National Electrical Code Articles and Information

National Electrical Code Top Ten Tips: Article 522 -- Control Systems for Permanent Amusement Attractions

1. Article 522 applies to control circuit power sources and conductors for permanent amusement attractions.
    
2. A control circuit carries the electrical signals for controlling the equipment, but does not carry the power. Example: The 120V motor speed control and start/stop circuits belong to the controls, the 480V power to the motor itself does not.
    
3. What does the NEC mean by "permanent?" For Article 522, it means that transporting or relocating the equipment is impractical. That does not mean it's impossible. Basically, if you don't typically remove the equipment at the end of the season (or during), it's permanently installed.
    
4. Only "qualified personnel" can service this equipment [522.7]. An untrained operator with a pair of pliers isn't a qualified person. A technician with specific, documented training on this specific equipment is.
    
5. The two types of control circuits are power-limited (under 30V and under 1,000A) and non power-limited. The latter cannot exceed 300V [522.10].
    
6. The overcurrent protection devices for power-limited control circuits can't be rated for more than 167% of the following: VA rating divided by the rated voltage [522.10].
    
7. You can't use aluminum conductors in the control circuits [522.20]. It's actually a good idea not to use aluminum conductors at all for amusement attractions, because you have more voltage drop to accomodate and there are other drawbacks to aluminum. Furthermore aluminum conductors may cost more to install, due to larger raceways and larger means of supporting them even if you *might* save money on the actual conductors.
    
8. If using conductors 16AWG or smaller, ensure they comply with Table 522.22.
    
9. Though it's a poor engineering decision unless they are the same voltage (and they usually are not), you can run control and power wiring in the same raceway. But to do so you must meet the criteria of 522.24(B). Note that running them in a cable, enclosure, or raceway does nothing to stop voltage induction, because you cannot insulate against magnetism. The extra space gained via those methods will help, since the magnetic field weakens as the distance from it increases. The situation is much worse when signal wiring is run with power wiring, and that issue is not addressed in Article 522. As a general practice, you want to avoid running different voltages of wiring close to each other in parallel runs. You could, for example, run signal wiring up from the bottom and power wiring down from the top.
    
10. Where wet contact is likely to occur, ungrounded 2-wire control circuits are limited to 30VDC (or 12.4VDC peak for DC that's continually interrupted at a rate of 10 to 200 Hz) [522.28].

When in doubt as to how rigorous to be, go with the higher degree of rigor. People's lives depend on that, as does the reputation of the amusement park or similar for which you are doing the work.