1. Subpart K Electrical 29 CFR 1926.400
Vincent J. Giblin, General President
Phone: (304)
Fax: (304)
1293 Airport Road
Beaver, WV
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2. This material was produced under grant number 46C5-HT16 from the Occupational Safety and Health Administration, U.S. Department of Labor. It does not necessarily reflect the views or policies of the U.S. Department of Labor, nor does mention of trade names, commercial products, or organizations imply endorsement by the U.S. Government.

3. Operating Engineers National Hazmat Program
Introduction
Electricity is the flow of electrons through
a conductor.
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4. Operating Engineers National Hazmat Program
Introduction
This flow is called a current. Any material
that allows electrons to flow through it is a
conductor. A good good example would
be copper wire, allowing electricity to flow
much like water through a hose.
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5. Operating Engineers National Hazmat Program
Introduction
This conductor must be covered by an
insulator made of materials that do not
conduct electricity easily. Glass, rubber,
plastic, and dry wood are insulators.
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Operating Engineers National Hazmat Program

6. Operating Engineers National Hazmat Program
Introduction
This brings up the topic of resistance.
Insulators have high resistance to the current
flow because it takes the path of least
resistance which would be the conductor
inside the insulator.
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Operating Engineers National Hazmat Program

7. Operating Engineers National Hazmat Program
Introduction
The human body can be used as a conductor,
sending electrical
currents through the
body much like
water through a
sponge.
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8. Operating Engineers National Hazmat Program
Introduction
When you have had an electrical shock you may:
A. Stop breathing
B. Burn the skin
C. Cook internal organs
D. Have internal bleeding
E. Stop the heart
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9. Operating Engineers National Hazmat Program
Introduction
This - of course - is to be avoided. What may
cause this to happen? It could be a short
circuit or a ground fault.
A short circuit may happen when two hot
wires or a hot wire and a neutral wire of a
circuit contact each other. This causes the
resistance to lower.
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10. Operating Engineers National Hazmat Program
Introduction
A ground fault may be caused by the hot
conductor coming into contact with an outlet
or tool casing. The tool may continue to run
until something touches the outlet or the tool
case, thus creating a multiple path to ground
and casing shock.
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11. Operating Engineers National Hazmat Program
Introduction
By using this standard, you will become
aware of the electrical safety requirements
that must be applied for the practical safe-
guarding of employees using temporary or
permanent electrical installations at a
construction job-site.
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12. Operating Engineers National Hazmat Program
Introduction
This standard was first issued in It
has since been updated in The
subpart K is divided into four major
divisions:
: Installation Safety
Requirements
& .417: Safety-Related Work
Practices
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13. Operating Engineers National Hazmat Program
Introduction
The subpart K is divided into four major
divisions:
Safety-Related & .432: Maintenance &
Environmental Considerations
: Safety Requirements
for Special Equipment
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14. Installation Safety Requirements 1926-403 General Requirements
These general requirements would apply to
all electrical conductors and equipment:
1. Approved 5. Suitable
2. Strong and durable 6. Insulated
3. Heat and arc effects 7. Classified location
4. Safeguarding
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15. Installation Safety Requirements 1926-403 General Requirements
(a) Approval of all electrical conductors and
equipment shall be approved.
(b) Examination, installation, and use of
equipment. The employer is to ensure that
electrical equipment is free from recognized
hazards that are likely to cause death or
serious physical harm to employees.
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16. Installation Safety Requirements 1926-403 General Requirements
(c) Interrupting rating:
Equipment intended to break current shall
have an interrupting rating at system
voltage sufficient for current that must be
interrupted.
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17. Installation Safety Requirements 1926-403 General Requirements
(d) Mounting and cooling of equipment:
Mounting-Electric equipment is to be
firmly secured to the surface on which it is
mounted. No wooden plugs are to be used.
Cooling- Electrical equipment depending
upon the natural circulation of air is to be
installed so that the air floe is not hindered
by any obstacles.
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18. Installation Safety Requirements 1926-403 General Requirements
(e) Splices:
Conductors are to be spliced or joined with
splicing devices designed for the use or by
brazing, welding, or soldering with a
fusible metal or alloy. Splices, joints, and
free ends are t be covered with proper
insulation
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19. Installation Safety Requirements 1926-403 General Requirements
(f) Arcing parts:
Electrical equipment
producing arcs, sparks,
flame, or molten metal
shall be enclosed or
separated from all
combustible material
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20. Installation Safety Requirements 1926-403 General Requirements
(g) Marking:
Electrical equipment is not to be used unless
it is properly marked with the manufacturer’s
name or if it does not provide voltage,
current, wattage, or other ratings necessary.
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21. Installation Safety Requirements 1926-403 General Requirements
(h) Identification of disconnecting means and circuits:
Each disconnecting means shall be legibly
marked to indicate its purpose. Each
service, feeder, and branch circuit shall be
legibly marked to indicate its purpose.
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22. Installation Safety Requirements 1926-403 General Requirements
(i) 600 volts, nominal, or less
Working Clearances are to follow Table K-1
Table K-1
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23. Installation Safety Requirements 1926-403 General Requirements
(i) 600 volts, nominal, or less
Clear spaces are not to be used for storage.
There should be at least one entrance for access to the working space about electric equipment
The working space in front of service equipment
that is exposed should not be less than 3 feet and the minimum headroom shall be 6’3”.
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24. Installation Safety Requirements 1926-403 General Requirements
(i) 600 volts, nominal, or less
Live parts of electric equipment are to be guarded against accidental contact. Partitions, screens, and placement on elevated levels of 8 feet or more above the work surface, are all means of guarding and are to be accessible only to qualified persons.
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25. Installation Safety Requirements 1926-403 General Requirements
(j) Over 600 volts, nominal
This electrical equipment shall be surrounded by a wall, screen, or fence, access to which is controlled by lock and key or under the observation of a qualified person at all times.
Those installations that have exposed live parts are to be accessible to qualified persons only.
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26. Installation Safety Requirements 1926-403 General Requirements
(j) Over 600 volts, nominal
Sufficient space is needed to permit ready and safe operation and maintenance. The minimum clear workspace shall not be less than 6’6” high, or less than 3’ wide with adequate space to permit at lest a 90o opening or doors or panels.
There should be at least one entrance to this
work space not less than 24” wide and 6’6” high.
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27. Installation Safety Requirements 1926-403 General Requirements
(j) Over 600 volts, nominal
The minimum clear working space in front of electric equipment shall not be less than specified in Table K-2
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28. 1926.404 Wiring Design and Protection
(a) Conductors used as either grounded or as
an equipment grounding conductor are to be
distinguishable from all other conductors.
Grounded- Neutral color, current carrying conductor
Grounding- Bare or green color dedicated to frames
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29. 1926.404 Wiring Design and Protection
The polarity connections shall not be changed
by the use of grounded conductors. A
grounding terminal or device on a receptacle,
cord connector,or attachment plug shall not be
used for purposes other than grounding.
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30. 1926.404 Wiring Design and Protection
(b) Branch circuits are used for ground-fault
protection. Ground fault circuit interrupters or
an assured equipment grounding conductor
program are to be used to protect the
employees on the construction site. repairs
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31. 1926.404 Wiring Design and Protection
(c) Outside conductors and lamps
(i) Power Conductors on poles are to be
separated from communication conductors as
follows:
 30 inches if below communication
conductors
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32. 1926.404 Wiring Design and Protection
(c) Outside conductors and lamps
(i) Power Conductors on poles are to be
separated from communication conductors as
follows:
 24 inches if above communication and
300 volts or less
 30 inches if above communication and
more than 300 volts
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33. 1926.404 Wiring Design and Protection
(c) Outside conductors and lamps
(ii) Clearance from ground:
10 ft - above sidewalks, grade, platform
12 ft - vehicular traffic
15 ft - other than public streets, alleys, roads, and driveways
18 ft - above public streets, alley, roads, and driveway
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34. 1926.404 Wiring Design and Protection
(c) Outside conductors and lamps
(iii) Clearance from building openings is
to be at least 3 feet
(iv) Clearance over roofs
8 ft - insulated conductors
10 ft - covered conductors
15 ft - bare conductors
18 ft - if used for vehicles
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35. 1926.404 Wiring Design and Protection
(c) Outside conductors and lamps
Outdoor lamps are to be located below all live
conductors, or electric equipment unless
other specific safeguards are required for
relamping.
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36. 1926.404 Wiring Design and Protection
(d) Services
Means will be provided to disconnect all
conductors in a building or other structure
from the service-entrance conductors,
indicating whether it is in the open or closed
position. They shall be installed at a readily
accessible location nearest the point of
entrance of the service-entrance conductors.
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37. 1926.404 Wiring Design and Protection
(e) Overcurrent protection- (1)600 volts or less
Protection of conductors and equipment from
overcurrent of circuits can be done by making
certain:
(i) Conductors have sufficient ampacity for job
( ii) No interruptions from overcurrent devices
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38. 1926.404 Wiring Design and Protection
(e) Overcurrent protection-(1) 600 volts or less
(iii) All cartridge fuses are provided with
disconnecting means.
(iv) Overcurrent devices are readily accessible
(v) Fuses, circuit breakers, and moving parts are
shielded to protect employees
(vi) Circuit breakers are clearly ON of OFF
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39. 1926.404 Wiring Design and Protection
(e) Overcurrent protection-
(2) 600 volts or more
Feeders and branch circuits over 600 volts, nominal, shall have short-circuit protection.
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40. 1926.404 Wiring Design and Protection
(f) Grounding
Grounding keeps you from becoming part of the
circuit by providing a separate low resistance
pathway for electricity when it does not follow
normal flow from hot to neutral.
OSHA lists extensive requirements for grounding
in (f)(1) through(11), focusing on things that give
a continuous grounding path.
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41. 1926.404 Wiring Design and Protection
(f) Grounding
In order to assure proper grounding, the path must:
 Be permanent and continuous
 Be of ample capacity
 Have low resistance
 Bond all circuit parts together
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42. 1926.404 Wiring Design and Protection
(f)(7) Equipment connected by cord and plug
that must be grounded.
1. Handheld motor-operated tools
2. Equipment 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
3. Portable and mobile X-ray equipment
4. Tools used in wet and/or conductive locations
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43. 1926.404 Wiring Design and Protection
(f)(11) Grounding of systems and circuits of 1000 volts and over
1. Portable and mobile high voltage equipment shall be supplied from a system having its neutral grounded through an impedance.
2. Provided ground-fault protection is to automatically de-energize any high voltage system component which has developed a ground fault.
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44. 1926.404 Wiring Design and Protection
(f)(11) Grounding of systems and circuits of 1000 volts and over
3. The grounding electrode to which the portable or mobile equipment system neutral impedance is connected shall be isolated from and separated in the ground by at least 20 feet from any other system or equipment grounding electrode
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45. 1926.404 Wiring Design and Protection
(f) Grounding
Systems to be grounded
3 wire DC systems
2 wire DC systems
AC circuit less than 50 volts
AC circuits 50 volts to 1000 volts
Exempted if less than 50 volts and isolation
transformer and also if double insulated.
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46. 1926.405 Wiring Methods, Components, and Equipment
We will touch briefly on each of the
elements of this section.
(a)In discussing the general requirements of wiring methods, metal raceways, cable armor, and other metal enclosures for conductors shall be metallically joined together into a continuous electric conductor.
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47. 1926.405 Wiring Methods, Components, and Equipment
Temporary power and wiring methods shall
be removed immediately upon completion of
construction or the purpose for which the
wiring was installed.
The general requirements for temporary
wiring are listed in (a)(2)(ii)(A-J).
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48. 1926.405 Wiring Methods, Components, and Equipment
Covering lights in this section ,(F-G),
temporary lights shall not be suspended by
their electric cords unless cords and lights are
designed for this means of suspension.
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49. 1926.405 Wiring Methods, Components, and Equipment
Portable electric lighting used in wet and/or
other conductive locations, such as drums,
tanks, and vessels, shall be operated at 12 volts
or less. 120-volt lights may be used if protected
by a ground-fault circuit interrupter.
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50. 1926.405 Wiring Methods, Components, and Equipment
Covering, also,the commonly used flexible
extension cords and cables, section (I). They are
to be protected from damage as they may pass
through doorways or other pinch joints. Sharp
corners and projections shall be avoided. Never
pass extension cords through walls, floors,
ceilings, windows, or doors.
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51. 1926.405 Wiring Methods, Components, and Equipment
(J) explains extension cords shall be of three-wire
type and designed for hard or extra-hard usage, as
in those used by portable lights.
Never use a cord without a ground, the odds
increase that a fault current will flow through you.
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52. 1926.405 Wiring Methods, Components, and Equipment
(b)Conductors entering boxes, cabinets, or
fittings are to be protected from abrasion.
Openings through which conductors enter and
those not in use shall be effectively closed.
These boxes and fittings shall be provided with
the appropriate covers.
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53. 1926.405 Wiring Methods, Components, and Equipment
(c) Knife switches:
Single-throw knife switches shall be so connected that the blades are dead when the switch is in the open position. They are to be placed so that gravity will not tend to close them and have a locking device that ensures the blades remain in the open position when set.
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54. 1926.405 Wiring Methods, Components, and Equipment
(c) Knife switches:
Double-throw knife switches may be mounted so that the throw will be either vertical or horizontal. A locking device shall be provided to ensure the blades remain in the open position when so set.
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55. 1926.405 Wiring Methods, Components, and Equipment
(d) Switchboards and panelboards.
Switchboards with exposed
live parts are to be located
in permanently dry locations
and accessible only to qualified
persons. They should be
mounted appropriately and
have dead fronts.
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56. 1926.405 Wiring Methods, Components, and Equipment
(e) Proper Enclosures for damp or wet locations are to prevent moisture or water from entering and accumulating within the enclosures. For this reason, switches and circuit breakers are to be placed in weatherproof enclosures.
(f) All conductors used for general wiring shall be insulated unless otherwise permitted in this Subpart.
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57. 1926.405 Wiring Methods, Components, and Equipment
(g) Flexible cords and cables are to used only for:
A. Pendants B. Fixture wiring
C. Portable appliances D. Elevator cables
E. Crane/Hoist wiring
F. Connection of stationary equipment
G. Noise/Vibration prevention
H. Removable connections for maintenance
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58. 1926.405 Wiring Methods, Components, and Equipment
(h) Portable cables over 600 volts shall consist of No. 8 or larger conductors employingflexible stranding. Cables operated at over 2000 volts are to be shielded in order to confine the voltage stresses to the insulation.
(i) Fixture wires are to be suitable for the voltage, temperature, and location of use.
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59. 1926.405 Wiring Methods, Components, and Equipment
(j) Requirements are covered fore general
equipment use inclusive of:
1. Lighting fixtures, lampholders, lamps and
receptacles
2. Receptacles, cord connectors, and
attachment plugs
3. Appliances Transformers
4. Motors Capacitors
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60. 1926.406 Specific purpose equipment and installations
(a) Cranes and hoists
(b) Elevators, escalators, walks
(c) Electric welders-disconnecting means
(d) X-ray equipment
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61. Operating Engineers National Hazmat Program
Hazardous Locations
This section covers requirements for electric
equipment and wiring in locations which are
classified depending on the properties of the
flammable vapors, liquids or gases, or
combustible dusts or fibers which may be
present.
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62. Operating Engineers National Hazmat Program
Hazardous Locations
These hazardous locations are assigned six
designations as follows:
Class I - Division1 and 2 - Gasses & Vapors
Class II - Division 1 and 2 - Dusts
Class III - Division 1 and 2 - Fibers
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63. Operating Engineers National Hazmat Program
Hazardous Locations
Electrical installations of equipment in hazardous locations shall be approved as intrinsically safe (permitted in any hazardous location included in its listing or labeling) or approved for the hazardous location (class of location and ignitable or combustible properties of any specific element present).
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64. Operating Engineers National Hazmat Program
Special systems
(a) Systems over 600 volts
(b) Class 1, Class 2, Class 3 remote control, signaling, and power-limited circuits
(c) Communication systems
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65. 1926.416 Safety-Related Work Practices
(a) Protection of employees
(b) Passageways and open spaces
(c) Load ratings
(d) Fuses
(e) Cords and cables
(f) Interlocks
(g) Use of equipment
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66. 1926.417 Lockout and tagging of circuits
(a) Controls
(b) Equipment and circuits
(c) Tags
(d) Lockout and tagging
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67. 1926.431 Maintenance of equipment
The employer shall ensure that all wiring components and utilization equipment in hazardous locations are maintained in a dust-tight, dust-ignition-proof, or explosion-proof condition, as appropriate.
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68. 1926.432 Environmental deterioration of equipment
(a) Deteriorating agents
1. Damp or wet locations
2. Exposure to gases, fumes, vapors, liquids, or other agents having a deteriorating effect on the conductors or equipment
3. Exposure to excessive temperatures.
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69. 1926.432 Environmental deterioration of equipment
(b) Protection against corrosion. Metal raceways, cable armor, boxes, cable sheathing, cabinets, elbows, couplings, fittings, supports, and support hardware shall be of materials appropriate for the environment in which they are to be installed.
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70. 1926.441 Batteries and battery charging
(1) Unsealed batteries are to be located in well ventilated areas to (2)ensure diffusion of the gases and prevent the accumulation of and explosive mixture. (3)Substantial racks and trays are to be supplied and treated to make them resistant to the electrolyte. (4) Floors are to be acid resistant and (5) workers who handle acids or batteries are to be provided with face shields, aprons,and rubber gloves.
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71. 1926.441 Batteries and battery charging
(6) Facilities for quick drenching of the eyes and body shall be provided within 25 feet of battery handling areas.
(7) Facilities shall be provided for flushing and neutralizing spilled electrolyte and for fire protection.
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72. This material was produced under grant number 46C5-HT16 from the Occupational Safety and Health Administration, U.S. Department of Labor. It does not necessarily reflect the views or policies of the U.S. Department of Labor, nor does mention of trade names, commercial products, or organizations imply endorsement by the U.S. Government.

73. Operating Engineers National Hazmat Program
End
This publication was made possible by grant numbers 5 U45 ES AND 5 U45 ES from the National Institute of Environmental Health Sciences (NIEHS), NIH. Its contents are solely the responsibility of the authors and do not necessarily represent the official views of the NIEHS, NIH.
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