General rules and definitions—Articles 90, 100, 110
Choose the best answer:
1. In a remote area with no available utility electric supply, the property owner decides to build a house with a windmill (and storage batteries) as the sole power source. Which of the following NEC section(s) applies(y):
a. Sec. 225-30
b. Sec. 230-2
c. Both of the above
d. None of the above
2. Duplex receptacles consist of a single piece of manufactured equipment capable of receiving two plugs at the same time. If you mount two duplex receptacles side-by-side in the same box, how many receptacle devices are present?
d. depends on the brand
3. Suppose you have 61kA available fault current at the service disconnect (including all motor contributions), and to meet this requirement you install a 65kA series-rated system of circuit breakers. At a downstream panel, with enough impedance in the intervening feeder to reduce this current to 22kA, which of the following numbers needs to be included in the field labeling?
4. Which equipment, under the conditions indicated, can be located 4 ft below a trap from a roof drain? Is drip protection needed? Assume you’ll need to work the equipment hot.
a. over 600V, yes
b. industrial plants, yes
c. residential, yes
d. on floor if < 25ft below, no
e. two of the above
f. three of the above
g. all of the above
5. How much workspace (minimum) must you provide in front of a floor-mounted panelboard and control cabinet that’s 80 in. high and 50 in. wide?
a. 78 in x 230 in.
b. 80 in x 230 in.
c. 78 in x 250 in.
d. 80 in x 250 in.
6. If you put a 6-in.-deep panelboard above an 8-in.-deep sprinkler main (which runs tight to the wall), how far out from the wall do you have to mount the back of the panelboard?
a. 0 in.
b. 2 in.
c. 6 in.
d. 8 in.
Answers and Discussion
1. a, Art. 100, Feeder and Service definitions. Only a utility can supply a service. If there isn’t a utility supply, then the source becomes a feeder, originating at a separately derived system, and other Code rules apply to its overcurrent protection. When it arrives at the building served, it will have overcurrent protection ahead of it, and it only needs to comply with the disconnection requirements in Part B of Art. 225.
2. c, Art. 100, Receptacle definition. A receptacle is a contact device, and the reworded definition is very clear. A duplex receptacle, for example, has two contact devices (emphasis on the plural) mounted on a single yoke, for a total of four at this outlet.
3. b, Sec. 110-22. Instead of the fault current available at the point of application, this section now calls for the system value. Although not entirely clear, this reference is intended as applying to the electrical supply system, and not the series connected equipment. In changing the wording, the panel stated that the marking was for “the level of fault current for which the system has been installed.”
4. f, Sec. 110-26(f), 110-34(f)(1). Three responses are correct on both the 1996 and 1999 Codes, although not the same responses. Both “a” and “b” are correct for both Codes, since old Sec. 710-9 and old Sec. 384-4(a)(1) Ex. allowed these placements. However, the 1999 NEC allows all occupancies to use the relief formerly afforded industrial occupancies only. The 1996 NEC, on the other hand, literally allowed such a placement anywhere if the drip source was over 25 ft above the floor. This has been corrected.
5. d, Sec. 110-26(a)(2) and (3). The 1996 NEC clarified that the traditional 6-ft-6-in. height rule increased if the equipment went higher, and the 1999 NEC completed the clarification by expressly referring to the width of the equipment if it was wider than the traditional 30 in.
6. b, Sec. 110-26(a)(3), 110-26(f)(1)(a) Ex., -26(f)(1)(b). The 6-in. allowance for equipment to enter a workspace is only for equipment associated with the electrical installation, so the front plane of the panelboard must not set behind the sprinkler pipe. The old rule requiring a dedicated footprint to the floor no longer applies to a pipe below a panel, only to a drip or condensation hazard above the panel. As a result you have to move the panel 2 in. out so the front plane misses the pipe, but not out the full 8 in. as previously.