National Electrical Code Articles and Information

National Electrical Code Top Ten Tips: Article 550, Mobile Homes, Manufactured Homes, and Mobile Home Parks

1. In its vernacular, Article 550 includes "manufactured homes" when it speaks of "mobile homes;" it does not separate the two ideas the way the manufactured home industry does except in the definitions the NEC provides [100]. In reality, there is not a whole lot of difference.
    
2. A mobile home must comply with Article 550, even if it's not installed in a trailer park. A mobile home not intended as a dwelling unit (e.g., one used as a construction office) doesn't need to comply with the requirements in Article 550 regarding the number or capacity of circuits. [550.4].
    
3. A common area of confusion is whether the supply cord permanently attaches to the mobile home box. It does not. It permanently attaches to the distribution panel board. Note that the supply cord [550.10(B)] is not the same thing as a supply feeder [550.10(A)].
   
4. If a mobile home has a power-supply cord, that cord must be permanently attached to the mobile home [550.10(B)].
    
5. The attachment plug cap must meet specific criteria. You can't use just any large amperage connector [550.10(C)]. You have to use 3-pole, 4-wire, grounding type that is rated 50A, 125/250V. And its configuration must match 550.10(C).
    
6. The supply cord must be at least 20 feet long (down from 21 feet in earlier revisions, such as the 2011), and no longer than 36.5 ft [550.10(D)].
    
7. Each mobile home must have its own disconnecting means [550.11(A)]. And it must be installed in a readily accessible location near the point of entrance of the supply cord or conductors.
    
8. The receptacle requirements are very similar to those for non-mobile homes, and you'll find these in 550.13.
    
9. Where Article 550 discusses "grounding" in 550.16, it is referring to "bonding" in almost all instances. Before applying 550.16, carefully read the Article 100 definitions of grounding and bonding. Don't make the mistake of driving ground rods in place of required bonding connections.
    
10. Beginning with 550.18 and continuing on through the end of Article 550, you find the requirements for calculating the loads, branch circuits, feeders, and service. These amend the requirements for Articles 210, 215, 220, and 230.