Chapter 3.5, 3.6, 3.7, 3.8 Flashcards
From System and Circuit Grounding to Cable, Raceway, and Enclosure
3.5 Title
System and Circuit Grounding
___________ offers excess electricity the most effective and safest route from an appliance back to the ground by way of an _________________.
Grounding, electrical panel
____________________ is a backup pathway that is generally only used if a fault in the wiring system.
Electrical grounding
It is a continuous conductor that connects the ground to the neutral bus bar and the grounding conducting bus bar in the service equipment/ main panelboard.
Grounding Conductor
It safely carry current to ground in the event of a lightning strike or in cases of damage or defect in the circuiting, appliances, devices, or equipment. It also provide safety feature to the wiring system.
Grounding Conductor
Is the part of a building electrical system that provides protection against electrical shock, lightning, and fires.
System Grounding
It also relates to bonding (connecting) all building electrical system components at the service entrance equipment at the neutral bus of the main panelboard or switchboard.
System Grounding
It refers to a grounding conductor or grounding path that connects the non-current carrying metal components of equipment.
Equipment Grounding
Both Equipment and System grounding must be bonded. It accomplished by installing an additional grounding conductor or by permanently joining metal components in a circuit.
Bonding
The ________________ is a bare conductor or a green- colored, insulated conductor that connects (bonds) the outlet boxes, metallic raceways, other enclosures and frames on motors, appliances, and other electrical equipment
equipment- grounding conductor
_____________ of an appliance or power tool protects the user from electric shock by creating a nonconducting barrier between the user and the electric components inside the appliance or tool.
Double insulation
____________ and ______________ with double insulation are not required to have a ___________- that is, they are allowed to have a two prong plug.
Small appliance, power tools,grounding conductor,
The primary difference between an appliance with a three prong plug and an appliance with a two prong plug is the _________________.
appliance casing
If an ____________ is a good conductor, then it must have a ______________ and ____________.
appliance casing, grounding conductor, three- prong plug
3.6 Title
The Building Electrical System
There are many possible ___________ that can be used to distribute _______ in a building.
electrical systems, power
Typically, __________ begins with selection of a building system ______, which is dependent on _______ and ____ of the connected loads, utilities near the building, local codes and ordinances, economics, and safety.
system design, voltage, sizes, types
- means a ground- mounted or roof top distributed solar generation system designed and installed for residential applications, which is leased by, or subject to a power purchase agreement with, the owner of a residence for the purpose of generating Electricity for that residence.
Residential Systems
- is a single building that is set up to accommodate more than one family living separately. That can range from a duplex, which has two dwellings within a single building, to homes or small apartment building with up to four units.
Multifamily dwelling
Multifamily dwelling units, _____ is brought from a ____________ to the ______________. It is then divided at a _____________, passes through ___________, and is distributed to the individual dwelling units through _________.
power, utility transformer, building service equipment, main distribution panel, individual meters, feeders
Each __________ is served by a separate ________ located in the dwelling unit. _____________ extend from a panelboard to feed outlets within the unit. A ____________ has branch circuits that serve common areas.
dwelling unit, panelboard, Branch circuits, house panelboard
Large commercial and industrial facilities have large and varied power requirements that necessitate different types of systems for different building occupancies.
T
Essentially, there are so many variations that there is no standard type of system. In a typical large building, electrical power is provided to a ___________ located outside the building or it enters a ___________ located at the service level in the building.
transformer, transformer vault
- lines serving a residential development being buried in a trench.
Underground Electrical Distribution
-lines readied for connection to exterior transformer.
Underground Distribution Lines
A 120/240 V- 150A, underground service entrance for a single family residence.
Electric Meter
Underground service entrance for a multifamily dwelling unit.
Electrical Meter for Multifamily dwelling unit
A ____________ with the electrical meter and main disconnect (below meter and above circuit breakers). ____________ are properly marked on the panelboard face.
Electric Meter and Main Disconnect/ service entrance, Circuit breakers
A close-up view of the inside of the panelboard.
Panelboard
________________ can pass through floor and ceiling joists.
Circuit cables
exposed lighting fixture
Exposed lighting
A ____________ in finished drywall
Exposed box
Unattached receptacle and faceplate
Receptacle and Faceplate
Covered convenience receptacle
Outlet
3.7 title
Conductor Requirements
__________ and ___________ are the most common conductor materials used in building electrical wiring, although other materials can be used.
Copper and aluminum
As a general rule, ____________ conductors are used in small conductor sizes (up to about 8 AWG) because safety issues associated with aluminum are avoided and weight and cost are not significantly affected.
solid copper
______________ conductors are widely used on larger (above 30 A) circuits serving large motors, equipment, and appliances
Stranded aluminum
Electronic circuits and phone extensions
No. 20 AWG and smaller
Light gauge extension cords, door chime wiring, small appliance cords
No. 16 to 18 AWG
Normal 15 A and 20 A branch circuits serving small appliances, convenience (receptacle) outlets, and luminaires
No.12 to 14 AWG
Larger branch circuits at 30A and above serving electrical appliances such as electric water heaters, clothes dryers, air conditioning equipment, and water pumps
No. 4 to 10 AWG
Residential and light commercial service entrance conductors and feeders to panelboards.
No. 2 to 4/0 AWG
Heavy commercial and industrial service entrance conductors, large feeders to closet transformers, and panelboards
250 kcmil and larger
__________ are covered with insulation to provide electrical isolation and physical protection of the conductor material.
Conductors
The _________ of insulation material determines the environment in which a wire or cable can be used safely.
type
__________ like ______ and ______ are used as a covering for electric wires.
Insulators, plastic, rubber
This makes electric wires safer to handle because the insulator protects you from the current
Insulators/ Conductor insulation
In building electrical systems, the ___________ of a conductor may need to be adjusted with correction factors when conditions related to the temperature of the surroundings and the number of conductors in a raceway fall outside normal operating ranges.
ampacity
_______________ typically applied are addressed in the following sections.
Correction factors
Ampacities provided in these tables are values based on a normal operating temperature of ____________________.
86 degrees F (30 degrees C)
___________ values for each conductor size are for different equipment terminal (where connections of wiring are made) temperatures.
Ampacity
______ generated at the equipment terminals can damage the conductors if it is not properly dissipated.
Heat
_____________ is the temperature of a surrounding medium.
Ambient temperature
In the case of electrical wiring, it is the _________ of the medium surrounding.
temperature
As ______________ rises, __________ generated heat is needed to reach the temperature rating of the insulation. Therefore, _________ is governed by contribution of ambient heat.
ambient temperature, less current, ampacity
The ________________ of a conductor refers to the normal temperature range in the environment in which that conductor is to be used (eg. the temperature of the surrounding air, water, or earth).
ambient temperature rating
_____________ is adjusted for changes in ambient temperature, including temperatures below 78 degrees F (26 degrees C) and above 86 degrees F (30 degrees C_
Conductor ampacity
A _______________________ for conductors is applied based on the ambient temperature of the conductor.
temperature correction factor
When several current carrying conductors are contained in a raceway or cable, the temperature of the conductors will increase under normal loading conditions.
T
A ___________________ must be applied for four or more conductors in a raceway or cable installed in the same raceway or conduit or any bundled cables that are more than 24 in (0.63m) long.
bundling correction factor
In addition to ampacity requirements, ________ and _______ should be analyzed for voltage drop because of the adverse effect it can have on performance and operating life of appliances and equipment.
branch circuits and feeders
______________ in the feeders and branch circuits should nit exceed ____.
Total voltage drop, 5%
The ___________________ is determined by the ration of voltage drop and system voltage.
percentage of voltage drop
The insulation on small and medium size conductors is __________or identification.
color coded
________________ requiring color identification are marked at the terminal ends with a hand-painted stripe or colored tape wrapped around the conductor insulation.
Larger conductors
The _________________ must be color coded green, green with one or more yellow stripes, or may be a bare conductor on small conductors in cables.
grounding (ground) conductor
3.8 title
Cable, raceway, and enclosure requirements
CABLE AND RACEWAY REQ
All building _______ must be enclosed in a cable, conduit, wireway, or raceway.
wiring
CABLE AND RACEWAY REQ
During installation:
________ are snaked through conduit or tubing, are laid in a wireway, or are contained in cables, and
secured to structural framing.
conductors
CABLE AND RACEWAY REQ
______ must be exercised in placing conductors, as conductors and insulation can be easily damaged.
Care
CABLE AND RACEWAY REQ
Example: if a conductor is pulled through a tight conduit, it can stretch. ( ___________ caused by stretching reduces the ______________ of the wire, thereby reducing its _________. This creates an unsafe condition because the conductor can overheat.
Deformation, cross- sectional area, ampacity
CABLE AND RACEWAY REQ
_________ that are run through a raceway must have sufficient open air space to prevent overheating.
Conductors
CABLE AND RACEWAY REQ
The number of current carrying conductors that can run through a raceway is limited by ______.
code
CABLE AND RACEWAY REQ
A ___________ conductor found in a raceway is any ungrounded conductor or grounded conductor.
current carrying
CABLE AND RACEWAY REQ
_____________ (bare or green colored) and _________________ are not current carrying and are not counted.
Equipment grounding, shared neutral conductors
CABLE AND RACEWAY REQ
- rigid metal and nonmetallic conduit
- IMC
- EMT
- ENT
Rigid conduit and tubing
CABLE AND RACEWAY REQ
are favorite raceway materials used to protect conductors in all types of building.
Rigid conduit and tubing
CABLE AND RACEWAY REQ
it is available in straight lengths, therefore, must be bent to accommodate changes in direction.
- bends must be made no smaller than the minimum radius specified by code, about _______ times the conduit diameter.
- conduit and tubing can have up to four _________ bends or the equivalent 360 degrees total in one run.
- In runs requiring more bends, a _________ is added in the run to assist in pulling conductors and to allow access.
- _______ can be made at the factory or at the job site for small to medium conduits.
Rigid conduit and tubing, 6 to 8, 90 degrees, pull box, bends
CABLE AND RACEWAY REQ
- flexible metal conduit
- liquid tight flexible metal
- nonmetallic conduit
Flexible conduit
CABLE AND RACEWAY REQ
- offers the advantage of easier installation and can be salvaged easily when circuits are rearranged.
Flexible conduit
CABLE AND RACEWAY REQ
It is used where mechanical protection is needed and easy relocation of equipment is desired
Flexible conduit
CABLE AND RACEWAY REQ
It can have up to four 90 degrees bends or the equivalent 360 degrees total in one run.
Flexible conduit
CABLE AND RACEWAY REQ
__________ should be supported to prevent wearing away against structure and to avoid stressing its end fittings.
Conduit
CABLE AND RACEWAY REQ
_______________________ must be supported within 3ft of a box or other connection and at intervals of 10 ft (about 3m)
Rigid conduit and tubing
CABLE AND RACEWAY REQ
Continuous, ___________ can be used as the grounding conductor.
metal conduit
CABLE AND RACEWAY REQ
__________ must be supported every 4 to 6 in (1.35m and within 12 in (300mm/0 of a box, except up to 36 in (about 1m is allowed at usage points where flexibility is required (e.g.. a pump motor or air conditioner condensing unit) and 6ft ( about 2m) between a recessed light fixture and a box.
Flexible conduit
CABLE AND RACEWAY REQ
_______ and _________ can be used as
grounding conductor if it is continuous and properly bonded.
IMC and EMT
CABLE AND RACEWAY REQ
It is required for flexible conduit
Grounding conductor
CABLE AND RACEWAY REQ
It can be bare or insulated.
Grounding conductor
CABLE AND RACEWAY REQ
Cannot be use as the grounding conductor.
Rigid nonmetallic conduit and tubing (ENT)
CABLE AND RACEWAY REQ
Manufactured from thermoplastics that have very high rates of thermal expansion (over 6 in for a 100 degrees F temperature change per 100 ft/over 300mm in a 50 degree C temperature change per 30 m.
- provisions must be made if it is exposed to significant temperature changes.
Rigid nonmetallic conduit and tubing
CABLE AND RACEWAY REQ
Permitted in sing and multifamily dwelling units and some other buildings.
Nonmetallic sheathed cable (NM and NMC)
CABLE AND RACEWAY REQ
Restriction of use in
- underground
-buildings that are more than three stories above grade or in commercial garages
- Motion picture studious
- Theaters
-Places of assembly
-Elevator hoist ways
- Other corrosive or hazardous locations
Nonmetallic sheathed cable (NM and NMC)
CABLE AND RACEWAY REQ
______ and _______ must be supported every 4-6 (1.35m) and within 12 in (300mm) of a box.
NM and NMC
CABLE AND RACEWAY REQ
- is for use in dry, indoor applications
Armored cable
CABLE AND RACEWAY REQ
Restriction of use in
- commercial garages
-motion picture studious
-Theaters
- Places of assembly
- Elevator hoist ways
- Other corrosive or hazardous locations
Armored cable
CABLE AND RACEWAY REQ
Bends are limited to no less that five times the diameter
Armored cable
BOX/ ENCLOSURE REQ
All electrical connections must be made in a protective enclosure such as panelboard, junction, or device box, fixture, or appliance.
T
BOX/ ENCLOSURE REQ
Every switch, outlet, and connection must be contained in an electrical box and every lighting fixture must be mounted in a box.
T
BOX/ ENCLOSURE REQ
All wirings must begin or terminate at a panelboard or in a box that is housing switch, luminaire connection, receptacle, conductor junction or similar terminal fitting.
T
BOX/ ENCLOSURE REQ
Junction boxes must be mounted so that the black cober plate is visible and readily accessible.
T
BOX/ ENCLOSURE REQ
All electrical boxes must be made adequately secure to the t=building structure.
T
BOX/ ENCLOSURE REQ
Any box can be used for any purpose
Jojowain
BOX/ ENCLOSURE REQ
There are no requirements that specify that a certain type of electrical box be installed for a specific purpose
T
BOX/ ENCLOSURE REQ
_______ and ______ boxes for lighting outlets
- Normally installed overhead for lightning installation
T
BOX/ ENCLOSURE REQ
_________ and _______ boxes for switches and receptacle outlets.
Rectangular and square
BOX/ ENCLOSURE REQ
The size and number of conductors to be installed in a box influences selection if type of box and box size
T
BOX/ ENCLOSURE REQ
The more conductors and/ or the conductor size, the bigger the box must be.
T
BOX/ ENCLOSURE REQ
The capacity if a box, in cubic inches, is determined by its length, width, and depth.
T
BOX/ ENCLOSURE REQ
An increase in one or more of these dimensions increases box capacity.
- Some boxes are designed so they can be ganged together to increase box capacity
T
BOX/ ENCLOSURE REQ
By convention, a conductor that runs through the box us counted as one conductor and each conductor that terminates in the box counts as one.
T
BOX/ ENCLOSURE REQ
The size and number of conductors to be installed in a box influences selection of type of box and box size.
T
BOX/ ENCLOSURE REQ
Fixture wires and conductors that do not leave the box, such as an internal grounding wire, are counted.
F (not counted)
BOX/ ENCLOSURE REQ
One conductor is deducted for one or more grounding conductors that enter the box.
T
BOX/ ENCLOSURE REQ
Conductors in an electrical box must have sufficient open air space to prevent overheating.
T
