Wall Space in Dwelling Units, Bonding Metal Water and More


Article 110 Requirements for Electrical Installations

Article 210 Branch Circuits

Article 250 Grounding

Article 310 Conductors for General Wiring

Article 314 Outlet, Device, Pull and Junction Boxes; Conduit Bodies; Fittings; and Manholes

Article 410 Luminaires (Lighting Fixtures), Lampholders and Lamps

Article 430 Motors, Motor Circuits and Controllers

Article 518 Places of Assembly

Article 680 Swimming Pools, Fountains and Similar Installations

Part of the 2003 edition of the General Information for Electrical Equipment Directory published by Underwriters Laboratories Inc. is also mentioned.

Wall space in dwelling units

Q: When spacing wall receptacles in various rooms in a residential occupancy, is it permissible to start the measurements where the door stops against the wall when the door is open?

A: No, it is not. All measurements must be taken along the wall where it starts at the door opening. This generally results in a receptacle being located about 3 or 3.5 feet from the edge of the door when it is open. Previous issues of the National Electrical Code used the phrase “useable wall space,” but these words no longer appear.

This is the requirement as it now appears in 210.52(A)(1): “Spacing. Receptacles shall be installed so that no point measured horizontally along the floor line in any wall space is more than 1.8m (6 feet) from a receptacle outlet.”

Part (2) of 210.52(A) clarifies the meaning of “wall space,” and reads like this: “Any space 600mm (2 feet) or more in width (including space measured around corners) and unbroken along the floor line by doorways, fireplaces and similar openings.” Notice that there is no exception for wall space that is located behind a door when it is open.

Location of disconnect for pools, spas and hot tubs

Q: In the 1999 edition of the NEC, Section 680-12 included a requirement that the disconnecting means for pools, spas and hot tubs be located at least 1.5m (5 feet) from the inside walls of this equipment. Since there is no distance specified in 680.12 of the 2002 edition of the National Electric Code, may a disconnect switch be located closer than 5 feet from the inside walls of swimming pools, spas and hot tubs?

A: Although there is no distance mentioned in 680.12, other parts of Article 680 do specify minimum distances for switches from pools, spas and hot tubs.

For swimming pools, this requirement appears in 680.22(C): “Switching Devices. Switching devices shall be located at least 1.5m (5 feet) horizontally from the inside walls of a pool unless separated from the pool by a solid fence, wall or other permanent barrier. Alternatively, a switch that is listed as being acceptable for use within 1.5m (5 feet) shall be permitted.”

There is also a requirement for an emergency switch for spas and hot tubs in 680.41. This switch must be labeled emergency shutoff. The purpose of this switch is to stop a motor or motors that provide power to the re-circulation system and jet system. It must be readily accessible, within sight, but at least 5 feet away from the spa or hot tub. However, this requirement does not apply to single-family dwellings.

There are also requirements for disconnecting means for motors in 430.101 through 430.110. These rules require that the disconnecting means be readily accessible and within sight (visible and not more than 50 feet away) of the motor it controls.

The exceptions in 430.102 do not apply to this installation. For motors rated 2 hp or less and 300V or less, a general-use AC/DC snap switch with an Ampere rating that is twice the full-load current of the motor is acceptable, or a general-use AC snap switch that is suitable for use on AC circuits only is acceptable provided that the motor full-load current does not exceed 80 percent of the switch Ampere rating.

Finally, the manufacturer’s installation instructions that accompany the spa or hot tub may require a switch behind the skirt of the unit. If such instructions are provided, 110.3(B) requires compliance with these instructions.

In the absence of any instructions for a switch behind the skirt of the equipment, a single disconnecting means properly rated, marked and located should satisfy all of the NEC rules previously mentioned.

Bonding metal water pipe

Q: In a one-family dwelling unit, a sub-panel is fed from a feeder that originates at the service. The underground water pipe that supplies the home is plastic but is copper in the residence. The copper water pipe is not underground and there is no metal water pipe in the earth. Does the NEC allow the water pipe to be bonded to the feeder grounded circuit conductor in the feeder sub-panel because the water pipe is not being used as a grounding electrode?

A: The interior metal water pipes must be bonded to the grounding electrode system. The requirement for bonding the metal water pipe is found in 250.104(A)(1) and reads like this: “The metal water piping system shall be bonded as required in (1), (2), (3) or (4) of this section. The bonding jumper(s) shall be installed in accordance with 250.64(A), (B) and (E). The points of attachment of the bonding jumper(s) shall be accessible.”

Part (1) of 250.104(A) specifies which parts of the grounding electrode system are suitable for bonding the water pipe. They are the service equipment enclosure, the grounded conductor at the service, the grounding electrode conductor if it is large enough, or to the one or more grounding electrodes used.

The size of the bonding jumper cannot be smaller than shown in Table 250.66. For example, a 200A service that consists of 3-3/0 Type THWN conductors would require a 4 copper bonding conductor. If the grounding electrode conductor is 6 copper because the grounding electrode is two 8-foot ground rods, the bonding conductor from the water pipe would have to terminate on the service equipment enclosure, or the grounded circuit conductor (neutral) at the service.

This is because the bonding conductor is required to be larger than the service grounding electrode conductor.

Wiring method in places of assembly

Q: Are rigid nonmetallic conduit and electrical nonmetallic tubing permitted as wiring methods in places of assembly?

A: Article 518—Places of Assembly only applies to buildings or portions of building or structures that are designed or intended to accommodate 100 or more persons.

Any wiring methods that comply with the rules in Chapter 3 apply to all occupancies that are too small (less than 100 persons) or that are posted to limit the number of people to less than 100.

In assembly occupancies that accommodate 100 or more people and the assembly space is required to be of fire rated construction, wiring methods are generally restricted to metal raceways, flexible metal raceways, nonmetallic raceways encased in not less than 2 inches of concrete and Type MI, MC or AC cable containing an insulated equipment grounding conductor sized in accordance with Table 250.122.

Where non-rated construction is acceptable by the building code, permitted wiring methods are nonmetallic-sheathed cable, Type AC cable, electrical nonmetallic tubing and rigid nonmetallic conduit.

Electrical nonmetallic tubing and rigid nonmetallic conduit are permitted concealed in floors, walls and ceilings that provide a thermal barrier that has a least a 15-minute finish rating in the following occupancies: club rooms; college and university classrooms; conference and meeting rooms in hotels or motels; courtrooms; drinking establishments; dining facilities; restaurants; mortuary chapels; museums; passenger stations and terminals of air, surface, underground and marine public transportation facilities; libraries; and places of religious worship.

Device boxes for ceiling lighting fixture support

Q: Am I permitted to support ceiling- mounted lighting fixtures from device boxes? How about smoke detectors?

A: Under some conditions you are allowed to support lighting fixtures from device boxes. Part (A) of 410.16 allows outlet boxes or fittings installed as required by 314.23 to support lighting fixtures.

And 310.23(B)(1) allows nails and screws to support outlet boxes provided that the fasteners pass through the interior of the box within one-quarter of an inch of the back or ends of the box. Device boxes may be purchased with nails already in place, ready to be driven.

There is a requirement in 314.27 that says boxes for support of lighting fixtures must be designed for the purpose.

Also the box must be designed or installed so that a lighting fixture may be attached. An exception to this rule allows boxes or plaster rings to support wall-mounted lighting fixtures that do not weigh more than 6 pounds to be secured to the box with no less than two No. 6 or larger screws.

The 2003 edition of the General Information for Electrical Equipment Directory (White Book) published by Underwriters Laboratories Inc. has this statement on the use of device boxes for lighting fixture support: “Metallic device boxes or metallic device boxes intended to be installed in an existing structure have been investigated for the support of fixtures, smoke detectors and carbon monoxide detectors weighing not more than 6 pounds.” EC

FLACH, a regular contributing Code editor, is a former chief electrical inspector for New Orleans. He can be reached at 504.734.1720.


About the Author

George W. Flach

Code Q&A Columnist
George W. Flach was a regular contributing Code editor for Electrical Contractor magazine, serving for more than 40 years. His long-running column, Code Q&A, is one of the most widely read in the magazine's history. He is a former chief electrical in...

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