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LED lighting systems provide many advantages for a variety of applications. Among those is sign illumination systems.
It’s common to encounter secondary circuit voltage exceeding 1,000V in neon systems. But an LED typically runs on 5V. This has implications for installation requirements, which is why Article 600 has special requirements just for LED sign illumination systems [600.33].
Naturally, you’d follow manufacturer’s instructions when installing these. But the NEC explicitly requires you to follow them.
You can use any applicable Chapter 3 wiring method, a freedom you don’t have with neon secondary circuits exceeding 1,000V [600.32(A)(1).
With neon, the minimum conductor size is 18AWG [600.31(B) and 600.32(B)]. There is no such restriction with LED.
Measure the outputs of any desktop computer power supply, and you’ll find 12Vdc and 5Vdc leads. The 12Vdc are typically for fans, while the 5Vdc are typically for such things as, you guessed it, LEDs.
This means the power supply for an LED sign illumination system is a class 2 power supply. The requirements for these are in Article 725. If you install the system’s power supply per the manufacturer’s instructions (as required by the NEC), then you’re almost certain to be in compliance with Article 725. But you still need to review your application against Part III of that Article.
In part 7, we’ll look at more of the LED requirements.