|
By Mike Holt for EC&M Magazine
Q1. Is GFCI protection required for a 15A or 20A, 125V receptacle that is located within 6 ft of a janitorial closet sink in a commercial building?
A. No. However, GFCI protection is required for all 15 and 20A, 125V receptacles located within 6 ft of a dwelling unit utility sink [210.8(A)(7)].
Q2. How far away must a 120/208V, three-phase panelboard be located from a janitorial closet sink?
A. The panelboard may be installed as close as you would like to a janitorial sink, however a minimum of 36 in. deep by 30 in. wide of clear working space is required in front of the panelboard [110.26(A)].
Q3. I have a facility that contains a small data center for a call center. The CATV, telephone, and satellite dish are individually grounded to standalone ground rods. The designer claims that the individual ground rods are not required to be grounded to the building grounding electrode system. Is this true?
A. No. The NEC requires all communications systems on or in a structure to be grounded to the building grounding electrode system.
- Communications Systems (Telephone), 800.100
- Radio and Television Equipment (Satellite), 810.21
- CAT, 820.100
- Network-Powered Broadband Communications Systems, 830.100
The purpose of grounding all systems to the same electrode (basically bonding the systems together) is to reduce differences in potential between communications circuits and the power system during a lightning event.
Q4. What are the NEC requirements for the installation of a transfer switch ahead of the service disconnecting means?
A. A transfer switch is not permitted to be installed on the supply side of the service disconnecting means unless it is rated ‘suitable for use as service equipment’ (transfer switch containing a disconnecting means) [230.66 and 230.82].
Q5. My buddy told me that a GFCI or AFCI protected circuit could not be used to supply power to a GFCI receptacle? Is that true?
A. No, both GFCI’s and AFCI protection devices will operate just fine if supplied by a GFCI or AFCI protected circuit.
Q6. Can a flexible cord with and attachment plug be located below the raised floor of an information technology equipment room?
A. Maybe. Flexible cords under the raised floor of an information technology equipment room are permitted, but the cable must have adequate fire-resistant characteristics suitable for use under raised floors of an information technology equipment room. To meet this requirement, the cable be listed as Type DP (Data Processing) [645.5(D)(5)].
Q7. Can an optional stand-by generator be connected to premises wiring by the use of an extension cord having double male attachment plugs?
A. No. The Code requires all fixed or portable optional standby power systems be connected to the premises via a transfer switch [702.6]. In addition, attachment plugs are not permitted to be installed so their prongs, blades, or pins aren’t energized, unless inserted into an energized receptacle [406.6(B)].
Q8. I came across 120V utility wiring for a metal light pole. I told the lineman that the NEC requires the metal cover of the handhole and metal pole to be bonded so that dangerous touch voltage from a ground fault would be removed by the opening of the circuit protection device. His response… “we are not required to comply with the NEC and that his installation was safe because the metal cover and pole was grounded to a ground rod. Is this true?
A. The lineman is correct that his installation is not required to comply with the NEC [90.2(B)(5)] and he’s right that the National Electric Safety Code (utility code) does not require the metal parts of this installation to be bonded to an effective ground-fault current path with the purpose of clearing a ground fault.
Is the utility installation safe? No. There have been and will continue to be many deaths to individuals making contact to energized metal parts that are grounded to the earth, but not bonded to an effective ground-fault path, as required by 250.4(A)(3).
Q9. Is GFCI protection required for a pool pump motor circuit?
A. GFCI protection is not required for hardwired circuits that supply pool pump motors. However, receptacles rated 15 or 20A, single phase, that supply pool pump motors must be GFCI protected [680.22(A)(5)].
Note: The outlet that supplies a self-contained indoor spa or hot tub, a packaged spa or hot tub equipment assembly, or a field-assembled spa or hot tub must be GFCI protected [680.44]. Because this rule applies to all outlets and not just receptacle outlets, the wiring for a hardwired self-contained indoor spa or hot tub, a packaged spa or hot tub equipment assembly would require GFCI protection.
Q10. What type of wiring can I used for 70V speaker circuits? The rear of the amplifying equipment states ‘Class 2 wiring permitted.’
A. Since the amplifying equipment specifies that Class 2 circuit wiring is permitted, you can use any Class 2 cable, or any of its permitted substitutions, in accordance with 725.61.
Q11. Can the disconnecting means for air-conditioning equipment be directly mounted on the air-conditioner equipment?
A. Yes, but it’s not a good idea to mount the disconnecting means over machine data tags [440.14].
Q12. What are the NEC grounding requirements for a satellite dish?
A. The metal mast [810.15] for radio and television equipment and it’s lead-in cable via a discharge unit [810.20] must be grounded to the building grounding electrode system in accordance with 810.21.
Grounding of the metal mast and lead-in antenna cable serves to reduce voltage surges (caused by static discharge or nearby lightning strikes) from reaching the center conductor of the lead-in coaxial cable. Because the satellite sits outdoors, wind creates a static charge on the antenna as well as on the cable attached to it. This charge can build up on both antenna and cable until it jumps across an air space, often passing through the electronics inside the low noise block (LNBF) or receiver.
Q13. What size wire and breaker is required for an air-conditioner whose nameplate specifies that the circuit conductor must have a minimum rating of 44A, with overcurrent protection not to exceed 60A. The terminals on the equipment are rated 75°C.
A. The branch-circuit conductors and short-circuit and ground-fault protection device must be sized according to the equipment’s nameplate [110.3(B)]. In this example, a 10 AWG conductor having a rating of 50A at the 75°C column of Table 310.16 [240.4(G)] protected by a 60A circuit breaker or fuse will be fine.
Q14. Can single-pole circuit breakers be used for a multiwire branch circuit that supplies power for office partitions?
A. Yes, provided the individual single-pole circuit breakers utilize handle ties that are identified for the purpose [240.20(B)(1) and 605.6]. A common internal trip circuit breaker could be used for this application as well, but all of the individual branch circuits will open in the event of a ground fault in only one of the circuits.
Q15. Is it a good practice to bond the lightning protection system to the building grounding electrode system?
A. The Code requires the lightning protection system, if provided on a premise, to be bonded to the building or structure grounding electrode system [250.106]. This bonding connection is to minimize the difference of potential between the lightning protection system and the electrical system, which should reduce arcing between metals parts within the building.
Q16. I understand that Type AC cable with an equipment grounding (bonding) conductor is permitted to be used for branch circuits serving patient care areas. Can Type MC cable with an equipment grounding (bonding) conductor be use for luminaires located above 7.5 ft in a patient care area?
A. No. Branch circuits that serve patient care areas must be installed in a metal raceway or listed cable with a metallic armor or sheath that qualifies as an effective ground-fault current path in accordance with 250.118 [514.13(A)]. This includes the branch circuits that supply luminaires in patient care areas.
The metal armored sheath of Type AC cable is listed as a suitable ground-fault current path for this application because it contains an internal bonding strip in direct contact with the metal sheath of the cable [250.118(8)].
Typically, the outer metal sheath of interlocked Type MC cable isn’t listed as a suitable ground-fault current path [250.118(10)]. Therefore, Type MC cable of the interlock type, where the outer sheath is not listed as an effective ground-fault current path, is not permitted to supply any branch circuit in patient care areas of health care facilities [517.13].
| NEC Exam Practice Questions Textbook |
 |
The NEC Exam Practice Questions Book contains 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
Price:
$40.00 each
|
| |
|
|
