NEC Chapter 9 Flashcards

Questions and Answers

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.

securely fastened within 3'

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.

insulated bushing Signup and view all the answers

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.

greater than Signup and view all the answers

If the conductors are 8 AWG TW, you may install ____ of these in a 1-1/4" EMT.

13 Signup and view all the answers

Conductors fill may be up to ____ percent of the cross-sectional area in underfloor raceways.

40 Signup and view all the answers

Thread-less couplings for rigid metal conduit installed in a wet location shall be ____.

enclosed in concrete Signup and view all the answers

Regarding polyvinyl chloride conduit, extreme cold may cause some nonmetallic conduits to become brittle and therefore more susceptible to damage from physical contact.

True Signup and view all the answers

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.

1/16" Signup and view all the answers

In vertical raceways, 3/0 AWG aluminum conductors must be supported if the vertical rise is greater than ____ Ft.

180' Signup and view all the answers

Luminaires shall be used as a raceway for circuit conductor unless ____ for use as a raceway.

Listed & Marked Signup and view all the answers

Raceways on the outside of a building shall be ____.

Weatherproof and covered Signup and view all the answers

When an outlet from an underfloor raceway is discontinued, the sections of the circuit conductors supplying the outlet ____.

shall be removed from the raceway Signup and view all the answers

Nonmetallic surface extension must be secured in place by approved means at intervals not exceeding ____ inches.

8" Signup and view all the answers

When an outlet is removed from a cellular metal floor raceway, the sections of the circuit conductors supplying the outlet shall be ____.

removed from the raceway Signup and view all the answers

When installing 2" rigid metal conduit with threaded fittings, the NEC requires the maximum distance between supports to be no more than ____.

16' Signup and view all the answers

Determine the minimum trade size EMT required to enclose eight 6 AWG THHW copper conductors installed in a 50-ft conduit run.

1-1/4" Signup and view all the answers

What size schedule 40 PVC is required for eight 6 AWG XHHW conductors?

1-1/4" Signup and view all the answers

When calculating the conductors, all of the same size, includes a decimal fraction, the next higher whole number shall be used if ____.

.8 and larger Signup and view all the answers

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.

40% Signup and view all the answers

The installation of outside wiring on surfaces of building shall be permitted for circuits not over 1000 volts nominal, as ____.

Flexible metal conduit (FMC) Signup and view all the answers

A fixture rated at 7 amps requires a size ____ AWG fixture wire, as a minimum.

14 AWG Signup and view all the answers

Raceways on exterior surfaces of buildings shall be arranged to drain and shall be ____ for use in wet locations.

Suitable Signup and view all the answers

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.

22' Signup and view all the answers

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?

.003 ohms Signup and view all the answers

Three-way and four-way switches shall be wired so that all switching is done ___.

Only in the ungrounded circuit conductors Signup and view all the answers

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.

12' Signup and view all the answers

Determine the voltage drop on a branch circuit given the following: Current = 5 amps, Length = 300ft, Resistance = 4 Ohms/1000ft.

6 volts Signup and view all the answers

Determine the resistance, in ohms, of a 100 watt, 120 volt incandescent light bulb.

144 ohms Signup and view all the answers

What is the AC resistance of 500 feet of 1000 KCMIL aluminum wire in a steel conduit?

.0125 Signup and view all the answers

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.