Jim Dollard has an extensive background in codes and standards. Send questions about the National Electrical Code (NEC) to Jim at [email protected]. Answers are based on the 2023 NEC.

Drip pan over a busway

We installed a 2,000A busway in a commercial midrise to supply power to each floor. After the busway leaves the electrical room, it travels approximately 60 feet through a mechanical space before going vertically through the building. The engineer is telling us that we need a drip pan over the busway where a sprinkler main passes over it in the mechanical space. Is that correct?

No, a drip pan is not required. The requirements in 110.26(E)(1)(b) are commonly misapplied. This is a good example of why the Code user must understand how the NEC is structured. Section 110.26 addresses spaces about electrical equipment and ensures access and working space to facilitate ready and safe operation and equipment maintenance. There are six first-level subdivisions in this section and 110.26(E) covers dedicated equipment space. It is important to read the parent text in 110.26(E) because it limits the equipment addressed by this requirement to switchboards, switchgear, panelboards and motor control centers. 

Second-level subdivision 110.26(E)(1)(b) covers protection from foreign systems (such as a sprinkler main as in your question) where the equipment is installed indoors. This requirement does not apply to busway; it applies to switchboards, switchgear, panelboards and motor control centers located in dedicated spaces. This is an important limitation because the term “equipment” includes more than what is covered in this section, including, but not limited to, busway, conduits, luminaires, receptacles and more.

Tamper-resistant receptacles

An inspector failed an installation, claiming that receptacles needed to be tamper resistant. The structure is a large, detached garage used for storing tractors and such on a residential property. Isn’t that rule limited to where kids would be?

The inspector is correct. Section 406.12 list item (1) clearly requires all 15A and 20A, 125V and 250V nonlocking-type receptacles in all dwelling units, boathouses, mobile homes and manufactured homes, including their attached and detached garages, accessory buildings and common areas, be tamper resistant. It is understood that detached garages and dwelling units with accessory buildings, such as sheds or pool houses, will be accessible to children.

Is a ground rod required?

We are hoping you can settle a Code disagreement on the job. Where a concrete-encased electrode is installed in the footer of a dwelling unit, are two ground rods still required?

No. A concrete-encased grounding electrode can stand alone; it is not required to be supplemented with another electrode. It is important to understand that Section 250.50 requires all the grounding electrodes listed in 250.52(A)(1) through (A)(7), provided they exist, be bonded together to form the grounding electrode system. It further clarifies that if none of those electrodes exist, one or more electrode(s) listed in 250.52(A)(4) through (A)(8) must be installed, meaning we are creating an electrode.

The confusion here exists because in typical construction, the only electrode that exists when the electrical contractor arrives is a metal underground water pipe. In all cases where a metal underground water pipe is used as a grounding electrode, Section 250.53(D)(2) requires that it be supplemented by an additional electrode. 

At that stage in a job, the most feasible additional electrode is a ground rod. Where a single rod is installed, 250.53(A)(2) requires it be supplemented by an additional electrode of a type specified in 250.52(A)(2) through (A)(8). Note that the electrode in 250.52(A)(1) is the metal underground water pipe being supplemented. This is the rule that requires a second ground rod, which must be installed not less than 6 feet from the first ground rod.

Burial depth measurements

When applying the burial depth requirements, do we measure from the trench depth only or from the top of the conduit? When trenching for 4-inch conduit, it makes a difference.

The requirements of Table 300.5 address cover requirements, meaning the distance above a conduit or cable. See Note 1 to Table 300.5, which clarifies that cover is the shortest distance measured between the top surface of any direct-buried conductor, cable, conduit or other raceway and the top surface of finished grade, concrete or similar cover. When applying the requirements of tables in the NEC, it is extremely important to understand that table notes are enforceable, not informational.

Work surface or countertop?

There are several NEC requirements directed at countertops and work surfaces. Some requirements vary—do we need to know the difference?

Both terms are defined in Article 100 of the NEC. Countertops are defined as always being stationary or fixed in place, while a work surface may be portable. 

Countertops are intended for food preparation and serving (kitchens), personal lavation (bathrooms), laundering or a similar use that presents a routine risk of spillage of larger quantities of liquids upon any outlets mounted directly on or in the countertop surface.

Work surfaces are intended for dry use and tasks other than food preparation (kitchens), lavation (bathrooms) or laundering that presents an incidental risk of spillage of smaller quantities of beverages and other liquids on outlets mounted directly on or recessed in the work surface. 

More than one neutral per circuit?

I am confused by the rules in 200.4(A) and 200.4(B). One says only one neutral per circuit and the next states multiple. They seem to contradict each other. Can you help?

There is no conflict between those requirements. Section 200.4(A) provides a general rule mandating that a neutral conductor can only be used for one branch circuit, one multiwire branch circuit or for one set of ungrounded feeder conductors. This is the general rule, and there are modifications elsewhere in the NEC.

Section 200.4(B) is a different requirement addressing installations where an enclosure, such as a cabinet containing a panelboard, may contain many ungrounded conductors and neutrals of different circuits. Where this occurs, the neutrals (grounded circuit conductors) of each different circuit must be identified (number tags, Ty-Raps or other) or grouped to associate the neutral conductor with the ungrounded conductors of the circuit. This can be accomplished by wire markers, cable ties or similar means in at least one location within the enclosure. Where the association is evident, as when there is a single circuit per cable assembly or raceway, the marking is not required. Where conductors are pulled straight through a junction box and a loop is not provided for future expansion, marking is not required.

Equipment near a fire pump

Are electric water heaters permitted in a fire pump room? A mechanical contractor is installing two electric water heaters in the same room as the fire pump. Is this permitted? The electrical engineer on the job is requesting they be removed.

What is and is not permitted in a fire pump room is outside the NEC’s purview. NFPA 20 has purview over the performance of electric fire pumps, and the NEC simply provides installation requirements meeting those performance objectives. 

NFPA 20, Section 4.14.1.1 contains requirements for indoor fire pumps. Section 4.14.1.1.6 permits equipment related to domestic water distribution to be located within the same room as the fire pump equipment. Explanatory material in Annex A of NFPA 20 offers more insight into what is not permitted in a fire pump room, e.g., fuel-fired water heaters and any equipment that increases the fire hazard (such as boilers) and is not related to fire protection systems should not be in a fire pump room.

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