Published In July 2000
CODE CITATIONS: Article 100-Definitions; Article 110-Requirements for Electrical Installations; Article 210-Branch Circuits; Article 220-Branch-Circuit, Feeder, and Service Calculations; Article 373-Cabinets, Cutout Boxes, and Meter Socket Enclosures; Article 400-Flexible Cords and Cables; Article 410-Lighting Fixtures, Lampholders, Lamps, and Receptacles. Branch Circuits for Cooking Equipment Q: I am installing a microwave/exhaust hood combination unit with a factory-installed cord and a 15-ampere branch circuit with a grounding receptacle in a one-family residence. The unit nameplate is marked 120-volt, 13.5 amperes. The manufacturer's instructions state "... use a 15 or 20-ampere separate circuit." Based on Sections 110-3(b), 210-23, and Table 210-24, I have installed a 15-ampere individual branch circuit for this unit. The inspector is requiring a 20-ampere branch-circuit because the unit is in the kitchen and is cord and plug connected. Am I missing something? A: I question the use of flexible cord and an attachment cap for this equipment. The exhaust hood is certainly fixed in place and my interpretation of Section 400-8(1) is that the flexible cord is being used as a substitute for the fixed wiring of a structure and therefore is not permitted. On the other hand, if the combination microwave oven-hood meets the requirements in Section 400-7(8), the cord and plug connection is acceptable. Item 8 says, "Appliances where the fastening means and mechanical connections are specifically designed to permit ready removal for maintenance and repair, and the appliance is intended or identified for flexible cord connection." Assuming that the appliance has been tested and listed by a nationally recognized testing laboratory, it may be connected to an individual 15-ampere branch circuit. This means you must use a single (not duplex) 15-ampere receptacle. If a 20-ampere individual branch circuit is provided, a single 20-ampere grounding-type receptacle must be installed. You mentioned Section 110-3(b) in your question. This part (b) requires that listed or labeled equipment be installed in accordance with instructions that are furnished with the equipment. I also assume that the 15-ampere circuit for the microwave oven is in addition to the two 20-ampere small appliance branch circuits that supply kitchen countertop receptacles and other areas mentioned in Section 210-52(b). Since the 15-ampere branch circuit that you installed is dedicated to the combination microwave oven/exhaust hood and is in agreement with the manufacturer's instructions, there is nothing in the NEC that would require a 20-ampere branch circuit for this appliance. Sealing Locknuts Q: Will sealing locknuts installed in the top of an outdoor distribution panel keep rain from entering the enclosure? May sealing locknuts be used in place of a hub for metal conduit terminations on the top of a panel installed outdoors? A: Section 373-2 (a) requires distribution panel enclosures be designed to prevent the entrance of water where installed in damp or wet locations. And according to the Definitions in Article 100 "outdoors" is considered to be a wet location. This information appears in the 1999 edition of the General Information for Electrical Equipment Directory published by Underwriters Laboratories Inc. "Sealing locknuts are intended for use with threaded rigid metal conduit and intermediate metal conduit with one sealing locknut in the outside or the inside and either an ordinary or sealing locknut on the opposite side of the enclosure for wet locations or liquid-tight applications." In my opinion the preferred location of the sealing locknut is on the outside of the enclosure. With this arrangement, the sealing locknut protects the raw metal edge of the hole in the enclosure from moisture and water on the outside of the distribution panel. Circuit for Home Refrigerator Q: A 15-ampere, 120-volt branch circuit is installed for the refrigerator in the kitchen of a multifamily dwelling unit. The local electrical inspector wants me to change the circuit to 20-amperes because it is a receptacle outlet circuit in the kitchen and Section 210-52 requires that these circuits be at least 20 amperes. This circuit is permitted by Section 210-52(6) Exception No. 2, is it not? A: If the 15-ampere receptacle is installed on the wall below the counter top in the space the refrigerator will occupy, you appear to have satisfied the exception that reads, "The receptacle outlet for refrigeration equipment shall be permitted to be supplied from an individual branch circuit rated 15 amperes or greater." Although the exception does not specify where this receptacle must be located, it should not be above a counter top adjacent to the space occupied by the refrigerator. Also, this receptacle cannot be counted as one of the receptacles required at the countertops by part (c) of Section 210-52. Notice the exception uses the words "individual branch circuit," meaning no other loads can be supplied from this circuit. The definition in Article 100 for "Branch Circuit, Individual" is one that supplies only one piece of utilization equipment. Therefore, the 15-ampere branch circuit should terminate in a single (not a duplex) receptacle. However, at least one member of Code-making Panel No. 2 has stated that it was not the Panel's intent to require the more expensive single receptacle for this application. To be safe, a single receptacle located about 2 feet above the floor and in the space to be occupied by the refrigerator should be used. I believe it is also necessary to point out that no additional load is added to the feeder and service calcuations for this 15-ampere branch circuit. The exception to Section 220-16( a) allows this branch circuit load to be excluded from the calculations. Wiring Fluorescent Fixtures Q: Is it necessary to secure or support Type AC cable run from one fluorescent fixture to the next in a lay-in ceiling? The length of cable between fixtures varies from 5 to 8 feet. Does Item (3) to Section 333-7(b) apply to this installation? A: The answer to the second question is no. Item (3) only applies to wiring from an outlet box to a lighting fixture. Item (3) says, "Not more than 6 feet (1.83 m) in length from an outlet for connections within an accessible ceiling to lighting fixtures or equipment." Since the armored cable does not originate from an outlet, the regular support requirements apply." These are within 12 inches of a cable fitting and every 4.5 feet along the cable run. For the 5-feet lengths at least two staples, cable ties, straps, and so on are required. For all lengths greater than 6.5 feet, three supports are required. These support requirements appear in Section 333-7. Finally, Section 410-14(a) permits the inner connection of fluorescent fixtures with Type AC cable. This Part A permits running Type AC cable from fixture to fixture. And since the cable contains 90 degrees C insulated conductors, there is no concern about being within 3 inches of the ballast and having to use 90 degrees C conductor insulation. This requirement for 90 degrees C insulated conductors where the branch circuit conductors are within 3 inches of the ballast is in Section 410-31. Multiwire Branch Circuit Serving Kitchen Receptacles Q: May a 20-ampere, two-pole circuit breaker supply a multiwire branch circuit for the small appliance branch circuits in the kitchen? Is it permissible to connect a 125-volt GFCI receptacle to the circuit after the multiwire branch circuit is split into separate two-wire circuits? A: A 120/240 volt, single-phase multiwire branch circuit is recognized as two circuits by Section 210-4(a). Therefore, this circuit complies with the requirement for at least two 20-ampere small appliance branch circuits in Section 210-11(c)(1). Receptacles installed in the kitchen to supply countertop surfaces also required ground-fault circuit-interrupter (GFCI) protection. This requirement appears in Section 210-8(a)(6). One-hundred-twenty-five-volt GFCI Type receptacles may be installed where the multiwire branch circuit splits into two two-wire circuits. There cannot be a shared neutral on the load side of the GFCI receptacles. In other words, each GFCI receptacle must have its own neutral to supply receptacles downstream. If a common neutral is used, at least one of the GFCIs will trip whenever a 120-volt load is placed on the protected circuit. Dedicated Space for Electrical Equipment Q: Section 110-26(a)(3) describes the height of working space above electrical equipment such as switchboards and motor control centers. Do these requirements prohibit a transformer from being installed above a motor control center even though it is 6 feet above the equipment? A: The answer is no. Section 450-13(a) allows dry-type transformers rated 600 volts or less to be on walls, columns, or structures. This Section allows transformers to be located out of reach from the floor. The dedicated electrical space for electrical equipment is found in Section 110-26(f)(1)(a). This part requires a space equal to the width and depth of the equipment extending from the floor to a height of 6 feet above the equipment to be dedicated to the electrical installation. Therefore, a transformer located above the motor control center does not violate the requirement in Section 110-26(f)(1)(a). FLACH, a regular contributing Code editor, is a former chief electrical inspector for New Orleans. He can be reached at (504) 254-2132.