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Questions and Answers
The Code requires all conductors that attach to a cable bus to be in the same raceway because ____.
The Code requires all conductors that attach to a cable bus to be in the same raceway because ____.
of Inductive Current
In general, rigid metal conduit shall be ____ of each outlet box, junction box, device box, cabinet, conduit body, or other conduit termination.
In general, rigid metal conduit shall be ____ of each outlet box, junction box, device box, cabinet, conduit body, or other conduit termination.
securely fastened within 3'
Aluminum fittings and enclosures shall be permitted to be used with ____ conduit.
Aluminum fittings and enclosures shall be permitted to be used with ____ conduit.
Steel rigid, Polyvinyl chloride, Aluminum rigid metal
When a 4 AWG or larger conductor enters a panel board, a _____ must be provided.
When a 4 AWG or larger conductor enters a panel board, a _____ must be provided.
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The number of 12 AWG THW conductors allowed in a 3/4" IMC conduit will be ____ the number of 12 AWG TW conductors allowed in the 3/4" EMT conduit.
The number of 12 AWG THW conductors allowed in a 3/4" IMC conduit will be ____ the number of 12 AWG TW conductors allowed in the 3/4" EMT conduit.
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If the conductors are 8 AWG TW, you may install ____ of these in a 1-1/4" EMT.
If the conductors are 8 AWG TW, you may install ____ of these in a 1-1/4" EMT.
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Conductors fill may be up to ____ percent of the cross-sectional area in underfloor raceways.
Conductors fill may be up to ____ percent of the cross-sectional area in underfloor raceways.
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Thread-less couplings for rigid metal conduit installed in a wet location shall be ____.
Thread-less couplings for rigid metal conduit installed in a wet location shall be ____.
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Regarding polyvinyl chloride conduit, extreme cold may cause some nonmetallic conduits to become brittle and therefore more susceptible to damage from physical contact.
Regarding polyvinyl chloride conduit, extreme cold may cause some nonmetallic conduits to become brittle and therefore more susceptible to damage from physical contact.
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Where nails or screws are likely to penetrate electrical nonmetallic tubing installed through metal framing members, a steel sleeve, steel plate, or steel clip not less than ____ inch in thickness shall be used to protect the cable or tubing.
Where nails or screws are likely to penetrate electrical nonmetallic tubing installed through metal framing members, a steel sleeve, steel plate, or steel clip not less than ____ inch in thickness shall be used to protect the cable or tubing.
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In vertical raceways, 3/0 AWG aluminum conductors must be supported if the vertical rise is greater than ____ Ft.
In vertical raceways, 3/0 AWG aluminum conductors must be supported if the vertical rise is greater than ____ Ft.
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Luminaires shall be used as a raceway for circuit conductor unless ____ for use as a raceway.
Luminaires shall be used as a raceway for circuit conductor unless ____ for use as a raceway.
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Raceways on the outside of a building shall be ____.
Raceways on the outside of a building shall be ____.
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When an outlet from an underfloor raceway is discontinued, the sections of the circuit conductors supplying the outlet ____.
When an outlet from an underfloor raceway is discontinued, the sections of the circuit conductors supplying the outlet ____.
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Nonmetallic surface extension must be secured in place by approved means at intervals not exceeding ____ inches.
Nonmetallic surface extension must be secured in place by approved means at intervals not exceeding ____ inches.
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When an outlet is removed from a cellular metal floor raceway, the sections of the circuit conductors supplying the outlet shall be ____.
When an outlet is removed from a cellular metal floor raceway, the sections of the circuit conductors supplying the outlet shall be ____.
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When installing 2" rigid metal conduit with threaded fittings, the NEC requires the maximum distance between supports to be no more than ____.
When installing 2" rigid metal conduit with threaded fittings, the NEC requires the maximum distance between supports to be no more than ____.
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Determine the minimum trade size EMT required to enclose eight 6 AWG THHW copper conductors installed in a 50-ft conduit run.
Determine the minimum trade size EMT required to enclose eight 6 AWG THHW copper conductors installed in a 50-ft conduit run.
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What size schedule 40 PVC is required for eight 6 AWG XHHW conductors?
What size schedule 40 PVC is required for eight 6 AWG XHHW conductors?
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When calculating the conductors, all of the same size, includes a decimal fraction, the next higher whole number shall be used if ____.
When calculating the conductors, all of the same size, includes a decimal fraction, the next higher whole number shall be used if ____.
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When calculating the conductor fill for strut-type channel raceway with external joiner, the raceway shall be permitted to be filled to ____ percent of the cross-sectional area.
When calculating the conductor fill for strut-type channel raceway with external joiner, the raceway shall be permitted to be filled to ____ percent of the cross-sectional area.
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The installation of outside wiring on surfaces of building shall be permitted for circuits not over 1000 volts nominal, as ____.
The installation of outside wiring on surfaces of building shall be permitted for circuits not over 1000 volts nominal, as ____.
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A fixture rated at 7 amps requires a size ____ AWG fixture wire, as a minimum.
A fixture rated at 7 amps requires a size ____ AWG fixture wire, as a minimum.
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Raceways on exterior surfaces of buildings shall be arranged to drain and shall be ____ for use in wet locations.
Raceways on exterior surfaces of buildings shall be arranged to drain and shall be ____ for use in wet locations.
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A branch-circuit voltage that exceeds 277 volt to ground and does not exceed 600 volts between conductors is used to wire the auxiliary equipment of electrical discharge lamps mounted in poles. The minimum height of these luminaires shall not be less than ____ feet.
A branch-circuit voltage that exceeds 277 volt to ground and does not exceed 600 volts between conductors is used to wire the auxiliary equipment of electrical discharge lamps mounted in poles. The minimum height of these luminaires shall not be less than ____ feet.
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A 120-volt, single phase, 300ft branch circuit carries 5 amps and has a 5.0 voltage drop. What is the resistance of the conductors per foot in this circuit?
A 120-volt, single phase, 300ft branch circuit carries 5 amps and has a 5.0 voltage drop. What is the resistance of the conductors per foot in this circuit?
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Three-way and four-way switches shall be wired so that all switching is done ___.
Three-way and four-way switches shall be wired so that all switching is done ___.
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At least one receptacle outlet shall be installed directly above a show window for each ____ Ft or major fraction thereof of show window area measured horizontally at its maximum width.
At least one receptacle outlet shall be installed directly above a show window for each ____ Ft or major fraction thereof of show window area measured horizontally at its maximum width.
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Determine the voltage drop on a branch circuit given the following: Current = 5 amps, Length = 300ft, Resistance = 4 Ohms/1000ft.
Determine the voltage drop on a branch circuit given the following: Current = 5 amps, Length = 300ft, Resistance = 4 Ohms/1000ft.
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Determine the resistance, in ohms, of a 100 watt, 120 volt incandescent light bulb.
Determine the resistance, in ohms, of a 100 watt, 120 volt incandescent light bulb.
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What is the AC resistance of 500 feet of 1000 KCMIL aluminum wire in a steel conduit?
What is the AC resistance of 500 feet of 1000 KCMIL aluminum wire in a steel conduit?
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Study Notes
NEC Code Conductor Requirements
- Conductors attached to a cable bus must be in the same raceway to avoid inductive current interference (300.20(A)).
- Rigid metal conduit requires secure fastening within 3 feet of various boxes and terminations (344.30(A)(1)).
- Conduits can mix aluminum fittings with steel rigid, polyvinyl chloride, or aluminum rigid metal types (344.14).
Conductor and Raceway Specifications
- An insulated bushing is required when a 4 AWG or larger conductor enters a panel board (300.4(G)).
- The capacity for 12 AWG THW conductors in a 3/4" IMC conduit exceeds that in a 3/4" EMT conduit.
- In a 1-1/4" EMT conduit, a maximum of 13 conductors of 8 AWG TW can be installed.
- Raceway fill in underfloor raceways may reach up to 40% of cross-sectional area (390.22).
Installation and Protection Regulations
- Thread-less couplings for rigid metal conduit in wet locations must be enclosed in concrete (344.42 > 352.12(B)).
- Nonmetallic conduits can become brittle in extreme cold and are vulnerable to physical damage (352.12(B)).
- Protective measures, like a steel sleeve, are needed for nonmetallic tubing where nails or screws may penetrate, requiring protection of at least 1/16" thickness (300.4(D)).
Vertical and Outdoor Installation Guidelines
- In vertical raceways, 3/0 AWG aluminum conductors must be supported if the vertical rise exceeds 180 feet (T300.19(A)).
- Luminaires can serve as a raceway for circuit conductors only if they are listed and marked for that use (410.64(A)).
- External raceways must be weatherproof and covered (225.22 & 230.53).
Specific Outlet and Raceway Management
- When an outlet from an underfloor raceway is discontinued, associated circuit conductors must be removed from the raceway (390.57).
- Nonmetallic surface extensions must be secured every 8 inches (382.30(A)).
- Circuit conductors in cellular metal floor raceways need removal upon outlet removal (374.58).
Conduit Length and Size Calculations
- For a 2" rigid metal conduit, maintain no greater than 16 feet between supports (T344.30(B)(2)).
- To enclose eight 6 AWG THHW copper conductors across a 50-ft run, a minimum trade size EMT of 1-1/4" is required (Annex C > Chapter 9).
- Eight 6 AWG XHHW conductors necessitate a size of 1-1/4" schedule 40 PVC piping (Annex C > Chapter 9).
Calculating Conductor Fill and Wiring Specifications
- When calculating conductors of the same size, round up any decimal fraction greater than or equal to 0.8 to the next whole number (Chapter 9 Table Notes).
- Strut-type channel raceways with external joiner can fill up to 40% of their cross-sectional area (T384.22).
- Outside wiring installations are allowed for circuits under 1000 volts nominal when using flexible metal conduit (225.10).
Electrical Requirements and Safety
- A fixture rated at 7 amps requires a minimum of 14 AWG fixture wire (T402.5).
- Exterior raceways must drain properly and be suitable for wet locations (225.22).
- For auxiliary equipment of electrical discharge lamps, the minimum mounting height of luminaires should be no less than 22 feet, used in circuits exceeding 277 volts to ground (210.6(D)(1)(A)).
Receptacles and Voltage Information
- Receptacles on different circuits must be designed so attachment plugs are not interchangeable based on current (AC or DC), frequencies, and voltage requirements.
- Voltage drop calculations can ascertain circuit efficiency, for instance, a 120-volt, single-phase circuit carrying 5 amps over 300 feet results in a drop of 6 volts (Vd=).
Resistance Calculations
- The resistance of a 100-watt, 120-volt incandescent light bulb measures 144 ohms.
- AC resistance of 500 feet of 1000 KCMIL aluminum wire within a steel conduit is determined to be 0.0125 ohms (Chapter 9 Table 9, Column AL).
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Explore key concepts from the National Electrical Code (NEC) Chapter 9 with our flashcards. Each card provides definitions and important clauses that guide electrical installations. Test your knowledge and ensure compliance with the NEC standards.
