National Electrical Code Top Ten Tips: Article 530, Motion Picture and Television Studios and Similar Locations
- 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, 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]
- 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]. This parameter is bound to change as the equipment continues to evolve and more digital-only recording equipment is used. The sets are the issue, not the camera. The film width was just a convenient demarcation metric when this rule was written. If there is some doubt, contact the AHJ for a ruling. Understand that legal implications do exist.
- 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].
- For any stage or set, the portable wiring (cords and cables) 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.
- If you use any DC plugging boxes, the smallest permitted rating is 30A [530.14]. That doesn't mean to use all 30A boxes because you can get by with doing that per the NEC. Install the boxes that are needed to get the job done safely and efficiently. It may help to consult a set designer or the director for guidance on what the actual needs are likely to be.
- For the permanently-wired feeders, you can use the demand factors listed in Table 530.19(A) [530.19(A)].
- For the portable feeders, you can use a demand factor of 50% [530.19(B)]. That doesn't mean automatically go with 50%. That's the lowest you can go, but your particular application might call for a demand factor of 75%. Know the loads and the intended usage.
- 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.
- Single-pole portable cable connectors for AC power must be of the interlocking type [530.22].
- 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.