This article was posted 01/15/2008 and is most likely outdated.

2008 NEC Questions and Answers January - Part 2
 

 

Topic - NEC Questions
Subject - 2008 NEC Questions and Answers January Part 2

January 15, 2008
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NEC Questions and Answers Based on the 2008 NEC

January Part 2

 

Here is the follow up to yesterday’s newsletter. This includes all of the answers to the questions sent yesterday so you can see how you did.

 

By Mike Holt for EC&M Magazine

 

Q1. Is GFCI protection required for drinking water fountains in office buildings?

A1. Yes [422.52].

 

Q2. A 400Aservice is made up of two 200A main breaker panelboards that are nipple together. Can the service conductors pass through one of the cabinets to supply the other panelboard?

A2. Yes [230.7].

 

Q3. Section 680.51 of the NEC requires GFCI protection for fountain equipment. Is there a maximum fault current to ground requirement with this section that should be used when providing ground fault protection for fountain equipment?

A3. When the Code requires GFCI protection, it is a “Class A” type. A “Class A” ground-fault circuit interrupter opens the circuit when the current-to-ground has a value of 6 mA or higher and doesn’t trip when the current-to-ground is less than 4 mA [Art 100 Ground-Fault Circuit Interrupter FPN].

 

Q4. Is a receptacle required within 25 ft of a roof-top exhaust fan?

A4. No. A 15A or 20A, 125V receptacle outlet must be installed at an accessible location for the servicing of heating, air-conditioning, and refrigeration equipment [210.63]. An exhaust fan is not heating, air-conditioning or refrigeration, so a receptacle is not required.

 

Q5. What is the minimum burial depth for cable TV cables?

A5. There is no minimum cover requirement for coaxial cable.

 

Q6. What size conductors are required to supply a 75A load, if the device terminals are rated for 75°C?

A6. 4 AWG, rated 85A at 75°C [Table 310.16].

 

Q7. What is the ampacity of three 8 XHHW conductors installed in a wet location at an ambient temperature of 45°C?

A7. XHHW conductors are rated 75°C in a wet location [Table 310.13(A)].

Conductor Ampacity [75°C] = 50A

Correction Factor [Table 310.16] = 0.82

Corrected Ampacity = 50A x 0.82 = 41A

 

Q8. What is the separation distance of communication raceway on the same rack with raceways containing power and lighting conductors?

A8. None.

 

Q9. What are the Code requirements for bonding bushings on 277V or 480V circuits?

A9. Metal raceways or cables containing 277V and/or 480V circuits terminating at ringed knockouts must be bonded to the metal enclosure with a bonding jumper sized in accordance with 250.122, based on the rating of the circuit overcurrent device [250.102(D)]. A bonding jumper isn’t required where ringed knockouts aren’t encountered, totally punched out, or where the box is listed to provide a reliable bonding connection [250.97].

 

Q10. Is the lighting in a bathroom allowed to be fed from the load side of the bathroom GFCI receptacle, which means that the lights will go out when the GFCI trips?

A10. Yes, as long as the circuit to the bathroom receptacles only supplies that bathroom [210.11(C)(3) Exception], and no single load fastened in place is rated more than 10A [210.23(A)].

 

Q11. Is it a Code violation to install 15A rated duplex receptacles on the 20A circuit?

A11. No [210.23(B)(3)].

 

Q12. In a school science lab are 15A or 20A, 125V receptacle within 6 ft of the lab sink, required to be GFCI-protected?

A12. Yes, all 15A and 20A, 125V receptacles installed within 6 ft of the outside edge of a sink must be GFCI-protected [210.8(B)(5)].

 

Q13. What are the NEC requirements for the installation of smoke detectors in dwelling units?

A13. The NEC doesn’t specify the locations of smoke alarms in a dwelling unit. That information is best obtained in the locally adopted building code. The NEC does require smoke alarms located in dwelling units to be AFCI-protected [210.12(B)].

 

Q14. Does the Code require a paddle fan to be switch controlled, or can the paddle fan be wired directly without a switch?

A14. The Code doesn’t specify, so a direct wired fan would be fine.

 

 
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Comments

  • Does the bonding bushing requirements apply to a 120/208 volt 3-phase service panel? We punched the holes in the side of the tub, ran 3" EMT with insulated connectors and did not use bonding bushings and our service was rejected. I was always under the assumption that if you don't use eccentric or concentric KO's, then you don't need the bonding bushings.

    Thanks,

    Mike

    Mike Huskey
    Reply to this comment

  • Regarding:

    Q5. What is the minimum burial depth for cable TV cables? A5. There is no minimum cover requirement for coaxial cable.

    That's a correct statement relying only on the NEC, but be cautioned that many cable TV franchises, local ordinances, and state rules do specific a minimum cover depth, especially for trunk and distribution cables that carry power to energize amplifiers, fiber nodes, etc.

    In some cases, the current level in energized cable TV coaxial cables can reach 15 amps.

    Jonathan L. Kramer, Esq., FSCTE Kramer Telecom Law Firm, PC Los Angeles, California www.TelecomLawFirm.com

    Jonathan L. Kramer, Esq.
    Reply to this comment

  • Question #11 answer should be 210.21(B)(3).

    Jason Oliver
    Reply to this comment

  • NEC Questions and Answers January part 2 Question #8. What is the separation distance of communication raceway on the same rack with raceways containing power and lighting conductors? A. None What about article 800.133(2) states 2 inches.

    William Anderson
    Reply to this comment

  • regards to GFCI protection 422.52. what is considered a "vending machine" for the purpose of this article?? Is a water cooler with a bottle of water considered a "vending machine"?? Is a permantantly installed wall mounted drinking water fountain that has a cord and plug connected cooling system considered a "vending machine"??

    roger
    Reply to this comment

  • how does 210-8(B)(5) apply to science lab sinks?

    roger
    Reply to this comment

  • Re: Question 14 A paddle fan would be classified as an appliance, so the disconnect rules for appliances would apply. This would require some kind of switch if the fan is rated over 1/8 hp. (this could be the unit switch built into the fan)

    Greg Porter
    Reply to this comment

  • why can you put a 15amp plug on a 20amp breaker?i've seen a plug melt from to many amps on it so this doesn't make any sense to me.

    jimmy
    Reply to this comment

  • Q: Can you have a 800a breaker feeding two seperate Disc. side by side that enturn feeds a upstairs and downstairs panels in a building

    Alfred Matkin
    Reply to this comment

  • If you have 1400 duplex oulets, how many circuits 120v 20 amps can you have???

    vasiliy
    Reply to this comment

  • Qu. 6: Shouldn't you add 25% to the 75 amp load to determine the wire size?

    Norm
    Reply to this comment

  • Q2: The article on panelboards prohibits this application. I do not have a NEC book ion front of me to quote the particular section, but conductors are not allowed to pass through a panelboard without termination, particularly if they go to another panelboard.

    There is an exception for riser panelboards that are built for the purpose of having extra gutter space for tapping a feeder. There is also a way to argue that a 14 inch 20 slot panel has room for extra wires as it is the same width as a 40 or 42 slot panelboard.

    The original intent is that if somebody is trying to do deenergized maintenance they can expect all of the branch circuit conductors to be deenergized when they turn off a main breaker or fusible switch. Worse, you do not want 480 volt conductors passing through a 120Y208 panelboard.

    Ideally, you should use an auxiliary gutter if you are running 2 or 3 voltages through the same conduit to serve an industrial machine or so forth. I have found that most 18 inch or 20 inch wide have enough gutter space to accomodate Omron trim profile 4 pole power relays to control lighting.

    Michael R. Cole
    Reply to this comment

  • Good job. I really appreciate your dedication. But i have a question. On a residntial grounding electrode system, The ground electrode coductor has to be buried, buried at some cover requirement, or simply doesn't mater?

    manny
    Reply to this comment

  • Correct website address in previous comment to www.eaton.com./consultant . Sorry typing error

    Chuck Nochumson
    Reply to this comment

  • can i use white electrical conductor with color tape as ungrounded conductor

    mario valdes
    Reply to this comment

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