Article 210 Branch Circuits; Article 230 Services; Article 250 Grounding and Bonding; Article 366 Auxiliary Gutters; Article 422 Appliances; Article 517 Health Care Facilities; Various articles in Chapters 6, 7 and 8 are mentioned. The 2008 edition of the Guide Information for Electrical Equipment (White Book), published by Underwriters Laboratories Inc., also is mentioned.
What is the meaning of the phrase “combination type” used in the description of arc-fault circuit interrupters (AFCI) for use in various rooms and areas in dwelling units?
The phrase “combination type” in 210.2(B) describes the type of AFCI that must be provided for installations in dwelling units.
According to the 2008 edition of the Guide Information for Electrical Equipment (White Book), published by Underwriters Laboratories Inc., six categories of AFCIs are listed. They are the branch/feeder type, which senses parallel arcing faults; series arcing faults with ground on branch-circuit wiring; and parallel arcing faults on cord sets, extension cords and power supply cords. The combination-type AFCI detects parallel arcing faults; series arcing faults with or without an equipment-grounding conductor on branch circuit wiring; and parallel and series arcs on cord sets, extension cords and power supply cords. Cord-type AFCIs are for connection to a receptacle and provide arc-fault protection to the supply cord and protect appliances plugged into the receptacle. The outlet branch-circuit type ground-fault circuit interrupter (GFCI) provides protection of branch-circuit conductors with or without a grounding conductor and cord sets, extension cords and power supply cords from series and parallel arcs. The outlet circuit-type AFCI is intended to be installed in an outlet box and protects against arcs in the power supply cord. They may have connections for additional receptacles. Finally, there is the portable-type AFCI. These types are intended to be connected to a receptacle outlet and are provided with one or more outlets. These devices protect power supply cords and extension cords from unwanted arc faults.
For a more complete description of the various types of AFCIs, see pages 51–53 of the White Book.
Coin-operated machines in store foyer
Do coin-operated, electric horse-riding machines in a grocery store foyer require GFCI protection for the 20-ampere, 125-volt receptacle?
A horse-riding machine for children does not fit the definition of a vending machine in section 422.51. A riding machine is an amusement device, not a vending machine, and 422.51 does not apply. This section has been expanded in the 2008 edition of the National Electrical Code (NEC) and clears up some of the ambiguity that appeared in previous editions of the NEC. Section 422.51 states, “For the purpose of this section, the term vending machine means any self-service device that dispenses products or merchandise without the necessity of replenishing the device between such vending operation and is designed to require insertion of a coin, paper currency, token, card, key, or receipt of payment by other means.”
Vending machines manufactured after Jan. 1, 2005, must be provided with GFCI protection as an integral part of the attachment plug or be located within 12 inches of the attachment plug. Vending machines manufactured before Jan. 1, 2005, must be connected to a GFCI-protected outlet.
Dishwasher and disposal circuit
Does the NEC permit a three-wire, 14-AWG copper branch circuit to supply a dishwasher and garbage disposal from two single-pole, 15-ampere circuit breakers?
The 15-ampere multiwire branch circuit is permitted to supply these appliances, but the two single-pole circuit breakers are not. The disconnecting means for a multiwire branch circuit is required to disconnect all ungrounded conductors of the multiwire branch circuit by the use of a two-pole circuit breaker or two single-pole circuit breakers provided with a handle tie. Article 210.4(B) states, “Disconnecting Means. Each multiwire branch circuit shall be provided with a means that will simultaneously disconnect all ungrounded conductors at the point where the branch circuit originates.” Also, if this multiwire branch circuit is supplied by a raceway with other circuits in the same raceway, the multiwire branch circuit must be grouped with a tie wrap or other similar means in the panelboard or point of origination. Where three-wire nonmetallic sheathed cable is the wiring method, a wire tie or tie wrap is not required by the Exception to 210.4(D).
Removal of low-voltage abandoned cable
What parts of the 2008 edition of the NEC require removal of low-voltage wiring that is no longer in use?
Let’s start with Article 640—Audio Signal Processing, Amplification, and Reproduction Equipment. Section 640.2 has a definition of abandoned cable and 640.6(C) requires removal of the accessible portions of abandoned cables. Article 645—Information Technology Equipment requires that abandoned supply circuits and interconnecting cables be removed unless installed in a metal raceway. Article 725—Class 1, Class 2, and Class 3 Remote Control, Signaling, and Power Limited Circuits requires removal. Section 725.25 requires removal of abandoned cables unless a tag is provided on the cable for future use. Article 760—Fire Alarm Systems has a requirement for removal of abandoned cables not tagged for future use in Section 760.25. Article 770—Optical Fiber Cables and Raceways contains a definition for Abandoned Optical Fiber Cable in 770.2 and 770.25 requires removal of abandoned cables unless identified with a tag for future use. Article 800—Communication Circuits has a definition for abandoned cable in 800.2 and a requirement for removal of abandoned cable not provided with a tag for future use in 800.25. Article 820—Community Antenna Television and Radio Distribution Systems has a definition for abandoned coaxial cable in 820.2 and a requirement for removal of abandoned coaxial cable that does not have a tag for future use in Section 820.25. Article 830—Network-Powered Broadband Communications Systems has a definition for abandoned cable and a requirement for removal of abandoned cable that does not have a tag for future use.
Ampacity of aluminum bus bars
What is the ampacity of ½-inch-by-2-inch bare aluminum bus bars installed in an auxiliary gutter?
The continuous current rating of bare aluminum bus bars installed in a metal auxiliary gutter is 700 amperes per square inch. A ½-inch-by-2-inch aluminum bar has a cross section of one square inch; therefore, the ampacity of the aluminum bus bar is 700 amperes. In Section 366.23(A), the continuous current rating of a bare copper bus bar is listed as 1,000 amperes per square inch, and for bare aluminum bus, the current is limited to 700 amperes per square inch.
Checking ground-fault protection
Is there a timetable for checking the performance of ground-fault protection on a 480Y/277 volt service that is rated 1,200 amperes?
There are two separate requirements for testing ground-fault protection (GFP) of electrical equipment. One is in 230.95, and the other is in 517.17. In 230.95, ground-fault protection is required for all services rated 1,000 amperes or more with a voltage of 150 volts or more to ground but not exceeding 600 volts. Part (C) of 230.95 requires performance testing, and it must be done when the equipment is first installed on-site. This testing must be done in accordance with instructions furnished with the GFP. There is no requirement for a periodic test. The electrical inspector should be furnished with the date and time of the test, so he or she can witness it.
Where the service supplies healthcare facilities, 512.12 also applies. This section requires GFP on the feeder(s) that are supplied directly from the service--disconnecting means. A delay of at least six cycles is required between the feeder GFP tripping time and the service overcurrent protective device. This six-cycle delay between opening of the feeder overcurrent device when a ground fault occurs and the service disconnect ensures selectivity between the feeder overcurrent protection and service-overcurrent protection. Testing to ensure compliance must be conducted soon after the equipment is installed. Here again, the electrical inspector should be notified of the date and time of the test so that he/she may be present to witness it.
Feeders protected at 1,000 amperes or more must also be protected by GFP to comply with 215.10.
Grounding separately derived systems
A 120/208-volt transformer is supplied from a 277/480 volt, three-phase service. If the secondary side of the transformer is properly grounded at the transformer neutral terminal, is it necessary to include a grounded circuit conductor in the raceway for the feeder? Metal water pipe is close to the transformer. This is the reason for connecting the grounding--electrode conductor to the neutral bus in the transformer.
Yes, the grounding-electrode conductor can be connected to the metal water pipe and the neutral bus in the transformer. Article 250.30 permits this method of grounding the grounded circuit conductor of the derived system, provided that the grounded-circuit conductor is isolated from ground at the disconnecting means for the secondary. The grounded-circuit conductor (neutral) must not be connected to a grounded terminal in the transformer secondary-disconnecting means. In addition, a bonding conductor must be installed between the grounded terminal in the transformer and the grounded bus that is secured to the disconnect enclosure. Exception No. 2 to 250.30(A)(1) reads, “A system bonding jumper at both the source and the first disconnecting means shall be permitted where doing so does not establish a parallel path for the grounded conductor.”
FLACH, a regular contributing Code editor, is a former chief electrical inspector for New Orleans. Questions can be sent to firstname.lastname@example.org.