Site Preparation Glossary - HP Integrity rx8620 Site Preparation Manual

General Site Preparation Guidelines
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Site Preparation 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 term 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 British thermal units. The amount of heat required to raise one pound of water 1° F/hr, 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. Refer
tohttp://www.picmg.org/compactpci.stm for details.
CFM 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 in. in
height. So then, 1U equals 1.75 in. (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 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, 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 Kilovolt-amperes. (1000 x volt-amperes)
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Chapter 2