18.4 Mobile & Manufactured Homes, RV Parks, and Marinas & Docks (Articles 550, 551 & 555)
Key Takeaways
Mobile home service equipment must be located outside of and not mounted in or on the mobile home, within sight and not more than 30 ft from its exterior wall (550.32(A)).
Mobile home service equipment must be rated at least 100 A at 120/240 V (550.32(C)).
Every RV site with electric supply needs a 20 A, 125 V receptacle; at least 70% of sites need a 30 A, 125 V receptacle; and at least 40% need a 50 A, 125/250 V receptacle (551.71).
The 2026 NEC 555.35(A) requires GFPE with a trip setting of not more than 100 mA on feeders and branch circuits supplying docking facilities and piers.
Marina and floating dock service equipment must be located on land, not on the floating structure, adjacent to the structure it serves (555.4).
Mobile and manufactured homes (Article 550)
A mobile home is a factory-assembled structure on a permanent chassis, transportable in one or more sections, designed as a dwelling without a permanent foundation. A manufactured home is built to the HUD code and may be placed on a permanent foundation.
Service equipment (550.32)
| Rule | Requirement |
|---|---|
| Location (A) | Service equipment must be located adjacent to the mobile home and not mounted in or on it; within sight and not more than 30 ft from the exterior wall it serves. The 2026 NEC points to Article 230 for the general service disconnect rules |
| Manufactured homes (B) | Service equipment may be installed in or on a manufactured home placed on a permanent foundation, if the home's grounding and bonding meet Article 250 and the manufacturer's instructions |
| Rating (C) | At least 100 A at 120/240 V, with provisions for connecting the feeder by a permanent wiring method; power outlets used as service equipment may contain receptacles rated up to 50 A with appropriate overcurrent protection |
| Mounting height | Outdoor mobile home disconnecting means installed so the bottom of the enclosure is at least 2 ft above finished grade or working platform, and the center of the operating handle grip in its highest position is not more than 6 ft 7 in. above grade |
| Replacement home (2026) | Where existing service equipment is reconnected to a replacement mobile or manufactured home, a surge-protective device per 230.67 must be provided |
Feeder to the home
The feeder from the service equipment is a permanent wiring method with four insulated, color-coded conductors: two ungrounded conductors, a neutral, and an equipment grounding conductor. The neutral and EGC are not connected together in the home's panelboard. A mobile home may alternatively use a single listed 50 A, four-conductor power-supply cord, where permitted. An outdoor receptacle and other required outlets in the home follow Article 550 and Article 210.
Mobile home park demand factors
Mobile home park and RV park load calculations were relocated to Article 120 in the 2026 NEC (Parts VIII and IX). For a mobile home park, each lot feeder is calculated at the larger of a minimum of 16,000 VA per lot at 120/240 V or the calculated load of the home, and the park service and feeders apply demand factors that decrease with the number of lots, such as 100% for one lot and 55% for two lots, down to 28% for 61 or more lots.
Recreational vehicle parks (Article 551, Part VI)
| Rule | Requirement |
|---|---|
| Receptacles at each site (551.71) | Every RV site with electrical supply: at least one 20 A, 125 V receptacle; at least 70% of sites: a 30 A, 125 V receptacle (TT-30); at least 40% of sites: a 50 A, 125/250 V receptacle (14-50); tent sites may have only 20 A receptacles |
| GFCI | 125 V, single-phase, 15- and 20-ampere receptacles at RV sites must be GFCI protected |
| Supply equipment location | On the left (road) side of the parked vehicle, in a line 5 ft to 7 ft from the left edge of the stall, from the rear of the stall to 15 ft forward of the rear |
| Disconnecting means | A switch or circuit breaker in the site supply equipment to disconnect the power supply to the RV |
| Grounding (551.76) | All electrical equipment and installed wiring must be connected to an EGC; the neutral is not bonded to the EGC at the site supply equipment |
| Load calculations (2026 Article 120, Part VIII) | Site base loads such as 9,600 VA for a 50 A, 120/240 V site, 3,600 VA for a 20 A and 30 A site, 2,400 VA for a 20 A only site, and 600 VA for a tent site, with demand factors by number of sites |
Marinas, boatyards, and docks (Article 555)
Article 555 covers commercial and noncommercial docking facilities, including one- and two-family dwelling docks, which Minnesota's lakes make very common.
| Rule | Requirement |
|---|---|
| Service equipment location (555.4) | On land, not closer than 5 ft horizontally from and adjacent to the structure served, and not on or in a floating structure |
| Engineered design (555.9, new in 2026) | Documentation of an engineered electrical design must be provided upon request of the AHJ; not required for one- and two-family dwelling docks at 240 V single phase or less |
| Shore power receptacles | Rated at least 30 A, single type, locking and grounding or pin-and-sleeve; mounted at least 12 in. above the deck of a fixed pier or 12 in. above the surface of a floating pier |
| Wiring methods | Chapter 3 methods identified for wet locations; extra-hard-usage portable power cables where flexibility is required |
| Bonding (555.13) | Non-current-carrying metal parts likely to become energized must be connected to the circuit EGC with a bonding conductor not required to be larger than 8 AWG |
| Equipotential planes (555.14) | Where system voltage exceeds 250 V to ground and equipment is within 10 ft of the water, an equipotential plane must be constructed and bonded as specified |
| GFPE (555.35(A), 2026) | Feeders and branch circuits on docking facilities and piers must have GFPE with a trip current not exceeding 100 mA, coordinated and performance tested by qualified persons, with a written record for the AHJ |
| GFCI (555.35) | 125 V, single-phase, 15- and 20-ampere receptacles other than shore power receptacles must have GFCI protection for personnel |
| Servicing and replacement (555.15, 2026) | Equipment may be serviced to the Code edition under which it was installed; replaced equipment must comply with the current Code, and the circuit must be inspected |
| Load calculations | Marina feeders and services may use demand factors based on the number of shore power receptacles |
Electric shock drowning: water around a dock with a ground fault can carry enough current to paralyze a swimmer. The GFPE and bonding rules of Article 555 exist to prevent it.
Worked example: a lake-home dock in Minnesota
A homeowner wants power on a seasonal dock for a boat lift and two receptacles at a 120/240 V single-phase house.
- Engineered design: not required, because the system is 240 V single phase or less at a one-family dwelling.
- Supply: a feeder or branch circuit from the house, with the disconnect on land.
- Protection: GFPE not exceeding 100 mA on the circuits serving the dock, performance tested and recorded, and GFCI protection for the 125 V, 15- and 20-ampere receptacles.
- Bonding: connect metal parts likely to become energized, such as the boat lift frame, to the EGC.
How far from a mobile home may its service equipment be located under 550.32(A)?
Within sight and not more than 30 ft from the home
Inside the home, near the entrance
Mounted on the exterior wall of the home
Anywhere in the park, if the enclosure is lockable
What percentage of RV sites with electrical supply must have a 50 A, 125/250 V receptacle under 551.71?
20%
70%
100%
40%
Under the 2026 NEC 555.35(A), what protection is required for the feeders and branch circuits on docking facilities and piers?
AFCI protection
GFPE with a trip current not exceeding 100 mA
GFPE set at 1200 A
No protection at docks serving one-family dwellings
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