Glossary - HP 9000 rp3410 Manual

Glossary

A-B
apparent power 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.
ASHRAE Industry-standard term for air filtration efficiency set forth by the American Society of Heating,
Standard 52-76 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 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 Cubic feet per minute, commonly used to measure the rate of air flow in an air-conditioning
system.
chilled water A type of air-conditioning system that has no refrigerant in the unit itself. The refrigerant is
system contained in a chiller, which is located remotely. The chiller cools water and is piped to the air
conditioner to cool the space.
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
www.picmg.org/v2internal/compactpci.htm
D-K
daisy chain Hardware devices that are connected one to another in series.
dehumidification The process of removing moisture from the air.
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. It is 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. For example, 1 U equals 1.75 in. (1 U equals 44.45 mm).
ESD Electrostatic discharge.
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 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.
KVA Kilovolt-amperes (1,000 x volt-amperes).
L-N
LAHJ Local authority has jurisdiction.
latent cooling The capability of an air-conditioning system to remove heat from the air.
capacity
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-Hz current, which flows through the EMI filter capacitors that are connected between
the AC lines and ground.
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