Jim Dollard has an extensive background in codes and standards. If you have a query about the National Electrical Code (NEC), Jim will help you solve it. Send questions to email@example.com. Answers are based on the 2017 NEC.
We recently had a spirited discussion on the job about the term “readily accessible” and what that really means in the NEC. There was general agreement that climbing over or under something would render equipment accessible but not readily accessible. The biggest hang up we had was the use of the word “obstacle.” What is and—just as important—what is not an obstacle?
To answer your question, we need to review the definition of “readily accessible,” which provides the clarity you need. Where this term is used, the equipment or device required to be readily accessible must be capable of being reached quickly for operation, renewal or inspections. The key here is the word “quickly.” Throughout the NEC, there are requirements that mandate switches or devices, etc., be readily accessible because they must be capable of being reached quickly. “Obstacle” is defined as “a thing that blocks one’s way or prevents or hinders progress.” Anything that would delay ready access to electrical equipment or devices would be considered an obstacle.
For example, a coffeemaker on a dwelling unit kitchen countertop would not delay access to a GFCI receptacle because the appliance is very easily moved out of the way. However, a GFCI receptacle located behind a coffeemaker with permanent water connections in a commercial kitchen is not easily moved. This delays access to the receptacle, so it would be considered an obstacle. A determination must be made on a case-by-case basis with respect to equipment being recognized as readily accessible.
One of our customers recently had a survey done of their entire electrical distribution system to label their equipment with available incident energy and working distance. They called us because the survey revealed that their main service entrance circuit breaker does not have a proper interrupting rating. Apparently the available short-circuit current exceeds the rating of the circuit breaker. Can we put current limiting fuses in a disconnect upstream and be in compliance with series ratings in the NEC?
No, Section 240.86 provides prescriptive requirements for series ratings. There are two permitted methods to achieve compliant series ratings in this scenario: selection under engineering supervision and tested combinations. In this case, you cannot simply add upstream current limiting fuses and be in compliance with Section 240.86. A licensed professional engineer that is primarily engaged in the design or maintenance of electrical installations must make the selection. T
There is significant reason for that requirement. Where an engineer provides series ratings through selection under engineering supervision, he or she must ensure the downstream circuit breaker(s) that are part of the series combination remain passive (meaning they do not begin to open) during the interruption of the line side fully rated current limiting fuses. The other option, series ratings with tested combinations, is very common.
For example, circuit breaker manufacturers provide panelboards with a main overcurrent protective device that typically has a higher interrupting rating than the branch circuit devices in the panelboard. These are “tested combinations.” All overcurrent protective device manufacturers provide data and literature on their tested combinations.
Conduit fill calculations have always puzzled me a bit. My question is about the “jam factor.” I remember this being discussed when I was an apprentice. I personally have never seen conductors jam during a pull, nor have I ever even heard of it. Should there be a requirement in Article 310 to mandate that installers consider the jam factor?
Two informational notes following Table 1 in Chapter 9 provide some background to help answer your question. The first note informs the Code user that this table and the permitted conduit fill are based on common conditions and proper cabling/alignment of the conductors being pulled where the length and number of bends are within reasonable limits.
The second note explains that, where three conductors or cables are pulled into a raceway, there is a possibility jamming may occur. Where three conductors are pulled, there is a greater likelihood that they will flatten out in the raceway as they are pulled through 90-degree bends. The likelihood of jamming is very low when four or more conductors are pulled. This informational note clarifies that the Code user can determine the ratio of the raceway inside diameter to the outside diameter of the conductor or cables being pulled. If the ratio is between 2.8 and 3.2, jamming can occur. There are not many raceways-to-conductor combinations that result in a ratio between 2.8 and 3.2. The informational note explains that jamming can occur; it does not state that it will occur. I, too, have not seen or heard of conductor jamming when pulling conductors, but I am certain that, under the right conditions, it can occur. There is no practical reason to require a calculation before each conductor pull.
Spa/hot tub emergency switch
Spas and hot tubs require an emergency shut-off switch. Section 680.41 requires that the switch be not less than 5 feet away from the spa or hot tub. Where do we measure from, the outside of the unit or the inside wall of the unit? If we are installing a switch for a permanently installed pool, it cannot be closer than 5 feet horizontally from “the inside walls” of the pool. Does the same of measurement hold true for spas and hot tubs?
Yes. Your question did not clarify if this is an indoor or outdoor installation. We will address both. Part IV of Article 680 contains requirements for the installation of spas and hot tubs. As you stated in your question, Section 680.41 requires an emergency switch that is readily accessible to the users, not less than five away, adjacent to and within sight of the spa or hot tub.
Section 680.42 requires that outdoor installations of spas/hot tubs must comply with parts I and II of Article 680. In part II (for permanently installed pools), Section 680.22(C) requires switches be located at least 5 feet from the inside walls of the pool. For indoor installations of spas or hot tubs, Section 680.43(C) requires switches to be located at least 5 feet from the inside walls of the spa or hot tub. In summary, the emergency switch cannot be located any closer than 5 feet from the inside walls of the spa or hot tub and cannot be located more than 5 feet away from any part of the spa or hot tub. The NEC does give the installer prescriptive requirements for the exact location of the required emergency switch. Get involved in the NEC revision process by submitting a public input for the 2020 edition to provide necessary clarity in Section 680.41.
GFCI, 6 feet from sink
In the bar area of a new restaurant, there is a receptacle in the wall directly above the sinks in the bar. The receptacle will be located 4 feet above the bar sinks to supply a flat-screen TV. It seems obvious that this receptacle will be within 6 feet of the sink. It is GFCI protection required? The only people in this area will be the bartenders.
Yes, GFCI protection is required in the scenario you have described. Section 210.8 provides prescriptive instructions on how to measure distances provided. The distance is the shortest path the cord of an appliance connected to the receptacle would follow without piercing a floor, wall, ceiling, fixed barrier or passing through a door, doorway or window. If the measurement is 6 feet or less, GFCI protection is required. It is also important to note that Section 210.8 requires that the GFCI device be readily accessible. If the receptacle will be behind the TV, the GFCI protective device must be upstream and readily accessible.
Direct buried raceways
Is it required to use flexible raceways where entering a building from an underground raceway? In one local township, the inspector requires that we install short sections of flexible raceway or use two condulets at 90 degrees to prevent damage from settlement of the ground. The inspector tells us that the NEC specifically calls out expansion fittings or equivalent. We do not get many frosts in this area. Is this an NEC requirement?
The NEC does not specifically require that the installer take additional steps where an underground raceway will enter a building or structure. The requirement in Section 300.5(J) addresses earth movement. This only applies where we know earth movement through settlement or frost will impact direct-buried conductors, raceways or cables. If the ground is properly compacted, settlement should not be an issue. Frost is not an issue in all areas and movement due to frost is based on the depth of the wiring method and the temperatures involved. The informational note simply refers to compliant methods where there is a likelihood that the earth will move. Informational notes are not a mandatory part of the NEC. See Section 90.5(C).