If you have a problem related to the National Electrical Code (NEC), are experiencing difficulty in understanding a Code requirement or are wondering why or if such a requirement exists, ask Charlie, and he will let the Code decide. Questions and comments can be sent to firstname.lastname@example.org. Answers are based on the 2011 NEC.
What do you do?
In your September 2010 CodeFAQs column, there was a question about two-pole circuit breakers. You used the example of a duplex receptacle with the tab removed and two circuits on the outlet. By all means, both should disconnect simultaneously as you stated. The question I have, and I believe the author of the aforementioned question also had, is this: with a 12/3 home run for two small appliance circuits, nowhere do both circuits connect to the same outlet (yoke). The 12/3 goes to a box in the kitchen, red conductor ties through, neutrals pigtail, each circuit goes a different direction. This is the problem with the breaker ties, every 3-wire home run ties two breakers together. Something trips, and you lose twice as much. I think this Code article applies only to the case where two circuits are on the same yoke. This confuses inspectors, too. I’ve been told if I have more than one circuit in a box, I have to tie the handles. If I have a four-gang box with four circuits on separate switches, should I tie all those?
The purpose of the Code relates to the practical safeguarding of people and property from hazards arising from the use of electricity (90.1). De-energizing one circuit with a shared neutral does not eliminate current flow in the neutral. This could present a shock hazard problem to someone working on that circuit. I don’t know where you picked up this “tying” together of switch handles in an outlet box. A careful reading of NEC 210.4(B) will show you that the simultaneous disconnection is required where the circuits originate, which is in the panelboard. Be sure to read the informational note (formerly a fine print note), which is new in the 2011 Code relating to single-pole circuit breakers as the disconnecting means.
Exothermic or irreversible compression
Is an exothermic or irreversible compression connection to fireproofed structural metal required to be accessible?
NEC 250.68(A) Exception No. 2 shows that exothermic connections used at terminations to fireproofed structural metal are not required to be accessible.
I’m an electrician in rural New York state. In my area, a service-disconnecting means “is required” to be installed ahead of the service-entrance cable to single-family dwellings if the distance from the utility metering device to the panelboard is more than 6 feet. I can find no such requirement in the NEC. Is this a locally mandated code?
NEC 230.70(A)(1) requires the service-disconnecting means to be located in a readily accessible location either outside of the building or inside nearest the point of entrance of the service conductors. No definite or maximum distance is specified and the authority having jurisdiction is responsible in determining the maximum distance allowable in each installation. The service-entrance conductors should be kept to a minimum length in the building because they are protected only by the limited overcurrent protection offered by the utility company. In your area, the authority apparently allows 6 feet of unprotected service-entrance conductors in a building or structure.
When in Romex …
Is it required that each Romex be fastened to the panel with a Romex connector? Why can’t I pull several into the panel through a 2-in. bushing?
NEC 312.5(C) establishes the general rule requiring that each cable must be secured to the panel. An exception to this requirement permits nonmetallic-sheathed cables to enter the top of a surface-mounted enclosure through one or more nonflexible raceways not less than 18 inches and not more than 10 feet in length provided conditions (a) through (g) are followed. Read these conditions carefully and note that this exception applies only to surface-mounted panels. Ensure the raceway does not penetrate a structural ceiling as access to the outer end must be accessible, and note that if the raceway exceeds 24 in., the cable-fill requirements of Table 1, Chapter 9 apply.
Encasing electrodes in concrete?
I recently inspected a house, and they did not put a concrete-encased electrode in the new foundation. When I questioned them, they indicated that the electrode was not needed because the foundation and footings did not have any reinforcing rods in the concrete. They used ground rods driven into the soil adjacent to the foundation. I have read through several sections of Article 250 and have found no absolute requirement to put in a concrete-encased grounding electrode into the foundation or footing.
NEC 250.52(A)(3) covers concrete-encased electrodes. If reinforcing rods are not present, you must use the alternate method of using a bare copper conductor not smaller than 4 AWG installed horizontally in the concrete foundation or footing or within vertical foundations that are in direct contact with the earth.
Cables need space, too
I understand 310.15(B)(2), but what constitutes the spacing mentioned? For example, if I use 3M’s cable stackers, which can hold four AWG 12 cables but maintains a small space between them, do I have to derate? I frequently use the “V” in attic trusses to homerun cables to the breaker box (above the insulation). The cables in the “V” and the runs in-between are in close proximity but not necessarily touching. Do I have to derate?
Spacing is not defined, but as long as there is space between the cables, heat dissipation is possible. NEC 310.15(B)(2) requires only that the cables are not touching each other.
Spare the ground rod?
It says in 250.66(A) that a sole connection to rod and pipe grounding electrode is not required to be larger than AWG 6 cu or AWG 4 al. If I have driven two ground rods to meet the requirement of 250.56, am I outside of the sole connection and therefore required to size the grounding-electrode conductor to Table 250.66?
A rod or pipe grounding-electrode conductor is not required to be sized according to Table 250.66. The reasoning for this requirement relates to the establishment of the grounding--electrode system as shown in 250.50, where all grounding electrodes as described in 250.52(A)(1) through (A)(7) that are present must be bonded together to form the grounding-electrode system. In the process of bonding all of the grounding electrodes together, there are different requirements regarding the size of the grounding-electrode conductor required for each type of grounding electrode that must be considered. The bonding together of the different types of grounding electrodes must ensure these sizing requirements are not compromised.
My local inspector says that, when installing a 30-amp, 120-volt or 50-amp, 120/240-volt shorepower receptacle on a single-family residential boat dock, the receptacle must be ground-fault circuit interrupter-protected per NEC 682.33(B). I don’t see how this article can apply to boat docks on navigable waterways. What is your opinion?
NEC 682.33(B) requires all circuits rated not more than 60 amperes (A) at 120 through 250 volts, single-phase must have GFCI protection. The requirements apply where the municipality having jurisdiction has adopted these requirements by ordinance.
Section 240.4(B) allows the next size up only when the next higher standard rating selected does not exceed 800A. Why is it not permitted above 800A?
Reasonable protection is afforded the conductors up to 800A, but the effective protection is reduced by the greater diversity in standard overcurrent protection after 800A. The difference in ratings for conductors below 800A is 100A or less, whereas above 800A, the difference can be from 200A to 1,000A.
Dealing with condensation
Where is the information in the Code detailing requirements for sealing conduit that passes from ambient temperature through a cold room. I know that condensation will form inside the raceway unless sealed.
NEC 300.7 covers raceways exposed to different temperatures. Note that it specifies only raceways and does not specify enclosures nor jar-type fixtures. However, if you have worked in coolers or refrigeration rooms and had to empty the water from half-full jar-type fixtures or clean the water out of refrigeration room equipment disconnects, you can recognize that they are subject to the same condensation effects as the raceways. This condensation effect is similar to the reasoning behind 300.5(B), where the interiors of enclosures and raceways installed underground are considered to be wet locations and 300.9, where the interior of raceways in wet locations above grade are specified as being wet locations. However, the interior of enclosures, although subject to the same condensation effects, is not specified as being a wet location.
TROUT answers the Code Question of the Day on the NECA Web site. He can be reached at email@example.com.