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The NEC specifies acceptable numbers of conductors in crowded areas such as inside conduit, referred to as the fill rating. If the accepted fill rating is exceeded, then all the cables in the conduit are derated, lowering their acceptable maximum ambient operating temperature. Derating is necessary because multiple conductors carrying full-load ...
Derating curves are included in data sheets for such capacitors. Derating can also provide a safety margin for transient voltages or currents (spikes) that exceed normal operation or prolong life. For example, the life of electrolytic capacitors is dramatically increased by operating them below their maximum temperature rating.
The allowed current in a conductor generally needs to be decreased (derated) when conductors are in a grouping or cable, enclosed in conduit, or an enclosure restricting heat dissipation.
This is similar to the preceding, but rated for dry or wet environments and conductor temperatures up to 75 °C (167 °F), [18] and is commonly used in subsurface conduits which may fill with water. A great deal of THWN wire is actually dual-rated, and meets THHN the specification as well, so may be used in wet environments up to 75°C or dry ...
Galvanized rigid conduit (GRC) is galvanized steel tubing, with a tubing wall that is thick enough to allow it to be threaded. Its common applications are in commercial and industrial construction. [1] It is designed to protect wire and connectors. Intermediate metal conduit (IMC) is a steel tubing heavier than EMT but lighter than RMC. It may ...
The nature and thickness of any passive fire protection materials used in conjunction with wiring and raceways has a quantifiable impact upon the ampacity derating, because the thermal insulation properties needed for fire resistance also inhibit air cooling of power conductors. A cable tray can be used in stores and dwellings.
Fill capacity is provided for furniture systems. Fill capacity is provided for perimeter raceways. Design requirements for poke-thru fittings. Access floor heights are adjusted. In-floor systems include underfloor duct and cellular raceways. Pathway fill is provided for cable tray. A discussion of telecommunications diversity has been added.
IEC 61386 Conduit systems for cable management; IEC TS 61390 Ultrasonics – Real-time pulse-echo systems – Test procedures to determine performance specifications; IEC 61391 Ultrasonics – Pulse-echo scanners; IEC 61394 Overhead lines – Requirements for greases for aluminium, aluminium alloy and steel bare conductors