Official Electric Sutdy Guide Flashcards
What are the most frequent electrical citations?
- branch circuits
- Grounding Path
- Ground Fault-circuit interrupters
- Grounding live parts
- Equipment installation and use
About __ workers are
electrocuted every week.
5
Causes the deaths of __ of the
younger workforce
12%
What are the three direct electrical hazards?
- Shock, Electrical
- Electrocution or death due to electrical shock
- Burns
What are the three indirect electrical hazards?
Indirect –
- Falls
- Fires
- Explosions
An electrical shock is received when _____ passes through the body.
electrical
current
You will get
an electrical shock if a part of your body
completes an electrical circuit by…
- Touching a live wire & an electrical ground, or
- Touching a live wire & another wire at a
different voltage.
Severity of Shock - depends on:
- Path of current thru the body
- Amount of current flowing through the body (amps)
- Duration of the shocking current through the body,
___DOES NOT MEAN LOW
HAZARD!!!
LOW VOLTAGE
Hazard 1 -
Electrical Shock
Currents above __ * can
paralyze or “freeze” muscles.
10 mA
Currents more than ___ can cause a rapid, ineffective heartbeat
death will occur in a few minutes
unless a defibrillator is used
75 mA
75 mA is not much current – a small power drill uses ___ times as much.
30
mA = milliampere =
1/1,000 of an ampere
Hazard 2 -
Electrocution
Painful shocks… causing indirect accidents.
3mA+ -
Muscle contraction… “not able to let go”.
10mA+ -
Lung paralysis… usually temporary.
30mA+ -
Ventricular Fibrillation… is possible
50mA+ -
Certain Fatal Ventricular
Fibrillation
100mA to 4amp -
- Severe burns, heart paralysis.
Over 4 amps
Hazard 3 -
Burns
Most common… shock
related injury
burns
How do most people get shocked?
By touching Wires -
Touching electrical wiring or
equipment that is improperly
used or maintained
Hands get it -Typically
occurs on hands
burns
Hazard 4
Falls
Can cause Death -
Workers in elevated locations who
experience a shock may __,
resulting in serious injury or death
fall
Hazard 5
fires
most commonly caused by current flowing
through high resistance due to faulty wiring igniting
insulation and / or other material.
Fires
Heat is created from high ___ flowing through a
wire. This is analogous to two objects being rubbed together.
high currents
(At full speed, ‘skin’ of an
SST jet is about __ )
6000F
HEAT of Friction - To maintain continuity of
flow, as the diameter of a pipe decreases, the velocity of the fluid must increase, and ____.
the heat of friction increases
When a wire decreases in _____ due to damage, current must increase through that portion of the wire, & heat increases possibility to the point that surrounding materials are set on fire.
cross-sectional area
Hazard 6
Explosions
can be caused when electricity provides
the ignition source (arc) “jumping” through an air-’fuel’ mixture in the atmosphere.
Explosions
What should be used Isolate Electrical Parts.
covers,
guards
barriers
Guard live parts… of electric equipment operating at \_\_\_ or more against accidental contact
50 volts
Conductors going into live parts must be protected,
and unused openings must be closed. What do you use?
cabinets,
boxes
fittings
J-boxes (etc) must have
_____ Unused openings must be closed (no missing knockouts)
approved covers
Don’t get near power lines! watch out for what?
Cranes Ladders Scaffolds Backhoes Scissors lifts Raised dump truck beds
De-energize power lines before working on them. What are two ways this can be done?
- Lock Out/Tag Out
2. Power Provider to de-energize.
If you don’t want to de-energize power lines then:
Guard or insulate the lines
Always Call “One Call”:
before digging around underground power lines.
Always Locate & De-Energize:
before digging
Re-Call “One Call” if in Doubt:
If obvious signs of utilities (power boxes, poles
etc.) exist but are not marked, call for the locator
to re-mark before working.
Select wire size based on:
- bldg materials,
- electrical load, and
- environmental factors
- operation
Use fixed cords:
not flexible cords
What type of wire must be used?
Must be 3-wire type and
designed for hard or extra-hard use
Temp Lighting is Temporary:
remove it immediately upon completion of construction
Protect Temporary Lights from Breakage:
use bulb guards.
Don’t “hang” Temporary Lights by wires:
unless designed for this use
When dealing with temporary light, All branch
circuits must come from panel board & ____.
have breaker protection
NO Temp wiring on floors -
Branch circuits cannot be run on floors.
Wall Outlets must have:
Covers
Protect conductors entering boxes, etc from ___.
abrasion
Close Unused Openings -
in J-boxes.
When dealing with temporary wiring use ___ In wet locations.
Weatherproof Enclosures
When dealing with temporary wiring, protect Hardware from Water, by____.
…
Cabinets, boxes, switches, circuit breakers, etc.
extension cord rules for repairs:
- Repairs to Extension Cords - can only
be made to 12 gauge or larger extension
cords. - Repairs must maintain insulation -
Repairs (splices) must maintain outer sheath
insulation properties (No electrical tape).
3.Strain relief - must be provided.
a low resistance
path from a tool
to the earth to disperse unwanted
current.
Grounding
When a short occurs,
energy flows through the “___” wire and NOT YOU!! … to the ground, protecting you from
electrical shock, injury and death.
ground
Energized Tools -
Tools plugged into improperly grounded circuits may become…
energized
They Automatically
open circuit if unsafe
current is detected – they
“shut off” electricity
Electric Circuit Protective
Devices
Fuses
melt
Circuit breakers
trip
GFCI’s
“isolate” the load
GFCI cuts electricity
off in ___ of a second if a
ground fault is detected.
1/40th
Use GFCI’s on all:
120-volt, single-phase, 15- and 20-ampere receptacles.
“Tripping” GFCI’s - are designed to trip at \_\_\_ (painful shock level).
4-6 milliamps
GFCI’s required on temporary ____ – (not part of permanent wiring system).
120v 15-20 amp outlets
GFCI not required on permanent power, unless ____.
tool used with extension cord
GFCI protection is required on all portable generators _____ or greater.
5kW (5,000 watts)
GFCI protection can be built in or added as a_______.
pig-tail
Written program –The must be kept onsite.
Assured Grounding program
Who must implement Assured Grounding Program?
competent person
What is covered by Assured Grounding Program?
equipment (connected by plug & cord),
all cords, plugs, receptacles (not part of a building or
structure), & power tools.
When dealing with assured ground, Test Records kept -
by color coding, other
means, & by written log.
When should assured grounding program be tested?
(1) before 1st use,
(2) at least every 3 mo.,
(3) after service, &
(4) after possible damage.
Electrical equipment must be inspected before use. What two things should you be looking for?
(1) inspected before installation &
(2) suitable for the intended use.
All ___ must
be labeled.
circuit breakers
Access to live parts 50+ volts must be Controlled by what two things?
restricted areas or physical locations
– (accessible by only
qualified /authorized persons), i.e. room,
enclosure, partition, screened area, balcony,
platform, etc., or by
Restricted Areas
Elevated 8 feet or
more above the floor or working surface.
Physical Locations
must be used where
electrical equipment is exposed to physical damage.
Enclosures or Guards
Electrical Rooms must be ___.
marked
Must use _____ designed for that purpose (wire nuts) or by brazing, welding, or soldering.
splicing devices
This must be done to controls on equipment during service/repair with clear identification.
lock out/tag-out
Circuits or equipment that are de-energized must be ___ to prevent unauthorized reenergizing at any point.
locked & tagged
At what amperage will a GFCI trip?
4-6 milliamps
What type(s) of electrical cords are acceptable for use in construction?
3-wire type & hard or extra hard duty
What is the proper way to repair an
extension cord?
Repair only 12 gauge or larger; Repair must maintain insulation properties, use shrink sleeve.
- What should we do to protect
unauthorized employees from entering
electrical rooms with live parts?
Mark the room with Warning Signs forbidding entrance by unqualified, unauthorized persons.
Severity of Shock - depends on:
- Path of current thru the body
- Amount of current flowing through the body (amps)
- Duration of the shocking current through the body,
Hazardous (Electrical) Conditions
- Exposed Electrical Parts
- Proximity to Power Lines
- Inadequate Wiring
- Defective Cords
- Poor or No Grounding
- Overloaded Circuits
Power line rules:
- Keep Away - 10’ – minimum
- Post Signs – warning of danger
- Assume Lines are “Hot”
- Use No Metal - Use wood or fiberglass ladders, not metal
- Use PPE - Power line workers need special training & Personnel Protective Equipment
What causes damaged cords?
- Aging, wear
- Edges of doors, window
- staples or fastenings
- Abrasion from adjacent materials
- Impact from activity in the area
- Don’t Pull on Cords - Remove cords by pulling on the plugs, not the cords
- Use Only Hard Service Rated Cords
Extension cord rules:
- Use only 3 wire type, hard duty - All extension cords must be 3-wire type & hard or extra hard duty.
- Protect from Damage – must protect flexible cords & cables from damage.
- No “Pinch Points” – must not run cords through pinch points.
- No Nails, Staples, etc – must not suspend extension cords by nails, staples, or wires.
Cords and wiring rules:
- Use Plugs with Ground Pins - Path to ground must be continuous (only use plugs with ground pins; no missing ground pin).
- No Reversing Polarity - No grounded conductor can be attached to any terminal reversing its designated polarity.
- Must Have General Disconnect – (Main Breaker) Must have a disconnect that allows all conductors to be disconnected from service entrance.
The four grounding rules:
- Ground your equipment - power supply systems, electrical circuits, and equipment
- Inspect frequently - electrical systems to insure path to ground is continuous
- Inspect before use - electrical systems and equipment
- Don’t remove Ground prongs - from tools or extension cords
What are the reasons that circuits get overloaded?
a. Too many devices plugged in
b. Using Damaged tools
c. No Over-current protection
d. Melting Wire insulation
11.How does a GFCI work?
- GFCI monitors - the amount of current flowing from “hot” to “neutral”.
- GFCI trips the circuit - If it detects an imbalance as small as 5 milliamps,… and it can react as quickly as 1/30 th of a second.
- GFCI rendered useless - Never snip off the “ground” prong on a plug; that will negate the safety feature a GFCI provides
When should an Assured grounding system be tested?
(1) before 1st use,
(2) at least every 3 mo.,
(3) after service, &
(4) after possible damage.
Working Spaces
- Cannot be used for Storage
- Must have Access and “Elbow Room” - Sufficient access and working space must be provided and maintained around all electrical equipment.
- Work-Space Clearances - Minimum working clearances per Table K-1. 3 ft2 – In front of the elec. Equip. (in the direction of access to the live parts).
- Lockout/Tag out of Circuits
- Apply locks to power source after de-energizing
- Tag (de-activated) controls
- Tag (de-energized) equipment and circuits at all points where they can be energized
- Tags must identify equipment or circuits being worked on
. Protect employees from electrical shock:
- Use barriers/guards –
- Pre-plan work - post warnings & use protective measures
- Keep work areas clear - of cords, debris, trip hazards
- Cord Safety
- Plan your work with others
- Plan to lock-out/tag-out equipment
- Remove jewelry
- Avoid wet conditions
- Avoid overhead power lines
Train employees - to use safe practices including
- De-energize before starting to work
- Use only cords, tools, etc that are in good repair
- Lockout/Tag out procedures
- Use PPE Proper Protective Equipment
