VI. Recreational Vehicle Parks
551.71 Type Receptacles Provided
Every recreational vehicle site with electrical supply shall be equipped with at least one 20-ampere, 125-volt receptacle. A minimum of 20 percent of all recreational vehicle sites, with electrical supply, shall each be equipped with a 50-ampere, 125/250-volt receptacle conforming to the configuration as identified in Figure 551.46(C). These electrical supplies shall be permitted to include additional receptacles that have configurations in accordance with 551.81. A minimum of 70 percent of all recreational vehicle sites with electrical supply shall each be equipped with a 30-ampere, 125-volt receptacle conforming to Figure 551.46(C). This supply shall be permitted to include additional receptacle configurations conforming to 551.81. The remainder of all recreational vehicle sites with electrical supply shall be equipped with one or more of the receptacle configurations conforming to 551.81. Dedicated tent sites with a 15- or 20-ampere electrical supply shall be permitted to be excluded when determining the percentage of recreational vehicle sites with 30- or 50-ampere receptacles.
Additional receptacles shall be permitted for the connection of electrical equipment outside the recreational vehicle within the recreational vehicle park.
At least one 20-ampere, 125-volt receptacle must be installed at each RV campsite. Existing recreational vehicle campgrounds may have some sites that are equipped with 30-ampere receptacles only. Adapter plugs or “cheater” cords are often used to connect an RV with a 20-ampere supply cord to a 30-ampere receptacle outlet. This practice does not provide adequate overload protection for the cord or the connected load. The requirement ensures the availability of the properly rated receptacle.
Some newer recreational vehicles have a 50-ampere, 120/240-volt supply installed, and 20 percent of RV sites must be provided with 50-ampere, 125/250-volt receptacles to accommodate the larger electrical systems in some RVs. This requirement increases the load capacity for RV park services and feeders. Receptacle configurations are shown in Figure 551.46(C), and receptacle ratings are described in 551.81.
All 125-volt, single-phase, 15- and 20-ampere receptacles shall have listed ground-fault circuit-interrupter protection for personnel.
Informational Note: The percentage of 50 ampere sites required by 551.71 may be inadequate for seasonal recreational vehicle sites serving a higher percentage of recreational vehicles with 50 ampere electrical systems. In that type of recreational vehicle park, the percentage of 50 ampere sites could approach 100 percent.
551.72 Distribution System
Receptacles rated at 50 amperes shall be supplied from a branch circuit of the voltage class and rating of the receptacle. Other recreational vehicle sites with 125-volt, 20- and 30-ampere receptacles shall be permitted to be derived from any grounded distribution system that supplies 120-volt single-phase power. The neutral conductors shall not be reduced in size below the size of the ungrounded conductors for the site distribution. The neutral conductors shall be permitted to be reduced in size below the minimum required size of the ungrounded conductors for 240-volt, line-to-line, permanently connected loads only.
The distribution system of an RV park must supply the sites by a 120-volt, 2-wire circuit; a 120/240 volt, 3-wire circuit; or a 3-wire 120/208-volt circuit derived from a 208Y/120-volt, 3-phase, 4-wire system. See the commentary on 551.40(A) for information regarding the voltage rating of line-to-line connected appliances in RVs.
551.73 Calculated Load
(A) Basis of Calculations.
Electrical services and feeders shall be calculated on the basis of not less than 9600 volt-amperes per site equipped with 50-ampere, 208Y/120 or 120/240-volt supply facilities; 3600 volt-amperes per site equipped with both 20-ampere and 30-ampere supply facilities; 2400 volt-amperes per site equipped with only 20-ampere supply facilities; and 600 volt-amperes per site equipped with only 20-ampere supply facilities that are dedicated to tent sites. The demand factors set forth in Table 551.73(A) shall be the minimum allowable demand factors that shall be permitted in calculating load for service and feeders. Where the electrical supply for a recreational vehicle site has more than one receptacle, the calculated load shall be calculated only for the highest rated receptacle.
The calculated load for dedicated tent sites supplied with electricity can be smaller since these sites are not intended to accommodate recreational vehicles.
Where the electrical supply is in a location that serves two recreational vehicles, the equipment for both sites shall comply with 551.77, and the calculated load shall only be calculated for the two receptacles with the highest rating.
This second paragraph of 551.73(A) requires that, where receptacle outlets are installed at a location that can serve two RVs, the load is to be calculated for the two receptacles with the highest rating.
(B) Transformers and Secondary Distribution Panelboards.
For the purpose of this Code, where the park service exceeds 240 volts, transformers and secondary distribution panelboards shall be treated as services.
(C) Demand Factors.
The demand factor for a given number of sites shall apply to all sites indicated. For example, 20 sites calculated at 45 percent of 3600 volt-amperes results in a permissible demand of 1620 volt-amperes per site or a total of 32,400 volt-amperes for 20 sites.
Informational Note: These demand factors may be inadequate in areas of extreme hot or cold temperature with loaded circuits for heating or air conditioning.
(D) Feeder-Circuit Capacity.
Recreational vehicle site feeder-circuit conductors shall have an ampacity not less than the loads supplied and shall be rated not less than 30 amperes. The neutral conductors shall have an ampacity not less than the ungrounded conductors.
Informational Note: Due to the long circuit lengths typical in most recreational vehicle parks, feeder conductor sizes found in the ampacity tables of Article 310 may be inadequate to maintain the voltage regulation suggested in the fine print note to 210.19. Total circuit voltage drop is a sum of the voltage drops of each serial circuit segment, where the load for each segment is calculated using the load that segment sees and the demand factors of 551.73(A).
Loads for other amenities such as, but not limited to, service buildings, recreational buildings, and swimming pools shall be calculated separately and then be added to the value calculated for the recreational vehicle sites where they are all supplied by a common service.
551.74 Overcurrent Protection
Overcurrent protection shall be provided in accordance with Article 240.
All electrical equipment and installations in recreational vehicle parks shall be grounded as required by Article 250.
551.76 Grounding — Recreational Vehicle Site Supply Equipment
(A) Exposed Non–Current-Carrying Metal Parts.
Exposed non–current-carrying metal parts of fixed equipment, metal boxes, cabinets, and fittings that are not electrically connected to grounded equipment shall be grounded by an equipment grounding conductor run with the circuit conductors from the service equipment or from the transformer of a secondary distribution system. Equipment grounding conductors shall be sized in accordance with 250.122 and shall be permitted to be spliced by listed means.
The arrangement of equipment grounding connections shall be such that the disconnection or removal of a receptacle or other device will not interfere with, or interrupt, the grounding continuity.
(B) Secondary Distribution System.
Each secondary distribution system shall be grounded at the transformer.
(C) Grounded Conductor Not to Be Used as an Equipment Ground.
The grounded conductor shall not be used as an equipment grounding conductor for recreational vehicles or equipment within the recreational vehicle park.
(D) No Connection on the Load Side.
No connection to a grounding electrode shall be made to the grounded conductor on the load side of the service disconnecting means except as covered in 250.30(A) for separately derived systems, and 250.32(B) Exception for separate buildings.
551.77 Recreational Vehicle Site Supply Equipment
Where provided on back-in sites, the recreational vehicle site electrical supply equipment shall be located on the left (road) side of the parked vehicle, on a line that is 1.5 m to 2.1 m (5 ft to 7 ft) from the left edge (driver’s side of the parked RV) of the stand and shall be located at any point on this line from the rear of the stand to 4.5 m (15 ft) forward of the rear of the stand.
For pull-through sites, the electrical supply equipment shall be permitted to be located at any point along the line that is 1.5 m to 2.1 m (5 ft to 7 ft) from the left edge (driver’s side of the parked RV) from 4.9 m (16 ft) forward of the rear of the stand to the center point between the two roads that gives access to and egress from the pull-through sites.
The left edge (driver’s side of the parked RV) of the stand shall be marked.
These requirements are intended to accommodate vehicles towing boats or other trailers. The location of the site supply equipment permitted for pull-through sites reduces the use of extension cords.
(B) Disconnecting Means.
A disconnecting switch or circuit breaker shall be provided in the site supply equipment for disconnecting the power supply to the recreational vehicle.
All site supply equipment shall be accessible by an unobstructed entrance or passageway not less than 600 mm (2 ft) wide and 2.0 m (6 ft 6 in.) high.
(D) Mounting Height.
Site supply equipment shall be located not less than 600 mm (2 ft) or more than 2.0 m (6 ft 6 in.) above the ground.
(E) Working Space.
Sufficient space shall be provided and maintained about all electrical equipment to permit ready and safe operation, in accordance with 110.26.
Where the site supply equipment contains a 125/250-volt receptacle, the equipment shall be marked as follows: “Turn disconnecting switch or circuit breaker off before inserting or removing plug. Plug must be fully inserted or removed.” The marking shall be located on the equipment adjacent to the receptacle outlet.
The marking is to reduce the possibility of a partially engaged attachment plug, which could result in intermittent neutral (grounded conductor) contact. Loss of the neutral could momentarily apply the line-to-line voltage (240 volts) across 125-volt equipment, causing malfunction or damage.
551.78 Protection of Outdoor Equipment
(A) Wet Locations.
All switches, circuit breakers, receptacles, control equipment, and metering devices located in wet locations shall be weatherproof.
If secondary meters are installed, meter sockets without meters installed shall be blanked off with an approved blanking plate.
551.79 Clearance for Overhead Conductors
Open conductors of not over 600 volts, nominal, shall have a vertical clearance of not less than 5.5 m (18 ft) and a horizontal clearance of not less than 900 mm (3 ft) in all areas subject to recreational vehicle movement. In all other areas, clearances shall conform to 225.18 and 225.19.
Informational Note: For clearances of conductors over 600 volts, nominal, see 225.60 and 225.61.
551.80 Underground Service, Feeder, Branch-Circuit, and Recreational Vehicle Site Feeder-Circuit Conductors
All direct-burial conductors, including the equipment grounding conductor if of aluminum, shall be insulated and identified for the use. All conductors shall be continuous from equipment to equipment. All splices and taps shall be made in approved junction boxes or by use of material listed and identified for the purpose.
(B) Protection Against Physical Damage.
Direct-buried conductors and cables entering or leaving a trench shall be protected by rigid metal conduit, intermediate metal conduit, electrical metallic tubing with supplementary corrosion protection, rigid polyvinyl chloride conduit (PVC), nonmetallic underground conduit with conductors (NUCC), high density polyethylene conduit (HDPE), reinforced thermosetting resin conduit (RTRC), liquidtight flexible nonmetallic conduit, liquidtight flexible metal conduit, or other approved raceways or enclosures. Where subject to physical damage, the conductors or cables shall be protected by rigid metal conduit, intermediate metal conduit, Schedule 80 PVC conduit, or RTRC listed for exposure to physical damage. All such protection shall extend at least 450 mm (18 in.) into the trench from finished grade.
Informational Note: See 300.5 and Article 340 for conductors or Type UF cable used underground or in direct burial in earth.
A receptacle to supply electric power to a recreational vehicle shall be one of the configurations shown in Figure 551.46(C) in the following ratings:
50-ampere — 125/250-volt, 50-ampere, 3-pole, 4-wire grounding type for 120/240-volt systems
30-ampere — 125-volt, 30-ampere, 2-pole, 3-wire grounding type for 120-volt systems
20-ampere — 125-volt, 20-ampere, 2-pole, 3-wire grounding type for 120-volt systems
Informational Note: Complete details of these configurations can be found in ANSI/NEMA WD 6-2002, National Electrical Manufacturers Association’s Standard for Dimensions of Attachment Plugs and Receptacles, Figures 14-50, TT, and 5-20.