Subpart S
Electrical Hazards
Video
Designed by:
Major Components
Examination of Equipment
Working Clearances
Overcurrent Protection
Grounding
Wiring Methods
Electrical Boxes
Flex Cord & Cable
Hazardous Locations
Safe Work Practices
Revision of Subpart S
OSHA is revising its electrical installation standard in
§§1910.302 through 1910.308 of Subpart S and
definitions in §1910.399 in order to reflect the most
current practices and technologies in the industry
The revised standard strengthens employee
protections and adds consistency between OSHA's
requirements and many state and local building
codes which have adopted updated National Fire
Protection Association (NFPA) and National Electrical
Code (NEC) provisions.
Copyright 2000 PROSAFE Solutions
Revision of Subpart S
It updates Subpart S requirements to the 2000
edition of the NFPA 70E, which is based on the 1999
edition of the NEC. The updated standard includes
an alternative method for classifying and installing
equipment in Class I hazardous locations, new
requirements for ground-fault circuit interrupters, and
new provisions on wiring for carnivals and similar
installations.
Federal Register a Final Rule Publish date – February
14, 2007.
Goes into effect on August 13, 2007
Copyright 2000 PROSAFE Solutions
Examination of Equipment
Electrical equipment must be free of
recognized hazards that are likely to cause
death or serious physical harm to
employees.
Examination of Equipment
Safety of equipment must be determined
using the following considerations:
Suitability for installation and use
Mechanical strength and durability
Electrical insulation
Heating effects
Arcing effects
Classification
Marking
Electrical equipment must be marked
with the manufacturer’s name,
trademark or other identification
Other markings must be provided giving
voltage, current, wattage, or other
ratings as necessary
Markings must be durable enough to
withstand the environment
Identification
Each disconnecting means must be
legibly marked to indicate its
purpose, unless located and
arranged so that its purpose is
evident
Markings must be durable enough
to withstand the environment
600 volts, Nominal, or Less
Working Clearances:
Working space around electrical
equipment
This section refers to a person qualified
to work on electrical equipment, usually
an electrician
Working Clearances
Working space in front of live parts
(operating at 600 volts or less) must be at
least three feet
The workspace in front of electrical
equipment must not be less than 30 inches
wide
Working spaces may not be used for
storage
Proper Clearances!
600 Volts or Less
Guarding of live parts.
Any person who is in the vicinity of
electrical equipment must be protected
against accidental contact
Location must be accessible only to
qualified persons
Permanent, substantial partitions or
screens
600 Volts or Less
Guard against accidental contact by:
Location on a suitable elevated balcony or
platform
Elevation of 8 feet or more above the floor
or other working surface
600 Volts or Less
Enclosures or guards must be installed in
locations where electrical equipment is
exposed to physical damage.
Over 600 Volts
Sufficient space must be provided and
maintained around electrical equipment to
permit safe operation and maintenance
Illumination (Over 600 Volts)
Adequate illumination must be provided for
working spaces around electrical equipment
The lights and switches must be arranged so
that persons wont contact live parts
Unguarded Live Parts
Unguarded live parts above the working
space must be maintained at elevations not
less than specified in Table S-3
The minimum is 8 feet
Identification of Conductors
The grounded conductor is an energized
circuit that is connected to earth through
the system ground. It is commonly
referred to as the neutral.
The grounding conductor is not energized
under normal conditions. It is energized
only if there is a leak or fault in the
normal current path and directs current
back to the source.
Identification of Conductors
The National Electric Code requires that:
The grounded conductor (neutral) be
continuous white or natural gray
The equipment grounding conductor be
green, green with yellow stripes or bare
Polarity of Connections
No grounded conductor may be attached
to any terminal or lead so as to reverse
designated polarity
Reversed polarity is a condition when a
neutral conductor is incorrectly connected
to the “hot” terminal of a plug, receptacle
or other connector.
Overcurrent Protection
600 volts or less.
Conductors and equipment must be
protected from overcurrent.
Fuses and circuit breakers are designed
to disconnect a circuit from its supply
source when a maximum allowable heat
is reached.
Overcurrent Protection
600 volts or less
Overcurrent devices must be readily
accessible
Must not be located where they will be
exposed to physical damage or in the
vicinity of easily ignitable material
Grounding
The path to ground from circuits,
equipment, and enclosures must be
permanent and continuous
Grounding
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 not over 50 volts
Grounding
Tools and appliances protected by an
approved system of double insulation,
need not be grounded
They must be distinctively marked
Double Insulated Tools
Work with GFCIs
Casing must be labeled
Tool must be inspected
Extension cord must be three-prong
Wiring Methods
No wiring system of any type may be in
ducts used to transport dust, flammable
vapors, or ventilation of commercial-type
cooking equipment.
Wiring Methods
Temporary electrical power and lighting
wiring may be of a class less than would
be required for a permanent
installation.
Wiring Methods
Temporary wiring.
Uses permitted, 600 volts or less.
During and for remodeling, maintenance
repair, demolition or similar activities.
Wiring Methods
Uses permitted, 600 volts or less.
For experimental or developmental work
For a period not to exceed 90 days for
Christmas decorative lighting, carnivals, and
similar purposes.
Wiring Methods
Temporary wiring.
Uses permitted, over 600 volts.
Only during tests, experiments and
emergencies.
Wiring Methods
Lamps for general illumination must be
protected from accidental contact or
breakage.
Protection can be provided by an elevation
of 7 feet or by a suitable fixture with a
guard.
Wiring Methods
Flexible cords and cables must be protected
from accidental damage. Sharp corners or
projections must be avoided.
Protection must be provided when passing
through doorways or other pinch points.
Conductors Entering Boxes
Conductors entering boxes, cabinets, or
fittings must be protected from abrasion.
Unused openings in cabinets, boxes, and
fittings must be effectively closed.
Proper Example!
Electrical Box Covers
All pull boxes, junction boxes, and
fittings must be provided with
approved covers.
Metal covers must be grounded.
Electrical Box Covers
Outlet boxes must have a cover or a
faceplate.
Outlet box covers with holes for flexible
cords must have bushings or smooth, well-
rounded surfaces.
Switchboards & Panelboards
Panelboards must be mounted in
approved cabinets or boxes and must be
dead front.
Others are accessible only to qualified
persons.
Flexible Cords & Cables
Allowed uses:
Pendants
Wiring fixtures
Portable lamps or appliances
Elevator cables
Wiring cranes or hoists
Flexible Cords & Cables
Allowed uses:
Connect stationary equipment to facilitate
frequent interchange
Prevent transmission of noise or vibration
For removal for maintenance/repair
Flexible Cords & Cables
May not be used:
As a substitute for the fixed wiring of a
structure
Where run through holes in walls, ceilings
or floors
Flexible Cords & Cables
May not be used:
Where run through doorways, windows, or
similar openings
Where attached to building surfaces
Where concealed behind building walls,
ceilings, or floors
Flexible Cords & Cables
Flexible cords must be used only in
continuous lengths without splice or tap
Damaged cords must be properly repaired
or removed from service
Flexible Cords & Cables
Hard service flex cords, No. 12 or larger,
may be repaired if spliced so that the
splice retains the insulation, outer sheath
properties, and usage characteristics of
the original cord
Splices
Conductors must be spliced with:
Splicing devices suitable for the use
Brazing, welding or soldering (with a
mechanically and electrically secure joint
before soldering & then soldered)
Splices
All splices and joints must be covered
with an insulation equivalent to that of
the conductors
Flexible Cords & Cables
Flexible cords must be connected to
devices so that strain relief is provided to
prevent pull off from being directly
transmitted to joints or terminal screws.
Equipment for General Use
A receptacle installed in a wet or damp
location must be suitable for the location.
Hazardous Locations
Electrical installations.
Equipment, wiring, and installations of
equipment in hazardous (classified)
locations must be intrinsically safe,
approved for the location, or safe for the
location.
Hazardous Locations
Class I locations
Locations in which flammable gasses or
vapors are or may be present in the air
in quantities sufficient to produce
explosive or ignitable mixtures.
Hazardous Locations
Class I, Division 1
Location in which hazardous
concentrations of flammable gases or
vapors may exist:
Under normal operating conditions
Because of repair or maintenance
operations or leakage
Because of breakdown or faulty operation
Hazardous Locations
Class I, Division 2
Location in which flammable gases or
vapors are:
Normally confined within closed
containers or systems
Normally kept below hazardous
concentrations by ventilation
Normally kept below hazardous
concentrations by positive-pressure
ventilation (adjacent to Division 1)
Hazardous Locations
Class II Locations
Locations which are hazardous because
of the presence of combustible dust.
Hazardous Locations
Class II, Division 1
Location where combustible dust may be
present due to:
Normal operations
Mechanical failure or abnormal operation
of machinery or equipment
Combustible dust of an electrically
conductive nature may be present.
Hazardous Locations
Class II, Division 2
Location where:
Combustible dust will not normally be in
suspension in ignitable quantities
Dusts may be in suspension as a result of
an infrequent malfunction of handling or
processing equipment.
Hazardous Locations
Class III Locations
Locations that are hazardous because of
the presence of easily ignitable fibers
but in which such fibers are not likely to
be in suspension in the air in quantities
sufficient to produce ignitable mixtures.
Hazardous Locations
Class III, Division 1
Locations in which easily ignitable
fibers or materials producing
combustible flyings are handled,
manufactured or used.
Safe Work Practices
Covers work practices rather than
electrical equipment and installations
This should be a part of your
Lockout/Tagout program
