Electrical Systems Flashcards
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Ampacity
the maximum current that a conductor or device may carry continuously without exceeding its temperature rating
AMPERES(AMPS)=current
Ohm’s Law symbol = I
AWG
the abbreviation for American Wire Gauge, a system for identifying the diameter of electrical wires; larger numbers identify smaller diameter wires; #14 (pronounced number 14 or 14 gauge) is the smallest wire used in house wiring, and 4/0 (pronounced four-oh) is usually the largest.
Bonding
the process of connecting, both physically and electrically, metal components of the electrical system that are not intended to carry electrical current to provide a low resistance return path to the circuit breaker or fuse to clear ground faults; bonding is an electrical safety system.
Branch circuit
Conductors that begin at a circuit breaker or fuse and serve one or more outlets.
Branch circuit, multiwire
a branch circuit in which two energized conductors share one neutral conductor; examples can include clothes dryers, ranges and other cooking appliances, and split-wire receptacle circuits; 240 volt water heaters and condensers for air conditioners and heat pumps are not usually multiwire branch circuits
Bus (buss, busbar)
The heavy, rigid metal part of a panelboard on which circuit breakers or fuses are mounted; sometimes used to describe metal terminals to which the neutral(Grounded Conductor) and Equipment Grounding Conductors(EGC) are connected.
Cable
two or more conductors encased in sheathing; examples include non-metallic sheathed cable (often referred to by the brand name Romex) and armored cable (often referred to by the brand name BX)
Circuit breaker
A fuse or a circuit breaker; Overcurrent Protection Devices(OPD) interrupt the flow of electricity when a set current flow is exceeded (an overload), or when a short circuit fault is detected; these devices prevent conductors and devices from overheating and causing fires
Conductor
a material, such as copper or aluminum, that permits electricity to flow with low resistance; wires are conductors
Current
The amount of electricity in a circuit; (similar to water gallons per minute; water flow in a pipe); unit of measure is the Ampere (Amp); expressed as I in Ohm’s Law and Watt’s Law equation
Dead front cover
a panel that is removed to gain access to the energized components inside an enclosure; the dead front cover is usually behind a door that must be swung or lifted to gain access to the dead front cover
EGC
Equipment Grounding Conductor
A bare or green insulated conductor that provides a ground fault current path (a bonding connection) for equipment with metal cases and parts; these have been installed in most house branch circuit wiring since around 1960
Enclosure (electrical)
a case or cabinet intended to prevent accidental contact with energized parts; a panelboard is housed inside an enclosure
Feeder conductors
Conductors from the service equipment, or from a panelboard that supply electricity to another panelboard - such as a subpanel.
Fuse
A fuse or a circuit breaker; Overcurrent Protection Devices(OPD) interrupt the flow of electricity when a set current flow is exceeded (an overload), or when a short circuit fault is detected; these devices prevent conductors and devices from overheating and causing fires.
Grounded
A conductor that is intentionally connected to the earth; this describes what is often called the neutral conductor.
Grounding
Providing an intentional connection to the earth; grounding provides an alternate path for current to return to its source; in an electrical power system, the source is the utility’s transformer and ultimately the power plant.
Equipment Grounding Conductor
A bare or green insulated conductor that provides a ground fault current path (a bonding connection) for equipment with metal cases and parts. These have been installed in most house branch circuit wiring since around 1960.
Grounding electrode
metal that is in direct contact with the earth and serves as the electrical system grounding connection; examples include copper-coated steel rods, galvanized steel pipes, water service and well pipes, and reinforcing steel encased in the footings.
Grounding Electrode Conductor (GEC)
A conductor that runs between the grounding electrode and an accessible point downstream from where the grounded service entrance conductor connects to the service drop or lateral; the GEC connection is usually at the service equipment.
Ground fault
An event that occurs when metal that should not conduct electricity (such as a metal water pipe) becomes energized; if the metal is properly bonded, current flow should increase in the circuit and trip the circuit breaker or fuse.
Ground fault circuit interrupter (GFCI)
A circuit breaker or receptacle that detects a Ground Fault by monitoring the imbalance in Current flow between the energized(Ungrounded Conductor), and neutral conductors(Grounded Conductor) and stops Current flow (opens the circuit) when a Ground Fault is detected.
Joules Law
A formula for calculating heat in an electrical circuit expressed as Heat = Current2 X Resistance X Time.
P=I²R
Knockouts
stamped openings in an enclosure where conduit or cable clamps are installed to secure conductors or cables. See Tabs (twistouts).
Load Center
Panel (panelboard, load center): the equipment on which circuit breakers or fuses are mounted; panels include associated terminal bars; a panelboard is contained in an Enclosure; the first and usually the largest panel is often referred to as the main panel or the service panel; however, there are no generally accepted terms to identify panels
Lug
A connection point where conductors are inserted and secured; examples include the connection points on panelboards for service entrance and feeder conductors, on terminal bars for neutral(Grounded Conductors) and EGCs(Equipment Grounding Conductor), and on circuit breakers(Overcurrent Protection Device[OPD], Fuse) for branch circuit conductors.
Ohm’s Law and Watt’s Law
Expressions of the relationship between current, volt-age, power, and resistance; expressed as Power = Volts X Amps and Resistance = Volts/ Amps
Ohms - V=IR
Watts - P=IV
Outlet
a place where current is taken for use; examples include receptacles, light fixtures, and connections at electric appliances such as water heaters.
Overcurrent Protection Device (OPD)
a fuse or a circuit breaker; overcurrent protection devices interrupt the flow of electricity when a set current flow is exceeded (an overload), or when a short circuit fault is detected; these devices prevent conductors and devices from overheating and causing fires
Panel (panelboard, load center)
the equipment on which circuit breakers or fuses are mounted; panels include associated terminal bars; a panelboard is contained in an enclosure; the first and usually the largest panel is often referred to as the main panel or the service panel; however, there are no generally accepted terms to identify panels
Power
A measure of the work performed by electricity; unit of measure is the Watt
The rate at which energy is absorbed or produced within a circuit
Raceway
enclosed metallic or nonmetallic components designed and listed for holding conductors or cables between points in the electricity distribution system of the house; examples include various types of conduit and tubing
Receptacle
an outlet designed to accept a plug that supplies electricity to an appliance
Resistance
The property of a material to allow or restrict the flow of electricity; materials with low resistance are conductors and materials with high resistance are insulators; unit of measure is the Ohm.
R in ohms law
Service drop and service lateral:
Service drop and service lateral: the conductors between the transformer belonging to the utility and the house; a service drop is above-ground and a service lateral is below ground
Service entrance conductors:
the conductors between the service drop or service lateral and the service equipment.
Service equipment
the circuit breakers, switches, or fuses that shut off electricity to the house; all electricity should be shut off using six or fewer circuit breakers, switches, or fuses; often called the main shutoff or main disconnect
Service point
the place where the service drop or service lateral conductors end and the house service entrance conductors begin; this is usually at the drip loops for service drops; the service point for service laterals is more difficult to distinguish, but is often at the meter
Single phase electrical service
electrical service consisting of two energized 120 volt conductors and one grounded conductor; this is by far the most common residential electrical service
Short circuit
this event occurs when current flows between conductors in an unintended manner, such as between the hot and neutral conductors
Subpanel
a panelboard that receives power from an upstream panelboard, usually the main panelboard; also called a downstream or a distribution panel; however, there are no generally accepted terms to identify panels
Tabs (Twistouts (Knockouts)
rectangular metal pieces on the dead front cover that are removed before installing a circuit breaker; a tab must be replaced by a filler plate if a tab has been removed and no circuit breaker is installed. See Knockouts
Terminal bars
metal bars associated with a panelboard on which neutral and equipment grounding conductors (EGCs) are mounted; called a neutral bar when neutral conductors or neutral and EGCs are connected; called a ground bar if only EGCs are connected
Three phase electrical service
electrical service consisting of three energized conductors and one grounded conductor; this service type is mostly for commercial and industrial buildings
Voltage
the pressure of electricity in a circuit, similar to water pressure in a pipe; unit of measure is the Volt
Ohm’s Law = V
Wiring Methods
cables and raceways approved for distributing electricity from the service point to panelboards and outlets; examples include armored cable, nonmetallic sheathed cable, and various types of conduit and tubing
Updating Electrical System to Current Standards (2 Rules)
- existing work does not need to be updated if it complied with rules in effect when installed, and if the system or component is functioning safely.
- new work and existing work that is modified or extended should comply with rules in effect when the work is done.`
Bonding occurs when (1, 2, 3)
- metal that could carry electricity (but is not supposed to),
- is intentionally connected together to provide a permanent low resistance return path,
- that is capable of conducting all electricity accidentally carried by the metal back to its source.
Ohm’s Law
I(current in amps) = E(voltage in volts) / R(resistance in ohms).
V=IR
2 Reasons for minimal impact on clearing ground faults (myths)
- electricity wants to return to ground
2. electricity takes the path of least resistance back to its source. It really takes all available paths
2 Ways to think about Grounding
- The grounding system of the house acts like a voltage surge suppressor that helps safely shunt voltage surges to ground.
- Bonding is a safety system that helps clear ground faults in normally non-current carrying materials.
EGCs are really bonding wires (Explain their function)
Their function is to provide a low resistance return path for components like metal switch plates and metal equipment cabinets that may become energized.
Grounding electrode system consists of:
- Grounding Electrode
2. Grounding Electrode Condcutor (GEC)
GEC should be at least
4 AWG copper wire is required for ufer grounding electrodes with 200 amp and greater service.
Best way to remember Bonding requirments
if it is metal and it is or could be near electrical wires, then it probably needs to be bonded to the grounded wire of the utility
Minimum voltage
Almost all utility-supplied residential electrical service is 240 volt single phase
single phase 120 volt service to a house is usually considered a reportable deficiency
Minimum Current
The minimum electrical service current for a modern single-family house is 100 amps.
Determining Service Amperage
if the service entrance wires are 2/0 copper (rated for 200 amps), but the service equipment and panelboard are rated for 150 amps, then the service to the house is 150 amps
Required and Dedicated Branch Circuits
two-20 amp, 120 volt branch circuits that serve only kitchen countertop receptacles and receptacles in the breakfast and dining rooms; one of these circuits may serve the refrigerator,
•120 or 240 volt branch circuits that serve only one furnace or air handler,
•a 20 amp, 120 volt branch circuit that serves only receptacles in the laundry room,
•one-20 amp, 120 volt branch circuit to serve only receptacles in bathrooms (exception: one 20 amp, 120 volt branch circuit for each bathroom may serve both lights and receptacles in the bathroom
What 2 types of kitchen appliances should be on a dedicated circuit
- Kitchen exhaust fan
2. Microwave Oven
Service Drop Clearance Above the Roof Minimum Distance
a slope less than 4/12 is 8 feet
a slope 4/12 or greater is 3 feet.
Service Drop clearance to Building Openings Minimum Distance:
lowest individual service drop or service entrance conductor and the side or sill of an operable window, door, deck, balcony, or similar point is 3 feet
OPDs and wires generate heat, especially ______ and ______.
AFCIs
GFCIs
Location, Access and Working Clearances of Service Equipment
The service equipment, panelboards, and equipment disconnect devices, such as for furnaces and condensers, should be located where access is safe, and should be provided with a safe space around them for inspection and repair.
in front = 36 deep x 30 wide x 78 tall
cabinet door should swing 90 degrees
not higher than 79 inches above adjacent waking surface
Service Equipment Working clearance minimum space and accessibility.
36 inches deep, 30 inches wide, and 78 inches tall, measured from the floor.
Equipment should be readily accessible, including a key if locked.
Typical Defects, Electical Service
- service drop conductors in and around tree limbs,
- damaged service drop and service entrance conductor insulation,
3 .no insulation at service drop connection to service entrance conductors, - drip loops inadequate to drain water,
- loose, bent, or damaged service mast or service head
- absent, deteriorated, damaged, improperly installed service mast flashing,
7 .loose or damaged service drop connection at house, - inadequate clearances between service drop and service entrance conductors and roofs, ground, and building openings,
- loose, damaged, deteriorated meter bases and electrical enclosures,
- meter bases and electrical enclosures not sealed where attached to wall coverings, this is a water infiltration point,
- loose or damaged conduit at or around enclosures,
- service equipment and panelboard upgraded to larger capacity, but service drop and service entrance conductors not changed.
Typical Defects, Grounding and Bonding
- damaged, disconnected, loose GEC at grounding electrode connection,
- GEC too small for service (minimum #8 copper for under 150 amp service and #4 or #6 copper for 150 amp or larger service),
3 .absent, loose grounding or bonding clamp, - grounding or bonding clamp connected to surfaces that are corroded, painted, dirty, or are covered by other high-resistance contaminants,
- GEC improperly spliced; GEC may be spliced using a listed compression connector or by welding (not soldering),
- metallic conduit connected with plastic fittings (electrical connection disrupted),
- underground water pipe GEC connection located more than 5 feet from where water pipe enters the house (do not confuse this with the water distribution pipe bonding connection),
- absent, loose, broken metal conduit connections (bonding path interrupted by absent or poor physical or electrical connection),
- absent, loose, corroded metal water pipe bonding connection,
- bonding jumper absent around water meter, water pressure regulator, water softeners and filters, and similar removable non-metallic components in metal water distribution pipes,
- improper bonding connection installed for phone, cable, or similar services,
- CSST gas tubing not bonded at first metal gas pipe or fitting after gas meter.