BCN3521 - Exam 1
Arc-Blasts occur when
Tremendous temperatures of the arc cause explosive expansion of both the surrounding air and the metal in the path of the arc
Equipment that is loaded _______ will produce more heat, and the electric material used for these loads must be designed to handle the higher heat loads
continuously
Electrical loads that run ______ will heat up a piece of electrical equipment, but when the load drops allows for the temp to drop
interminttently
Lighting load is found by
largest of either the NEC or Connected Load
In a building, continuous loads tend to be ______
lights
Single or Duplex receptacle has a load of no less than ___ VA per receptacle
180
a continuous load is defined an something that operates at its full capacity for ______ or more continuously
3 hours
_________ nonfatal electrical shocks accidents occur each year
300,000
Arc-Flashes can reach a temp of
35,000 F
If the device contains more than two receptacles, then use ____ VA/receptacle
90
Differences in plugs and receptacles are based on
Ampacity and voltage rating
The rate of electricoty flow is measured in
Amperes (amps)
Majority of hospital admissions are due do? (Shocks, Arc-Flashes)
Arc Flashes
Equipment grounding conductor color coding
Never use insulated conductor that is green or green with yellow stripes for a hot phase conductor
______ are installed to reduce the use of energy and are considered a "green" control
Occupancy Sensors
_____ is a cover placed on a surface mounted box
Raised Cover
____ converts electricity to heat
Resistance
_____ materials are required to install an electrical rough-in
Tabulate
Typical color coding for cable wiring
When wiring with cable (NMC, AC, or MC), choice of colors is limited to those that are furnished with the cable
Tips for Exam
-Be able to read working drawings -Drawings will be on Steinbrenner Hall -Be able to calculate load
Tips for reading electrical working drawings
-Be certain that there is clear understanding of how the system is to be installed -Take special note of long runs of raceway and determine whether voltage drop is a problem
Ungrounded conductor color coding
-Must have outer finish that is other than green, white, gray, or three continuous white stripes -Popular colors are black, white, red, blue, green, yellow, brown, orange, and gray -Conductors 1 AWG and larger are generally available in black only
Switches are divided into two categories
-NEC® 404.14(A) covers ac general-use -NEC® 404.14(B) covers ac-dc general-use
Color coding when there are two electrical systems in one building
-Use white as grounded conductor for one system and gray as grounded conductor for the other system
Most important numbers on nameplate that gives electrical requirements of motors is
-Voltage -Horsepower -Full Load Current
Conductor insulation colors for connecting switches
-When wiring method is conduit or tubing, many colors available -When wiring method is cable, only black, white, and red colors available -Insulation color coding is well established for phase conductors, switch returns, and travelers of electrical systems
______ fatalities each year due to electrocution, more than half of them while servicing energized systems of less than 600 volts
1,000
Outlined in NEC Article 424 for receptacles in electric baseboard heaters
- the requirement for fixed electric space heating equipment -Receptacle may be counted as one of the required outlets for wall space utilized by the heater -Receptacle shall not be connected to heater's branch circuit
Resistance of wet human skin
1,000 Ohms
Arc-Flashes can and do kill a distances of
10 ft
Resistance of dry human skin
100,000 Ohms
GFCI protection is required for all
125-volt, single-phase, 15- and 20-ampere receptacles installed in bathrooms, in kitchens, on rooftops, outdoors, and within 6 ft (1.8 m) of any sink
Used to protect against the possibility of electric shock
15- and 20-ampere branch circuits can be protected with GFCI receptacles or GFCI circuit breakers
NEMA terminal identification for receptacles (What is the brass label for?)
Connect HOT conductor to this terminal (black, red, blue, etc). There is no NEMA standard for a specific color conductor. It is good practice to pick a color code and stick with it
NEMA terminal identification for receptacles (What is the white/silver label for?)
Connect white or gray grounded circuit ONLY to this terminal
Load of what is actually connected, calculated by number of fixtures and connected load for each
Connected load
Ohm's Law is
Current = Voltage/Resistance
NEMA terminal identification for receptacles (What is the green label for?)
Has hexagon shape. Connect equipment grounding conductor ONLY to this terminal
In a building, HVAC is typically a ____ load
Intermittent
Type of receptacle used to (an insulated grounding conductor is run from neutral terminal at the main service entrance to the isolated ground terminal on the receptacle)
Isolated ground receptacle
The allowable load specified by per (floor, equipment, etc) for lighting
NEC load
Resistance of punctured human skin
500 Ohms
Location not normally subject to dampness
Dry
What NEC code lists different items that are considered acceptable equipment grounding conductors
NEC® 250.118
Grounded conductor color coding
NEC® requires that grounded (identified) conductor have an outer finish of either continuous white or gray color, or have outer finish that has three continuous white stripes
Typical color coding for conduit wiring
-Color coding is not code mandated -Be sure not to use white, gray, green, and bare conductors other than for their permitted uses -CAUTION: In old installations, conductor having gray insulation was sometimes used as ungrounded "hot" conductor
4 safety procedures
-De-energize circuits before working -Lock out/ Tag out -Justify working on live circuits -Provide proper PPE
How to ground snap switches
-Metal box is considered adequately grounded provided the metal raceway, Type AC or Type MC, is properly grounded at its origin -Metal yoke of snap switch is considered grounded when secured by metal screws -Metal faceplate is considered grounded when secured to metal yoke of snap switch
When electric current passes thru air between conductors
Arc-Flash
locations protected from weather and not subject to saturation with water or other liquids but subject to moderate degrees of moisture
Damp
Load used by appliances and other equipment that connects to the general purpose receptacles in a building
Duplex
Type of receptacle used to reduce "noise," circuits with receptacle outlets that serve loads such as computers or other sensitive electronic equipment should be supplied by isolated ground receptacles
Electronic equipment receptacle
_____ is a cover placed on a recessed box
Faceplate
_____ leading cause of industrial fatalities, after traffic, homicide, and construction accidents
Fourth
_____ developed standards for receptacles
NEMA, National Electrical Manufacturers Association
Disturbances that call for grounding of electrical equipment
Voltage sags, spikes, and surges Static charges Lightning strikes and surges on the system Electromagnetic interference (EMI) Radio frequency interference (RFI) Improper grounding
installations underground or in concrete slabs or masonry in direct contact with the earth; in locations subject to saturation with water or other liquids, such as vehicle washing areas; and in unprotected locations exposed to weather
Wet
an electric water heater with a capacity of 120 gallons or less is considered a _____ load
continuous