How Many 250 MCM Wires Fit in PVC Conduit?
Complete NEC-compliant fill chart for 250 MCM THHN wires in Schedule 40 PVC (PVC) conduit. Maximum wire counts for all standard conduit sizes.
Quick Answer
For 250 MCM THHN wires in PVC conduit at 40% fill (3+ wires):
- • 1-1/4" PVC: 1 wires
- • 1-1/2" PVC: 2 wires
- • 2" PVC: 3 wires
250 MCM in PVC Conduit Fill Chart
| Conduit Size | Max Wires (40% Fill) | Fill % | Max Wires (Nipple 60%) | Fill % |
|---|---|---|---|---|
| 1-1/4" | 1 | 28% | 2 | 56% |
| 1-1/2" | 2 | 40% | 3 | 60% |
| 2" | 3 | 36% | 4 | 48% |
| 2-1/2" | 5 | 36% | 8 | 58% |
| 3" | 8 | 37% | 13 | 59% |
| 3-1/2" | 11 | 38% | 17 | 59% |
| 4" | 14 | 39% | 21 | 58% |
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 250 MCM THHN conductors that can fit in each PVC conduit size while maintaining NEC compliance.
Calculation Example
Question: How many 250 MCM THHN wires can fit in 1-1/2" PVC conduit?
Wire area: 0.397 sq in per conductor
Conduit internal area: 1.986 sq in
Allowable fill (40%): 0.7944 sq in
Maximum wires: 0.7944 ÷ 0.397 = 2 wires
Answer: You can fit up to 2 wires of 250 MCM THHN in 1-1/2" PVC conduit.