Based on the 2020 NEC

by Mark Lamendola

National Electrical Code Tips: Article 682 -- Bodies of Water

Humans have enjoyed and used natural and manmade bodies of water for thousands of years, but they haven't always installed pumps, aerators, or decorative lighting in them. Adding electrically-powered  features makes these bodies of water potentially lethal, and the requirements of Article 682 protect against such an outcome.

Article 682 covers bodies of water that have been constructed or modified to fit some decorative or commercial purpose. Such purposes include fish farm ponds, water settling ponds (which have aerators, fire pump supply ponds (which also have aerators), geese ponds (Hey, aerators again! and sometimes even lights!), and just about any sort of pond you can imagine where someone doesn't want the water to stink or breed mosquitoes. And, of course, ponds installed to make a facility, park, or other venue look pretty by dint of decorative lighting.

Data centers often have ponds serving as protective moats (try driving a bomb truck through 6 feet of water, and you'll see why these make sense). Of course, no credit card company or other data center operator wants expects employees to walk through a wall of stench and mosquitoes so these ponds are also aerated.

The main job Article 682 tries to do is keep electricity and water separated, so that when people are in the water or in contact with related equipment, they are also separated from electricity. And not just people are protected. A decorative pond full of dead birds or dead fish isn't exactly appealing.

  1. If you install any electrical wiring or equipment in, or adjacent to, bodies of water not covered by other Articles in the NEC, the installation must conform to Article 682 [682.1].
  2. All of the electrical equipment and enclosures must be specifically approved for the location [682.10].
  3. Some electrical connections are intended to be submerged (and thus meet certain requirements). All other electrical connections must be located at least 300mm (a foot) above the datum plane [682.12].
  4. Submersible or floating equipment must use an extra-hard usage cord designated in Table 400.4 and listed with a "W" suffix [682.14].
  5. The disconnect for submersible or floating equipment must be specifically marked to designate which receptacle or other outlet it controls. That is, you can't just write "receptacle" on the breaker panel directory. You have to mark the particular breaker on the breaker to show exactly what it's controlling [682.14(A)]. Contact your electrical distributor for a suitable marking means. Masking tape and ink pen do not suffice.
  6. The disconnect for submersible or floating equipment can't be more than 30 inches from the equipment it controls [682.14(B)]. Bummer. That means you are unlikely to be able to get away with using a breaker in your main panel as the disconnect. However, this problem is easily solved by using a suitable switch in a suitable enclosure.
  7. If you install a receptacle in the datum plane area, GFCI-protect it [682.15]. The NEC requires this for all 15A and 20A receptacles, 125V through 250V. Make sure the GFCI protective device is at least a foot above the datum plane (also required), so it's not going to fail due to being submerged. Take care you don't pigtail any neutrals, or the GFCI will not work. Also note that in addition to the GFCI requirements of Article 682, you must apply the requirements of 210.8 [682.15].
  8. Don't try to use earth as your ground fault path for a feeder supplying a remote panelboard (or other distribution equipment). Instead, run an insulated grounding conductor from a grounding terminal in the service to a grounding terminal and busbar in the remote panelboard (or other distribution equipment) [682.31(B)].
  9. Bond all non-current-carrying metal parts [682.32]. This means you connect them all with metallic jumpers. It does not mean you drive ground rods and expect, somehow, that high-resistance earth will be as good a path as copper wire.
  10. Install an equipotential plane wherever required [682.33]. Exactly what is this? See the definition in Article 100. Where it's not required, should you not install it? Just because it's not required doesn't mean you are prohibited from installing it.

    In situations where you're relying on GFCI protection (last sentence of 682.33(B)), it's a good engineering decision to install an equipotential plane there as well. The reason is that GFCIs can, and often do, fail. They will still allow current to flow, but they won't trip when needed. That's not because of any manufacturing defect. The cause of this is nearly always a power surge, something typically caused by lightning. The risk is higher when located near a body of water, so you see the problem here.

    In the other situation described by 682.33(B), it's a matter of cost. The small additional protection afforded by an equipotential plane in these applications may not be worth the money. Simply bonding all non-current-carrying metallic objects together achieves pretty much the same effect, and you need to to that anyhow.