HP Superdome SX2000 Generic Site Preparation Guide, Fourth Edition - Page 37

Glossary A-B apparent power ASHRAE Standard 52-76 ASL board Btu/h A value of power for AC circuits that is calculated as the product of root mean square (RMS) current times RMS voltage, without taking the power factor into account. Industry-standard term for air filtration efficiency set forth by the American Society of Heating, Refrigerating, and Air-Conditioning Engineers, Inc. Above sea level. A printed circuit assembly (PCA). Also called a card or adapter. British thermal unit. The amount of heat required to raise one pound of water 1°F in an hour, a common measure of heat transfer rate. C CFM chilled water system CompactPCI Cubic feet per minute, commonly used to measure the rate of air flow in an air-conditioning system. A type of air-conditioning system that has no refrigerant in the unit itself. The refrigerant is contained in a chiller, which is located remotely. The chiller cools water and is piped to the air conditioner to cool the space. The newest specification for PCI-based industrial computers is called CompactPCI. It is electrically a superset of desktop PCI with a different physical form factor. See http:// www.picmg.org/v2internal/compactpci.htm for details. D-K daisy chain dehumidification derate downflow EIA unit ESD humidification inrush current KVA Hardware devices that are connected one to another in series. The process of removing moisture from the air. To lower the rated capability of an electrical or mechanical apparatus. Refers to a type of air-conditioning system that discharges air downward directly beneath a raised floor. It is commonly found in computer rooms and modern office spaces. The Electronic Industries Association (EIA) defines this unit of measurement to be 1.75 inches in height. For example, 1 U equals 1.75 in. (1 U equals 44.45 mm). Electrostatic discharge. The process of adding moisture to the air within a critical space. The peak current flowing into a power supply the instant AC power is applied. This peak is usually much higher than the typical input current because of the charging of the input filter capacitors. When switching power supplies are first turned on, they present high initial currents as a result of filter capacitor impedance. These large filter capacitors act like a short circuit and produce an immediate inrush surge current with a fast rise time. The peak inrush current can be several orders of magnitude greater than the typical input current. Kilovolt-amperes (1,000 x volt-amperes). L-N LAHJ latent cooling capacity leakage current Local authority has jurisdiction. The capability of an air-conditioning system to remove heat from the air. A term relating to current flowing between the AC supply wires and earth ground. The term does not necessarily denote a fault condition. In power supplies, leakage current usually refers to the 60-Hz current, which flows through the EMI filter capacitors that are connected between the AC lines and ground. 37