Equipment-bonding jumper

Q

In the 2002 NEC Section 350.60 “Grounding and Bonding,” the title of Section 351.9 of the 1999 Code has been changed by adding “..and Bonding” and the Section re-identified as 350.60. The 2002 NEC Section 250.118 Types of Equipment Grounding Conductors paragraph (7)c indicates that the Code does not consider the liquidtight flexible metal conduit above 1 ¼-in. (trade size) to form a Code-conforming equipment grounding path. 2002 NEC Section 250.96 Bonding Other Enclosures calls for “metal raceways, etc., that are to serve as grounding conductors with or without the use of supplementary equipment grounding conductors shall be effectively bonded where necessary to ensure electrical continuity, etc.” Lawrence Livermore National Laboratories (LLNL) specifications call for a separate equipment-grounding conductor to be installed in all feeders and branch circuits and terminated at the panelboard ground bus, with each end on a grounding lug, bus or grounding bushing. Where there is possible damage of conduit connections due to vibration, we are also specified the installation of about 3 ft of liquidtight flexible metal conduit, which is sometimes larger than 1 ¼-in. (trade size). Under these conditions, where the liquidtight flexible metal conduit is greater than 1 ¼-in., do we need to specify the installation of a outside ground wire around the liquidtight flex, providing a ground bond jumper from the rigid metal conduit to the enclosure and specify equipment grounding conductor inside the conduit?

A

Section 250.96 is not applicable in this case because you are not using the LFMC as an equipment-grounding conductor. Even if you were, such as where the circuit is not over 60A and the LFMC is size 1 ¼-in. or smaller, the listed LFMC fittings would often satisfy this bonding requirement if properly connected. Since the LFMC is not used as an equipment grounding conductor, a separate conductor is required by 250.118 (1) and 250.134(A) and (B). This equipment-grounding conductor is usually run inside the raceway. However, this equipment-grounding conductor is also an equipment-bonding jumper according to the definition of “Bonding Jumper, Equipment” in Article 100: “The connection between two or more portions of the equipment-grounding conductor.” According to 250.102(E) an equipment-bonding jumper may be installed either inside or outside of a short length of raceway. Whether installed inside or outside, the conductor can satisfy the requirements for both the equipment-grounding conductor and the equipment-bonding jumper. When installed on the outside, it's more likely to be called an equipment-bonding jumper, and when installed on the inside it's more likely to be called an equipment-grounding conductor, but either way, the function is basically the same and one conductor can meet both requirements. Where it's installed is essentially a design preference. On the outside, it's easier to examine, but perhaps more likely to be damaged and therefore more likely to need periodic examination.
Noel Williams

Four questions about circuits

Q

I do residential wiring on the side. I've run into some situations in a town where there is no Code inspection required, so some things I learned are not being followed. I have four questions:

Question 1. Circuit is fed with 20A and 12-2 AWG to a bedroom. The 12-2 AWG daisy-chains around the room to the light switch for the closet light and the room light J-boxes. From there up to the light fixture J-box, the previous electrician (maybe I'm generous with that term) ran 14-2 AWG. I was taught breaker or fuse protection must be used to protect the smallest wire in the circuit because a short in 14-2 could overheat, cause a fire and not trip a 20A breaker. I was also taught not to mix wire so breakers get sized right. Does the Code allow feeders from a switch to a light on a 20A circuit with #12 wire to be feed with #14?

Question 2. I was wiring a home in which the previous electrician ran 12-3 AWG to the fuse box, landed the red on one 20A breaker and the black on another 20A breaker. The catch is he supplied only one neutral (white) wire for effectively two circuits. Also, the breakers were not tandem (i.e., handles were separate and not connected). Example: I ran 12-3 AWG to kitchen. One “hot” to the refrigerator, one “hot” to the disposal both relied on the common single white neutral. Isn't this a violation because the white or neutral could be overloaded if both circuits drew heavy loads?

Question 3. The Code calls for GFCI in kitchen garages and baths. How about the light switches in those rooms. Do they need protected by GFCI? Does it matter how close the switch is to the sink in the bath and kitchen? Does it matter at all in the garage? Is it just related to outlets? The same question would apply for the disposal switch, which is usually close to the sink. Does it need to be protected by a GFCI?

Question 4. Are enclosed fixtures with incandescent fixtures OK in a closet? What if a fluorescent screw-in light bulb is used versus an incandescent? I appreciate your reply to these questions. My goal is always to maximize safety.

A

Question 1. The wire used to “hook up the light” is probably a fixture wire, covered by 240.5(B)(2). These conductors have limited loads, so only short-circuit and ground-fault protection is provided. They are not permitted as branch circuit conductors. The “switch leg tap” is still part of the branch circuit, according to the definition of “Branch Circuit” in Article 100, so it must comply with 240.4, specifically, 240.4(D), which would permit the 14 AWG tapped to a 12 AWG only if the entire branch circuit were protected at 15A. The branch circuit taps permitted by 240.4(E) and 210.19(A)(3) and (A)(4) do not recognize the type of tap you describe. (This is an errata in the first printing of the 2002 NEC. The reference to 210.19(C) and (D) in 240.4 should read 210.19(A)(3) and (A)(4) to correlate with the renumbering of this section. Errata for the first printing is available from NFPA's NECDirect Web site.)

Question 2. The circuit you describe is a multiwire branch circuit as defined in Article 100. Such circuits are permitted, with certain restrictions, by 210.4. The primary caution is that the black and red wires must go on different ungrounded legs. In a typical single-phase, 120V/240V system, the neutral will only carry the difference in the loads on the ungrounded conductors, which if both circuits are loaded to 20A, would be zero. This is no different than loading on a service neutral, which is sized according to 220.22. The primary risk of overloading on the neutral in small branch circuit conductor sizes occurs only if the red and black wires are connected to the same “phase” in the panel.

Question 3. Most of the GFCI protection requirements in dwelling units are found in Section 210.8. This section is concerned only with “125V, single phase, 15A or 20A receptacles.” The rule does not cover lighting outlets or switches. Other rules in the NEC cover switches where there is a special risk. For example, Section 410.4(D) excludes luminaires from the reach area around a tub or shower. Section 680.43(C) excludes switches from being located within 5 ft of a spa or hot tub. Similar rules apply to swimming pools, although in some cases, GFCI protection is required for luminaires (Section 680.22(B)(3) and (4)) and the switches in such cases are probably going to be GFCI protected as well. In Sections 620.23 and 24, the required lighting for elevator pits and machine rooms is prohibited from being connected on the load side of GFCIs. The one place where most electrical equipment, switches and luminaires are required to be GFCI protected is in wet locations in health care facilities, and even here in Section 517.20, isolated power systems can be used instead.

Question 4. Lighting in clothes closets is covered by Section 410.8, which prohibits any fixtures from the defined spaces described and illustrated there. As long as the luminaire is not installed in the prohibited spaces, a surface or recessed incandescent fixture can be used if it has a completely enclosed lamp. Section 410.8(C) describes the luminaires that cannot be used in closets even in the permitted areas. As for location, the luminaires you describe must be located in accordance with 410.8(D). For incandescent luminaires, this rule requires at least 12 in. of clearance from the defined storage space for enclosed surface fixtures, and 6 in. for enclosed recessed fixtures. Since fluorescent lamps do not burn as hot as incandescent, the spacing for surface fluorescent fixtures is only 6 in. For the purpose of these rules, an incandescent luminaire with a fluorescent self-ballasted lamp installed is still an incandescent luminaire.
Noel williams