Marinas and Boatyards Practice Questions

C. A docking facility serving a one-family dwelling

The scope names fixed and floating piers, wharves, docks, floating buildings and the other areas of marinas and boatyards, and it reaches docking facilities at one-family and two-family dwellings as well as multifamily ones. Wiring aboard the vessel itself is not premises wiring and stays outside. Candidates lose this one by assuming a single private dock is too small to be covered.

NEC 2026 555.1

A. Listed ground-fault protection of equipment rated not more than 30 milliamperes

The tight equipment-grade number belongs at the receptacle, because that device watches one boat and the background leakage under it is one boat's worth. Personnel-grade protection is a different requirement that applies to marina outlets other than shore power. Holding these two values in the wrong order is the most expensive mistake in the article.

NEC 2026 555.35

B. 100 milliamperes

The looser setting sits upstream, where the device carries the summed leakage of every vessel under it. Forty wet boats on a shared feeder would keep a tighter device open all weekend. In the 2026 edition the requirement is written to reach piers as well as docking facilities.

NEC 2026 555.35

D. The tight setting now sits on the conductor carrying every boat's leakage, and the slack one sits on the single boat the article wants watched closely

The split is arithmetic rather than caution. A device with one boat under it can hold a tight setting and still stay closed, while a feeder with a whole dock under it cannot. Reversed, the facility trips constantly at the top and protects nobody at the slip.

NEC 2026 555.35

B. Where more than three receptacles supply shore power to boats

The trigger is a receptacle count and nothing else, so a small dock with three shore power receptacles is outside it. The device also has to be listed for use in marina applications, which rules out whatever clamp meter is in the truck. Both qualifiers sit in the middle of the sentence, which is why they get read past.

NEC 2026 555.35

C. Determining the leakage current from each boat that will use shore power

The device earns its keep before the boat is plugged in rather than after something trips, because a tripped feeder tells you a dock has a problem and not which vessel caused it. Nothing in the requirement sets a testing interval, so an answer offering a frequency is offering something the section does not state. An exception releases the separate device where the shore power equipment already carries a leakage indicator and alarm.

NEC 2026 555.35

A. The shore power equipment already includes a leakage indicator and a leakage alarm

One exception releases the requirement where the equipment itself already indicates and alarms on leakage, since the screening function is built in. The 30 milliampere protection is a separate requirement and satisfying it does not buy relief here. Fresh water is why the hazard exists in the first place, not a reason to skip a measurement.

NEC 2026 555.35

D. 30 amperes

Shore power is supplied by single receptacles rated not less than that value, and each one gets an individual branch circuit of the matching voltage class and rating. The 15 and 20 ampere figures come from the separate requirement for a receptacle other than shore power. Article 555 uses the number thirty for three unrelated things, so read the unit before the number.

NEC 2026 555.33

B. Pin and sleeve type

The article splits the requirement by rating: the 30 and 50 ampere receptacles are the locking and grounding type, and anything at 60 amperes or above is pin and sleeve. Reading the rule as one type for all shore power receptacles is what produces the wrong pick. The rating in the stem is the whole item.

NEC 2026 555.33

C. Not less than 12 inches above the deck surface and not below the electrical datum plane

Two floors apply at once, one measured from the deck and one from the datum plane, and the receptacle has to clear both. On a fixed pier at low water the datum plane can be the higher of the two. A question that gives you only one of the two measurements is testing whether you went looking for the other.

NEC 2026 555.33

A. Not more than 30 inches from the receptacle it controls, ahead of that receptacle

The section asks for a disconnect for each shore power connection, readily accessible, identified as to which receptacle it controls, and within that distance in the supply circuit ahead of the receptacle. Circuit breakers or switches in a marina power outlet may serve as the disconnect. The thirty here is inches, not amperes and not milliamperes.

NEC 2026 555.36

B. A listed emergency shutoff device or electrical disconnect, marked for that purpose, that de-energizes every circuit the outlet supplies

The emergency disconnect has to be within sight of the outlet, readily accessible, externally operable, manually resettable and listed for wet locations, and its marking follows the general field marking rules. It kills every circuit supplied by that outlet rather than one slip. The section says outright that a circuit breaker handle is not acceptable for this purpose.

NEC 2026 555.36, 110.22(A)

C. Coordination and performance testing by a qualified person following the manufacturer's instructions, with a written record available to the authority having jurisdiction

This is a commissioning requirement rather than an installation one, which makes it the kind of new material that turns up as a knowledge item long before anyone meets it in the field. The record is the part people forget, since the testing itself is the visible half. Nothing in the section sets a repeat interval.

NEC 2026 555.35

D. It may be insulated, covered or bare, and is not required to be larger than 8 AWG copper

The section gives a ceiling rather than a floor, which is the opposite of how most conductor sizing rules read. That ceiling is what keeps a long dock bond from turning into a service-sized conductor. Reaching for a sizing table here is the error the option list is built around.

NEC 2026 555.13

A. Wire type, insulated, sized from Table 250.122 and never smaller than 12 AWG

Three conditions stack here: the conductor is a wire and not the raceway, it is insulated, and the ordinary sizing table result gets a floor put under it. A 20 ampere circuit would otherwise take a 12 AWG conductor from the table, so the floor bites on the smallest circuits. The wiring method rules in the same article also ask for a wire-type insulated equipment grounding conductor.

NEC 2026 555.37, Table 250.122

B. A specified vertical distance above the normal high-water level at which equipment may be installed and connections made

It is a horizontal reference tied to water level, and it moves with tidal range, with the highest normal water level where there is no tide, and with flooding. The definition sits in Article 100 with the others while Article 555 sets the distances. Everything in the article about mounting height is measured from either the deck or this plane, and often from both.

NEC 2026 Article 100

C. 2 feet above the highest water level for the area occurring under normal circumstances

The article gives three cases and each one has its own reference. Land areas subject to tidal fluctuation use the same 2 foot figure measured from the highest high tide instead. The flood-of-record answer sounds careful and is not what the section states.

NEC 2026 555.16

D. A horizontal plane 30 inches above the water level at the floating pier and at least 12 inches above the level of the deck

A floating pier moves with the water, so a plane fixed to a shoreline elevation would be meaningless on it. The subsection therefore ties the plane to the water at the pier and puts a second floor above the deck. Both conditions apply, and the plane is whichever of the two lands higher.

NEC 2026 555.16

A. On land, no closer than 5 feet horizontally from the structure served, and at least 12 inches above the electrical datum plane

The section keeps the service off the structure entirely and off any other floating structure, then adds a horizontal setback and a vertical clearance above the datum plane. The point is that the supply stays put while the dock moves. Both numbers are testable and they are measured in different directions.

NEC 2026 555.17

B. 600 volts phase to phase

This is a short lookup near the front of the article and it is stated phase to phase. Candidates guess 480 because it is the common distribution voltage they see, or 1000 because that is the general dividing line elsewhere in the book. Neither is the number the section prints.

NEC 2026 555.5

C. All electrical equipment installed in those areas has to be listed

A listing requirements section sits near the front of the article and it sweeps in piers, wharves, docks, floating buildings, marinas, boatyards, boat basins, boathouses, yacht clubs and boat condominiums. Sections in the low-numbered positions of an article are worth a glance for exactly this reason. Narrowing it to one class of equipment is the trap.

NEC 2026 555.2

D. It is provided on request of the authority having jurisdiction, and it is not required for one- and two-family dwelling units at 240 volts single-phase or less

The requirement is triggered by a request rather than by a size threshold, and the release is written around the occupancy and the system voltage together. A private dock at a house on 240 volt single-phase service falls outside it. Answers built on slip counts and service sizes are inventing a threshold the section does not carry.

NEC 2026 555.9

A. Single-phase circuits not exceeding 150 volts to ground and rated 60 amperes or less

The subsection sets two parallel conditions, one for single-phase and one for three-phase, and each carries its own ampere ceiling alongside the same voltage-to-ground limit. This is the personnel-grade level, which is tighter than either equipment-grade number in the same section. An item that offers a value in the single milliamperes is testing whether you noticed that the stem left out the words shore power.

NEC 2026 555.35

B. Ground-fault circuit interrupter protection for personnel, for outlets not exceeding 240 volts

A hoist is a single load on its own outlet, so it gets the personnel-grade device rather than either equipment-grade setting. The subsection puts a voltage ceiling on the outlets it reaches, and it permits a ground-fault protected receptacle for other than shore power to supply the hoist. Counting what sits downstream of the device sorts the three levels reliably.

NEC 2026 555.35

D. Signs warning that electrical currents may be present in the water, clearly visible from all approaches to the facility

The wording is prescribed by the section rather than left to the owner, and the placement requirement is about approaches rather than a single entrance. The signs also have to meet the general durability rules for field marking. Prescribed text plus a placement rule makes this an easy item to write and a cheap one to answer.

NEC 2026 555.10