Prior to , however, the aluminum wire used was manufactured to conform to the series aluminum alloy, but this alloy was eventually deemed unsuitable for branch circuits due to galvanic corrosion where the copper and aluminum touched, resulting in poor contact and resistance to current flow, connector overheating problems, and potential fire risk.
Today, a new aluminum wire AA has been approved for branch circuits that does not cause corrosion where it contacts copper, but it is not readily available and is not manufactured below size 8 AWG. Hence, copper wire is used almost exclusively in branch circuitry. A ground fault circuit interrupter GFCI is required for all receptacles in wet locations defined in the Code.
The NEC also has rules about how many circuits and receptacles should be placed in a given residential dwelling, and how far apart they can be in a given type of room, based upon the typical cord length of small appliances. As of the NEC required that new Volt household receptacle outlets, for general purpose use, be both grounded and polarized. NEMA connectors implement these requirements. The Code required that new Volt receptacles be grounded also, which necessitates a fourth slot in their faces.
Changes in standards often create problems for new work in old buildings. Unlike circuit breakers and fuses, which only open the circuit when the current exceeds a fixed value for a fixed time, a GFCI device will interrupt electrical service when more than 4 to 6 milliamperes of current in either conductor leaks to ground.
A GFCI detects an imbalance between the current in the 'hot' side and the current in the 'neutral' side. One GFCI receptacle can serve as protection for several downstream conventional receptacles. GFCI devices come in many configurations including circuit-breakers, portable devices and receptacles. Another safety device introduced with the code is the arc-fault circuit interrupter AFCI. This device detects arcs from hot to neutral that can develop when insulation between wires becomes frayed or damaged.
While arcs from hot to neutral would not trip a GFCI device since current is still balanced, circuitry in an AFCI device detects those arcs and will shut down a circuit. AFCI devices generally replace the circuit breaker in the circuit. As of the National Electrical Code, AFCI protection is required in new construction on all and amp, volt circuits to bedrooms.
In home construction, wiring is commonly allowed directly in walls without additional protection. However, in commercial and industrial buildings, wiring must be protected from damage, so it is more commonly installed inside metal or plastic conduit or ductwork, or passageways cast in concrete.
While some types of cable are protected by flexible spiraled metal armor, it is more common to install conduit and empty ductwork and pull the wire in later. The NEC spends considerable time documenting safe methods of installing cable in conduit, the primary concerns being the abrading of insulation, damage to the wire or insulation caused by sharp bends, kinking, and damage due to excess pulling strain.
A wire pulled with excessive force may break inside the conduit, requiring costly removal and replacement. However, a wire pulled with enough force to stretch the wire, but not break it, creates a hazard of future failure or fire. The stretched wire section will have a thinner cross section and higher resistance than other parts of the cable, and may have damaged insulation.
Breaks may form in the stretched insulation, which may not be discovered until the circuit is powered and damage from arcing or shorting has occurred. Wires must be protected from sharp metal edges of cut conduits or cabinet holes. The NEC specifies measures to protect wire insulation from damage by these edges during installation and use. For example, insulated cables may not be inserted directly through knockouts, due to the sharp edge around nearly all knockout holes.
Clamping and other wire protection is often not required for plastic conduit parts, as plastic is not likely to damage insulation in contact with it. In hazardous locations, more robust cable protection may be necessary.
Common conduit and ductwork protects against direct physical abuse, but is neither air nor water tight. In wet locations, conduit may resemble standard threaded pipe in appearance, with gasketed box openings to keep moisture out.
This document was posted by Public. Org, which is not affiliated with nor authorized by the United States government, the State governments, or the National Fire Protection Association. We posted this document in order to allow citizens to read the laws that govern us.
Note that many of these documents had to be procured on the used marketplace. Many of the laws in this collection were re-keyed into HTML and diagrams redrawn for increased usability and accessibility. Please note that the process of scanning, OCR, and rekeying might introduce errors. In addition, standards bodies will frequently issue errata or reissue standards over time and governmental bodies may change which standards they incorporate to law.
You are urged to check with the standards organizations or governmental authorities for further information and access to definitive versions of these important laws. Criminal penalties may apply for noncompliance. Since , the NFPA has developed standards directly affecting the fire service at the department level. As an advocate of fire prevention and an authoritative source on public safety, the NFPA develops, publishes, and disseminates. In this document, we will share what NFPA is, why it is important, and how firefighters and chief officers can use it on an individual and organizational level.
This is just one of the solutions for you to be successful. As understood, attainment does not recommend that you have. Box , Quincy, MA Users of this document should be aware that this document may be amended from time to time through the issuance of Tentative Interim Amendments, and that an official NFPA document at any point in time consists of the current edition of. Schools Details: About home structure fires Download a fact sheet underscoring America's home fire problem from Schools Details: Safety tip sheets Tip sheets on a variety of fire and life safety topics.
Schools Details: NFPA only defines systems with a direct impact on life safety—even the failure of a Level 2 system would have significant ramifications for occupants if it failed 1. The signature page and documentation should be kept on.
Schools Details: E. NFPA 72 - edition - Chapter 10, as adopted without modifications by the NYC Fire Code, shall be used for all acceptance and re-acceptance testing and maintenance of fire alarm systems. Thus the kidnapped vampire is a N.
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