Chapter 4 EO test
The NEC in Table 210.24 shows that the minimum conductor size for branch-circuit wiring is ____.
14 AWG
Nonmetallic-sheathed cable is manufactured with copper conductors ranging in size from ____________________ AWG to ____________________ AWG and with aluminum or copper-clad aluminum conductors ranging in size from ____________________ AWG to ____________________ AWG.
14, 2 12, 2
When fire stopping material is used where more than ____________________ nonmetallic sheathed-cables pass through wood framing members, their ampacities must be adjusted, according to 310.15(B)(3)(a).
2
Although old fashioned knob-and-tube wiring is no longer used for new construction, NEC Article ____________________ applies when this wiring method is encountered during remodeling work.
394
The total rating of utilization equipment fastened in place, other than luminaires, is not permitted to exceed ____ of the branch-circuit rating if the branch circuit also supplies lighting, other cord-and-plug-connected equipment, or both types of loads.
50%
Lengths of flexible metal conduit longer than ____________________ feet are not acceptable as an equipment grounding conductor. In such cases a separate bonding jumper is required to run outside of the flexible conduit to maintain the continuity of the grounding path.
6
The ampacity of the conductors in nonmetallic-sheathed cable is based on that of ____ conductors.
60°C (140°F)
3. A dual-rated conductor marked THHN/THWN is rated ____ when used in dry locations.
90°C (194°F)
Connectors marked ____ are suitable for use with aluminum, copper, or copper-clad conductors.
AL/CU only
Article 210 applies to branch circuits, but branch-circuit calculations are covered in ____.
Article 220
Match the following conductor insulations with their temperature rating. a. 60°C b. 75°C c. 90°C Type THWN Type THHN Type TW
B C A
In which location(s) is Type NM cable NOT allowed to be run?
Both damp and moist locations and when conealed in dry locations
Liquidtight flexible nonmetallic conduit is subject to which of the following limitations?
Both of these choices are limitations
What is the difference between Type NM-B and Type NMC-B cable?
NM-B has a flame-retardant, moisture-resistant outer jacket. NMC-B has a flame-retardant, moisture-, fungus-, and corrosion-resistant outer jacket.
The NEC requires that conductors 8 AWG and larger must be ____ when installed in a raceway.
Stranded
Type ____ is the most common building wire used today.
THHN/THWN
Explain what must be done when cables are bundled together for more than 24 inches.
The heat generated by the bundled conductors cannot easily dissipate; therefore, they must be derated.
If the 1-1/4 in. (32 mm) distance from the edge of the hole to the edge of the framing member cannot be maintained, what thickness of steel plate must be used to protect the cable?
The steel plate must be at least 1/16 in. thick, or 1.6 mm thick.
Explain what flexible metallic and nonmetallic conduits are typically used for in residential construction.
These are used for connections to motorized appliances, such as food waste disposers, washers, and dryers, that may be subject to vibration.
Low voltage (high voltage drop) in a home can be caused by ____.
all of these
Type AC cable is manufactured with ____ conductors.
all these types of
Under certain circumstances, the grounded (neutral) conductors of a residential service ____ permitted to be sized smaller than the phase conductors.
are
Although the National Electrical Code contains requirements for making holes and notches in framing members, in order to protect the cables installed in them, electricians must also be aware that ____________________ also have requirements for holes and notches in framing members, in order not to weaken the structure of the building.
building codes
For a given conductor size, which material has the greatest ampacity?
copper only
When Type NM cable is run through holes in metal framing members, ____________________ must be provided to protect the cable from sharp metal edges.
grommets
When a 4 ft. piece of nonmetallic-sheathed cable is used as a fixture whip above an accessible ceiling, it ____.
is not required to be secured
Conductor sizes up through 4/0 AWG are expressed in American Wire Gauge (AWG). Conductor sizes larger than 4/0 AWG are expressed in ____.
kcmil
Older texts used the term "MCM" which means the same things as __________.
kcmil
Branch circuit conductors must have an ampacity ____ the maximum to be served.
not less than
The rating of a branch circuit is determined by its ____.
overcurrent protective device (fuse or circuit-breaker)
The National Electrical Code does NOT allow rigid PVC conduit to ____.
support lighting fixtures
The NEC recommends a voltage drop no greater than ____________________ percent for feeders and no greater than ____________________ percent total for feeders and branch circuits together.
three, five
The suffix "B" in Type NM-B nonmetallic cable means that the conductors have an insulation temperature rated ____.
90°C (194°F)
The NEC specifies that 60°C ampacity be used for circuits rated 100 amperes or less, except when the equipment terminals are marked for use with higher temperature wire. What is one potential problem with using higher-temperature, higher-ampacity wire?
Using higher-ampacity wire rated 75°C or 90°C may sometimes result in the use of a smaller conductor size and subsequent excessive voltage drop.
Describe at least three effects of voltage drop in residences.
Voltage drop causes lights to dim, TV pictures to "shrink," motors to run slower and hotter, electric heaters not to produce their rated output, and appliances not to work properly.
Explain why particular care has to be taken when making aluminum wiring connections.
When aluminum is exposed to air it oxidizes, forming a non-conductive surface coating that prevents good connections. Aluminum conductors must have the oxide removed and an inhibitor compound applied to joints to ensure an electrically sound connection.
