The development of effective standards and
guidelines for the design and construction of safe electrical
facilities in water-related recreation, landscaping and
commercial areas is an evolving discipline that is gaining in
importance as these types of facilities become more popular.
While the general class of facilities addressed here has
existed for many years, there has been no specific guidance
and regulation until development of NEC-2005. This
discussion addresses the new requirements for such facilities.
While the emphasis is on inspection and
construction-related issues, it also includes a few
theoretical and design-related topics to provide some
background from a technical perspective.
As with swimming pools and spas, which were
only nonspecifically regulated prior to the introduction of
Article 680 in NEC-1962, designers, installers and
authorities having jurisdiction (AHJs) have been left in the
dark as to the specific means of addressing shock-related
electrical issues associated with aquatic facilities not
covered specifically in the Code. Involved personnel
were literally "up the creek" (pun intended) if they
were developing a permanent facility on or near the water that
did not involve a floating building (Article 553), a marina or
boatyard (Article 555), or one of the several variants on pool
and spa technology addressed in Article 680. In the past,
requirements for facilities not covered by these three
articles were imbedded as general principles throughout the
first four chapters of the NEC, but they were never
specifically called out. Until the introduction of Article 682
in the 2005 edition, the Code did not directly address
pertinent design and installation issues unique to such other
water-related installations.
Efforts to address aquatic facilities not
included in Articles 553, 552 and 680 date back at least to
1993, as cited in the substantiating information for the
proposal by the NEC CMP-17 Task Group on Other Bodies of Water
that spawned the new Article 682. The 1993 proposal
specifically addressed "storm retention basins, sewage
treatment ponds, and similar bodies of water not covered under
the scope of Article 680," and inclusion of such
facilities within Article 680 was rejected by the CMP as
"impractical." The appointment of the task group
provided a means whereby the specific issues associated with
these other facilities could begin to be addressed in their
own context, and not piggybacked on some other, only partially
relevant, portion(s) of the Code.
And, as with the three preexisting articles
cited above, it should be expected that the breadth, scope and
level of detail in 682 will expand over time as technology
changes and relevant topics are worked out. One only has to
compare the original version of 680 (1962) with the current
version to see that they are very different, even though the
general thrust is the same. The 2005 inaugural version of
Article 682 is a good start, but nonetheless it is only a
start.
Purpose and Scope
of Article 682
With regard to the scope of Article 682, as delineated in
682.1, the 2005 NEC Handbook states in part:
"Electrical equipment such as pumps, luminaires and their
associated supply wiring are frequently installed in lakes,
ponds, aeration and treatment basins, and similar bodies of
water, and the new requirements are designed to minimize the
shock hazards inherent in those wet and damp locations."
In fact, the article goes much further, incorporating all
wiring and equipment located adjacent to the water and serving
the equipment on, in, adjacent to, or under the water.
It is important to understand that 682.1
references "natural or artificially made bodies of water
… such as but not limited to [author’s emphasis]
aeration ponds, fish farm ponds, storm retention basins,
treatment ponds, irrigation (channel) facilities." The
same wording appears in 682.2. While the article’s scope as
to naturally occurring bodies of water is obvious from the
definition, there may be some room for confusion as to which
artificially made water bodies are included. A superficial
reading of these two sections potentially can result in a
conclusion that the article deals with a specific class of
relatively small special-purpose facilities like those on the
list, but such a conclusion would be in error. In fact, the
article’s wording is general enough to include all natural and artificially created bodies of water, including
creeks, rivers, lakes, ponds, reservoirs, flood control
impoundments and channels, drainage ditches, decorative
man-made ponds and livestock tanks (which are simply small
reservoirs), in addition to facilities on or similar to those
on the list. The wording is clarified somewhat in the 2005
NEC Handbook, which states "the term artificially
made bodies of water includes all bodies of water that are
not naturally created … the uses of artificially made bodies
of water include decorative, agricultural, municipal
infrastructure, and industrial." The Handbook’s explanatory text then cites an example and photograph of a
decorative pond with a fountain. It is reasonable to expect
that subsequent editions of the Code likely will
clarify the actual wording to eliminate any potential
confusion.
Electrical Datum
Plane — Defining the Limits
The limits of the physical area addressed by Article 682 are
defined by the electrical datum plane, a term
originally used in Section 555.2. Understanding this
definition and how to apply it is essential to understanding
the requirements of Article 682.
Paraphrasing the 2005 NEC Handbook,
the electrical datum plane provides a "horizontal
benchmark" to which the location of electrical equipment
on or near the water is referenced. All locations addressed in
the article—inside, outside, over and under—are with
respect to the surface and boundary of the electrical datum
plane. Note that the definition in 682.2 is not identical to
the one in 555.2, and therefore they cannot be used
interchangeably. Although both Articles 555 and 682 define
physical areas where the water is subject to natural
variations due to tidal movement or climatic changes and
man-made intervention associated with dam and gate operation,
the more extensive scope of 682 by necessity requires an
expanded definition. Consequently the electrical datum plane
for facilities addressed in 682 is defined by the following
four definitions (paraphrasing the article’s language in
682.2—all italics author’s emphasis):
1. A horizontal plane 2 feet (600 mm) above
the highest normal high tide (tidal areas–figure
1), or
2. A horizontal plane 2 feet (600 mm) above
the highest normal water level (areas not subject to
tides–figure 2),
or
3. A horizontal plane 2 feet (600 mm) above
the "prevailing high water mark or an equivalent
benchmark based on seasonal or storm-driven flooding,"
obtained from the AHJ (flood-prone areas–figure
3), or
4. A horizontal plane 30 inches (750 mm)
above the water level and a minimum of 12 inches (300
mm) above the deck elevation [floating structures that can
rise and fall with the water level and that can rise
and fall to the elevations defined in (1) and (2) above]
(floating structures not subject to lateral movement–figure
4).
The shoreline is defined as the
horizontal boundary of the datum plane where the water meets
the land at datum plane elevation (items 1, 2, and 3 above).
Several specific issues should be
recognized when applying the above four definitions to datum
plane determination. These issues can pose the potential in
certain cases for confusing and/or inconsistent
interpretations of the Code language. Most of these
issues are associated with definition (3) above. They are
presented here not as criticism, but to provide some technical
insight into concerns that will be faced by many AHJs,
designers and installers in implementing the requirements of
682. Common sense, safety, and good planning should be the
norm when faced with such interpretative concerns.
First, according to Code language
none of these four definitions apply to any extreme condition
associated with disasters of any type. This restriction
somewhat contradicts item 3, at least in semantic terms, as
flooding is by definition an extreme condition that can be and
is generally associated with disasters (more on this issue
below). This issue can be resolved by the AHJ.
Second, there are clearly areas where very
extreme (not "normal" extreme) conditions must define the electrical datum plane. One of the bonuses
associated with Article 682 is that, while it was conceived to
enhance electrical safety, it also results in regulation of
installations within flood plains to provide more reliable
operation. For example, in some areas of the United States
that construct flash-flood-prone low water crossings on
roadways, electrically powered flood detection systems in the
stream bed are used to provide remote warning and monitoring
information, and to operate gates, bells and lights to create
warnings and barricades to motorists in the event of high
water over the road (photo
1). This author is aware of hard-wired flood warning
systems at various locations that were inspected and passed by
AHJs, which incorporated electrical equipment and wiring in
vulnerable locations inside the flood plain limits, and that
failed due to flood and water damage to the electrical plant
at precisely the times they were required to operate properly.
The new installation requirements in 682 should go far in
preventing malfunction of new installations of this and
similar purpose by providing tighter controls on types and
location of equipment. In these types of special cases, the
AHJ will need to define the datum plane in conformance with
the performance requirements of the system being installed,
and the project-specific definition so developed may not be
consistent with any other prevailing local definition that
they may have created for general use.
Third, development is allowed in various
flood plains, with specific weather events (e.g., 10-year,
50-year or possibly 100-year flood) defining these limits;
these events may not reflect maximum or anticipated
"normal" or "prevailing" worst-case
conditions. Similarly, the highest "normal" water
level in some reservoirs may or may not reflect building
restrictions that control electrical installations in areas
not conforming to the definitions. For example, some flood
control reservoirs allow residential and commercial
development in some or all of their upper flood pool, which is
an area within the contours of the reservoir that is designed
to be used routinely to accommodate normal seasonal and
weather-event-related floodwaters. AHJs regulating electrical
installations in either of these two flood-prone areas, that
have not done so already, now must develop and make available
sets of benchmarks and/or guidelines defining the datum plane
based on their development rules. Designers and installers
must recognize that, in these areas, an installation can be in
conformance with the NEC (as interpreted by the AHJ)
but still subject to routine flooding, and must coordinate
installation location limits and equipment types with the AHJ
based on the AHJ’s definition of the datum plane.
Fourth, the Code language in
definition (4) above specifically excludes floating structures
capable of moving laterally. Some of these structures may be
anchored and capable of a range of lateral movement, and some
can move laterally to follow an expanding or contracting
reservoir area. In some cases the AHJ will need to develop
policies for applying the definition in (4) to these
structures.
None of these datum plane issues are
insurmountable, but in some cases they may result in the
breaking of new ground for the AHJ. Policies developed in
association with installations covered by Article 555 may be
applicable directly in some cases and likely can be applied
with modification in others.
Installation
Requirements
With only a few exceptions, installation requirements are
straightforward.
Section 682.3 requires compliance with all
other applicable areas of the Code, and mandates that
installations in areas with boat traffic meet the wiring
method requirements of Section 555.13(B), as well as those in
Article 682. Section 682.13 allows wiring methods in Chapter 3
and Articles 553, 555 and 590 where identified for wet
locations. Section 682.12 states that all connections
"not intended for operation submerged shall be located at
least 300 mm (12 in.) above the deck of a floating or fixed
structure, but not below the electrical datum plane" (see photo 2).
Section 682.10 requires that electrical
equipment and transformers, and their enclosures, be
"specifically approved for their intended location."
It goes further and requires that "no portion of an
enclosure for electrical equipment not identified for
operation while submerged shall be located below the
electrical datum plane." This latter requirement directly
relates to the site-specific definition of the datum plane,
which has been discussed at length above. Electrical equipment
must be specified and installed to withstand
"normally" occurring high water events as defined by
the Code language and the AHJ. General good engineering
practice should provide an additional margin of safety in the
design. As discussed above, some project-specific requirements
will necessitate additional coordination between design
professionals, the contractor and the AHJ to define proper
datum plane elevations, some of which may encompass more area
than the datum plane elevation in general local use.
Additionally, inspectors who do not normally deal with
underwater equipment and methods will now be called upon to
become familiar with them. The use of improper electrical
equipment and wiring methods in aquatic environments is a
significant issue. IAEI News has published several
articles dealing with this specific problem as it applies to
pools and spas over the past ten years. The inclusion of
additional aquatic venues by the adoption of Article 682 will
allow needed additional control over misuse of these products.
Section 682.15 requires GFCI protection on
all 15- and 20-ampere single-phase, 125–250 volt
receptacles, if in-stalled outdoors or on floating buildings
or structures within the datum plane that are "used for
storage, maintenance, or repair where portable hand tools,
electrical diagnostic equipment or portable lighting are to be
used." The GFCI cannot be located less than 12 in. (300
mm) above the datum plane. This article clearly targets
protection of workers. It does not specifically address
permanent equipment that may be associated with swimming and
wading areas in creeks, reservoirs, lakes and ponds, all of
which are covered under 682 for pools and spas. These
swimming/wading areas may be located proximate to submersible
pumps that can pose an electrocution hazard, but that are not
generally subject to access by personnel while energized.
Additionally, it does not specifically address underwater
lights and submersible pumps associated with fountains in
natural lakes, rivers and ponds (photo
3).
However, Section 682.33(B) in Part III
Grounding and Bonding, adds a general provision that
"all circuits rated not more than 60 amperes at 120
through 250 volts, single phase, shall have GFCI
protection." This provision is unexpectedly located in a
section addressing areas not requiring equipotential planes,
and it’s location and wording will be a likely source of
confusion until all the details in the article are fleshed
out. A look at the history will assist in understanding the
scope of this language, regardless of its location. A
companion proposal regarding equipotential planes was also
adopted for inclusion in Article 682 by the NEC CMP-17 Task
Group on Other Bodies of Water, and this proposal included,
under the heading "Areas Not Requiring Equipotential
Planes," the statement that "all circuits providing
electric power to the controlled equipment [supplied by the
service equipment or disconnecting means] that is accessible
to personnel shall have GFCI protection." Note the
original emphasis is on controlled circuits that are
accessible to personnel; swimming and wading hazards
associated with the general public are not directly addressed.
This situation raises several challenges
for the AHJ, designer and installer. First, the Code language can be interpreted to imply that all circuits are to
be GFCI-protected, while the proposal language adopted 10-0 by
the CMP clearly deals with a subset of all equipment. Second,
the direction of these provisions is clearly toward protection
of authorized personnel accessing the equipment, while the
scope of the article is far broader, involving locations
accessible to the general public, some of whom may be in the
water.
Until such time as these matters are
specifically reconciled in 682, designers and installers would
be well-advised to err on the side of safety by following the
most conservative interpretation of the Code language
and protecting all circuits literally meeting the criteria in
both 682.15 and 682.33(B). Further, to address the public
access issue (in locations where the public has access),
designers and installers can find some technical guidance in
Section 680.51, which is directed at fountains not in
natural lakes, rivers and ponds, but which also contains
relevant approaches to providing a design and installation
with integral protection. Section 680.51 sets limits on
voltages, provides for overtemperature protection, spells out
servicing and stability requirements, establishes proper
wiring methods, and requires GFCI protection on all underwater
lights, submersible pumps and other submersible equipment
operating at over 15 volts to ground. It also specifies that
transformers servicing low voltage equipment comply with
680.23(A)(2).
Section 682.11 addresses requirements for
locating service equipment for floating structures and
submersible electrical equipment. Article 682.14 addresses
disconnecting means for the same equipment. They will be
discussed together here. Both service equipment and
disconnecting means must be located no closer than 5 ft. (1.5
m) horizontally from the shoreline (as defined by the datum
plane) and live parts must be at least 12 in. (300 mm) above
the datum plane. Also, the disconnecting means must meet the
following additional three requirements; it must be:
1. Readily accessible on land (not over
or on the water);
2. Located within sight of the edge of
the shoreline (as defined by the datum plane);
3. In the supply circuit ahead (on the
line side) of the structure or equipment connection, and
cannot be more than 30 in. (750 mm) from the structure or
the equipment connection.
Note that requirement (3) above does not mean that the structure itself must be 30 inches or less from
the disconnecting means. The Code wording here clearly
refers to the connection of the wiring that goes to the
structure.
Disconnecting means can be either or both a
circuit breaker or a switch, and must be clearly marked as to
what it controls. From an operations and maintenance
standpoint, the marking means should be capable of
withstanding the wet environment and should be resistant to
vandalism; laminated labels attached with vandal-proof screws
or rivets are a common solution.
Further, the service must disconnect when
the water reaches the level of the datum plane. This is a
safety measure to reduce the risk of water impingement on
electrical parts during flooding outside the
"normal" levels defining the datum plane, and it
must be reliable under trying conditions. In many cases,
meeting this requirement may be one of the most difficult and
potentially costly aspects of designing and operating an
installation. From a design standpoint, the automatic
disconnecting requirement will likely necessitate some sort of
arrangement involving a float switch or other high water
detector driving a shunt trip on the main service
disconnecting means. While in theory such a system is simple
and well-known, this arrangement in a waterway environment
subject to silting, flooding, drifting debris impingement,
etc., poses a number of design and operational challenges
associated with proper location of the detector and keeping
the detector clear of debris and mud to ensure proper
operation. Preventing detector clogging and jamming is an
issue that has been existent in high water and flood detection
systems for a number of years. Choice of a detector location
that is sheltered from flood-driven debris, and use of a
reasonably silt-resistant detector will help reduce problems,
but routine maintenance and inspection are required. Local
flood control agencies can usually provide area-specific data
on viable local design and maintenance/inspection strategies
and equipment selection for reliability.
Grounding/Bonding
and Establishment of Equipotential Surfaces
When dealing with grounding and bonding in aquatic
environments, the designer, installer and inspector need to
remember that a body of water can (and does) have
resistivities ranging from about 300 ohmcm (sea water) to
about 1800 ohmcm (fresh water). On the other hand, the land
surrounding the water and containing the system grounding
electrodes to earth is far less conductive, with resistivities
that can be many times higher than water, ranging from lows of
1000–5000 ohmcm for wet, high-plasticity inorganic clays to
100,000–250,000 ohmcm for poorly graded gravels and
gravel-sand mixtures. The differences in conductivity
associated with grounding pathways in the earth create
challenges in grounding and bonding any aquatic facility.
These challenges are exacerbated when dealing with open bodies
of water where there is no possibility of employing an
equipotential bonding grid, as is used in concrete/gunite
pools and spas. Installations covered under Article 682
therefore may not provide ground and stray current performance
on a par with a properly grounded, properly bonded concrete/gunite
pool. However, they can still be effectively grounded and
bonded to reduce many significant personnel risks, provided
that solidly connected, low impedance metallic grounding paths
back to the utility are employed and maintained.
Bonding and grounding requirements in 682
are straightforward. Section 682.20 requires grounding in
conformance with Articles 250, 553, 555, and Sections 682.30
through 682.33. Most of the requirements in Articles 553, 555
and 682 track each other, and therefore involve no difficult
cross-references or unique applications; 682.31 requires:
A. Grounding conductor sizing in
conformance with 250.122 but no smaller than 12 AWG;
B. Insulated feeder grounds to remote
panelboards, originating at the ground bus in the service
panel and terminating at a grounding terminal and busbar in
the remote panel. Note the typographical error in this
subsection, where the equipment grounding conductor
is referred to as the "equipment grounded conductor";
C. Insulated branch circuit grounds
terminating at the grounding terminal in the originating
panel (either the service panel or the remote panel);
D. Equipment grounding conductors and
grounding plugs in all plug-and-cord-connected appliances
that are required to be grounded.
Note that the article requires that
separate, insulated, green equipment grounds 12 AWG or larger
be pulled for all branch circuits and feeders; the use of bare
wires or metallic conduit as an equipment ground is not
allowed.
As regards bonding, 682.32 requires that
"all metal parts in contact with the water, all metal
piping, tanks, and all non-current-carrying metal parts that
may become energized shall be bonded to the grounding bus in
the panelboard." Note that these bonds do not constitute an equipotential bonding grid as defined in Article
680. While these bonds have the general effect of maintaining
roughly equal potentials at the affected locations, they serve
primarily as equipment grounds.
Equipotential surfaces are covered in
Section 682.33, and are required in certain locations to
reduce hazards associated with step and touch potentials
caused by high fault currents. The substantiation comments for
682.33 state that "the addition of equipotential plane
requirements is based on IEEE standards 80 and 142 … to
mitigate step and touch voltages for persons coming in contact
with electrical equipment likely to become energized. A
typical 120/240-V, 200-A service with 3,200-A line-ground
fault current and 100 ohm-meters moist soil conditions can
have step and touch voltages exceeding tolerable levels as per
IEEE 80. The likeliness of energization results from the
proximity of controlling equipment located near a water body’s
shoreline." IEEE 142 is the Green Book standard
for grounding (reference 7), and IEEE 80 is the Guide for
Safety in AC Substation Grounding.
Equipotential planes, defined in 682.2, are
constructed of solid metal, wire mesh or "other
conductive elements" (generally rebar or solid copper
conductors) located on (e.g., metallic safety tread), within,
or within 3 in. (75 mm) beneath the walk surface (to
accommodate pavers). They are designed to prevent differences
in voltage between the earth (walkway surface) and metallic
objects within reach that may become energized, and thus they
are required to be "bonded to all metal structures and
fixed nonelectrical equipment that might become
energized." Section 682.33(A) requires the equipotential
plane to "encompass the area around the equipment"
and extend out no less than "36 in. (900 mm) in all
directions from which a person would be able to stand and come
in contact with the equipment" (figure 8). Section
682.33(C) requires that the equipotential plane be bonded to
the electrical grounding system. Bonding is to be accomplished
using a minimum 8 AWG solid copper conductor, with connections
made using exothermic welding or listed and labeled (as
suitable for the purpose) pressure connectors or clamps made
of stainless steel, brass, copper or copper alloy.
Equipotential planes are required by
682.33(A) to be "installed adjacent to all outdoor
service equipment or disconnecting means that control
equipment in or on the water, that have a metallic enclosure
and controls accessible to personnel, and that are likely to
become energized." They are not required for the
controlled equipment.
While Article 682 provides no specific
requirement for the design of the plane itself (other than
depth below a walkway), similar requirements for pool decks in
680.26(C) should provide guidance as to materials and
configuration. Note that 680.26 allows use of the structural
reinforcing steel to accomplish the same purpose for pool and
spa decks, and requires that any belowgrade grid be secured
"within or under" the walkway medium. From a
practical standpoint, the plane can be installed integral to a
concrete equipment pad associated with the service equipment
or disconnecting means.
While not required here by Code language except in specific cases, experience in the pool/spa
industry indicates that a safer and more reliable system in
the aquatic environment will result if equipment grounding and
bonding conductors are solid (rather than stranded) in sizes
at least up to 8 AWG. It is also worthwhile to note that
Section 680.23(F)(2) has required continuous equipment
grounding conductors from underwater lights back to the ground
bus or the controller, with few exceptions. This is done in
680 to minimize the likelihood of either loss of ground or
development of a high-impedance ground path that increases the
shock hazard by adversely affecting short-circuit currents
originating in energized underwater equipment. Employment of
the same philosophy with underwater equipment covered by 682,
particularly submersible pumps and lights, even though it is
not specifically mandated, should similarly enhance safety of
these installations. This is particularly important for
installations accessible to the general public, and who may be
in the water.
An additional action not required by the Code can also be taken to improve safety for workers and the
general public who may be in the water. Owing to the absence
of any equipotential bonding grid in these facilities,
designers and installers should consider requesting the
electric utility to install neutral separation (also called
"neutral blocking") equipment at the utility
transformer, acceptable under Section 097D2 of the National
Electrical Safety Code ANSI C2, in order to mitigate
propagation of stray ground currents into the water over the
green wire via submerged, grounded metallic equipment
enclosures and cases. Use of neutral separation equipment has
been employed to this end successfully at pool facilities
served by utility primary distribution systems operating at
voltages up to and including 34.5 kV.
Figure
5
Summary
The new Article 682, while in some respects a work in
progress, provides for safeguarding of aquatic installations
that heretofore were inadequately addressed by the Code.
These include natural and man-made water impoundments not
covered by Articles 553, 555 and 680, and are not limited to
the abbreviated list of examples in the Code language.
Requirements include use of equipment and wiring methods
consistent with the unique qualities of the aquatic
environment, use of GFCIs, specific grounding and bonding
requirements for personnel safety, and use of equipotential
planes around accessible service equipment and disconnecting
means. The article does present several challenges to AHJs as
well as to design and installation professionals, and several
strategies to assist in meeting these challenges and improving
safety have been discussed.
The design and implementation of safe
electrical systems involving any type of water body involves
subtleties and specialized approaches that may have little in
common with more conventional "landlocked" systems.
The unique interaction between water and the electrical and
supporting equipment and structures in and around it requires
that AHJs and design and installation professionals develop a
specialized understanding of electrical behavior and workable
methodologies for this environment. The development of Article
682 is timely, will assist in achieving the desirable end of
safe and reliable aquatic electrical systems, and
professionals should expect further development and
clarification of issues and solutions as the industry gains
experience with these systems. In any case, when applying this
or any other provision in the Code, designers,
installers and AHJ, should always err on the side of safety.
Dr. E. P. Hamilton III, P.E., is
president of E. P. Hamilton & Associates, Inc., an
Austin TX Architectural, Engineering and Technical
Services firm. Among his other duties and areas of
specialization, Dr. Hamilton has worked for over 15
years in the design and analysis of aquatic electrical
facilities, is a co-developer of bonding, grounding and
stray current test procedures, protocols and related
test equipment for pools and spas. |
