Shore power receptacles are being installed in the pedestals along the docks of a marina, each one intended to supply a boat in an adjacent slip. How does the Code require each of those receptacles to be supplied?
- By an individual branch circuit matching the receptacle rating, serving no other outlet
- BBy a 20-ampere multi-outlet branch circuit shared by no more than two adjacent slips
Sharing a circuit between slips is the dwelling-style thinking that this article specifically excludes. A boat's load is continuous and unpredictable, and two boats on one circuit would trip it and disconnect both.
- CBy a feeder tapped at the pedestal, with the overcurrent device back at the marina panelboard
Tapping a feeder at the pedestal leaves the receptacle without an overcurrent device rated for it. The circuit rating and the receptacle rating have to correspond.
- DBy any general-purpose circuit at the pedestal, provided the receptacle is of the locking type
The locking and grounding configuration is a separate requirement for the larger receptacles and does not substitute for the dedicated circuit.
Why A is correct
Each shore power receptacle must be supplied from a marine power outlet or panelboard by an individual branch circuit of the voltage class and rating that matches the receptacle, and that circuit serves nothing else. Receptacles rated 30 amperes and above must also be of the locking and grounding type.
What this question is testing
Tests whether you know that a shore power receptacle gets a dedicated branch circuit whose rating matches it rather than sharing a general-purpose circuit, and whether you can separate that requirement from the locking-configuration requirement that applies to the larger sizes.
On the job
Dock wiring lives in salt spray, sunlight and constant mechanical abuse from cords being dragged and yanked. One circuit per receptacle also makes the marina operable: a boat with a fault does not take its neighbors down, and the dockmaster can isolate one slip. Corrosion at pedestal terminations is the leading maintenance issue, and it is also the leading source of the leakage current that makes electric shock drowning possible.
Memory technique
Every slip gets its own circuit, because every boat is its own building.
Exam tip
One receptacle, one circuit, matched rating. Marinas do not share circuits between slips.
Where to look it up
Article 555 covers marinas, boatyards and docking facilities, with the receptacle and branch-circuit provisions grouped together.