National Electrical Code Top Ten Tips: Article 530, Motion Picture and Television Studios and Similar Locations

1. Note that the electrical inspector isn't the only Authority Having Jurisdiction (AHJ) for a motion picture studio installation. Others who can enforce the codes are the general contractor, OSHA, insurance providers, other trades, and the property owner. The producers and investors, having significant sums at stake, also need to be assured that their investment won't burn down. [530.1]
   
   
2. The intention is that Article 530 applies to business ventures in film, not to an amateur making a film of the local high school play. For this reason, any activity involving the use or editing of film or tape more than 22mm wide falls under Article 530 [530.1].
    
3. For any stage or set, the permanent wiring must be Type MC cable, type MI cable, or run in approved raceway. Alternatively, it can be Type AC cable if the cable contains an insulated equipment grounding conductor sized per Table 250.122 [530.11].
    
4. For any stage or set, the portable wiring must be listed for hard usage [530.12]. Where practical, use duct tape and guards to secure portable cords it in place and protect them if they run across the floor.
    
5. If you use any DC plugging boxes, the smallest permitted rating is 30A [530.14].
    
6. For the permanently-wired feeders, you can use the demand factors listed in Table 530.19(A) [530.19(A)].
    
7. For the portable feeders, you can use a demand factor of 50% [530.19(B)].
    
8. Bond together all of your metallic cable, raceway, and other non current-carrying metal parts [530.20]. Doing this eliminates dangerous differences of potential. The requirement here says "grounding" but read the Article 100 definitions that involve grounding and bonding. What is meant is to provide a metallic pathway between these parts and to the Equipment Grounding (bonding) Conductor.
    
9. Single-pole portable cable connectors for AC power must be of the interlocking type [530.22].
    
10. It's not recommended, but it is permitted, to supply stage set lighting loads from branch circuits that supply receptacles [530.23]. Now think about this practice. If you have to work on the lights, you won't have power for portable lights and power tools. If you have to work on the power, you still won't have power for portable lights and power tools and on top of that you will be working in the dark. Always put lights and power on different branch circuits. It's not an NEC requirement, but it is an inexpensive way to prevent expensive problems later.