Electrical
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any liability for damages arising from the use of this information or exhibits and attachments thereto and renders no opinion that
any of the terms, conditions, and/or cited federal standards in this document and the exhibits and attachments should be
explicitly followed by the fund member. Seek specific guidance from the appropriate regulator (OSHA) or professional advisor.
Serious Exposure
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Electrocution is one of the
top four causes of
construction fatalities
Nearly half of those
fatalities were the result of
contact with overhead
power lines
OSHA is making an effort to
focus more attention to
these exposures
Applicable Standards

Electrical standards are among the most
frequently cited by OSHA
No Lock Out/Tag Out
 Improper Wiring Methods
 Inadequate Components and Equipment
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
OSHA references the following for
guidelines
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Electric Safety Requirements for Employee
Workplaces and codes (NFPA 70E)
Basic Terminology
 Amps
– The amount of electricity
flowing
 Volts – The force at which the
power flows
 Ohms – A unit of electrical
resistance
 Watts – A unit of electrical power
Physical Effects
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Amps are the true measure of
current absorbed, not volts
We are good conductors, the
human body is 70% water
Involuntary muscle contraction
is the reason we are affected
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Can’t let go of energized object
Breathing is impaired
Heart rhythm is disrupted
Physical Effects
1 mA
Barely perceptible
16 mA
20 mA
Max current an average man can grasp and let
go
Paralysis of respiratory muscles
100 mA
Ventricular fibrillation threshold
2 amps
Cardiac standstill and internal organ damage
15 to 20 amps
Current required to trip common household
breaker
Influencing Factors of a Shock
Circumstances that affect the
outcome of an electric shock;
 Circuit voltage
 The bodies external (skin) and
internal resistance
 Total current flowing through
the body
 Current path
 The duration of the shock
Arc Flash
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The result of a rapid release of energy
due to an arcing fault, air is the
conductor.
Arc faults are generally limited to
systems where the voltage is in excess
of 120 volts.
Massive energy is discharged, vaporizing
the copper and causing an explosion.
Arcs can produce temperatures up to
35,000° F.
Flash hazards can produce pressure
waves, concentrated sound blasts, and
release deadly shrapnel.
Arc Flash
Arc flash and blast hazards were not
formally studied until the early 90’s
 Generally occur less frequently than
electric shock
 NFPA 70E provides directives on reducing
the occurrence and effects of arc flash

NFPA 70E – Flash Protection
Guidelines

Compliance of NFPA 70E, Arc Flash
Protection requires the following:
Justification for live work
 Work Permits when applicable
 Approach Boundaries

Approach Boundaries
Limited Approach Boundary
Electric

Panel
Entered only by a Qualified
Person or unqualified person
escorted by QP
Restricted Approach Boundary
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F
r
o
n
t
Entered only by a Qualified
Person required to use shock
protection techniques and PPE
Prohibited Approach Boundary

Entered only by a Qualified
Person requiring same protection
as if in direct contact with live
part
Flash Protection Boundary

Electric
Panel
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F
r
o
n
t
The Flash Protection
Boundary is the linear
distance to prevent any
more than 2nd degree
burns from a potential arc
flash
Distance is usually four feet
Distances for all shock
protection boundaries can
referenced in Table
130.2(C) of NFPA 70E
What kind of PPE is necessary?

The level of personal protective equipment
necessary for the exposure can be
determined one of two ways:
 Shock Hazard Analysis
- OR  Flash Hazard Analysis
Shock Hazard Analysis

Must determine the following:
The operating voltage of the system
 Shock protection boundaries
 Required personal protective equipment [

reference Tables 130.7(C)(9)(a) and 130.7(C)(10)
NFPA 70E ]
Flash Hazard Analysis

Must determine the following:
The flash protection boundary
 The incident energy exposure level
 Protective clothing and PPE

Flash Hazard Analysis

The flash protection boundary
Use the flash protection boundary formula OR
default 130.3(A)

The incident energy exposure level
distance between workers face and chest from the
arc source OR 130.7(C)(9) and 130.7(C)(10)

Protective clothing and PPE
Once incident energy is determined, safety equipment
has to have a rating greater than or equal to the
incident energy available
Personal Protective Clothing, NFPA
70E
Category
Cal/cm2
0
1
2
3
4
1.2
Clothing
Untreated Cotton
5
Flame retardant (FR) shirt and FR
pants
8
Cotton underwear FR shirt and FR
pants
25
Cotton underwear FR shirt, FR
pants and FR coveralls
40
Cotton underwear FR shirt, FR pants
and double layer switching coat and
pants
Employer Responsibilities

Equipment must be:
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Free from recognized hazards
Suitable and identified through listing,
labeling, or certification of purpose.
Designed with adequate mechanical
strength and durability
Other items for consideration
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Electrical insulation
Heating effects /conditions of use
Arcing effects
Use classifications
Guarding
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Live parts of electrical equipment operating at 50 volts or
more must be guarded against accidental contact.
Means of acceptable guarding include:
 Isolation in a cabinet, room, or vault accessible only by
qualified persons
 Use of partitions or screens to exclude unqualified
persons
 Elevation of eight feet or more above the floor
Electric installations over 600 require special protection
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metal-enclosed
Vault
controlled by lock
Lock Out / Tag Out
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LOTO written program
Components
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Documented energy
control procedures
Employee Training
program
Inspection program
Lock Out / Tag Out
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Purpose is to draw attention
to and disable a live energy
source during service and
repair work.
Lock Out physically disables
the energy source, Tag Out
provides a warning only
Only the employee who
placed the lock or tag may
remove it!
Safe Power Shutdown
- 5 Steps 
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Preparation and Notification–
Understanding energy source and alerting all
affected employees
Shutdown – De-energizing procedure
Isolation – Properly locking all power
sources
Lock & Tag Application
 Color coding for different trades
 Employee assigned locks
 Photo tags, helps locate employee, makes
association
Control and Verification– Control stored
and residual energy with locks in place
Re-energizing
- 3 Steps 
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Inspection – checking
the work area and
surrounding machinery
and for employees
Notification – Make
notice to all affected
employees as to what will
be re-energized
Removal of Tags and
Locks
Tags and Locks

Tags and Locks must be:
Durable – resist conditions of environment
 Standardized – color code and format
 Substantial – strong enough to minimize false
removal
 Identifiable – clear message, know who it is
protecting

Extension Cords
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Cords with missing ground prongs, insulation breeches,
crimping or crushing, must be removed from service.
Splicing is prohibited, but new connectors are acceptable
When unplugging, pull the plug, never tug on the cord
If a cord must cross a vehicle pathway it must be protected
OSHA considers an extension cord temporary power, no matter
the power source!
Service Ratings
Hard Service
(types S, ST, SO, STO)
Junior Hard Service
(types SJ, SJO, SJT,
SJTO)
Home use, small appliance
(type SP)
Ground Fault Circuit Interrupters
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Ground Fault Circuit Interrupters
(GFCI’s) sense changes in
current (5 milliamps) and stop
energy flow.
Devices stop current in 1/40 of a
second
Never bypass any protective
system or device designed to
keep you from contact with
electrical current.
All temporary power sources
must have GFCI protection
either at main box, extension
cord, or tool.
Portable Generators
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Never use a generator indoors
or in an attached garage.
Use extension cords with
adequate duty ratings.
To prevent electrical shock,
make sure your generator is
properly grounded.
Do not store fuel indoors or try
to refuel a generator while it's
running.
Turn off all equipment
powered by the generator
before shutting it down.
Other Considerations
Environmental Deterioration of Equipment Unless specified for use in such an
environment, no conductors or equipment
should be exposed to;
Damp or wet locations
 Gases, fumes, vapors, liquids, or
deteriorating agents
 Excessive Temperatures

other
Safe Work Practices
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Always check the location of
overhead power lines (most common
source of electrocution)
Stay away from energized power
circuits
Locate all utilities prior to digging or
jack hammering
Protect electrical equipment in
passageways from contact
Keep walking and working surfaces
free of electrical cords as much as
possible
Always de-energize equipment before
repair or service work
Electrical Checklist
Extension cords:
- No crimping or crushing
- No missing insulation
- No signs of stress at plug
All extension cords out
of high traffic areas:
- Road ways (protective cover)
- Driveways
- Hallway, entrance, stairwell
Lock Out / Tag Out plan for
all maintenance operations
Equipment rated for duty
and environment
Proper PPE when
necessary
GFCI protection at box,
cord, or tool
Awareness of all
overhead power lines
All tools double
insulated
Pre-job identification of
all underground utilities
Generators must have
earth ground