I’m building a weather sensor suite for a small privately-owned airport, and I’m wondering how to safely and compliantly get power into one of the enclosures. My concerns are safety and code-compliance (understanding that “legal” does not always mean “safe”). This is in the United States.
This unit is for the wind sensors, which have to be installed 30 feet above ground, away from buildings. The best site for this is an existing lamp post (ours, not public/utility) that has three-wire single-phase AC. There are no power receptacles; there are simply three wires running up the inside of the post from buried conduit.
The electronics in the enclosure are all 5V and 12V DC. The enclosure is fully gasketed and is UL-listed. I drilled holes in the bottom and installed listed, waterproof glands for cable entry.
What’s the best way to get power into the box? Two options I’ve considered are:
Running the hot and neutral AC lines into the enclosure and installing a power supply in there. Didn’t like this idea because I don’t know how to deal with mains power inside my own enclosure.
Purchasing a listed, IP-rated, constant-voltage LED driver designed for permanent connection to mains, and that outputs 12V. Fasten it outside the enclosure, run the DC leads up through one of the glands, and use a DC stepdown converter to create the 5V circuit.
Neither of these address the safety ground. The enclosure is plastic but the frame is metal (aluminum).