HP Integrity rx4640 Site Preparation Guide, Second Edition - HP Integrity rx46 - Page 47

Glossary A-B Apparent power A value of power for AC circuits that is calculated as the product of RMS current times RMS voltage, without taking the power factor into account. ASHRAE Standard 52-76 Industry standard for air filtration efficiency set forth by the American Society of Heating, Refrigerating, and Air-Conditioning Engineers, Inc. ASL Above sea level. board A printed circuit assembly (PCA). Also called a card or adapter. Btu/h The abbreviation for British thermal units. The amount of heat required to raise one pound of water one degree fahrenheit per hour, a common measure of heat transfer rate. C CompactPCI 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 for details. CFM The abbreviation for cubic feet per minute, commonly used to measure the rate of air flow in an air conditioning system. Chilled water 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, which is piped to the air conditioner to cool the space. D-K Dehumidification The process of removing moisture from the air within a critical space. Derate To lower the rated capability of an electrical or mechanical apparatus. Downflow Refers to a type of air conditioning system that discharges air downward, directly beneath a raised floor, commonly found in computer rooms and modern office spaces. EIA unit The Electronic Industries Association (EIA) defines this unit of measurement to be 1.75 inches in height. So then, 1U equals 1.75 inches (1U equals 44.45 mm). Humidification The process of adding moisture to the air within a critical space. Inrush current 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 due to 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, producing an immediate inrush surge current with a fast rise time. The peak inrush current can be several orders of magnitude greater than the supply's typical current. KVA Abbreviation for kilovolt-amperes. (1,000 x volt-amperes). L-N Latent cooling capacity An air conditioning system's capability to remove heat from the air. Leakage current 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 Hertz current, which flows through the EMI filter capacitors that are connected between the AC lines and ground. Maximum input current The operating current of the product equal to the maximum load divided by the minimum input voltage. NEBS All electronic equipment has the potential to interfere with other electronic equipment. Interference can be caused by electromagnetic radiation, the grounding system, the electrical power connection, excessive heat, or blocking the natural airflow, and connecting wires or cables. The FCC (Federal Communications Commission) regulates a portion of this problem through Part 15 of their rules and regulations. Even more stringent than the FCC Part 15 requirements, Network Equipment Building Standards (NEBS) covers a large range of requirements including criteria for personnel safety, protection of property, and Glossary 47