免费线管填充率计算器
计算线管中的导线填充率，确保符合电气规范要求。
sq in
sq in
Conduit Fill
45.0 %
NEC Max Fill40 %
Remaining Area-0.0436 sq in
Conduit Fill vs Conduit Internal Area
公式
NEC Conduit Fill Rules
The National Electrical Code limits fill percentages to prevent overheating:
Calculate fill by dividing total conductor area (including insulation) by the conduit internal area.
计算示例
4 conductors of 12 AWG THHN (0.0973 sq in each) in 3/4-inch EMT (0.864 sq in).
- 01Total wire area = 4 x 0.0973 = 0.389 sq in
- 02Fill = 0.389 / 0.864 x 100 = 45.0%
- 03NEC allows 40% for 3+ conductors
- 04This conduit is overfilled; upsize to 1-inch EMT.
常见问题
Where do I find wire and conduit areas?
NEC Chapter 9, Tables 4 and 5 list internal areas for common conduit types and conductor areas with insulation by wire type and gauge.
Do ground wires count toward fill?
Yes, equipment grounding conductors must be included in the fill calculation. Only internal conduit nipples 24 inches or less are exempt from the 40% rule.
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