Topics discussed in our “Code Forum” column involve complicated issues requiring extensive analysis. However, not every Code question warrants such in-depth treatment. Here are the latest short answers to questions posed on our Web site. Coverage includes topics in: Sec. 110-26, 300-5(d), 300-5(h), 410-58(d) and a general discussion of receptacle ground-hole orientation.
Q. We installed a control panel in front of an existing control panel. Both panels operate at 460V. The contractor mounted it approximately 2 ft from the existing panel (space is at a premium). He said as long as the door of the old panel opens freely, according to Art. 110, the distance meets Code requirements. I believe the Code establishes 3 ft as the minimum distance. I believe in this case the minimum separation distance should be 4 ft.
A. If the panels face each other, and if they must be worked hot, then you are correct about the 4-ft minimum workspace. Sec. 110-26(a)(2) does require the workspace to allow for enclosure doors to open unimpeded, but that doesn’t vary the workspace depth rule in Sec. 110-26(a)(1), as covered in Table 110-26(a). Author’s Note: This question originally referenced 1996 rules, prior to the reorganization of this section. The parent language in Sec. 110-26(a) now states that workspaces need to “comply with the dimensions of (1) [Depth], (2) [Width], and (3) [Height].” This should end the confusion that prompted this question.
Q. In Illinois we are installing communication tower sites for multiple users. On one site the installer used plumbing grade Schedule 40 PVC conduit instead of electrical grade. Is this acceptable? The conduit is 2 ft underground and we’re using direct burial type wire (200A ampacity).
A. The answer hinges upon the use of direct-burial cabling. This type of cable can go directly into the earth without raceway protection, provided you have enough cover per Table 300-5. As long as the raceway doesn’t detract from system performance, you could use nonelectrical-grade raceways.
Be aware, however, that this only holds in locations where the nonelectrical-grade raceway is Code superfluous. For example, if the conductors emerge from grade on the side of a building, Sec. 300-5(d) requires a raceway from the minimum cable burial depth to at least 8 ft above grade. This raceway needs to meet all relevant electrical standards. In addition, Sec. 300-5(h) requires a bushing or terminal fitting whenever you make an underground transition from direct burial to raceway, and this would apply even to nonelectrical-grade raceways.
You can’t use EMT for direct burial without supplemental corrosion protection beyond the galvanizing because of a listing restriction. Some inspectors have rejected its use as a sleeve for direct-buried service laterals where it crossed under a driveway, even though the cable type and depth met Code rules for the location without the raceway. One state added a fine print note explaining that in such cases, the raceway was a design feature of a complying installation.
Q. According to the UL directory listings, you don’t have to install receptacles with the ground prong facing up. Many people believe “ground up” is safer. If the cord end is pulled away from the receptacle without breaking contact, this could result in an object falling down between the cord end and the wall, making contact between the grounded and ungrounded prongs. However, if you put your receptacles in “ground up” would the ground prong be pulled away first if you use a “ground down” cord cap? The resulting loop of wire tends to pull away from a receptacle, top first.
A. Some say ground pin up, some say down. So far, every panel that’s looked at this question drew the same conclusion—it’s a design consideration. I agree with that assessment. Perhaps I’d think otherwise if so many cord and appliance manufacturers hadn’t produced so many molded-on angle cord caps with the ground pin down.
I don’t like to see cords reversed with a big loop of cord going up and then over and down due to a mismatch of ground-pin alignments. Since most all of my cords have the ground pin down, all the convenience receptacles in my house have the ground hole down. If I know I’ll be using a certain receptacle routinely for a different cap, I then reverse that particular receptacle.
However, Sec. 410-58(d) requires the ground pin to be first-make, last-break. That’s why they’re longer than the other contacts, and I doubt you’d disconnect a ground pin without disconnecting the blades.