(1) Metal cable trays, metal raceways, and
metal enclosures for conductors must be grounded.
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Exceptions:
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1. Metal enclosures such as sleeves that are used
to protect cable assemblies from physical damage need not be grounded;
or
2. Metal enclosures for conductors added to
existing installations of open wire, knob-and-tube wiring, and
nonmetallic-sheathed cable need not be grounded if all of the following
conditions are met:
a. Runs are less than 25 feet;
b. Enclosures are free from probable contact with
ground, grounded metal, metal laths, or other conductive materials; and
c. Enclosures are guarded against employee
contact.
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(2) Metal enclosures for service equipment
must be grounded.
(3) Frames of
electric ranges, wall-mounted ovens, counter-mounted cooking units, clothes
dryers, and metal outlet or junction boxes that are part of the circuit for
these appliances must be grounded.
(4) Exposed noncurrent-carrying metal parts
of fixed equipment that may become energized must be grounded under any of the
following conditions:
(a) If within 8 feet
vertically or 5 feet horizontally of ground or grounded metal objects and
subject to employee contact;
(b) If
located in a wet or damp location and not isolated;
(c) If in electrical contact with
metal;
(d) If in a hazardous
(classified) location;
(e) If
supplied by a metal-clad, metal-sheathed, or grounded metal raceway wiring
method;
(f) If equipment operates
with any terminal at over 150 volts to the ground; however, the following need
not be grounded:
(i) Enclosures for switches
or circuit breakers used for other than service equipment and accessible to
qualified persons only;
(ii) Metal
frames of electrically heated appliances that are permanently and effectively
insulated from ground; and
(iii)
The cases of distribution apparatus such as transformers and capacitors mounted
on wooden poles that are over 8 feet above ground or grade level.
(5) Under any of the
conditions below, exposed noncurrent-carrying metal parts of cord-connected and
plug-connected equipment that may become energized must be grounded.
(a) When equipment is in hazardous
(classified) locations.
(b) When
equipment is operated at over 150 volts to ground.
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Exception: |
Guarded motors and metal frames of electrically heated
appliances need not be grounded if the appliance frames are permanently and
effectively insulated from ground. |
(c) When equipment is one of the following:
(i) Refrigerators, freezers, and air
conditioners;
(ii) Clothes-washing,
clothes-drying and dishwashing machines, sump pumps, and electrical aquarium
equipment;
(iii) Hand-held
motor-operated tools;
(iv) The
following motor-operated appliances: Hedge clippers, lawn mowers, snow blowers,
and wet scrubbers;
(v)
Cord-connected and plug-connected appliances used in damp or wet locations or
by employees standing on the ground or on metal floors or working inside of
metal tanks or boilers;
(vi) Tools
likely to be used in wet and conductive locations; and
(vii) Portable hand lamps.
Tools likely to be used in wet and conductive locations
need not be grounded if supplied through an isolating transformer with an
ungrounded secondary of a maximum of 50 volts. Listed or labeled portable tools
and appliances protected by an approved system of double insulation, or its
equivalent, need not be grounded. The equipment must be distinctively marked to
indicate that the tool or appliance uses an approved system of double
insulation.
(6) The metal parts of the following
nonelectrical equipment must be grounded: Frames and tracks of electrically
operated cranes; frames of nonelectrically driven elevator cars to which
electric conductors are attached; hand operated metal shifting ropes or cables
of electric elevators, and metal partitions, grill work, and other metal
enclosures around equipment of over 750 volts between conductors.
