13.5 Manufactured Homes, RV Parks, Marinas & Temporary Installations

13.5 Manufactured Homes, RV Parks, Marinas & Temporary Installations

ICC 703's Special Occupancies, Equipment, and Conditions area (11% of the exam) and Prov's Special Occupancies and Special Conditions areas include occupancies whose power arrives in unusual ways: homes built on a chassis, campsites, docks over water, and temporary construction power. Each has its own Chapter 5 article (550, 551, 555) or Chapter 5 temporary-wiring article (590), and each builds on the general rules you already know.

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1. Mobile and Manufactured Homes (Article 550)

A mobile home is a factory-assembled structure built on a permanent chassis and designed to be used as a dwelling without a permanent foundation. A manufactured home is built on a chassis to the federal HUD construction standard and may be placed on a permanent foundation. Article 550 covers the electrical conductors and equipment installed within or on these homes, the conductors that connect them to a supply, and the installation of service equipment and feeders.

Service equipment (550.32)

• Location for mobile homes (550.32(A)): Service equipment must be located adjacent to the mobile home, not mounted in or on it, and within sight from and not more than 30 feet (9.0 m) from the exterior wall of the home it serves. It may be on a pole or a pedestal.
• Manufactured homes (550.32(B)): Service equipment may be installed in or on a manufactured home when a list of conditions is met, including installation under the manufacturer's instructions, a permanent foundation, and compliance with Article 230.
• Rating (550.32(C)): Mobile home service equipment must be rated at not less than 100 amperes at 120/240 volts.

Feeders and grounding

• Feeder conductors (550.33(A)): The feeder from the service equipment to the home is either a listed cord or a permanently installed feeder of four insulated, color-coded conductors: two ungrounded conductors, a grounded (neutral) conductor, and an equipment grounding conductor.
• Neutral isolation (550.16(A)): Inside the home, the grounded conductor must be insulated from the equipment grounding conductors and from equipment enclosures and other grounded parts. The home's panelboard is a feeder panel, so its neutral bar is not bonded to the enclosure.
• Power-supply cord (550.10(A)): The supply to a mobile home is either one listed 50-ampere mobile home power-supply cord or a permanently installed feeder.

Park service

A mobile home park's service and feeders are calculated at not less than 16,000 VA for each mobile home lot at 120/240 volts, then reduced by the demand factors in Table 550.31 based on the number of lots.

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2. Recreational Vehicle Parks (Article 551, Part VI)

Receptacles required at each site (551.71)

Each 50-ampere receptacle is supplied by its own branch circuit of the receptacle's voltage class and rating. The 125-volt, single-phase, 15- and 20-ampere receptacles at RV sites need listed GFCI protection.

Calculated load (551.73)

The park's electrical service and feeders are calculated on the following minimum loads per site, then reduced by the demand factors in Table 551.73(A):

• 9,600 VA for each site with a 50-ampere supply.
• 3,600 VA for each site with both 20-ampere and 30-ampere supply.
• 2,400 VA for each site with only a 20-ampere supply.
• 600 VA for each dedicated tent site with a 20-ampere supply.

Worked example: A new park has 12 sites with 50-ampere supply and 18 sites with 20- and 30-ampere supply. The connected load before demand factors is $12 \times 9{,}600 + 18 \times 3{,}600 = 115{,}200 + 64{,}800 = 180{,}000$ VA. The Table 551.73(A) demand factor for 30 sites is then applied to this total.

Site supply equipment location (551.77(A))

Site supply equipment is located on the left (road) side of the parked vehicle, on a line 5 to 7 feet from the left edge of the stall, at any point from the rear of the stall to 15 feet forward of the rear. A disconnecting switch or circuit breaker in the site supply equipment must disconnect the power supply to the RV.

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3. Marinas, Boatyards, and Docking Facilities (Article 555)

Article 555 applies to marinas, boatyards, and both commercial and noncommercial docking facilities, including private residential docks. Water and electricity create the risk of electric shock drowning, where current leaking into fresh water paralyzes a swimmer.

Electrical datum plane

The electrical datum plane sets the level below which electrical equipment and connections may not be installed:

• Land areas subject to tides: a horizontal plane 2 feet above the highest tide level for the area under normal conditions.
• Land areas not subject to tides: a horizontal plane 2 feet above the highest high-water level under normal conditions.
• Floating piers: a horizontal plane 30 inches above the water surface, with a minimum freeboard of 12 inches.

Ground-fault protection (555.35)

• Shore-power receptacles: Each must have individual ground-fault protection of equipment (GFPE) set to open at currents not exceeding 30 mA.
• Feeders and branch circuits: The overcurrent devices that supply the docking facility must have ground-fault protection not exceeding 100 mA, and coordination with downstream ground-fault protection is permitted.
• Other receptacles: 15- and 20-ampere, 125-volt receptacles that do not supply shore power need GFCI protection under 210.8.

Shore power and signs

Shore-power receptacles are rated at not less than 30 amperes, and each one is supplied by an individual branch circuit of the receptacle's voltage class and rating. A readily accessible disconnecting means within 30 inches of each shore-power receptacle isolates each boat from its supply (555.36). Permanent safety signs must warn of the potential shock hazard from electrical currents in the water (555.10).

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4. Temporary Installations (Article 590)

Time limits (590.3)

• During construction: for the period of construction, remodeling, maintenance, repair, or demolition.
• Holiday lighting: for not more than 90 days for holiday decorative lighting and similar purposes.
• Emergencies and tests: for emergencies and for tests, experiments, and developmental work.
• Removal: Temporary wiring must be removed immediately when the construction or purpose is finished.

Installation rules (590.4)

• Cables: Type NM and NMC cables are permitted for temporary feeders and branch circuits in any building or structure, without the usual height or construction-type limits.
• Receptacles: All receptacles must be the grounding type, and on construction sites they must not be on a branch circuit that supplies temporary lighting.
• Disconnects: Each temporary circuit needs a means to disconnect all ungrounded conductors, and multiwire branch circuits need simultaneous disconnection at the panel where they originate (handle ties permitted).
• Lamps: Lamps for general illumination must be protected from accidental contact or breakage by a suitable luminaire or a lampholder with a guard.
• Splices: On construction sites, a box is not required for splices in multiconductor cords or cables if equipment grounding continuity is maintained.
• Support: Cables and cords must be supported at intervals that protect them from physical damage. Vegetation may not support overhead spans, except for holiday lighting arranged with strain relief or tension take-up devices.

Ground-fault protection (590.6)

• 590.6(A): All 125-volt, single-phase, 15-, 20-, and 30-ampere receptacle outlets that are not part of the permanent wiring and are in use by personnel must have GFCI protection. Permanent receptacles used for temporary power also need GFCI protection, and listed cord sets with built-in GFCI protection are permitted.
• 590.6(B): Other receptacle outlets, such as 250-volt or larger receptacles, need GFCI protection or, where permitted, a written assured equipment grounding conductor program that tests cords and receptacles at set intervals.