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Quizzes on the Code

Jul 1, 2002 12:00 PM, By Mike Holt, NEC Consultant

Choose the best answer:

1. Snap switches may not be grouped or ganged in enclosures with other _____ if the voltage between adjacent devices exceeds 300V, unless they're installed in enclosures equipped with permanently installed barriers between adjacent devices.

   (a) snap switches
   (b) receptacles
   (c) similar devices
   (d) all of these

2. Snap switches, including _____ and similar control switches, must be effectively grounded and must provide a means to ground metal faceplates, whether or not a metal faceplate is installed.

   (a) dimmers
   (b) fan speed controls
   (c) timers
   (d) all of these

3. General-use _____ switches may be used only to control permanently installed incandescent luminaires unless otherwise listed for control of other loads. They aren't listed to control a receptacle that supplies luminaires with an attachment cord and plug.

   (a) dimmer
   (b) fan speed control
   (c) timer
   (d) all of these

4. When in the OFF position, a switching device with a marked OFF position must completely disconnect all ____ conductors of the load it controls.

   (a) grounded
   (b) ungrounded
   (c) grounding
   (d) all of these

5. The maximum rating or setting of motor branch-circuit, short-circuit, and ground-fault protective devices for a single-phase motor is _____% for an inverse-time breaker.

   (a) 125
   (b) 175
   (c) 250
   (d) 300

6. A disconnecting means must be located within sight of the motor location and the driven machinery location. Under no condition can the controller disconnect serve as the disconnecting means for the motor.

   (a) true
   (b) false

7. The ampacity of the conductors from the generator terminals to the first distribution device(s) containing overcurrent protection cannot be less than _____% of the nameplate current rating of the generator.

   (a) 80
   (b) 115
   (c) 125
   (d) none of these

Answers and Discussion

1. (d), all of these. Sec. 404.8(B) prohibits the ganging of switches, receptacles, and other devices in outlet boxes if the voltage between devices exceeds 300V.

2. (d), all of these. A change to 404.9 clarifies that fan control and other similar control switches, such as timers, must have the metal mounting yoke bonded to an effective ground fault current path in accordance with 250.4(A)(5).

3. (a), dimmer. This new requirement is contained in the listing and installation instructions for dimmers [404.14(E)]. The change is intended to ensure that dimmers will be installed in accordance with manufacturer/listing requirements.

4. (b), ungrounded. A change in 404.15 requires switches with an OFF marking to disconnect all power from the load. Where an electronic occupancy sensor is used, voltage can be present and a small current of up to 0.5mA can flow to maintain power to the device even when the switch is in the OFF position. This small amount of current can startle a person, perhaps causing a fall from a ladder.

5. (c), 250. Relocating the information from Table 430.52 to this section made it easier to size motor branch-circuit protection devices.

6. (b), false. Per 430.102(B), the motor disconnecting means isn't required to be in sight of the motor or the driven machinery location provided:

   • The controller disconnecting means can be locked in the OPEN position.

   • The locking provisions are installed on or at the switch or circuit breaker used as the controller disconnecting means.

   • Locating the motor disconnect within sight of the motor is impracticable or introduces additional or increased hazards to people or property.

7. (b), 115. A change to 445.13 clarifies that conductors originating at the generator can terminate in equipment that has multiple overcurrent devices, with or without a main overcurrent device. When sizing conductors, you must comply with all NEC requirements. Sec. 215.2(A)(1) requires all feeders to be no smaller than 125% of the continuous load. So if the generator supplies a continuous load, the conductors must be sized no smaller than 125% of the continuous load, but no less than 115% of the generator nameplate.

Questions and answers excerpted from Mike Holt's Illustrated Changes to the NEC, 2002 Edition.

Are you still confused by the Code? For additional information on Code-related topics please visit www.mikeholt.com or send an e-mail directly to the author at mike@mikeholt.com.

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