National Electrical Code Articles and Information

National Electrical Code Top Ten Tips: Article 551, Recreational Vehicles and Recreational Vehicle Parks. Part 2.

1. Article 551 amends the Chapter Three wiring methods; it does not replace them. Where Article 551 is silent, Chapter 3 requirements apply [551.47(A)].
    
2. You can't mix metallic and nonmetallic wiring methods. That is, use nonmetallic raceway (or non-metallic sheathed cable) if you use nonmetallic boxes [551.47(C)].
    
3. In these wiring systems, no bend can have a radius of less than five wire (or cable) diameters [551.47(H)].
    
4. Any prewiring must meet the applicable part of 551.47(Q), (R), or (S). This includes air conditioning and generator systems.
    
5. Any luminaire installed over a bathtub or in a shower stall must be GFCI-protected [551.53(B)]. The newer integrated LED fixtures make this rule unnecessary for such fixtures, but the NEC still does not provide an exception for them.
    
6. Do not ground interior electrical equipment. Where 551.55 speaks of "grounding," it means "bonding." If you review these terms in Article 100, you will see the terminology error when you read the requirements. Make sure you bond, not ground, interior equipment.
    
7. Bonding conductors for non-current carrying metal parts must be at least 8AWG [551.56(C)]. While it would be "nice" to use a larger conductor, keep in mind that if a number 8 eliminates differences in potential a larger conductor can't eliminate more differences (there aren't any) or eliminate them faster. If reliability is the concern, use bonding jumpers around raceway connections instead of simply upsizing bonding conductors.
    
8. You will find the requirements for RV Parks in Article 551, Part VI. Calculate loads per 551.73.
    
9. Don't use the grounded conductor (neutral) as an equipment bonding conductor [551.76(D)]. This applies to all circuits, not just RV ones. The reason is the neutral (which is, at these voltage levels, the grounded conductor) carries the unbalanced current back to the source. It does not provide a low impedance path for eliminating differences of potential. Confusion here can result in a lethal touch shock.
    
10. Don't connect the grounded conductor to a grounding electrode on the load side [551.76(E)]. Actually, don't connect anything on the load side to any ground electrode; such a connection serves no electrical purpose.