You can run the PVC conduit of either grade from the panel into the ground unless it is subject to physical damage. One example would be in a grassy area were power trimmers might be used. All PVC conduit must be eighteen inches deep to the top of the conduit unless it is encased in concrete or protected by a concrete pad or guard above it. If the raceway is subject to severe physical damage you would use rigid or intermediate metal conduit. An example of severe physical damage exposure is a driveway next to a house or a surface run on the interior of a garage at a height that may be struck by a vehicle.
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Tom H
