Article 552

Park Trailers

Part I. General

Scope. The provisions of this article cover the electrical conductors and equipment installed within or on park trailers not covered fully under Articles 550 and 551.
Definition. (See Articles 100, 550, and 551 for addi‐ tional definitions.)

Park Trailer. A unit that is built on a single chassis mounted on wheels and has a gross trailer area not exceeding 37 m2 (400 ft2) in the set-up mode.

552.4 General Requirements. A park trailer as specified in

552.2 is intended for seasonal use. It is not intended as a permanent dwelling unit or for commercial uses such as banks, clinics, offices, or similar.

552.5 Labels. Labels required by Article 552 shall be made of etched, metal-stamped, or embossed brass or stainless steel; plastic laminates not less than 0.13 mm (0.005 in.) thick; or anodized or alclad aluminum not less than 0.5 mm (0.020 in.) thick or the equivalent.

Informational Note: For guidance on other label criteria used in the park trailer industry, refer to ANSI Z535.4-2011, Product Safety Signs and Labels.

Part II. Low-Voltage Systems

552.10 Low-Voltage Systems.

Low-Voltage Circuits. Low-voltage circuits furnished and installed by the park trailer manufacturer, other than those related to braking, shall be subject to this Code. Circuits supply‐ ing lights subject to federal or state regulations shall comply with applicable government regulations and this Code.
Low-Voltage Wiring.
1. Material. Copper conductors shall be used for low-voltage circuits.Exception: A metal chassis or frame shall be permitted as the return path to the source of supply.
2. Conductor Types. Conductors shall conform to the requirements for Type GXL, HDT, SGT, SGR, or Type SXL or shall have insulation in accordance with Table 310.104(A) or the equivalent. Conductor sizes 6 AWG through 18 AWG or SAE shall be listed. Single-wire, low-voltage conductors shall be of the stranded type.Informational Note: See SAE J1128-2011, Low Tension Primary Cable, for Types GXL, HDT, and SXL, and SAE J1127-2010, Battery Cable, for Types SGT and SGR.
3. Marking. All insulated low-voltage conductors shall be surface marked at intervals not greater than 1.2 m (4 ft) as follows:
  1. Listed conductors shall be marked as required by the list‐ ing agency.
  2. SAE conductors shall be marked with the name or logo of the manufacturer, specification designation, and wire gauge.
  3. Other conductors shall be marked with the name or logo of the manufacturer, temperature rating, wire gauge, conductor material, and insulation thickness.
Low-Voltage Wiring Methods.
1. Physical Protection. Conductors shall be protected against physical damage and shall be secured. Where insulated conductors are clamped to the structure, the conductor insula‐ tion shall be supplemented by an additional wrap or layer of equivalent material, except that jacketed cables shall not be required to be so protected. Wiring shall be routed away from sharp edges, moving parts, or heat sources.
2. Splices. Conductors shall be spliced or joined with splic‐ ing devices that provide a secure connection or by brazing, welding, or soldering with a fusible metal or alloy. Soldered splices shall first be spliced or joined to be mechanically and electrically secure without solder, and then soldered. All spli‐ ces, joints, and free ends of conductors shall be covered with an insulation equivalent to that on the conductors.
3. Separation. Battery and other low-voltage circuits shall be physically separated by at least a 13-mm (1∕2-in.) gap or other approved means from circuits of a different power source. Acceptable methods shall be by clamping, routing, or equiva‐ lent means that ensure permanent total separation. Where circuits of different power sources cross, the external jacket of the nonmetallic-sheathed cables shall be deemed adequate separation.
4. Ground Connections. Ground connections to the chassis or frame shall be made in an accessible location and shall be mechanically secure. Ground connections shall be by means of copper conductors and copper or copper-alloy terminals of the solderless type identified for the size of wire used. The surface on which ground terminals make contact shall be cleaned and be free from oxide or paint or shall be electrically connected through the use of a cadmium, tin, or zinc-plated internal/ external-toothed lockwasher or locking terminals. Ground terminal attaching screws, rivets or bolts, nuts, and lockwashers shall be cadmium, tin, or zinc-plated except rivets shall be permitted to be unanodized aluminum where attaching to aluminum structures.The chassis-grounding terminal of the battery shall be connected to the unit chassis with a minimum 8 AWG copper conductor. In the event the unbonded lead from the battery
  exceeds 8 AWG, the bonding conductor size shall be not less than that of the unbonded lead.
Battery Installations. Storage batteries subject to the provisions of this Code shall be securely attached to the unit and installed in an area vaportight to the interior and ventilated directly to the exterior of the unit. Where batteries are installed in a compartment, the compartment shall be ventilated with openings having a minimum area of 1100 mm2 (1.7 in.2) at both the top and at the bottom. Where compartment doors are equipped for ventilation, the openings shall be within 50 mm (2 in.) of the top and bottom. Batteries shall not be installed in a compartment containing spark- or flame-producing equip‐ ment.
Overcurrent Protection.
1. Rating. Low-voltage circuit wiring shall be protected by overcurrent protective devices rated not in excess of the ampac‐ ity of copper conductors, in accordance with Table 552.10(E)(1).
2. Type. Circuit breakers or fuses shall be of an approved type, including automotive types. Fuseholders shall be clearly marked with maximum fuse size and shall be protected against shorting and physical damage by a cover or equivalent means.Informational Note: For further information, see ANSI/SAE J554-1987, Standard for Electric Fuses (Cartridge Type); SAE J1284-1988, Standard for Blade Type Electric Fuses; and UL 275-2005, Standard for Automotive Glass Tube Fuses.
3. Appliances. Appliances such as pumps, compressors, heater blowers, and similar motor-driven appliances shall be installed in accordance with the manufacturer’s instructions.Motors that are controlled by automatic switching or by latching-type manual switches shall be protected in accordance with 430.32(B).
4. Location. The overcurrent protective device shall be installed in an accessible location on the unit within 450 mm (18 in.) of the point where the power supply connects to the unit circuits. If located outside the park trailer, the device shall be protected against weather and physical damage.Exception: External low-voltage supply shall be permitted to have the overcurrent protective device within 450 mm (18 in.) after entering the unit or after leaving a metal raceway.
Switches. Switches shall have a dc rating not less than the connected load.
Luminaires. All low-voltage interior luminaires rated more than 4 watts, employing lamps rated more than 1.2 watts, shall be listed.

Table 552.10(E)(1) Low-Voltage Overcurrent Protection

18	6	Stranded only
16	8	Stranded only
14	15	Stranded or solid
12	20	Stranded or solid
10	30	Stranded or solid

Wire Size (AWG) Ampacity Wire Type

Part III. Combination Electrical Systems

552.20 Combination Electrical Systems.

General. Unit wiring suitable for connection to a battery or other low-voltage supply source shall be permitted to be connected to a 120-volt source, provided that the entire wiring system and equipment are rated and installed in full conform‐ ity with Parts I, III, IV, and V requirements of this article cover‐ ing 120-volt electrical systems. Circuits fed from ac transformers shall not supply dc appliances.
Voltage Converters (120-Volt Alternating Current to Low- Voltage Direct Current). The 120-volt ac side of the voltage converter shall be wired in full conformity with the require‐ ments of Parts I and IV of this article for 120-volt electrical systems.Exception: Converters supplied as an integral part of a listed appliance shall not be subject to 552.20(B).All converters and transformers shall be listed for use in recreation units and designed or equipped to provide over- temperature protection. To determine the converter rating, the following percentages shall be applied to the total connected load, including average battery-charging rate, of all 12-volt equipment:The first 20 amperes of load at 100 percent plus The second 20 amperes of load at 50 percent plus All load above 40 amperes at 25 percentException: A low-voltage appliance that is controlled by a momentary switch (normally open) that has no means for holding in the closed position shall not be considered as a connected load when determining the required converter rating. Momentarily energized appliances shall be limited to those used to prepare the unit for occupancy or travel.
Bonding Voltage Converter Enclosures. The non–current- carrying metal enclosure of the voltage converter shall be connected to the frame of the unit with an 8 AWG copper conductor minimum. The grounding conductor for the battery and the metal enclosure shall be permitted to be the same conductor.
Dual-Voltage Fixtures Including Luminaires or Appliances. Fixtures, including luminaires, or appliances having both 120-volt and low-voltage connections shall be listed for dual voltage.
Autotransformers. Autotransformers shall not be used.
Receptacles and Plug Caps. Where a park trailer is equip‐ ped with a 120-volt or 120/240-volt ac system, a low-voltage system, or both, receptacles and plug caps of the low-voltage system shall differ in configuration from those of the 120-volt or 120/240-volt system. Where a unit equipped with a battery or dc system has an external connection for low-voltage power, the connector shall have a configuration that will not accept 120-volt power.

Part IV. Nominal 120-Volt or 120/240-Volt Systems

120-Volt or 120/240-Volt, Nominal, Systems.
1. General Requirements. The electrical equipment and material of park trailers indicated for connection to a wiring system rated 120 volts, nominal, 2-wire with an equipment
  grounding conductor, or a wiring system rated 120/240 volts, nominal, 3-wire with an equipment grounding conductor, shall be listed and installed in accordance with the requirements of Parts I, III, IV, and V of this article.
2. Materials and Equipment. Electrical materials, devices, appliances, fittings, and other equipment installed, intended for use in, or attached to the park trailer shall be listed. All products shall be used only in the manner in which they have been tested and found suitable for the intended use.
Receptacle Outlets Required.
1. Spacing. Receptacle outlets shall be installed at wall spaces 600 mm (2 ft) wide or more so that no point along the floor line is more than 1.8 m (6 ft), measured horizontally, from an outlet in that space.Exception No. 1: Bath and hallway areas.Exception No. 2: Wall spaces occupied by kitchen cabinets, wardrobe cabinets, built-in furniture; behind doors that may open fully against a wall surface; or similar facilities.
2. Location. Receptacle outlets shall be installed as follows:
  1. Adjacent to countertops in the kitchen [at least one on each side of the sink if countertops are on each side and are 300 mm (12 in.) or over in width and depth]
  2. Adjacent to the refrigerator and gas range space, except where a gas-fired refrigerator or cooking appliance, requiring no external electrical connection, is factory- installed
  3. Adjacent to countertop spaces of 300 mm (12 in.) or more in width and depth that cannot be reached from a receptacle required in 552.41(B)(1) by a cord of 1.8 m (6 ft) without crossing a traffic area, cooking appliance, or sink
3. Ground-Fault Circuit-Interrupter Protection. Each 125-volt, single-phase, 15- or 20-ampere receptacle shall have ground-fault circuit-interrupter protection for personnel in the following locations:
  1. Where the receptacles are installed to serve kitchen coun‐ tertop surfaces
  2. Within 1.8 m (6 ft) of any lavatory or sinkException: Receptacles installed for appliances in dedicated spaces, such as for dishwashers, disposals, refrigerators, freezers, and laundry equip‐ ment.
  3. In the area occupied by a toilet, shower, tub, or any combination thereof
  4. On the exterior of the unit
  Exception: Receptacles that are located inside of an access panel that is installed on the exterior of the unit to supply power for an installed appliance shall not be required to have ground-fault circuit-interrupter protection.The receptacle outlet shall be permitted in a listed lumin‐ aire. A receptacle outlet shall not be installed in a tub or combination tub–shower compartment.
4. Pipe Heating Cable Outlet. Where a pipe heating cable outlet is installed, the outlet shall be as follows:
  1. Located within 600 mm (2 ft) of the cold water inlet
  2. Connected to an interior branch circuit, other than a small-appliance branch circuit
  3. On a circuit where all of the outlets are on the load side of the ground-fault circuit-interrupter protection for personnel
  4. Mounted on the underside of the park trailer and shall not be considered to be the outdoor receptacle outlet required in 552.41(E)
5. Outdoor Receptacle Outlets. At least one receptacle outlet shall be installed outdoors. A receptacle outlet located in a compartment accessible from the outside of the park trailer shall be considered an outdoor receptacle. Outdoor receptacle outlets shall be protected as required in 552.41(C)(4).
6. Receptacle Outlets Not Permitted.
  1. Shower or Bathtub Space. Receptacle outlets shall not be installed in or within reach [750 mm (30 in.)] of a shower or bathtub space.
  2. Face-Up Position. A receptacle shall not be installed in a face-up position in any countertop or other similar horizontal surface.
N
Branch-Circuit Protection.
1. Rating. The branch-circuit overcurrent devices shall be rated as follows:
  1. Not more than the circuit conductors
  2. Not more than 150 percent of the rating of a single appli‐ ance rated 13.3 amperes or more and supplied by an indi‐ vidual branch circuit
  3. Not more than the overcurrent protection size marked on an air conditioner or other motor-operated applian‐ ces.
2. Protection for Smaller Conductors. A 20-ampere fuse or circuit breaker shall be permitted for protection for fixtures, including luminaires, leads, cords, or small appliances, and 14 AWG tap conductors, not over 1.8 m (6 ft) long for recessed luminaires.
3. Fifteen-Ampere Receptacle Considered Protected by
20 Amperes. If more than one receptacle or load is on a branch circuit, 15-ampere receptacles shall be permitted to be protected by a 20-ampere fuse or circuit breaker.
Power Supply.
1. Feeder. The power supply to the park trailer shall be a feeder assembly consisting of not more than one listed 30- ampere or 50-ampere park trailer power-supply cord, with an integrally molded or securely attached cap, or a permanently installed feeder.
2. Power-Supply Cord. If the park trailer has a power-supply cord, it shall be permanently attached to the panelboard, or to a junction box permanently connected to the panelboard, with the free end terminating in a molded-on attachment plug cap.Cords with adapters and pigtail ends, extension cords, and similar items shall not be attached to, or shipped with, a park trailer.A suitable clamp or the equivalent shall be provided at the panelboard knockout to afford strain relief for the cord to prevent strain from being transmitted to the terminals when the power-supply cord is handled in its intended manner.The cord shall be a listed type with 3-wire, 120-volt or 4-wire, 120/240-volt conductors, one of which shall be identified by a
  continuous green color or a continuous green color with one or more yellow stripes for use as the grounding conductor.
3. Mast Weatherhead or Raceway. Where the calculated load exceeds 50 amperes or where a permanent feeder is used, the supply shall be by means of one of the following:
1. One mast weatherhead installation, installed in accord‐ ance with Article 230, containing four continuous, insula‐ ted, color-coded feeder conductors, one of which shall be an equipment grounding conductor
2. A metal raceway, rigid nonmetallic conduit, or liquidtight flexible conduit from the disconnecting means in the park trailer to the underside of the park trailer
Cord.

Permanently Connected. Each power-supply assembly shall be factory supplied or factory installed and connected directly to the terminals of the panelboard or conductors within a junction box and provided with means to prevent strain from being transmitted to the terminals. The ampacity of the conductors between each junction box and the terminals of each panelboard shall be at least equal to the ampacity of the power-supply cord. The supply end of the assembly shall be equipped with an attachment plug of the type described in 552.44(C). Where the cord passes through the walls or floors, it shall be protected by means of conduit and bushings or equiva‐ lent. The cord assembly shall have permanent provisions for protection against corrosion and mechanical damage while the unit is in transit.
Cord Length. The cord-exposed usable length shall be measured from the point of entrance to the park trailer or the face of the flanged surface inlet (motor-base attachment plug) to the face of the attachment plug at the supply end.The cord-exposed usable length, measured to the point of entry on the unit exterior, shall be a minimum of 7.0 m (23 ft) where the point of entrance is at the side of the unit, or shall be a minimum 8.5 m (28 ft) where the point of entrance is at the rear of the unit. The maximum length shall not exceed 11 m (361∕2 ft).Where the cord entrance into the unit is more than 900 mm (3 ft) above the ground, the minimum cord lengths above shall be increased by the vertical distance of the cord entrance heights above 900 mm (3 ft).
Attachment Plugs.
1. Units with Two to Five 15- or 20-Ampere Branch Circuits. Park trailers wired in accordance with 552.46(A) shall have an attachment plug that shall be 2-pole, 3-wire grounding type, rated 30 amperes, 125 volts, conforming to the configuration shown in Figure 552.44(C)(1) intended for use with units rated at 30 amperes, 125 volts.Informational Note: Complete details of this configuration can be found in ANSI/NEMA WD 6-2002 (Rev. 2008), Standard for Dimensions of Attachment Plugs and Receptacles, Figure TT.
2. Units with 50-Ampere Power Supply Assembly. Park trail‐ ers having a power-supply assembly rated 50 amperes as permit‐ ted by 552.43(B) shall have a 3-pole, 4-wire grounding-type attachment plug rated 50 amperes, 125/250 volts, conforming to the configuration shown in Figure 552.44(C)(1).Informational Note: Complete details of this configuration can be found in ANSI/NEMA WD 6-2002 (Rev. 2008), Standard for Dimensions of Attachment Plugs and Receptacles, Figure 14-50.
Labeling at Electrical Entrance. Each park trailer shall have a safety label with the signal word WARNING in minimum 6 mm (1∕4 in.) high letters and body text in minimum 3 mm (1∕8 in.) high letters on a contrasting background. The safety label shall be affixed to the exterior skin, at or near the point of entrance of the power-supply assembly and shall read, as appropriate:THIS CONNECTION IS FOR 110–125-VOLT AC, 60 HZ, 30 AMPERE SUPPLYorTHIS CONNECTION IS FOR 208Y/120-VOLT OR 120/240- VOLT AC, 3-POLE, 4-WIRE, 60 HZ, AMPERE SUPPLY.followed byDO NOT EXCEED THE CIRCUIT RATING. EXCEEDING THE CIRCUIT RATING MAY CAUSE A FIRE AND RESULT IN DEATH OR SERIOUS INJURY.The correct ampere rating shall be marked in the blank space.
Location. The point of entrance of a power-supply assem‐ bly shall be located on either side or the rear, within 450 mm (18 in.), of an outside wall.

552.45 Panelboard.

Listed and Appropriately Rated. A listed and appropri‐ ately rated panelboard shall be used. The grounded conductor termination bar shall be insulated from the enclosure as provi‐ ded in 552.55(C). An equipment grounding terminal bar shall be attached inside the metal enclosure of the panelboard.
Location. The panelboard shall be installed in a readily accessible location. Working clearance for the panelboard shall be not less than 600 mm (24 in.) wide and 750 mm (30 in.) deep.Exception: Where the panelboard cover is exposed to the inside aisle space, one of the working clearance dimensions shall be permitted to be reduced to a minimum of 550 mm (22 in.). A panelboard shall be considered exposed where the panelboard cover is within 50 mm (2 in.) of the aisle’s finished surface or not more than 25 mm (1 in.) from the backside of doors that enclose the space.
G
WGWReceptacles CapsGYXWGXYW30-A,125-V, 2-pole, 3-wire, grounding type
50-A,125/250-V, 3-pole, 4-wire, grounding type
FIGURE 552.44(C)(1) Attachment Cap and Receptacle Configurations.
70 –476 NATIONAL ELECTRICAL CODE 2017 Edition
Dead-Front Type. The panelboard shall be of the dead- front type. A main disconnecting means shall be provided where fuses are used or where more than two circuit breakers are employed. A main overcurrent protective device not exceeding the power-supply assembly rating shall be provided where more than two branch circuits are employed.

Branch Circuits. Branch circuits shall be determined in accordance with 552.46(A) and (B).or 120/240 volt maximum and
1. Two to Five 15- or 20-Ampere Circuits. A maximum of five 15- or 20-ampere circuits to supply lights, receptacle outlets, and fixed appliances shall be permitted. Such park trailers shall be permitted to be equipped with panelboards rated at 120 volt maximumlisted for a 30-ampere-rated main power supply assembly. Not more than two 120-volt thermostatically controlled appliances shall be installed in such systems unless appliance isolation switching, energy management systems, or similar methods are used.Exception No. 1: Additional 15- or 20-ampere circuits shall be permit‐ ted where a listed energy management system rated at 30 amperes maxi‐ mum is employed within the system.
  Exception No. 2: Six 15- or 20-ampere circuits shall be permitted with‐out employing an energy management system, provided that the added sixth circuit serves only the power converter, and the combined load of all six circuits does not exceed the allowable load that was designed for use by the original five circuits.
  Informational Note: See 210.23(A) for permissible loads. See552.45(C) for main disconnect and overcurrent protection requirements.
2. More Than Five Circuits. Where more than five circuits are needed, they shall be determined in accordance with 552.46(B)(1), (B)(2), and (B)(3).
  1. Lighting. Based on 33 volt-amperes/m2 (3 VA/ft2) multi‐ plied by the outside dimensions of the park trailer (coupler excluded) divided by 120 volts to determine the number of 15- or 20-ampere lighting area circuits, for example,
    [552.46(B)(1)]3  length  width 120  15 or 20 No. of 15- or 20-  ampere circuitsThe lighting circuits shall be permitted to serve listed cord- connected kitchen waste disposers and to provide power for supplemental equipment and lighting on gas-fired ranges, ovens, or counter-mounted cooking units.
  2. Small Appliances. Small-appliance branch circuits shall be installed in accordance with 210.11(C)(1).
  3. General Appliances. (including furnace, water heater, space heater, range, and central or room air conditioner, etc.) An individual branch circuit shall be permitted to supply any load for which it is rated. There shall be one or more circuits of adequate rating in accordance with (a) through (d).
Informational Note No. 1: For the laundry branch circuit, see 210.11(C)(2).Informational Note No. 2: For central air conditioning, see Arti‐ cle 440.
1. The total rating of fixed appliances shall not exceed 50 percent of the circuit rating if lighting outlets, general-use receptacles, or both are also supplied.
2. For fixed appliances with a motor(s) larger than 1∕8 horsepower, the total calculated load shall be based on 125 percent of the largest motor plus the sum of the other loads. Where a branch circuit supplies continuous load(s) or any combination of continuous and noncontinuous loads, the branch-circuit conductor size shall be in accordance with 210.19(A).
3. The rating of a single cord-and-plug-connected appli‐ ance supplied by other than an individual branch circuit shall not exceed 80 percent of the circuit rating.
4. The rating of a range branch circuit shall be based on the range demand as specified for ranges in 552.47(B)(5).
Calculations. The following method shall be employed in computing the supply-cord and distribution-panelboard load for each feeder assembly for each park trailer in lieu of the procedure shown in Article 220 and shall be based on a 3-wire, 208Y/120-volt or 120/240-volt supply with 120-volt loads balanced between the two phases of the 3-wire system.
1. Lighting and Small-Appliance Load. Lighting Volt- Amperes: Length times width of park trailer floor (outside dimensions) times 33 volt-amperes/m2 (3 VA/ft2). For exam‐ ple,Length × width × 3 = lighting volt-amperesSmall-Appliance Volt-Amperes: Number of circuits times 1500 volt-amperes for each 20-ampere appliance receptacle circuit (see definition of Appliance, Portable with fine print note) including 1500 volt-amperes for laundry circuit. For example,No. of circuits × 1500 = small-appliance volt-amperesTotal: Lighting volt-amperes plus small-appliance volt- amperes = total volt-amperesFirst 3000 total volt-amperes at 100 percent plus remainder at 35 percent = volt-amperes to be divided by 240 volts to obtain current (amperes) per leg.
2. Total Load for Determining Power Supply. Total load for determining power supply is the sum of the following:
  1. Lighting and small-appliance load as calculated in 552.47(A).
  2. Nameplate amperes for motors and heater loads (exhaust fans, air conditioners, electric, gas, or oil heating). Omit smaller of the heating and cooling loads, except include blower motor if used as air-conditioner evaporator motor. Where an air conditioner is not installed and a 50-ampere power-supply cord is provided, allow 15 amperes per phase for air conditioning.
  3. Twenty-five percent of current of largest motor in (B)(2).
  4. Total of nameplate amperes for disposal, dishwasher, water heater, clothes dryer, wall-mounted oven, cooking units. Where the number of these appliances exceeds three, use 75 percent of total.
  5. Derive amperes for freestanding range (as distinguished from separate ovens and cooking units) by dividing the following values by 240 volts as shown in the table below:
  6. If outlets or circuits are provided for other than factory- installed appliances, include the anticipated load.
  Informational Note: Refer to Informative Annex D, Example D12, for an illustration of the application of this calculation.
  Nameplate Rating (watts)Use (volt-amperes)0–10,00080 percent of ratingOver 10,000–12,5008,000Over 12,500–13,5008,400Over 13,500–14,5008,800Over 14,500–15,5009,200Over 15,500–16,5009,600Over 16,500–17,50010,000
3. Optional Method of Calculation for Lighting and Appli‐ ance Load. For park trailers, the optional method for calculat‐ ing lighting and appliance load shown in 220.82 shall be permitted.
Wiring Methods.
1. Wiring Systems. Cables and raceways installed in accord‐ ance with Articles 320, 322, 330 through 340, 342 through 362, 386, and 388 shall be permitted in accordance with their appli‐ cable article, except as otherwise specified in this article. An equipment grounding means shall be provided in accordance with 250.118.
2. Conduit and Tubing. Where rigid metal conduit or inter‐ mediate metal conduit is terminated at an enclosure with a locknut and bushing connection, two locknuts shall be provi‐ ded, one inside and one outside of the enclosure. All cut ends of conduit and tubing shall be reamed or otherwise finished to remove rough edges.
3. Nonmetallic Boxes. Nonmetallic boxes shall be accepta‐ ble only with nonmetallic-sheathed cable or nonmetallic race‐ ways.
4. Boxes. In walls and ceilings constructed of wood or other combustible material, boxes and fittings shall be flush with the finished surface or project therefrom.
5. Mounting. Wall and ceiling boxes shall be mounted in accordance with Article 314.Exception No. 1: Snap-in-type boxes or boxes provided with special wall or ceiling brackets that securely fasten boxes in walls or ceilings shall be permitted.Exception No. 2: A wooden plate providing a 38-mm (11∕2-in.) mini‐ mum width backing around the box and of a thickness of 13 mm (1∕2 in.) or greater (actual) attached directly to the wall panel shall be considered as approved means for mounting outlet boxes.
6. Cable Sheath. The sheath of nonmetallic-sheathed cable, and the armor of metal-clad cable and Type AC cable, shall be continuous between outlet boxes and other enclosures.
7. Protected. Metal-clad, Type AC, or nonmetallic-sheathed cables and electrical nonmetallic tubing shall be permitted to pass through the centers of the wide side of 2 by 4 wood studs. However, they shall be protected where they pass through 2 by 2 wood studs or at other wood studs or frames where the cableor tubing would be less than 32 mm (11∕4 in.) from the inside or outside surface. Steel plates on each side of the cable or tubing, or a steel tube, with not less than 1.35 mm (0.053 in.) wall thickness, shall be installed to protect the cable or tubing. These plates or tubes shall be securely held in place. Where nonmetallic-sheathed cables pass through punched, cut, or drilled slots or holes in metal members, the cable shall be protected by bushings or grommets securely fastened in the opening prior to installation of the cable.
8. Cable Supports. Where connected with cable connectors or clamps, cables shall be secured and supported within 300 mm (12 in.) of outlet boxes, panelboards, and splice boxes on appliances. Supports and securing shall be provided at intervals not exceeding 1.4 m (41∕2 ft) at other places.
9. Nonmetallic Box Without Cable Clamps. Nonmetallic- sheathed cables shall be secured and supported within 200 mm (8 in.) of a nonmetallic outlet box without cable clamps. Where wiring devices with integral enclosures are employed with a loop of extra cable to permit future replacement of the device, the cable loop shall be considered as an integral portion of the device.•
10. Physical Damage. Where subject to physical damage,exposed nonmetallic cable shall be protected by covering boards, guard strips, raceways, or other means.
11. Receptacle Faceplates. Metal faceplates shall comply with 406.5(A). Nonmetallic faceplates shall comply with 406.5(C).
12. Metal Faceplates Grounded. Where metal faceplates are used, they shall be grounded.
13. Moisture or Physical Damage. Where outdoor or under- chassis wiring is 120 volts, nominal, or over and is exposed to moisture or physical damage, the wiring shall be protected by rigid metal conduit, by intermediate metal conduit, by electri‐ cal metallic tubing, by rigid nonmetallic conduit, or by Type MI cable that is closely routed against frames and equipment enclosures or other raceway or cable identified for the applica‐ tion.
14. Component Interconnections. Fittings and connectors that are intended to be concealed at the time of assembly shall be listed and identified for the interconnection of building components. Such fittings and connectors shall be equal to the wiring method employed in insulation, temperature rise, and fault-current withstanding, and shall be capable of enduring the vibration and shock occurring in park trailers.
15. Method of Connecting Expandable Units. The method of connecting expandable units to the main body of the park trailer shall comply with 552.48(O)(1) and 552.48(O)(2) as applicable.
  1. Cord-and-Plug Connected. Cord-and-plug connections shall comply with 552.48(O)(1)(a) through (O)(1)(d).
    1. The portion of a branch circuit that is installed in an expandable unit shall be permitted to be connected to the portion of the branch circuit in the main body of the vehicle by means of an attachment plug and cord listed for hard usage. The cord and its connections shall comply with all provisions of Article 400 and shall be considered as a permitted use under 400.10. Where the attachment plug and cord are located within the park trailer’s interior, use of plastic thermoset or elastomer parallel cord Type SPT-3, SP-3, or SPE shall be permitted.
    2. Where the receptacle provided for connection of the cord to the main circuit is located on the outside of the park trailer, it shall be protected with a ground-fault circuit interrupter for personnel and be listed for wet locations. A cord located on the outside of a park trailer shall be identified for outdoor use.park trailer
    3. Unless removable or stored within theinterior, the cord assembly shall have permanent provisions for protection against corrosion and mechanical damage while the park trailer is in transit.
    4. The attachment plug and cord shall be installed so as not to permit exposed live attachment plug pins.N
  2. Direct Wires Connected. That portion of a branch circuit that is installed in an expandable unit shall be permitted to be connected to the portion of the branch circuit in the main body of the park trailer by means of flexible cord installed in accordance with 552.48(O)(2)(a) through (O)(2)(f) or other approved wiring method.
    1. The flexible cord shall be listed for hard usage and for use in wet locations.
    2. The flexible cord shall be permitted to be exposed on the underside of the vehicle.
    3. The flexible cord shall be permitted to pass through the interior of a wall or floor assembly or both a maximum concealed length of 600 mm (24 in.) before terminating at an outlet or junction box.
    4. Where concealed, the flexible cord shall be installed in nonflexible conduit or tubing that is continuous from the outlet or junction box inside the park trailer to a weatherproof outlet box, junction box, or strain relief fitting listed for use in wet locations that is located on the underside of the park trailer. The outer jacket of flexible cord shall be continuous into the outlet or junction box.
    5. Where the flexible cord passes through the floor to an exposed area inside of the park trailer, it shall be protected by means of conduit and bushings or equivalent.
    6. Where subject to physical damage, the flexible cord shall be protected with RMC, IMC, Schedule 80 PVC, rein‐ forced thermosetting resin conduit (RTRC) listed for exposure to physical damage, or other approved means and shall extend at least 150 mm (6 in.) above the floor. A means shall be provi‐ ded to secure the flexible cord where it enters the park trailer.
16. Prewiring for Air-Conditioning Installation. Prewiring installed for the purpose of facilitating future air-conditioning installation shall comply with the applicable portions of this article and the following:
  1. An overcurrent protective device with a rating compatible with the circuit conductors shall be installed in the panel‐ board and wiring connections completed.
  2. The load end of the circuit shall terminate in a junction box with a blank cover or other listed enclosure. Where a junction box with a blank cover is used, the free ends of the conductors shall be adequately capped or taped.N
  3. A safety label with the word WARNING in minimum 6 mm (1∕4 in.) high letters and body text in minimum 3 mm (1∕8 in.) high letters on a contrasting background shall be affixed on or adjacent to the junction box and shall read as follows:RATED 110–125-VOLT AC, 60 HZ, AMPERES MAXIMUM.DO NOT EXCEED CIRCUIT RATING.EXCEEDING THE CIRCUIT RATING MAY CAUSE A FIRE AND RESULT IN DEATH OR SERIOUS INJURYAn ampere rating not to exceed 80 percent of the circuit rating shall be legibly marked in the blank space.
  4. The circuit shall serve no other purpose.
  N
17. Prewiring for Other Circuits. Prewiring installed for the purpose of installing other appliances or devices shall comply with the applicable portions of this article and the following:
1. An overcurrent protection device with a rating compati‐ ble with the circuit conductors shall be installed in the panelboard with wiring connections completed.
2. The load end of the circuit shall terminate in a junction box with a blank cover or a device listed for the purpose. Where a junction box with blank cover is used, the free ends of the conductors shall be adequately capped or taped.
3. A safety label with the signal word WARNING in mini‐ mum 6 mm (1∕4 in.) high letters and body text in mini‐ mum 3 mm (1∕8 in.) high letters on a contrasting background shall be affixed on or adjacent to the junc‐ tion box or device listed for the purpose and shall read as follows:
WARNINGTHIS CONNECTION IS FOR RATED VOLT AC, 60 HZ, AMPERES MAXIMUM. DO NOT EXCEED CIRCUIT RATING. EXCEEDING THE CIRCUIT RATING MAY CAUSE A FIRE AND RESULT IN DEATH OR SERIOUS INJURY.An ampere rating not to exceed 80 percent of the circuit rating shall be legibly marked in the blank space.
Maximum Number of Conductors in Boxes. The maximum number of conductors permitted in boxes shall be in accordance with 314.16.
Grounded Conductors. The identification of groun‐ ded conductors shall be in accordance with 200.6.
Connection of Terminals and Splices. Conductor spli‐ ces and connections at terminals shall be in accordance with 110.14.
Switches. Switches shall be rated as required by 552.52(A) and (B).
1. Lighting Circuits. For lighting circuits, switches shall be rated not less than 10 amperes, 120/125 volts, and in no case less than the connected load.
2. Motors or Other Loads. For motors or other loads, switches shall have ampere or horsepower ratings, or both, adequate for loads controlled. (An ac general-use snap switch shall be permitted to control a motor 2 hp or less with full-load current not over 80 percent of the switch ampere rating.)WARNINGAIR-CONDITIONING CIRCUIT.THIS CONNECTION IS FOR AIR CONDITIONERS
3. Location. Switches shall not be installed within wet loca‐ tions in tub or shower spaces unless installed as part of a listed tub or shower assembly.
Receptacles. All receptacle outlets shall be of the grounding type and installed in accordance with 210.21 and 406.4.
Luminaires.
1. General. Any combustible wall or ceiling finish exposed between the edge of a canopy or pan of a luminaire or ceiling suspended (paddle) fan and the outlet box shall be covered with noncombustible material or a material identified for the purpose.
2. Shower Luminaires. If a luminaire is provided over a bathtub or in a shower stall, it shall be of the enclosed and gasketed type and listed for the type of installation, and it shall be ground-fault circuit-interrupter protected.•
3. Outdoor Outlets, Luminaires, Air-Cooling Equipment, and
So On. Outdoor luminaires and other equipment shall be listed for outdoor use or wet locations.
Grounding. (See also 552.57 on bonding of non– current-carrying metal parts.)
1. Power-Supply Grounding. The grounding conductor in the supply cord or feeder shall be connected to the grounding bus or other approved grounding means in the panelboard.
2. Panelboard. The panelboard shall have a grounding bus with sufficient terminals for all grounding conductors or other approved grounding means.
3. Insulated Grounded Conductor. The grounded circuit conductor shall be insulated from the equipment grounding conductors and from equipment enclosures and other groun‐ ded parts. The grounded circuit conductor terminals in the panelboard and in ranges, clothes dryers, counter-mounted cooking units, and wall-mounted ovens shall be insulated from the equipment enclosure. Bonding screws, straps, or buses in the panelboard or in appliances shall be removed and discar‐ ded. Connection of electric ranges and electric clothes dryers utilizing a grounded conductor, if cord-connected, shall be made with 4-conductor cord and 3-pole, 4-wire, grounding-type plug caps and receptacles.
Interior Equipment Grounding.
1. Exposed Metal Parts. In the electrical system, all exposed metal parts, enclosures, frames, luminaire canopies, and so forth, shall be effectively bonded to the grounding terminals or enclosure of the panelboard.
2. Equipment Grounding Conductors. Bare conductors or conductors with insulation or individual covering that is green or green with one or more yellow stripes shall be used for equipment grounding conductors only.
3. Grounding of Electrical Equipment. Where grounding of electrical equipment is specified, it shall be permitted as follows:
  1. Connection of metal raceway (conduit or electrical metal‐ lic tubing), the sheath of Type MC and Type MI cable where the sheath is identified for grounding, or the armor of Type AC cable to metal enclosures.
  2. A connection between the one or more equipment grounding conductors and a metal box by means of a grounding screw, which shall be used for no other purpose, or a listed grounding device.
  3. The equipment grounding conductor in nonmetallic- sheathed cable shall be permitted to be secured under a screw threaded into the luminaire canopy other than a mounting screw or cover screw or attached to a listed grounding means (plate) in a nonmetallic outlet box for luminaire mounting (grounding means shall also be permitted for luminaire attachment screws).
4. Grounding Connection in Nonmetallic Box. A connec‐ tion between the one or more grounding conductors brought into a nonmetallic outlet box shall be arranged so that a connection can be made to any fitting or device in that box that requires grounding.
5. Grounding Continuity. Where more than one equipment grounding conductor of a branch circuit enters a box, all such conductors shall be in good electrical contact with each other, and the arrangement shall be such that the disconnection or removal of a receptacle, fixture, including a luminaire, or other device fed from the box will not interfere with or interrupt the grounding continuity.
6. Cord-Connected Appliances. Cord-connected appliances, such as washing machines, clothes dryers, refrigerators, and the electrical system of gas ranges, and so on, shall be grounded by means of an approved cord with equipment grounding conductor and grounding-type attachment plug.
Bonding of Non–Current-Carrying Metal Parts.
1. Required Bonding. All exposed non–current-carrying metal parts that are likely to become energized shall be effec‐ tively bonded to the grounding terminal or enclosure of the panelboard.
2. Bonding Chassis. A bonding conductor shall be connec‐ ted between any panelboard and an accessible terminal on the chassis. Aluminum or copper-clad aluminum conductors shall not be used for bonding if such conductors or their terminals are exposed to corrosive elements.Exception: Any park trailer that employs a unitized metal chassis-frame construction to which the panelboard is securely fastened with a bolt(s) and nut(s) or by welding or riveting shall be considered to be bonded.
3. Bonding Conductor Requirements. Grounding terminals shall be of the solderless type and listed as pressure terminal connectors recognized for the wire size used. The bonding conductor shall be solid or stranded, insulated or bare, and shall be 8 AWG copper minimum or equivalent.
4. Metallic Roof and Exterior Bonding. The metal roof and exterior covering shall be considered bonded where both of the following conditions apply:
  1. The metal panels overlap one another and are securely attached to the wood or metal frame parts by metal fasteners.
  2. The lower panel of the metal exterior covering is secured by metal fasteners at each cross member of the chassis, or the lower panel is connected to the chassis by a metal strap.
5. Gas, Water, and Waste Pipe Bonding. The gas, water, and waste pipes shall be considered grounded if they are bonded to the chassis.
6. Furnace and Metal Air Duct Bonding. Furnace and metal circulating air ducts shall be bonded.
ARTICLE 553 — FLOATING BUILDINGS 553.7
Appliance Accessibility and Fastening. Every appliance shall be accessible for inspection, service, repair, and replace‐ ment without removal of permanent construction. Means shall be provided to securely fasten appliances in place when the park trailer is in transit.
Outdoor Outlets, Fixtures, Including Luminaires, Air- Cooling Equipment, and So On.

Listed for Outdoor Use. Outdoor fixtures, including luminaires, and equipment shall be listed for outdoor use. Outdoor receptacle outlets shall be in accordance with 406.9(A) and (B). Switches and circuit breakers installed outdoors shall comply with 404.4.
Outside Heating Equipment, Air-Conditioning Equipment, or Both. A park trailer provided with a branch circuit designed to energize outside heating equipment or air- conditioning equipment, or both, located outside the park trailer, other than room air conditioners, shall have such branch-circuit conductors terminate in a listed outlet box or disconnecting means located on the outside of the park trailer. A safety label with the word WARNING in minimum 6 mm (1∕4 in.) high letters and body text in minimum 3 mm (1∕8 in.) high letters on a contrasting background shall be affixed within 150 mm (6 in.) from the listed box or disconnecting means and shall read as follows:

(B) Low-Voltage Circuits. An operational test of low-voltage circuits shall be conducted to demonstrate that all equipment is connected and in electrical working order. This test shall be performed in the final stages of production after all outer coverings and cabinetry have been secured.

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