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.
- 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].
- All of the electrical equipment and enclosures must be specifically approved
for the location [682.10].
- 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].
- Submersible or floating equipment must use an extra-hard usage cord
designated in Table 400.4 and listed with a "W" suffix [682.14].
- 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.
- 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.
- 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.
- 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)
- 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
- Install an equipotential plane wherever required [682.33]. Exactly what is
this? See the definition in 682.2. Where it's not required, should you not
install it? Just because it's not required doesn't mean you are prohibited from
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