Underground feeder burial depths — UF cable 24″, PVC conduit 18″, rigid metal 6″
The wiring method sets the trench depth: 24″ for direct-burial UF, 18″ for PVC conduit, 6″ for rigid metal conduit (NEC Table 300.5).
What this diagram shows
Cross-section of three trenches below grade comparing NEC minimum burial cover: direct-burial UF cable needs 24 inches of cover, PVC conduit needs 18 inches, and rigid or intermediate metal conduit needs only 6 inches. Depths are drawn to scale, per NEC Table 300.5. Regular indoor NM-B cable is not permitted underground at all.
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