Article 555: Marinas and Boatyards

Article 555: Marinas and Boatyards

By Mike Holt for EC&M Magazine

Common as they are, marinas and boatyards present special challenges.

Almost every town of any size has non-private boating facilities, such as docks and piers. You’ll find these by natural bodies of water, of course. But you’ll also find them in any of the thousands of artificial lakes created for parks and for upscale residential communities.

The main thing that complicates marina and boatyard work is the fact that water level isn’t constant. As the earth and the moon play their eons-old game of tug-of-war, bodies of water rise and fall at the shoreline. Other forces also cause the water level to change. For example, lakes and rivers vary in depth in response to rain—sometimes dramatically.

To provide power to a marina or boatyard, you must allow for the variations in water level between the point of use and the power source. But other issues complicate this work, also. As you might expect, your installation must accommodate the high levels of moisture inherent in being so close to water. And as any water skier knows, sunlight reflected off the water is much more intense than it would otherwise be. This has implications for insulation.

Other factors include temperature extremes, abrasion caused by movement, oil, gasoline, diesel fuel, ozone, acids, and chemicals. Then, of course, docking a boat isn’t as easy as pulling into a shopping center parking spot with your automobile. Electrical equipment must meet certain spatial requirements, so it doesn’t interfere with mooring lines or masts.

Because of all these issues, we have Article 555. It covers the installation of wiring and equipment for fixed or floating piers, wharves, docks, and other areas in marinas, boatyards, boat basins, boathouses, any multiple docking facility, and similar occupancies. It doesn’t apply to docking facilities or boathouses for single-family dwellings.

Article 555 begins with the concept of the electrical datum plane. Think of this as a line that marks the beginning of a “no parking zone” where you simply don’t “park” (install) certain kinds of electrical equipment: transformers, connections, or receptacles.

The definition of the Electrical Datum Plane varies, depending on which of the three following applications you are dealing with [555.2]:

(1) Land areas subject to tidal fluctuation. The horizontal plane 2 ft above the highest high tide that occurs under normal circumstances (Figure 555-1).

(2) Land areas not subject to tidal fluctuation. The horizontal plane 2 ft above the highest water level that occurs under normal circumstances.

(3) Floating Piers. The horizontal plane 30 in. above the water level at the floating pier and a minimum of 12 in. above the level of the deck.

In addition to observing the datum plane, you will—for the typical installation project—use a “marine power outlet.” This is an assembly that can include receptacles, circuit breakers, fused switches, fuses, and watt-hour meters. The authority having jurisdiction (AHJ) must approve it for marine use [555.2] and [555.11]. You’ll need this for the application of shore power receptacles [555.19(A)(1)] and disconnecting means [555.17(B)].

You’ll also need the AHJ to approve any transformers you use. Ensure no part of a transformer is below the electrical datum plane [555.5].

Locate electrical connections no less than 12 in. above the deck of a floating pier, and no less than 12 in. above the deck of a fixed pier—but not below the electrical datum plane [555.9].

Load Calculations for Service and Feeder Conductors

You can calculate the service or feeder load for shore power receptacles, using the adjustment factors in Table 555.12 (see the Table). Where shore power provides two receptacles for an individual boat slip, you must use the receptacle with the larger kW demand (Figure 555-2).

Grounding

To ground wiring and equipment within the scope of Article 555, follow the specifications in Article 250 and 555.15(A) through 555.15(E).

You must connect the following items to an equipment grounding conductor run with the circuit conductors in the same raceway, cable, or trench:

(1) Metal boxes, metal cabinets, and all other metal enclosures

(2) Metal frames of utilization equipment

(3) Grounding terminals of grounding-type receptacles

The equipment grounding conductor (EGC) must be an insulated copper conductor with a continuous outer finish that is either green or green with one or more yellow stripes. For conductors larger than 6 AWG, or where you use multiconductor cables, you may re-identify conductors as allowed in 250.119(A)(2)(b) and (A)(2)(c) or 250.119(B)(2) and (B)(3). Size your EGC per 250.122—but not smaller than 12 AWG.

You must terminate the EGC for branch circuits at a grounding terminal in a remote panelboard or the grounding terminal in the main service equipment. Where a feeder supplies a remote panelboard, run an insulated EGC from a grounding terminal in the service equipment to a grounding terminal in the remote panelboard.

Boat Receptacle Disconnecting Means

A disconnecting means must isolate each boat from its shore power receptacle [555.17]. But, you must pay attention to:

Type of Disconnect. You can use a circuit breaker or switch as the required shore power receptacle disconnecting means. Identify each disconnect to show which receptacle it controls.
Location. The disconnecting means for shore power receptacles must be readily accessible and located not more than 30 in. from the receptacle. If circuit breakers or switches are in marine power outlets, you can use them for the boat receptacle disconnecting means (Figure 555-4).

This shore power receptacle disconnecting means is intended to eliminate the hazard of accidental contact with energized blades while engaging or disengaging the shore power attachment plug with wet, slippery hands. The 30-in. requirement helps someone not familiar with the marina layout to quickly reach the disconnecting means in an emergency.

Receptacles

Mount receptacles no less than 12 in. above the deck surface, and not below the electrical datum plane [555.19] (Figure 555-5). Article 555 distinguishes between shore power receptacles and other than shore power receptacles.

Shore power receptacles:

That provide shore power for boats must be rated not less than 30A.
Rated 50A and less must be of the locking and grounding (bonding) type (Figure 555-6).
Rated for 60A or 100A must be of the pin-and-sleeve type.

The length of the boat does not determine the rating of the shore power receptacle. Article 555 simply sets a minimum rating of 30A and leaves it up to the designer and/or owner to determine which receptacles are necessary, based on projected usage of the slips.

Other than shore power receptacles must comply with 210.8. But you must provide GFCI protection if these are 15 or 20A, 125V receptacles installed outdoors for portable electric hand tools, electrical diagnostic equipment, or portable lighting equipment (Figure 555-7). You must provide GFCI protection to all 15 (125V) and 20A (125V) receptacles in boathouses of dwelling units [210.8(A)(8)] (Figure 555-8). In addition to these rules for receptacle outlets, be mindful that any 125Vt, 15 or 20A branch circuit supplying power for a boast hoist at a dwelling must be GFCI protected as well [210.8(C)]. This applies whether the hoist is cord and plug connected or hard wired!

Flammable or combustible liquids

Electrical wiring and equipment located at or serving motor fuel dispensing equipment must comply with Article 514, in addition to Article 555 [555.21]. Install all electrical wiring for motor fuel dispensing equipment on the side of the wharf, pier, or dock opposite from the liquid motor fuel piping system.

Electrical wiring and equipment at marine craft repair facilities containing flammable or combustible liquids or gases must comply with the requirements contained in Article 511 [555.22] (Figure 555-9).

Important rules in Article 511 to consider include:

511.3 Classification of Hazardous (Classified) Areas
511.4 Wiring and Equipment In Hazardous (Classified) Locations
511.7 Wiring and Equipment Above Hazardous (Classified) Locations
511.9 Sealing and drainage
511.12 GFCI-Protected Receptacles

Safe docking

Any time you do electrical work on a boatyard or marina, Article 555 applies. The exception is when the facility is a non-commercial, private docking facility for the residents of a single-family home associate with that facility). Before you make any decisions on where to locate transformers, install receptacles, or make connections, clearly understand the electrical datum plane for that application.

The AHJ has more interaction with an Article 555 application than is typical for applications of other NEC Articles. You may find it helpful to create a checklist of needed AHJ approvals before even starting the job.

Table 555.12 Adjustment Factors

Number of Sum of the Rating

Receptacles of the Receptacles

1 – 4 100%

5 – 8 90%

9 – 14 80%

15 – 30 70%

31 – 40 60%

41 – 50 50%

51 – 70 40%

Over 71 30%