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View Full Version : 2005 NEC Changes Summary Articles 725 through 770



mr2channel
03-30-2005, 07:21 AM
This came to me from Mike Holts website, he has a good electrical forum as well, even a section dedicated to low voltage.

2005 NEC Changes Summary Articles 725 through 770
ARTICLE 725 Class 1, Class 2, and Class 3 Remote-Control, Signaling, and Power-Limited Circuits

Circuits that fall under Article 725 are remote-control, signaling, and power-limited circuits that aren't an integral part of a device or appliance. Article 725 includes circuits for burglar alarms, access control, sound, nurse call, intercoms, some computer networks, some lighting dimmer controls and some low-voltage industrial controls.

Let's take a quick look at the types of circuits:

A remote control circuit controls other circuits through a relay or solid-state device, such as a motion-activated security lighting circuit.
A signaling circuit that provides an output that is a signal or indicator, such as a buzzer, flashing light or annunciator.
A power-limited circuit operates at no more than 30V and 1,000VA
We'll cover these definitions in more depth later and explain the differences between Class 1, Class 2 and Class 3.

The purpose of Article 725 is to allow for the fact that these circuits "are characterized by usage and power limitations that differentiate them from electric light and power circuits." Article 725 provides alternative requirements for minimum wire sizes, derating factors, overcurrent protection, insulation requirements, wiring methods and materials.

As with all other articles in Chapters 5 through 8, the wiring methods required by Chapters 1 through 4 apply [90.3]. But because of the inherently lower danger of fire risk with qualifying circuits, Article 725 specifies conditions where these methods aren't required. For example, you do not need to put a Class 2 splice in a box or enclosure. At the same time, additional requirements apply to ensure safety. While there's not a net compromise on safety, there's a net cost-savings.

Article 725 consists of three parts. Part I provides general information, Part II pertains to Class 1 cabling, and Part III pertains to Class 2 and 3 cabling. The key to understanding and applying each of the three parts is knowing the voltage levels of the cabling involved and the purposes of that cabling. Article 725 allows you to save time and money when working with particular types of circuits.

Text revised to specify that accessible portions of abandoned Class 2, Class 3, and PLTC cables must be removed.
Changes clarify the types of cables and raceways permitted in ducts, plenums, and other space used for environmental air.
This section was revised to clarify that it's the equipment supplying the circuit that must be durably marked to indicate each Class 2 or Class 3 circuit.
New rule prohibits the installation of audio system circuits in the same cable or raceway with Class 2 or Class 3 conductors or cables.
New sentence identifies the type of nonmetallic raceway containing Class 2 or Class 3 cables that is permitted in "other spaces used for environmental air."
New subsections added to recognize the use of raceways designed for Class 2 and Class 3 cables.
ARTICLE 760 Fire Alarm Systems

Article 760 provides the requirements for the installation of wiring and equipment for fire alarm systems, including all circuits the fire alarm system controls and powers. Fire alarm systems include fire detection and alarm notification, voice communications, guard's tour, sprinkler waterflow and sprinkler supervisory systems. NFPA 72, National Fire Alarm Code provides other fire alarm system requirements.

As you study this material, pay close attention to the illustrations, which highlight important requirements. Many people have difficulty understanding Article 760 from the text alone, and the figures also show you common Article 760 violations.

Text revised to specify that accessible portions of abandoned fire alarm cables must be removed.
New FPN alerts the Code user to a comprehensive standard that identifies what "installed in a neat and workmanlike manner" means. And revised text specifies that fire alarm raceways and cables must be secured in place and the ceiling support wires or ceiling grid cannot be used for this purpose.
New rule prohibits AFCI protection of the 120V circuit that supplies power for a nonpower-limited fire alarm system.
New rule prohibits AFCI protection of the 120V circuit that supplies power for a power-limited fire alarm system.
This section was revised to clarify that "power-limited equipment" supplying power-limited fire alarm circuits must be durably marked to indicate each power-limited circuit. This change was necessary because some wiring method manufacturers have advertised boxes and raceways identified only with the "color red" as meeting this requirement.
Additional text clarifies when nonpower-limited wiring and power-limited cables can be installed together in the same conduit. For example, pull stations or smoke detectors could be wired with Type FPL cable and the horns or strobes could be wired with THHN conductors.
New rule prohibits the installation of audio system circuits in the same cable or raceway as power-limited fire alarm conductors or cables.
ARTICLE 770 Optical Fiber Cables and Raceways

Article 770 provides the requirements for installing optical fiber cables and special raceways for optical fiber cables. It also contains the requirements for composite cables, often-called "hybrid," that combines optical fibers with metallic current-carrying conductors.

While we normally think of Article 300 when we think of wiring methods, you need to use only Article 770 methods for fiber-optic cables, except where Article 770 makes specific references to Article 300. The first such reference, in 770.3, is to 300.21. This addresses requirements for stopping the spread of combustion. Another Chapter 3 reference is to 300.22, which applies if you're installing optical fiber cables and optical fiber raceways in ducts, plenums, or other air-handling spaces.

Article 770 doesn't refer to 300.15, so you do not have to use boxes for splices or termination of optical fiber cable. The FPN in 770.113 states that splice cases and terminal boxes are typically used as enclosures for splicing or terminating and splicing optical fiber cables. While this is a good practice, it's not required-no FPN is an enforceable Code requirement [90.5(C)].

Article 90 states that the NEC isn't a design guide or installation manual. Article 770 doesn't tell you how to ensure your system will meet, and test out to, the performance requirements you need or your contract specifies. For example, it doesn't mention bend radii. It doesn't tell you how to install and test cable safely, either, but that doesn't mean you should look into a cable, even if you cannot see any light coming through it. Light used in fiber-optic circuits usually isn't visible, but it can damage your eye.

Text revised to specify that the accessible portion of abandoned optical fiber cables must be removed.
New subsection permits listed optical fiber raceways to be installed as innerduct in any Chapter 3 raceway.
New FPN alerts the Code user to a comprehensive standard that identifies what "installed in a neat and workmanlike manner" means. And revised text specifies that optical fiber raceways and cables must be secured in place and that ceiling support wires or the ceiling grid are not permitted for this purpose in accordance with 300.11
Because unlisted optical fiber entrance cables can contribute to a fire and smoke hazard, the exception was revised to prohibit the installation of unlisted optical fiber entrance cables in risers, ducts, plenums, and other space used for environmental air.