How Many 400 MCM Wires Fit in IMC Conduit?
Complete NEC-compliant fill chart for 400 MCM THHN wires in Intermediate Metal Conduit (IMC) conduit. Maximum wire counts for all standard conduit sizes.
Quick Answer
For 400 MCM THHN wires in IMC conduit at 40% fill (3+ wires):
- • 1-1/4" IMC: 1 wires
- • 1-1/2" IMC: 1 wires
- • 2" IMC: 2 wires
400 MCM in IMC Conduit Fill Chart
| Conduit Size | Max Wires (40% Fill) | Fill % | Max Wires (Nipple 60%) | Fill % |
|---|---|---|---|---|
| 1-1/4" | 1 | 36% | 1 | 36% |
| 1-1/2" | 1 | 26% | 2 | 53% |
| 2" | 2 | 32% | 3 | 48% |
| 2-1/2" | 4 | 37% | 6 | 55% |
| 3" | 6 | 36% | 9 | 54% |
| 3-1/2" | 8 | 37% | 12 | 56% |
| 4" | 10 | 37% | 16 | 59% |
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 400 MCM THHN conductors that can fit in each IMC conduit size while maintaining NEC compliance.
Calculation Example
Question: How many 400 MCM THHN wires can fit in 1-1/2" IMC conduit?
Wire area: 0.5863 sq in per conductor
Conduit internal area: 2.225 sq in
Allowable fill (40%): 0.8900 sq in
Maximum wires: 0.8900 ÷ 0.5863 = 1 wires
Answer: You can fit up to 1 wires of 400 MCM THHN in 1-1/2" IMC conduit.