Article 210 Branch Circuits
Article 215 Feeders
Article 240 Overcurrent Protection
Article 300 Wiring Methods
Article 320 Armored Cable
Article 352 Rigid Nonmetallic Conduit
Article 404 Switches
Article 604 Manufactured Wiring Systems
Article 680 Swimming Pools, Fountains and Similar Installations
Article 695 Fire Pumps
Manufactured wiring systems
Q: Is it necessary to support manufactured wiring above a lay-in ceiling? These wiring harnesses are used to connect fluorescent fixtures in a suspended ceiling, and for switch legs in the walls.
A: Rules for the installation of these wiring systems are found in Article 604—Manufactured Wiring Systems. These systems are permitted in accessible and dry locations and in plenums and spaces used for environmental air where listed for this application.
If the space above a suspended ceiling is used as a duct or plenum, the manufactured wiring system must be marked, “Acceptable for use in ducts or plenums” or equivalent wording. Similarly, if the manufactured wiring is marked, “Acceptable for installation in environmental ceilings only” or equivalent, it cannot be used in a ceiling space that is a plenum or duct.
Armored cable, metal-clad cable, and flexible metal conduit are some of the wiring methods used for manufactured wiring systems. Contained conductors must be not smaller than 12 AWG copper with 600V insulation.
Part (E) of 604.6 covers support requirements for manufactured wiring systems and says: “Manufactured wiring systems shall be supported in accordance with the applicable cable or conduit article for the cable or conduit type employed.” Assuming that the wiring method for the manufactured wiring system is Type AC cable, it is not allowed in ducts or plenums used for environmental air, but may be used in a suspended ceiling where the space above the ceiling is used for movement of environmental air. This wiring method is permitted in this space by 300.22(C)(1).
To comply with part (E) of 604.6, Type AC cable must be secured and supported in accordance with 320.30. Generally, the cable has to be secured and supported every 4.5 feet and within 1 foot of each cable termination. However, part (B) of 320.32 allows various lengths of unsupported cable where the cable is fished and where the cable supplies lighting fixtures or equipment in an accessible ceiling.
GFCI protection for refrigerators
Q: In the January 2003 issue of ELECTRICAL CONTRACTOR magazine, there was a question dealing with Ground-Fault Circuit-Interrupter (GFCI) protection for refrigerators in commercial kitchens. In part of your answer, you stated that GFCI protection was required for refrigerators in kitchens in all occupancies. I cannot find this requirement in 210.8 for refrigerators in dwelling occupancies. Am I missing something?
A: No, you are not. There is no requirement for GFCI protection of a refrigerator in a dwelling-type occupancy. However, where a duplex 15 or 20A, 125V receptacle is installed above the height of a kitchen countertop and at or near the end of the countertop to supply a refrigerator, the receptacle must have GFCI protection because one-half of the receptacle is readily accessible for plugging in counter-type kitchen appliances such as electric coffee makers, toasters, microwave ovens, etc. A duplex receptacle installed low on the wall in back of the location for the refrigerator in a dwelling unit does not require GFCI protection.
I also agree that my answer in the January issue of the magazine was not as clear as it could have been.
Overcurrent protection for an on-site generator that supplies a fire pump
Q: What size overcurrent protection is required for a branch circuit that supplies a fire pump from an on-site generator? The generator is 750kVA, 480V, 3-phase and has adequate capacity to supply all essential loads while starting and running a 100-horsepower, 480V, 3-phase fire pump motor that is connected to an autotransformer motor starter. The normal power supply for the fire pump is from the utility company and is considered to be a reliable power source by the authority-having jurisdiction.
A: The on-site generator must have the ability to deliver about 370A of starting current to the fire pump motor. This is about 50 percent of the inrush current of a 3-phase, 480V, 100-horsepower motor.
Because the on-site generator is capable of delivering more than 225 percent of the full-load current of the fire pump motor, overcurrent protection for the fire pump branch circuit cannot exceed 350A for an inverse time circuit breaker or 225A for a dual element time-delay fuse. However, if these Ampere ratings of overcurrent devices do not allow the motor to start and run, the next larger size is permitted. These Ampere ratings for the fuses and circuit breaker for the fire pump motor are permitted by Exception No. 2 to 695.6.(D).
Expansion fittings for rigid nonmetallic conduit
Q: Is an expansion fitting required for a 20-foot length of PVC conduit outdoors that has elbows on each end and is subject to temperatures that vary from about 20 F to 95 F?
A: Rigid, nonmetallic conduit must be secured and supported as outlined in 352.30 and Table 352.30(B). Expansion fittings are required where the expected change in length is one-quarter inch or more in a straight length that is securely fastened at both ends by elbows, cabinets or boxes.
To determine the amount of expansion it is necessary to use Table 352.44(A). The temperature variation (20 to 95 F) causes an expansion of 3.04 inches in a 100-foot length of PVC conduit. Therefore, 20 feet of PVC will expand or contract 0.608 inch (20 divided by 100 times 3.04). Since the expected change in length exceeds 0.25 inch, an expansion fitting is required.
Q: Is it permissible to install receptacles at a distance of 3 feet or less from a bathtub or shower stall?
A: Receptacles cannot be installed in bathtub and shower spaces, but they can be installed within 3 feet of these locations. All 15 and 20A, 125V receptacles installed in bathrooms of dwelling-type occupancies must have ground-fault circuit-interrupter protection. This is required by 210.8(A)(8).
Where a hydro-massage bathtub is involved, any 125V receptacles rated 30A or less that are within 5 feet of the inside walls of a hydro-massage bathtub must have GFCI protection. This requirement appears in 680.71. At least one receptacle rated 15 or 20A, 125V must be installed not closer than 5 feet and not more than 10 feet from the inside walls of a hot tub. Also, receptacles rated 30A or less location within 10 feet of the hot tub must be protected by a GFCI. These requirements are found in 680.43.
Circuit breakers for air conditioning equipment
Q: Is a circuit-breaker without a HACR marking suitable as a disconnecting means for an outdoor air conditioner that consists of an hermetic motor-compressor and a condenser fan?
A: It depends on the information on the data plate of the remote compressor-condenser unit. If the marking indicates “fuses,” the air conditioning circuit must be protected by properly sized fuses. If the nameplate specifies an HACR circuit breaker, either properly sized fuses or an HACR circuit breaker are acceptable. If the marking specifies fuses or a circuit breaker, the circuit breaker does not have to be an HACR type.
If you have provided the proper type and Ampere rating of the overcurrent protective device(s) at the point where the air conditioning equipment branch circuit receives its supply, a nonfused switch with a proper horsepower rating, or a circuit breaker may serve as the disconnecting means at the unit.
High leg marking in a disconnect switch
Q: Is it necessary to identify by location, color, tagging, or marking the phase conductor with the higher voltage to ground in a disconnect switch for a 3-phase motor?
A: On a 3-phase, 4-wire, 240V delta system the conductor with the higher voltage (about 208) to ground is referred to in the NEC as the “B” phase. In switchboards and panelboards, the bus arrangement is A B C from front to back, top to bottom, and left to right. This results in an arrangement in which the phase with the higher voltage to ground is always in the middle.
Where the neutral or grounded circuit conductor is also present, the conductor with the higher voltage to ground must be identified. This is the requirement in 215.8: “On a 4-wire, delta-connected secondary where the midpoint of one phase winding is grounded to supply lighting and similar loads, the phase conductor having the higher voltage to ground shall be identified by an outer finish that is orange in color or by tagging or other effective means. Such identification shall be placed at each point where a connection is made if the grounded conductor is also present.”
Assuming that the 3-phase branch circuit to the motor does not include a grounded circuit conductor, the phase conductor with the higher voltage to ground does not have to be identified in any way.
Switching 277V lighting circuits
Q: I have been told that I cannot use circuit breakers to switch 277V fluorescent lighting circuits. This has been common practice. Is this a change in the 2002 edition of the NEC?
A: Circuit breakers are available for switching fluorescent lighting fixtures on and off. However, they must be marked ‘SWD’ or ‘HID.’ According to 404.11 circuit breakers are permitted to be used as switches. And 240.83(D) allows their use for switching fluorescent lighting where the circuit breakers are marked ‘SWD’ or ‘HID.’ The only change to this rule in the 2002 edition is the addition of HID marking on circuit breakers that are used to switch high intensity discharge lighting loads. EC
FLACH, a regular contributing Code editor, is a former chief electrical inspector for New Orleans. He can be reached at 504.734.1720.