Glossary Flashcards
The percentage of incoming energy that is absorbed. In measuring radiant energy (light or heat) it is a unitless ratio that may vary depending on the wavelength. In acoustics, it is called a sabin and may vary depending on frequency.
Absorption Coefficient
A cooling process resulting from the absorption of vapor by brine solution that is then heated to remove the moisture. The heat may be supplied by solar or other heating sources.
Absorption Refrigeration
The abbreviation for either air conditioning or alternating current, depending on the context.
AC
An unobstructed vertical path, open to the atmosphere, separating the outlet of a faucet from the overflow rim of the fixture it serves. The purpose is to prevent a momentary vacuum in the supply pipe from siphoning water from the fixture back into he supply pipe.
Air Gap
An electric current that reverses its direction at regular intervals, generally 60 times per second in the US. A plot of voltage over time is a sine wave.
Alternating Current
Relating to a general of all surrounding condition. In thermal processes, it refers to the air temperature, as distinct from that of surfaces or objects. In lighting, it refers to the background light level, and in acoustics it refers to the background noise level.
Ambient
The abbreviation for the American Society of Heating, Refrigerating, and the Air Conditioning Engineers, the source of most of the standardized information on the subject.
ASHRAE
The ratio of the longer to shorter dimension of an air conditioning duct, that affects duct friction, or of a room, that relates to light reflection.
Aspect Ratio
The automatic drain valve at the base of a dry standpipe.
Ball Drop
The drain that removes dirt that builds up in the floor pool of an evaporative cooling tower
Blow Down
The abbreviation for British Thermal Unit, a unit of heat energy, which is defined as the amount of heat required to raise the temperature of one pound of water by one degree Fahrenheit.
BTU
The abbreviation for Btu’s per hour, an energy flow rate.
BTUH
The control by automatic equipment of many functions in a large building, usually including HVAC system, the fire detection and alarm system, and building security.
Building Automation
The abbreviation for cubic feet per minute, which is the flow rate of air in a mechanical system or duct.
CFM
A piece of equipment that cools water for use in an air conditioning system.
Chiller
A fictitious temperature assigned to a combination of actual temperature and wind velocity that has the same physiological effect as still air at the chill factor temperature
Chill Factor
The addition of small amounts of chlorine to a water source to kill bacteria.
Chlorination
In sanitary drainage, any vent that serves two or more traps.
Circuit Vent
A window above eye level that admits daylight, such as the high windows in a cathedral.
Clerestory
An organized body of rules and regulations adopted and enforced by a governmental unit, such as building code.
Code
The ratio of the amount of heat energy delivered by a heat pump to the amount of energy removed by a refrigeration machine to the amount of energy expanded in its removal. It is similar to efficiency, but often exceeds 100 percent, and is therefore expressed as a number, i.e. 2.7 which is typical for a heat pump.
Coefficient of Performance
The ratio of useful light arriving at a work plane to the amount of light emitted by the source. The CU depends on the reflectivity of different surfaces and the aspect ratio of the ceiling, wall and floor cavities.
Coefficient of Utilization
The combination of thermal and environmental conditions within which a human is comfortable, often shown on a psychometric chart.
Comfort Zone
The rate at which a specific thickness of a given material conducts heat.
Conductance (C)
The heat transfer process that occurs when a warm fluid rises, displacing cold fluid which then falls.
Convection
One complete set of repeating events, typically used with alternating current or sound.
Cycle
A measure of frequency in electric current or acoustics, i.e., the number of cycles per second of a wave or oscillation. In acoustics, the term has been largely replaced by Hertz, where 1 cps=1Hz
Cycles per Second (CPS)
The use of natural light from outside to replace or augment electrical light outdoors, which produces energy savings.
Daylighting
A decibel measured in the A scale, that is weighted to account for the special sensitivities of the human ear.
dBA
A logarithmic measure of sound intensity level.
Decible (dB)
The amount by which the average outdoor temperature at a particular location is below 65 degrees F for one day. Degree days may also be summed and stated for a month or a year.
Degree Day (DD)
A method of connecting windings on a three phase transformer, end to end, that results in a triangular shape.
Delta Connection
The temperature of air at that the water contained in the air begins to condense and form dew. The dew point for a given sample is always lower than or equal to its current temperature.
Dew Point Temperature
A device through which the air from a duct enters a room, or a device through which the light from a fixture enters a room.
Diffuser
The temperature of air as read on an ordinary glass thermometer
Dry Bulb (DB)
A sprinkler system whose pipes are normally pressurized with only air, thus being invulnerable to freezing temperatures. Upon actuation, the air is vented and supply pressure forces water through the system.
Dry Pipe Sprinkler
An energy saving strategy in which part of the HVAC system is shut off while the rest is used, such as shutting off the refrigeration when the outside air temperature is low, while the fan continues to operate
Economizer Cycle
A fictitious temperature having the same physiological effect as air of a standardized temperature, humidity and velocity.
Effective Temperature
The ratio of the lumens emitted by a lamp to the electrical power consumed by the lamp.
Efficacy
A factor that represents the rate at which a given surface material gives off or emits radiant energy. The emissivity varies from 0 to 10, where 1.0 is the theoretical emissivity of a perfect black box at the same temperature.
Emissivity
The total of sensible plus latent heat stored in the air. It is also know as Total Heat.
Enthalpy
A continuous and unobstructed means of egress to a public way. Its minimum width is generally 44 inches.
Exit
A complete fire-resistive assembly consisting of a fire door, fire damper, or fire window and its mounting frame or hardware. The entire assembly, not just its components, must be approved and labeled by a testing agency that inspects the materials and workmanship during fabrication at the factory. Available ratings are 3/4, 1, 1-1/2 and 3 hours.
Fire Assembly
A unit of liquid flow used in sizing both supply and drainage pipes.
Fixture Unit
A numerical classification indicating the rate at which flame will spread in or on a given material, in which higher numbers flame up more rapidly.
Flame Spread Rating
A valve that releases a definite amount of water into a plumbing fixture each time its actuated.
Flushometer Valve
The basic unit of illumination arriving at a work plane. One footcandle is equal to one lumen per square foot.
Footcandle
A heating or cooling system that uses a fan to circulate heated or cooled air through ducts to the occupied spaces.
Forced Air System
The movement of a fluid by a fan or a pump, in order to force heat exchange.
Forced Convection
A hot and chilled water system having separate return lines for each supply line, and with no mixing of the two streams.
Four Pipe System
The number of cycles that occur per second, either in alternating current or acoustics. In acoustics, the frequency determines the pitch.
Frequency
In a given location, the maximum depth in soil that is expected to freeze in cold weather. Water piping must ordinarily be buried below the frost line to protect against freezing.
Frost Line
A piece of wax or paraffin that melts at a predetermined temperature, setting off a sprinkler head, an alarm system or otherwise actuating a fire protection device.
Fusible Link