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. Questions can be sent to [email protected]. Answers are based on the 2014 NEC.
Pull boxes for communications cable
We are involved in a large data center installation, and a question has arisen on how to size pull boxes. The design calls for pull boxes at multiple points for all of the conduit runs. Since we are in an existing facility, there are a few tight spaces where the pull boxes are smaller than the size required in Section 314.28. I have always been under the impression that the pull-box sizing rules do not apply to communications cable. However, we are using electrical metallic tubing (EMT), and one engineer has informed us that all of the rules in NEC Chapter 3 for raceways, including boxes, apply. Do the rules for sizing a pull box in 314.28 apply because we are using EMT?
No. The rules for sizing pull boxes in 314.28 do not apply in Chapter 8 articles, including Article 800 for communications circuits. Article 90, Section 90.3 provides the Code user with extremely important information for how the NEC is arranged and how it applies in a given installation. This section clarifies that Chapter 8 covers communications systems and is not subject to the requirements of chapters 1 through 7 except where the requirements are specifically referenced in Chapter 8. Installation methods for communications circuits are located in Part V of Article 800. Part V contains no requirements for the minimum size of pull boxes.
The engineer may be referring to Section 800.110(A)(1), which requires Chapter 3 “raceways,” such as EMT, to be installed in accordance with Chapter 3 requirements. This requirement applies to the physical installation of the EMT. Section 314.28 applies specifically to “pull boxes.” The issue here could be that the definition of the term “raceway” could apply to a box under given conditions. In your installation, the pull box is part of the raceway system, but the raceway is the EMT. Additional clarity in the NEC would be helpful.
Neat and workmanlike manner
The requirement in Section 110.12 is that electrical equipment be installed in a “neat and workmanlike” manner. What does that really mean?
“Neat and workmanlike” means that electrical equipment is installed in a professional manner. This requirement is really about workmanship and recognizing that the equipment was professionally installed. It includes, but is not limited to, installing enclosures, raceways and devices level, evenly spaced, along with neat conductor terminations. While these items are not specifically listed in the NEC requirements, Section 110.12, “Mechanical Execution of Work,” says the “neat and workmanlike” requirement gives the electrical inspector room to make such a decision in the field based on visible workmanship. We all know what a neat and workmanlike installation looks like, but it is hard to capture in a prescriptive NEC requirement. Specific workmanship requirements in Section 110.12(A) and (B) include closing all unused openings, ensuring that busbars, terminals and insulators, etc., are not damaged or contaminated by foreign materials and that there are no damaged parts in the installation.
The informational note after this section provides guidance to other standards for information on good workmanship. For further information on accepted industry practices, refer to NECA 1 2010, Standard Practice of Good Workmanship in Electrical Construction.
Ground rod effectiveness
Why does the NEC require ground rods to be spaced 6 feet apart? An informational note follows Section 250.53(A)(3) and recognizes you need more than 6 feet of spacing. If science tells us that we need more space between electrodes for them to be effective, why not require 20 feet?
Per Section 90.1(A) and (B), the purpose of the NEC is the practical safeguarding of people and property. It is not a design or specification manual, but it is the minimum requirement for safety. There is always room for system design to do more than these minimum requirements. The 6-foot spacing is simply the minimum requirement for a safe installation.
Section 250.53(A)(2) requires a single ground rod to be supplemented by an additional electrode, which can be any of the types listed in 250.52(A)(2) through (A)(8). Where two ground rods are used, Section 250.53(A)(3) requires them to be spaced a minimum of 6 feet apart to increase their efficiency. The informational note tells Code users that they can increase ground rod efficiency with additional spacing if they choose to do so. Many factors come into play and affect the minimum 6-foot spacing, including, but not limited to, physical space needed to install the rods and existing soil conditions.
Accessibility and 240.24(A)
The change in the 2014 NEC to the defined term “readily accessible” has created many problems for us when we install control panels that contain fuses. Where any type of tool is required, the inside of an enclosure is no longer “readily accessible.” On multiple occasions, an electrical inspector wrote us up because the control-panel design requires a half-turn on four screws to open it so that it stays closed and sealed. The inspector cited Section 240.24(A), which requires all overcurrent devices to be readily accessible. The inspector has given us special permission because the maintenance staff always has a screwdriver to open the panels. Is it the intent of Section 240.24(A) to prohibit the use of tools to access a fuse?
A literal reading of the requirements in Section 240.24(A) supports the position of the inspector. However, in my opinion, this requirement specifically addresses ready access to the operation of the switch or circuit-breaker handle. There are two general requirements contained here: (1) overcurrent devices must be readily accessible and (2) the center of the grip of the operating handle of the switch or circuit breaker, when in its highest position, is not more than 6 feet, 7 inches above the floor or working platform. In my opinion, this requirement simply gives us a maximum height at which the operating handle is considered to be readily accessible. In many cases, a revision in one part of the NEC can affect other requirements, and those ramifications may not be seen at first glance. The revision to the definition of “readily accessible” has certainly affected this requirement. There are public inputs submitted to revise this requirement for the 2017 NEC and I believe that this issue will be corrected in 240.24(A).
FMC in wet locations
We are involved in a large renovation project, and we are trying to use existing raceways where possible. Dozens of outdoor heating, ventilating and air conditioning units are being replaced, along with the branch-circuit conductors. The new conductors are smaller and will easily fit into the existing flexible metal conduit (FMC). We are now working under the 2014 NEC, which does not permit the use of FMC in wet locations. Since the FMC was installed under a previous Code, can we still use it?
No, FMC is not permitted to be installed in wet locations, per Section 348.12(1). The 2014 NEC does not contain an exception referencing the previous requirement to allow reuse of existing installations of FMC. The previous permission to use FMC in wet locations required that (1) the conductors were approved for the specific conditions and (2) the installation ensured that liquid did not enter enclosures through the FMC. That permission was deleted in 2008 because it was impossible to prevent moisture from getting into enclosures. FMC allows for water to accumulate in the conduit and then migrate into enclosures. Where flexible raceways are required in wet locations, liquid-tight flexible metal conduit or liquid-tight flexible nonmetallic conduit are feasible options.
Disconnecting means location
Why is the NEC vague on where the service disconnect must be located? The words “nearest the point of entrance” allow for a wide array of interpretations.
Section 230.70(A)(1) requires the disconnect to be “installed at a readily accessible location either outside of a building or structure or inside nearest the point of entrance of the service conductors.” This text is prescriptive, requiring the disconnect to be readily accessible and permits it to be installed outdoors or indoors.
The NEC cannot mandate a minimum or maximum distance in this situation because, in some cases, the disconnect may be installed within a few feet of the conductor entrance. In others, more distance is required. Each indoor service disconnect installation is unique. In some cases, the point of entrance can be anywhere on the outside of four building walls, providing the installer with many options. In other cases, there may be only one location for the conductor entrance.
About The Author
DOLLARD is retired safety coordinator for IBEW Local 98 in Philadelphia. He is a past member of the NEC Correlating Committee, CMP-10, CMP-13, CMP-15, NFPA 90A/B and NFPA 855. Jim continues to serve on NFPA 70E and as a UL Electrical Council member. Reach him at [email protected].