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Rack - Device for holding IT/Network equipment, also called a cabinet. Rack height is typically measured in units (U) with a \"full rack\" being 42U in height.
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Recirculation Air Handler (RAH) - A device that circulates the air but does not cool the air
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Raised Floor - A type of floor supported by a metal grid and typically used in “Data Centersâ€. Raised flooring can be removed in pieces to allow for cabling, wiring, and cooling systems to run under the floor space. When the floor is raised it usually can accommodate spaces of 12 inches below raised floor, 24 inches below raised floor or 36 inches below raised floor or Custom heights.
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Recirculation - Chilled airflow returning to cooling units without passing through IT equipment, also referred to as short cycling.
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Return Air - The heated air returning to air conditioning equipment
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Radio frequency interference (RFI) - Also called Electromagnetic Interference (EMI), a type of disturbance that affects electrical circuits due to electromagnetic radiation from an external source (e.g., radio, or television).
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Relative humidity (Rh) - The amount of water in the air at a give temperature relative to the maximum amount it could hold at that temperature; expressed as a percentage.
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Raised Metal Floor (RMF) - Alternate term for the more commonly used term ‘raised floor'.
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Return On Investment (ROI) - A measure of the amount of time required to recover an investment.
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Revolutions per minute (RPM) - A measure of fan speed in terms of the number of full revolutions which occur within 1 minute.
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Remote Power Panel (RPP) - An electrical device which distributes power to a number of branch circuits.
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Rooftop unit (RTU) - An air handler designed for outdoor use mounted on a rooftop.
