wire counts for all standard conduit sizes.
Quick Answer
For 350 MCM THHN wires in RMC conduit at 40% fill (3+ wires):
- • 1-1/4" RMC: 1 wires
- • 1-1/2" RMC: 1 wires
- • 2" RMC: 2 wires
350 MCM in RMC Conduit Fill Chart
| Conduit Size | Max Wires (40% Fill) | Fill % | Max Wires (Nipple 60%) | Fill % |
|---|---|---|---|---|
| 1-1/4" | 1 | 34% | 1 | 34% |
| 1-1/2" | 1 | 25% | 2 | 51% |
| 2" | 2 | 31% | 3 | 46% |
| 2-1/2" | 4 | 35% | 6 | 52% |
| 3" | 6 | 35% | 10 | 59% |
| 3-1/2" | 8 | 36% | 13 | 58% |
| 4" | 11 | 39% | 17 | 60% |
Understanding the Fill Chart
According to NEC (National Electrical Code) Chapter 9, Table 1, the maximum conduit fill percentage depends on the number of conductors:
- 1 conductor: 53% fill maximum
- 2 conductors: 31% fill maximum
- 3 or more conductors: 40% fill maximum
- Nipples (24" or less): 60% fill maximum
This chart shows the maximum number of 350 MCM THHN conductors that can fit in each RMC conduit size while maintaining NEC compliance.
Calculation Example
Question: How many 350 MCM THHN wires can fit in 1-1/2" RMC conduit?
Wire area: 0.5242 sq in per conductor
Conduit internal area: 2.071 sq in
Allowable fill (40%): 0.8284 sq in
Maximum wires: 0.8284 ÷ 0.5242 = 1 wires
Answer: You can fit up to 1 wires of 350 MCM THHN in 1-1/2" RMC conduit.