Article 210—Branch Circuits
Article 695—Fire Pumps
Article 725—Class 1, Class 2, and Class 3 Remote-Control, Signaling, and Power-Limited Circuits
Article 760—Fire Alarm Systems
Article 770—Optical Fiber Cables and Raceways
Article 800—Communication Circuits
Article 820—Community Antenna Television and Radio Distribution Systems
Article 830—Network-Powered Broadband Communications Systems
NFPA 20—1999 Standard for the Installation of Stationary Pumps for Fire Protection and the 2001 edition of the General Information for Electrical Equipment Directory published by Underwriters Laboratories Inc. are also mentioned.
Smoke detectors protected by AFCIs
Q: As an electrical inspector, I wonder if my interpretation of 210.12(B) of the 2002 National Electrical Code (NEC) is correct. Does the requirement for arc fault circuit interrupter (AFCI) protection of 15- and 20-ampere, 125-volt branch circuits in bedrooms of dwelling units include the line voltage smoke detector installed in the bedroom? Was it the intent of Code Making Panel No. 2 to include the smoke detector outlet in this rule?
A: Part (B) of 210.12 is revised to read as follows: “Dwelling Unit Bedrooms. All branch circuits that supply 125-volt, single phase, 15- and 20-ampere outlets installed in dwelling unit bedrooms shall be protected by an arc-fault circuit interrupter listed to provide protection of the entire branch circuit.”
In Article 100, an outlet is defined as: “A point on the wiring system at which current is taken to supply utilization equipment.” Therefore, a line voltage smoke detector installed in a dwelling unit bedroom must be AFCI protected. This is a good place to install a smoke detector with battery backup. And the occupant should be informed about the battery so will be replaced periodically.
The Code Making Panel was aware that this change covered outlets supplying smoke detectors. Public Comments were received to remove smoke detectors from the requirement for arc-fault protection. The Panel statement for rejection of one of the comments that recommended removal of smoke detectors from the requirement for AFCI protection is, “The panel reaffirms the requirement for AFCI protection in dwelling unit bedrooms, including smoke detector outlets. There has been no data submitted substantiating why smoke detectors should be deleted from the AFCI requirement.”
Transfer switch used with service equipment
Q: I have a service that consists of four main switches as permitted by 230.71(A). Is it permissible to install a transfer switch on the line side of one of these service disconnects? The transfer switch will supply normal and standby power to a branch circuit panelboard. The panelboard has a 100-ampere, two-pole main circuit breaker.
A: You are permitted to connect the transfer switch to the service-entrance conductors by 230.82(4). This rule lists equipment that may be connected to the supply side of a service disconnect and item (4) recognizes taps for standby power systems, fire pump equipment, and fire and sprinkler alarms where provided with service equipment and installed in accordance with service-entrance conductor requirements.
The transfer switch must be marked “Suitable for Use as Service Equipment” and must have an interrupting rating that is equal to or greater than the maximum fault current available at its line terminals. Also, the transfer switch must be in close proximity to the 100-ampere panelboard to satisfy 230.91, which reads: “The service overcurrent device shall be an integral part of the service disconnecting means or shall be located immediately adjacent thereto.”
In the 1999 edition of the NEC, Section 230-83 reads: “Transfer equipment, including transfer switches, shall operate such that all ungrounded conductors of one source of supply are disconnected before any ungrounded conductors of the second source are connected.” Two exceptions allowed parallel operation of power sources. This section specifically recognized transfer equipment as a legitimate part of a service. However, Code Making Panel No. 4 decided to delete this section from the 1999 NEC with the statement that Section 230-74 adequately covers the requirement for simultaneously disconnecting all ungrounded conductors from the premises wiring system. Deleting Section 230-83 has caused confusion about the proper installation of transfer switches at services. In fact, there were proposals to add transfer switches to 230.82. Public Comments received after the Report on Proposals was published resulted in the following action by Code Making Panel No. 4: Add item (8) to 230.82 to read: “(8) Transfer equipment installed in accordance with Sections 700-6, 701-7, and 702-6. A transfer switch installed under these provisions is not a service disconnect.” Although this revision received a unanimous affirmative vote by panel members, a motion was made, seconded, and accepted to reject the panel action at the NFPA Standards Adoption session during the May 2001 NFPA annual meeting.
Although the words “transfer switch” do not appear in “Article 230—Services,” they are available, and have the marking “Suitable for use as Service Equipment” and may be installed in accordance with the NEC.
Overcurrent protection for a fire pump
Q: There is no maximum ampere rating for the overcurrent devices protecting and electric motor-driven fire pump in Article 695. What method should be used to select these overcurrent devices?
A: I agree that the maximum ampere rating of the overcurrent protective device is not specified, but the minimum is. Guidance for overcurrent protection selection is found in 695.4(B)(1).This part requires that overcurrent protection be sized to carry fire pump motor locked-rotor current indefinitely. If the pressure maintenance pump is also connected to this power source, the overcurrent protection is required to be sized to carry the locked-rotor current of this motor indefinitely. Table 6-5.1.1 of NFPA 20—1999 Standard for the Installation of Stationary Pumps for Fire Protection lists locked-rotor currents for various motor horsepower ratings. These currents are based on NEMA Design B motors, and the values are within one ampere of those shown in Table 430.151(B) of the NEC.
To calculate the ampere rating of the overcurrent device, assume that the fire pump motor is 75 horsepower, 460 volts, three phase, and the jockey pump is 3 horsepower, 460 volts, three phase. The locked-rotor current for the fire pump motor is obtained from Table 430.151(B) and is 543 amperes. The locked-rotor current for the pressure maintenance pump is 32 amperes. This results in a total of (543 + 32) 575 amperes. The next-larger standard-size fuse or circuit breaker listed in 240.6 is 600 amperes. This size fuse or circuit breaker should be used for this application.
Where the service disconnecting means and overcurrent protection can be eliminated by running the service-entrance conductors directly to the fire pump controller; this should be done. For this application, the controller must be marked “Suitable for use as Service Equipment.” Since overcurrent and locked-rotor protection are provided by the circuit breaker in the controller, no additional overcurrent protection is needed.
Aluminum service entrance conductors
Q: The electrical inspector turned down my job because I used No. 1/0 aluminum service-entrance conductors and terminated them in a 125-ampere panelboard with a main 125-ampere, two-pole circuit breaker. The main lugs in the panelboard are marked AL7CU. The inspector says that I cannot install aluminum conductors in the panelboard because the wiring diagram in the panelboard does not say aluminum conductors are suitable. Is he right? The lugs furnished with the panelboard are designed for termination of copper or aluminum conductors.
A: The inspector is correct in his understanding of the requirements. To use aluminum conductors in the panelboard marking on the wiring diagram stating that aluminum conductors are acceptable must be present. Here is an excerpt from the 2001 edition of the General Information for Electrical Equipment Directory (White Book), published by Underwriters Laboratories, Inc. “Most terminals are suitable for use only with copper wire. Where aluminum or copper-clad aluminum wire can or shall be used (some crimp terminals may be listed only for aluminum wire), there is marking to indicate this. Such marking is required to be independent of any marking on terminal connectors, such as on a wiring diagram or other visible location. This marking may be in an abbreviated form, such as “AL-CU.” The panelboard was not tested with aluminum conductors connected to the terminals if this marking is absent. Among other things, the wire bending space in the enclosure may not be adequate for the larger aluminum conductors.
Removal of low-voltage cables
Q: Is there a requirement for the removal of unused low-voltage cables?
A: Yes, there is. Let’s look at all of the locations in Chapters 7 and 8 that require removal of abandoned cables. A definition for abandoned Class 2, Class 3, and PLTC cable appears in 725.2 under “Definitions.” These are described as cables that are not terminated at equipment and not identified for future use with a tag. Part (B) of 725.3 requires that the accessible portions of abandoned Class 2, Class 3, and PLTC cables not be permitted to remain. Similar requirements for removal of abandoned fire alarm cables appear in 760.2 and 760.3. For optical fiber cables, the references are 770.2 and 770.3.
Removal of communication cables is required by 800.2 and 800.52(B). Abandoned community antenna television and radio distribution wiring must be removed to comply with 820.2 and 820.3.
Abandoned network-powered broadband communications cables that are not terminated at equipment or tagged for future use must be removed. The references for this requirement are 830.2 and 830.3. EC
FLACH, a regular contributing Code editor, is a former chief electrical inspector for New Orleans. He can be reached at (504) 254-2132.