5424Ch04 - FM 5-424 CHAPTER 4 Cable Wiring Cable systems...

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FM 5-424 Cable Wiring 4-1 CHAPTER 4 Cable Wiring Cable systems are used where cost is a factor. They can be installed easily, and the material required is less expensive than that used for other systems. The absence of protection against mechanical injury and the fact that it is only moisture-resistant tend to restrict the areas where the cable system can be used. Temporary and expedient-wiring cable systems are ideally suited for the TO. Section I. Armored Cable Wiring ADVANTAGES AND USES Armored-cable wiring is permissible by reg- ulation for all interior installations, except where it is exposed to saturation by liquid or where it is in contact with acid fumes. In wet areas, a lead-covered cable is required. Because the material requirements for armored-cable wiring are greater, the over- all cost is generally higher than Type NM cable systems. This increased cost is often warranted because an armored conductor has greater mechanical-damage protection. The installation of armored cable is rela- tively simple and is similar to that of non- metallic-sheathed cable discussed in Section II. Much of the equipment and materials are the same. MATERIALS CABLE Armored-cable construction consists of two or three rubber- or thermoplastic-covered wire combinations encased in flexible steel armor. Cable is obtained from the manufac- turer as Type AC (without a lead sheath) and Type ACL (with a lead sheath under the armor). Type AC cable has a copper or alu- minum bonding strip. One of the conductors of armored cable is always white. Because of this color coding, the white wire in a switch installation (for both armored cable and nonmetallic- sheathed cable) can be used as a hot wire and be connected to a black wire. SUPPORT Armored cable may be fastened to wooden building members with a one- or two-hole mounting strap formed to fit the contour and size of the cable or by staples made spe- cifically for armored cable. The cable is nor- mally supported at the box entry either by integral armored-cable clamps built into the boxes or by armored-cable connectors. BOXES AND DEVICES Chapter 2 details boxes and devices recom- mended for use with armored-cable wiring. Electrical boxes with integral cable clamps and attached mounting brackets are used for quick installation.
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FM 5-424 4-2 Cable Wiring INSTALLATION CABLE SUPPORT Whenever possible, run armored cable through holes centrally drilled in the build- ing structural members and ensure that the holes are at least 1/8 inch oversize to facili- tate easy pull-through of the armored cable. Avoid the flush-type mounting of armored cable accomplished by notching the joists and studs if possible because this type of installation exposes the armored cable to possible short circuits (by locating the cable in a position where it could be accidentally pierced by nails) and materially weakens the structural member. When running armored cable between joists
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This note was uploaded on 05/21/2010 for the course ELECTRICAL Electrical taught by Professor N/a during the Spring '10 term at Open Uni..

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5424Ch04 - FM 5-424 CHAPTER 4 Cable Wiring Cable systems...

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