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Quizzes on the Code

Feb 1, 1999 12:00 PM, By Fred Hartwell, Senior Editor

Choose the best answer:

1. Which of the following methods does the Code allow you to use in selecting No. 8 grounded conductors?

a. White color
b. Three white continuous stripes
c. Gray
d. Answers “a” and “b”
e. Answers “a” and “c”
f. All of the above

2. Which of the following methods does the Code allow you to use in identifying No. 3 grounded conductors?

a. White paint on the visible side
b. White tape at the termination
c. Use a tag at the end saying “grounded”
d. More than one of the above

3. When can you use a No. 10 white wire as an ungrounded conductor?

a. Reidentified in Type NM cable
b. Reidentified in EMT
c. Reidentified only with qualified supervision
d. More than one of the above

4. When can you use a No. 10 black wire as a grounded conductor?

a. Reidentified in Type NM cable
b. Reidentified in EMT
c. Reidentified in cable, only with qualified supervision
d. More than one of the above

5. When can you use a No. 12 white wire, without reidentification, in a switch loop?

a. As a traveler between three-way switches
b. As the supply to a single-pole switch
c. Both of the above, if in a cable
d. None of the above

6. If you run a 13.8Y/8kV system with a neutral as overhead conductors, what insulation do you have to provide on the neutral within 10 ft of the building?

a. None
b. 600V
c. 8kV
d. 13.8kV

7. If you have a 208Y/120V multiwire circuit in the same box as a 480Y/277V circuit, how do you identify the neutral conductors?

a. 120V, white; 277V, gray
b. 120V, white w/stripe; 277V white
c. 120V, white; 277V white w/stripe
d. Either “b” or “c”
e. Any of the above

Answers and Discussion

1. d, Sec. 200-6. For the first time, three continuous white stripes join white as a permitted method for grounded conductor identification. The color “gray” is a controlled color, and can’t be used as a grounded conductor identifier. The term “natural gray” refers to the natural color of latex or unbleached muslin. Over 75 years ago when this first went into the Code, conductor insulation consisted of covered natural rubber. Although the term still survives in the Code, these conductors haven’t been in production for generations.

2. b, Sec. 200-6(b). The identifying method has to encircle the conductor. Taking a brush or marker to the outward side only of installed conductors doesn’t do it.

3. a, Sec. 200-7(c)(1). You can reidentify in this direction (making what was white, black) by right, without showing qualified supervision. However, the former allowance to do this on conductors in a raceway is no more. You can withdraw and replace raceway conductors with others having the appropriate insulation color.

4. c, Sec. 200—6(e) Ex. 1. This is the reverse of the previous question (making what was black, white). Here, you may do so only with qualified maintenance/supervision, only in cable assemblies.

5. d, Sec. 200-7(c)(2). Now the principle of reidentification applies to switch loops, just the same as in other cases where you want to take a white wire and use it as an ungrounded conductor. If you do reidentify these wires (as before, only in cable assemblies), then both answers are acceptable. Note this change makes Sec. 200-7(c)(2) functionally redundant to Sec. 200-7(c)(1). The first says you can reidentify white wires generally and use them as ungrounded conductors; the second says the same for switch loops, when you’re using them as ungrounded conductors. No difference.

6. a, Sec. 200-2, Sec. 250-184(a) Ex. 2, Sec. 225-4 Ex. Although overhead conductors are normally insulated, and medium-voltage neutral conductors normally need 600V insulation, grounded conductors need not be insulated if some Code rule expressly provides for this. Sec. 250-184(a) Ex. 2 waives the insulation rule for overhead medium-voltage neutrals.

7. d, Sec. 200-6(d). As previously discussed, gray isn’t allowed, even if this does happen to be a near universal convention. The options are white and white with a stripe. The Code doesn’t say which should be used with the lower system voltage, so it’s up to you to decide which system gets the plain white. Due to the universality of the 277V4gray convention, many local jurisdictions amend this requirement. However, so far, the panel has refused to modify this rule.

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