Ecmweb 6080 Rv Site Receptacle Requirements 2
Ecmweb 6080 Rv Site Receptacle Requirements 2
Ecmweb 6080 Rv Site Receptacle Requirements 2
Ecmweb 6080 Rv Site Receptacle Requirements 2
Ecmweb 6080 Rv Site Receptacle Requirements 2

Recreational Vehicles and RV Parks

Jan. 20, 2014
RVs and the parks that accommodate them have special electrical requirements.

The NEC Article providing requirements for RVs and RV parks is sandwiched between Art. 550 and 552, Mobile Homes/Parks and Park Trailers, respectively. At 12½ pages, Art. 551 is the longest of the three.

RV vs. the others

To apply the correct Article, you need to know which type of occupancy you actually have.

Though it’s mobile, an RV isn’t a mobile home. Oddly enough, a mobile home isn’t really mobile (not in the sense that your mobile phone is). It’s a permanent installation that can be moved (though it isn’t on a permanent foundation). But an RV really is mobile because it has its own motive power or is mounted on (or drawn by) another vehicle [551.2].

RV sites have specific receptacle requirements, which call for a variety of ampere ratings.

Because mobile homes are “permanent but movable,” they and the parks that accommodate them are intended for permanent residency. That isn’t the case with RVs. Because RVs are mobile, they and the parks that accommodate them are intended for short-term residency. That’s a use vacationers and tourists make of them all the time.

An RV drawn by another vehicle is typically a “travel trailer” [551.2]. Don’t confuse this with a park trailer. A park trailer is a unit built on a single chassis mounted on wheels [552.2], and it has a gross trailer area not exceeding 400 sq ft.

You can use an RV year-round, but park trailers are for seasonal use. For example, campers tow their park trailer to a summer vacation spot and set it up for short-term lodging. It’s better than a tent, and costs much less than a hotel.

RVs are often used as homes on wheels; thus, the term “motor home.” Many retired people have sold their primary residence and live in their RV. Traveling around the country to visit grandkids or just see the sights, they are perpetual tourists.

Entertainers increasingly make use of RVs. Rock bands who live on the road while on tour might use an RV park. But actors who want the amenities of an RV while filming on location need a custom RV park, right on location.

Combination systems

The typical motor home runs on the same sort of DC power source that a passenger vehicle does. It’s just beefier.

A combination electrical system is one that can connect to both a DC and an AC source [551.20]. One important requirement is that you connect the metal enclosure of the inverter to the vehicle frame using at least an 8 AWG copper conductor [551.20(C)]. Make sure to properly torque this connection.

Most of the other requirements in this subsection are satisfied by the manufacturer or parts supplier. For example, the plug caps for the DC plug must differ in configuration from the plug caps for the AC plugs.

Adding a generator

Modern internal combustion engines recharge their batteries using an alternator, not a generator. When the NEC speaks of a generator for an RV, it’s talking about an outside source. In fact, you must ensure the generator and the alternator aren’t connected to the vehicle circuits at the same time [551.30].

But if the engine can charge the batteries, why have a generator set for an RV? Because the RV engine operates at a power band that’s optimized for moving the vehicle down the road, not for turning a generator or alternator. When the RV is parked, it’s far more efficient to use an engine gen-set made specifically for RV charging.

If you want the flexibility of using multiple outside sources (e.g., power cord plus generator), you must ensure that only one source of supply can be connected to the RV’s circuits at any given time [551.33].

120/240V systems

Part IV takes up about two-thirds of Art. 551. Most of it pertains to manufacturers. But here are some highlights, in case you do something like add a receptacle.

• Receptacles must be GFCI-protected if used near a sink or bathroom [551.41(C)].

• Receptacles must be of the grounding type [551.52]

• Don’t install receptacles face up in any countertop [551.41(D)].

• If you use metal faceplates, they must be “grounded” [551.41(M)]. That means connecting the green equipment bonding lug to the metal faceplate. Typically, the assembly will accomplish this merely by screwing the plate into the “grounded” (“ground” wire connected) yoke. However, inspect it to make sure this is accomplished.

• If you add a circuit, note that going over five circuits means you must install a listed energy management system [551.42(D)].

You should also be familiar with the RV receptacle configuration requirements, which appear in Figure 551.46(C).

What about the wiring methods? You have several options available to you, including armored cable and surface raceways [551.47(A)]. For aesthetic reasons, try to stick with whatever is already being used.

However, if you’re reconditioning an RV, consider upgrading the aesthetics and functionality by changing the exposed raceway system. Just make sure you use one of the conduit or tubing methods if the wiring is exposed to moisture or physical damage [551.41(N)].

• If you use any of the permitted cable types, limit the bend radius to no less than five times the diameter of the cable [551.47(H)].

• If you use nonmetallic cable, add protection (e.g., guard strips) for it where it’s exposed to possible damage [551.41(K)].

The remainder of this Article pertains to RV parks.

Receptacles

An “RV site” is a plot of ground set up to accommodate one RV [551.2]. Each site must have at least one 20A, 125V receptacle [551.71].

In any given RV park, at least:

• 20% of sites must also have a 50A, 125/250V receptacle that conforms to 551.46(C).

• 70% of sites must also have a 30A, 125V receptacle that conforms to 551.46(C).

And the remainder of the sites must have one or more of the receptacle configurations conforming to 551.81. Also:

• 125V, 15A and 20A receptacles must be GFCI-protected [551.71].

• 125V, 20A and 30A receptacles can be supplied by any grounded system that supplies 120V single-phase power [551.72].

• Each 50A receptacle must be on its own branch circuit (the rating of which must match the rating of the receptacle) [551.72].

Calculated load

Calculate services and feeders on the basis of:

• At least 9,600VA for each site with a 50A supply.

• 3,600VA for each site with both 20A and 30A supplies.

• 2,400VA for each site with only a 20A supply.

• 600VA for dedicated tent sites with a 20A supply.

The demand factors in Table 551.73(A) are the minimum allowable ones you can use. For example, if the park has six sites, you can use a demand factor of 60% or higher.

If the site has more than one receptacle, the calculated load applies only to the highest rated receptacle (there’s one power cord going to the RV; thus, only one receptacle will be used).

These load calculations are for the RV sites, not the RV park. You must do separate load calculations for general lighting, swimming pools, service buildings, and other amenities [551.73(D)].

Grounding

Article 551 provides grounding requirements in subsections 75 and 76. Two of these requirements are often ignored for stick-built residential installations, possibly because they appear in 250.148(B) and 250.142(B) rather than in the Article 210 requirements for branch circuits:

1. Make equipment grounding connections such that the removal of a receptacle (or other device) won’t interrupt the grounding continuity [551.76(A)]. In other words, pigtail the green wires.

2. Don’t use the grounded conductor as an equipment ground [551.76(A)]. In residential panels, these are often interchanged.

Another key requirement here is that you (generally) don’t ground (connect to earth) on the load side [551.76(D)]. Unless you have a separately derived system, such a connection serves no electrical purpose but does have a tendency to create ground loops.

Supply equipment

Where you locate the site supply is critical, and it depends on whether the site is back-in or pull-through [551.77(A)]. There are also accessibility requirements, plus the minimum height off the ground is 2 ft. The minimum working space is whatever it takes for ready and safe operation. The bare minimums are listed in 110.26.

Overhead conductors must comply with the clearance requirements of 225.18 and 225.19 unless they are in areas subject to RV movement. Then, they must have a vertical clearance of at least 18 ft and a horizontal clearance of at least 3 ft.

Keeping it on the road

Article 551 is long and contains many dense passages, so it can be difficult to wade through. However, you can ignore two-thirds of it unless you’re modifying an RV. Except for a few things, that leaves the requirements that pertain to an RV park. Think of the RV park as a collection of individual RV sites. The requirements are the same for each site, except 20% of sites must have a 50A receptacle, and 70% must have a 30A receptacle.                                               

Lamendola is an electrical consultant located in Merriam, Kan. He can be reached at [email protected].

About the Author

Mark Lamendola

Mark is an expert in maintenance management, having racked up an impressive track record during his time working in the field. He also has extensive knowledge of, and practical expertise with, the National Electrical Code (NEC). Through his consulting business, he provides articles and training materials on electrical topics, specializing in making difficult subjects easy to understand and focusing on the practical aspects of electrical work.

Prior to starting his own business, Mark served as the Technical Editor on EC&M for six years, worked three years in nuclear maintenance, six years as a contract project engineer/project manager, three years as a systems engineer, and three years in plant maintenance management.

Mark earned an AAS degree from Rock Valley College, a BSEET from Columbia Pacific University, and an MBA from Lake Erie College. He’s also completed several related certifications over the years and even was formerly licensed as a Master Electrician. He is a Senior Member of the IEEE and past Chairman of the Kansas City Chapters of both the IEEE and the IEEE Computer Society. Mark also served as the program director for, a board member of, and webmaster of, the Midwest Chapter of the 7x24 Exchange. He has also held memberships with the following organizations: NETA, NFPA, International Association of Webmasters, and Institute of Certified Professional Managers.

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