HP Modular Cooling System Site Preparation Guide

Appendix C
Glossary
Table 13 lists technical terms and abbreviations used in this guide.
Table 13 Terms and Abbreviations
Term Description
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.
ASL Above sea level
BTU/hr
British Thermal Units per hour. The amount of heat required to raise one pound of water
1° F/hr, a common measure of heat transfer rate.
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 or HP Modular Cooling System to cool the space.
Derate To lower the rated capability of an electrical or mechanical apparatus.
Heat exchanger
Cooling unit that maintains two separate environments inside and outside of the cabinet
or room. It can be water-to-water, water-to-air, or air-to-air configurations, in either
direction.
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.
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.
Maximum input current
The operating current of the product equal to the maximum load divided by the
minimum input voltage.
Power factor
The ratio of true power (watts) to apparent power (VA) in an AC circuit. In power
conversion technology, power factor is used in conjunction with describing the AC input
current to the power supply.
RMS
Root-mean-square. Term that refers to the most common mathematical method of
defining the effective voltage or current of an AC wave. To determine RMS value, three
mathematical operations are carried out on the function representing the AC waveform:
(1) The square of the waveform function (usually a sine wave) is determined. (2) The
function resulting from step 1 is averaged over time. (3) The square root of the function
resulting from step 2 is found.
Theoretical maximum power
consumption
Maximum wattage of a given configuration, assuming worst-case conditions (thermal
tolerances, workloads, and so forth) on all system components. It is extremely unlikely
that any customer will experience this level of power consumption.
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