There are a variety of wire and cable products that are manufactured in plenum versions. The most commonly used is plenum cable. Plenum cables are used in electrical or telecommunication applications and are installed in the air spaces of most residential and commercial buildings. Plenum fire alarm cable, plenum coax cable and plenum cat 5 cable are examples of some of these applications. It is common practice to route communication cables for computers, data devices and alarm systems through the plenum in a buildings construction. A plenum is defined as a compartment or chamber in which one or more air ducts are connected to form part of the air distribution system of a structure. Plenum cable is simply the cable that has been rated to run through these plenum spaces.
Since plenum cables are routed through air circulation spaces which contain very few fire barriers, they need to be coated in flame-retardant, low smoke materials such as polyvinyl chloride (PVC), fluorinated ethylene polymer (FEP), or a polyolefin. These plastics offer good resistance against fire, and in the event that they do burn, they will not emit large quantities of harmful fumes. These features make plenum cables safer than riser or thermoplastic cables.
Originally most plenum cables were created with Teflon by DuPont. Teflon was manufactured for the wire and cable industry in several forms such as FEP, TFE and PTFE. The main drawback to plenum cable is its cost. Prices can range up to 10 times more per pound than a cheaper PVC compound. Due to the expense, many manufacturers produce lower cost plenum rated products to meet the demand of today’s construction industry.
Newer plenum compounds include Halar, Solef and a low smoke PVC which carriers a plenum rating. These plenum cables do not have the same durability or temperature rating as Teflon. However, these lower cost options are satisfactory for an application that only requires a plenum rating. According to the National Electrical Code (NEC), a plenum cable must comply with the specifications outlined by the National Fire Protection Association (NFPA) testing methods in order to receive a plenum rating.
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