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I'm builing a 48v DC LED system to be used inside a fountain in a public space. I'm using a 48DC 30A switching power supply.

What should I do to make it safe in case any conductor gets exposed to the water?

Should I ground the DC- output?

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  • \$\begingroup\$ Welcome to EE.SE. In the USA the NEC code book limits exposed conductors to 36 VAC or 48 VDC, as this is the point where most people feel a mild shock, especially with wet skin. If you could drop that voltage a bit and insulate all conductors you will legally be ok. \$\endgroup\$ – Sparky256 May 25 '18 at 1:06
  • \$\begingroup\$ Per @Sparky256 answer above, Powering half the LED's on 2 separate 24Vdc supply's would put you well within specifications. \$\endgroup\$ – Sara Heart May 25 '18 at 2:00
  • \$\begingroup\$ Connect your switching power supply to the mains through a GFCI outlet in case there's a fault in the power supply. \$\endgroup\$ – AlmostDone May 25 '18 at 2:58
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    \$\begingroup\$ Go to your local library and look at the 2017 NEC handbook, most will have a copy in their reference section. DO NOT act on the comments above. Read Section 680 of the code on Pools, SPAs, and Fountains. You need to have NEC rated transformers for low voltage lighting, and I'd bet you SMPS modules are not likely compliant. \$\endgroup\$ – Jack Creasey May 25 '18 at 3:17
  • \$\begingroup\$ The last NEC book I looked at was the 2011. Any newer version supersedes the older versions, so go by @JackCreasey comment-not mine. \$\endgroup\$ – Sparky256 May 25 '18 at 4:02
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If you choose water-proof stripleds then you will have added about 10kV or more of electrical insulation as most plastic is hydroscopic yet >>8kV/mm insulated. Moisture ingress to LEDs will result in rapid aging. Most suppliers rate the waterproof types to 1m depth.

Even chlorinated water has low conductance so the water will behave as a dielectric about 80x air. If you plan on using high slew rate PWM, keep in mind this rise in load step current and slower turn off time. But the waterproofing ought to protect you here as plastic is only about 4x air.

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