NEC Article 551 is the section of the National Electrical Code (NFPA 70) that governs electrical safety for recreational vehicles and the parks that power them. It covers internal AC and DC wiring, onboard generators, the shore-power cord and inlet, factory testing, and the park-side distribution system from the service entrance down to each site pedestal.1National Fire Protection Association. NFPA 70 – National Electrical Code The current edition is NFPA 70-2026, though the enforceable version in any given place depends on which edition the local jurisdiction has adopted.
What Article 551 Covers
Article 551 applies to self-propelled motor homes, travel trailers, truck campers, camping trailers, fifth-wheel trailers, and van conversions built for temporary living, along with the electrical infrastructure of the parks that serve them.2UpCodes. NFPA 70 – Article 551 Recreational Vehicles and Recreational Vehicle Parks If a unit is designed to be towed or driven and used as temporary housing, this is the governing standard.
Manufactured and mobile homes fall under a different section. Article 550 handles structures intended for permanent or semi-permanent occupancy, which sit on foundations and connect to utility services more like a conventional house.3UpCodes. Article 550 Mobile Homes, Manufactured Homes, and Mobile Home Parks Mixing the two articles up can result in undersized wiring, wrong receptacle configurations, or grounding that doesn’t account for a vehicle in motion.
Inside the RV: AC and DC Wiring
Recreational vehicles run on 120-volt or 120/240-volt systems depending on size and load. The internal distribution panelboard must be accessible and clearly labeled, with circuit breakers protecting each branch circuit from overcurrent. Branch circuits are sized around the expected draw of onboard equipment such as air conditioners, microwaves, and water heaters.
Because the vehicle moves, wiring methods differ from house construction. Outdoor or under-chassis wiring carrying 120 volts or more must be enclosed in conduit or raceway rated for wet environments. Interior wiring typically uses nonmetallic-sheathed cable, secured against chafing where it could rub on the frame as the rig travels.
Most RVs also run a 12-volt DC system that powers interior lights, water pumps, vent fans, and slide-out mechanisms off the house batteries. Article 551 requires physical separation between the 12-volt DC wiring and the 120-volt AC circuits, with a minimum clearance of half an inch except where conductors cross. In an RV, those systems share tight quarters and travel vibration can shift wiring over time, so this clearance gets attention during both factory assembly and aftermarket work.
Generators and Shore-Power Connections
Many larger motor homes and some travel trailers include a built-in generator. Under NEC 551.30, the generator must be securely mounted to the chassis in a way that maintains an effective bond, creating a reliable ground-fault return path when it is running.4UpCodes. Generator Installations Storage batteries and the generator itself must be secured against road vibration, which can loosen connections over time. Generator compartments require ventilation following the manufacturer’s guidelines, and exhaust must route safely away from living spaces and intake vents. Where both a generator and shore power are available, a transfer switch prevents the two sources from feeding the panel at the same time.
The cord that connects an RV to a park pedestal is specified under Section 551.46. It must be a single listed cord set with a factory-molded attachment plug, not a field-assembled extension cord. The cord’s ampere rating must match the vehicle’s main overcurrent protection, typically 30 or 50 amperes on modern rigs.5UpCodes. 551.46 Means for Connecting to Power Supply The inlet and plug must be configured for the correct amperage so that a 30-amp plug physically cannot connect to a 50-amp outlet.
The code also requires a warning label at the vehicle’s electrical entrance. The word “WARNING” must appear in letters at least 6 millimeters tall, with additional text in letters at least 3 millimeters tall, all on a contrasting background. The label states the voltage and amperage rating and warns against exceeding circuit capacity.
Factory Tests Every RV Must Pass
Every recreational vehicle with a 120-volt or 120/240-volt electrical system must pass a sequence of factory tests before it ships. Section 551.60 requires a dielectric strength test, applying 900 volts AC (or 1,280 volts DC) for one minute between the ungrounded conductors and the vehicle ground, with all switches in the on position. The test is performed twice: once after the branch circuits are completed and again after all outer coverings and cabinetry are installed.6National Fire Protection Association. NFPA 70 Article 551 Code Proposal Submittals
Beyond the dielectric test, every unit must also pass four additional checks:7UpCodes. Factory Tests (Electrical)
- A continuity test, confirming all metal parts are properly bonded to the grounding system.
- An operational test, verifying that all electrical equipment is connected and functioning.
- A polarity check, ensuring hot, neutral, and ground conductors are wired to the correct terminals.
- A GFCI test, confirming that ground-fault protection devices trip as designed.
These tests catch wiring errors that are far more dangerous and expensive to find after a sale. A reversed polarity connection, for example, can energize a metal chassis the owner assumes is safely grounded.
Park Pedestals and Site Receptacles
Part VI of Article 551 sets the standards for park electrical distribution. The service entrance must be sized to handle the combined load of every site, but Section 551.73 provides demand factors that reduce the calculated load as the number of sites grows. A park with just a few sites might apply a demand factor of 75 percent, while a park with 25 or more sites can calculate at roughly 42 percent of the total connected load. Feeder circuits serving small groups of sites use higher demand factors than the main service, because a cluster of sites is more likely to hit simultaneous peak demand than the park as a whole.
The code also specifies the minimum mix of outlet types each park must provide, based on site count and whether the park is new construction or an existing facility:8Leviton. Receptacle Requirements at RV Parks
- Every site with electrical supply must have at least one weather-resistant 20-ampere, 125-volt receptacle.
- At least 70 percent of all sites must include a 30-ampere, 125-volt weather-resistant receptacle.
- At least 20 percent of existing sites and 40 percent of all new sites must include a 50-ampere, 125/250-volt weather-resistant receptacle. Every site equipped with a 50-amp outlet must also have a 30-amp outlet.
The split between existing and new parks matters in practice. Older parks grandfathered at the 20 percent threshold for 50-amp service often cannot accommodate today’s larger rigs with dual air conditioners and residential refrigerators, while new parks face the 40 percent threshold. As of January 1, 2026, the weather-resistant requirement extends to 50-amp, 125/250-volt receptacles as well.8Leviton. Receptacle Requirements at RV Parks
Grounding, Bonding, and GFCI
The metal chassis of a recreational vehicle must be bonded to the grounding bus in the distribution panel. That bond creates a low-resistance path so a short circuit trips the breaker instead of energizing the frame or exterior skin. Every non-current-carrying metal part that could become energized, including appliance housings, metal plumbing, and the LP gas system, must connect to the same grounding system.
Ground-fault circuit-interrupter protection is required for 125-volt, single-phase, 15- and 20-ampere receptacles where water and electricity are likely to meet. Inside the RV, that includes receptacles in bathrooms and near kitchen sinks. At the park pedestal, GFCI protection applies to the 15- and 20-amp receptacles in the site supply equipment, but not to the 30-amp and 50-amp outlets that feed the vehicle’s main power cord. Protection beyond that point is handled by the rig’s own panel and internal GFCI devices.
GFCI devices should be tested monthly with the built-in test button. One that fails to trip, or trips but will not reset, needs immediate replacement. Vibration and temperature swings tend to shorten their lifespan compared with a stationary home.
What RV Owners Should Watch For
Article 551 is not only a manufacturer’s problem. Owners who modify their electrical systems, add solar, or install aftermarket inverters need to work within these standards or risk voiding insurance coverage, failing an inspection, or creating a hazard. Common DIY mistakes include tapping into circuits without recalculating load, bridging the required separation between AC and DC wiring, and using residential-grade components that cannot handle road vibration.
A professional electrical inspection before buying a used RV can catch problems a walk-through misses: bonding continuity, polarity, functional GFCI devices, and signs of overheating at the power inlet or distribution panel. An inlet that is discolored, melted, or warm to the touch is an urgent repair, not a cosmetic issue.
State and local jurisdictions adopt the NEC on their own timelines, so the enforceable edition in a given area may lag behind the 2026 release.1National Fire Protection Association. NFPA 70 – National Electrical Code A park built under an older edition is not automatically required to retrofit, but new construction or major renovation typically triggers compliance with whichever edition is locally adopted. When in doubt, the local authority having jurisdiction decides which rules apply.