When individual service entrance conductors enter a structure via the roof, they must enter through roof bushings. If they enter through the wall, they must do so at an upward slant through individual, noncombustible, nonabsorbent insulating tubes [230.52] and the conductors must be arranged in drip loops before entering the tubes.
When exposed to the weather, raceways enclosing service entrance conductors must be suitable for wet locations and arranged to drain. If enclosed in masonry, they must be arranged to drain [230.53].
You’ve probably guessed the rationale behind these NEC requirements. You don’t want water entering the service panel by following along the service entrance cables. You may be tempted to “exceed the NEC” in an effort to decrease any chance of water intrusion, but carefully consider any measures before implementing. For example, don’t:
- Apply additional sealant over the bushings unless doing so is specifically approved by the bushing manufacturer.
- Construct a protective hood over the top. It will become a nesting place for birds, and those droppings aren’t good for the conductors or the bushings.
You will get good reliability if you install the bushings (or tubes) per the manufacturer’s recommendations then add the recommended maintenance to your maintenance schedule.
