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NEC Questions and Answers Based on the 2005 NEC II

By Mike Holt, for EC&M Magazine

NOTE: There are no photos, images, or graphics included in this newlsetter.

Q11 Are receptacles required to be installed so that they can be removed without interrupting the power to any downstream receptacles?

A11 Continuity of the grounded neutral conductor of a multiwire branch circuit must not be interrupted by the removal of a wiring device. Therefore, the grounded neutral conductors must be spliced together, and a pigtail must be provided for the wiring device.

CAUTION: If the continuity of the grounded neutral conductor of a multiwire circuit is interrupted, the resultant over- or undervoltage could cause a fire and/or destruction of electrical equipment. Use graphic.

Note: The opening of the ungrounded conductors, or the grounded neutral conductor of a 2-wire circuit during the replacement of a device doesn't cause a safety hazard, so pigtailing of these conductors isn't required [110.14(B)].

Q12 Does the NEC restrict the placement of a light switch in a bathroom? What about pools, spas, and hot tub areas?

A12 Switches can be located next to, but not within, a bathtub, hydromassage bathtub, or shower space [404.4 and 680.70 and 680.72]. According to 680.2, as hydromassage bathtub is a permanently installed bathtub with a recirculating piping system designed to accept, circulate and discharge water after each use.
Switches must be located not less than 5 ft from pools [680.22(C)], outdoor spas and hot tubs [680.41], and indoor spas or hot tubs [680.43(C)].

Q13 Where there are two service disconnects installed on one side of the meter, can I run the service conductors through one disconnect to feed the second disconnect?

A13 Yes if adequate space is provided in the first disconnect [312.8]. Use the graphic we have on this.

Mike's Comment: This is the way I have my service installed. Photo.

Q14 If a single 20A, 125V laundry receptacle is located within six feet from the laundry tub, is GFCI protection?

A14 Yes, GFCI protection is required for all 15 and 20A, 125V receptacles located within an arc measurement of 6 ft from the dwelling unit laundry, utility, and wet bar sink [210.8(A)(7)].

Q15 Can I terminate two wires on a single-pole circuit breaker?

A15 Yes, if the terminal is identified for two conductors, either within the equipment instructions or on the terminal itself. It's my understanding that only Square D circuit breakers (15A, 20A, and 30A) are rated for two conductors.

Q16 What is minimum and maximum height for electrical equipment containing circuit breakers or switches?

A16 There is no minimum height for switches and circuit breakers. However, 550.32(F) requires the service disconnecting means enclosure for mobile and manufactured homes to be mounted a minimum of 2 ft above the finished grade.

All switches and circuit breakers must be installed so the center of the grip of the operating handle of the switch or circuit breaker, when in its highest position, isn't more than 6 ft 7 in. above the floor or working platform. But switches and circuit breakers can be mounted above 6 ft 7 in. if they are next to the equipment they supply and are accessible by portable means [240.24(A) and 404.8(A)].

Q17 A three phase breaker is installed in a three phase panel, but the connected load is single phase. Is this a code violation?

A17 No.

Q18 Where is the system bonding jumper at a transformer required to be installed?

A18 The metal parts of the separately derived system must be bonded to the secondary grounded neutral terminal by the installation of a system bonding jumper. This bonding jumper ensures that dangerous voltage from a secondary ground fault can be quickly removed by opening the separately derived system circuit's overcurrent protection device [250.2(A)(3) and 250.30(A)(1)].

DANGER: During a ground fault, metal parts of electrical equipment, as well as metal piping and structural steel, will become and remain energized providing the potential for electric shock and fire if the system bonding jumper is not installed.

The system bonding jumper can be installed at the transformer, the first system disconnecting means, or any point in between the transformer and the first disconnecting means, but not at both locations.

CAUTION: Dangerous objectionable current will flow on conductive metal parts of electrical equipment as well as metal piping and structural steel, in violation of 250.6(A), if the system bonding jumper is installed at the transformer and the secondary system disconnecting means.

Q19 What size equipment grounding (bonding) conductor is required in each of four raceways for a 1600A, 120/208V, three-phase feeder?

A19 4/0 AWG. When circuit conductors are run in parallel [310.4], an equipment grounding (bonding) conductor must be installed with each parallel conductor set and it must be sized to the ampere rating of the circuit-protection device in accordance with Table 250.122.

Q20 Does the Code require an electric motor driven fire pump to be connected to a standby generator if a standby generator is installed on the premises?

A20 Power to fire pump motors must be supplied by a reliable source of power that has the capacity to carry the locked-rotor current of the fire pump motors, pressure maintenance pump motors, and the full-load current of any associated fire pump equipment. Reliable sources of power includes:

  • A separate service from a connection located ahead of but not within the service disconnecting means.
  • An on-site power supply, such as a generator, located and protected to minimize damage by fire is permitted to supply a fire pump.

The determination of a reliable source of power is subject to the approval of the authority having jurisdiction.

23. NEC Exam Practice Questions Textbook
The NEC Exam Practice Questions Book contains over 2,400 questions from the National Electrical Code. There are 12 review quizzes of 100 questions each that are in code order and take you step-by-step through each of the 9 chapters of the National Electrical Code. The 12 practice quizzes of 50 questions each follow the NEC Review quizzes, but are presented in random order and contain questions different than those in the review quizzes.

In addition, this book contains 12 challenge quizzes of 50 questions each that cover all 9 chapters of the National Electrical Code. The questions in the challenge quizzes do not follow the chapters of the Code book as the other quizzes do, they are also organized in a random manner, and you might find them harder to answer. Scores for the first few challenge quizzes might be somewhat lower than you would like to see. But, as you go through this book and take the review and practice quizzes, you’ll learn a great deal and gain a better understanding of the material. This improved knowledge and understanding will help you improve on the challenge quizzes as you go.

Product Code: 05PQ
ISBN: 1-932685-28-6

Available March, 2005


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