Understanding NEC Article 555: Marinas, Boatyards, and Docking Facilities

NEC Article 555 provides comprehensive guidelines for the electrical systems used in marinas, boatyards, floating buildings, and docking facilities. It emphasizes safety to mitigate hazards like electrical shock drowning and fire risks in these water-adjacent environments.

Scope of Article 555

This article applies to:

• Fixed or floating piers, wharves, docks, marinas, boatyards, yacht clubs, and similar facilities.
• Docking facilities for residential buildings.
• Floating buildings used for residential, commercial, or other purposes.

Referenced Standards:

• NFPA 303: Fire Protection Standard for Marinas and Boatyards.
• NFPA 307: Standard for Marine Terminals and Piers.

Key Requirements for Marinas and Boatyards

1. Electrical Datum Plane
   • Establishes a horizontal benchmark for electrical installations relative to water levels to prevent submersion:
     • Floating Piers: At least 12 inches above the deck.
     • Tidal Areas: 2 feet above the highest high tide.
     • Non-Tidal Areas: 2 feet above the highest normal water level.
2. Service Equipment
   • Service equipment must be located on land, at least 5 feet horizontally from the structure served, and 12 inches above the electrical datum plane.
3. Ground-Fault Protection
   • Docking Facilities:
     • Feeders: Maximum 100 mA ground-fault protection for equipment (GFPE).
     • Shore Power: 30 mA GFPE for receptacles.
   • Boat Hoists: GFCI protection is required for outlets supplying hoists up to 240 volts.
4. Equipotential Planes
   • Required near service equipment within 10 feet of water to mitigate step and touch voltage hazards.
   • Must include bonded metal parts and extend at least 36 inches around the equipment.
5. Signage
   • Permanent signs at docking facilities must state:
     “WARNING — POTENTIAL SHOCK HAZARD — ELECTRICAL CURRENTS MAY BE PRESENT IN THE WATER.”

Receptacles and Power Distribution

1. Shore Power Receptacles
   • Each receptacle must be supplied by an individual branch circuit with GFPE.
   • 30-amp and 50-amp receptacles must be locking and grounding types.
2. Branch Circuits and Wiring Methods
   • Must be suitable for wet locations and protected against physical damage.
   • Portable power cables may be used on floating piers if rated for wet locations and secured appropriately.

Floating Buildings

• Each floating building must have a single feeder connected to a grounding electrode system onshore.
• Flexible wiring methods, like liquidtight conduits, are required to account for water movement.

Applications

NEC Article 555 applies to:

• Marinas and Boatyards: For docking, fueling, and maintenance of small craft.
• Residential Docks: For private mooring facilities.
• Floating Structures: Including homes, restaurants, and offices.

Conclusion

NEC Article 555 ensures the safe operation of electrical systems in marinas, boatyards, and docking facilities. Its focus on proper grounding, waterproofing, and shock prevention is essential for protecting people and property in these water-adjacent environments.