1408
Modern Refrigeration and Air Conditioning
electron. A negatively charged subatomic particle that orbits
around the nucleus of an atom. (9)
electronic air cleaner. An air cleaning device that puts a
static electrical charge on all particles in the air that pass
through it. These particles are then attracted to collector
plates with an opposite electrical charge. (22)
electronic expansion valve (EEV). An expansion valve that
uses an electric operator instead of the diaphragm power
assembly of the TXV or the spring assembly of the AXV. (16)
electronic leak detection. A leak detection method that uses
an electronic sensor capable of detecting very small leaks. (7)
electronically commutated motor (ECM). A programmable,
brushless dc motor that uses electronic switching devices to
control polarity and power in the stator windings. (12)
embrittlement. A weakening of metal caused by long-term
corrosion, which can lead to structural failure along seams,
under rivets, and at tube ends. (33)
emissivity. The relative ability of a surface to allow light
rays to pass through. (30)
end bell. The caps or plates at either end of a motor frame
that house the bearings and support the rotor. (12)
end switch. A device used to detect combustion blower
operation in a furnace. An end switch connects to the end of
a damper motor shaft and closes when the damper is turned
open a certain amount or angle. (35)
endplay. The axial movement of a motor shaft as it rotates. (14)
energy. The ability to effect a change in matter. (1)
energy audit. A recording and calculation of energy con-
sumption in a building. (40)
energy conservation. Reducing the amount of energy used
for a particular process. In HVACR, this includes replacing
older systems with more efficient systems, correctly install-
ing equipment, using proper service techniques, performing
preventive maintenance, and upgrading existing systems
and buildings to improve their efficiency. (41)
energy efficiency ratio (EER). A performance ratio that
expresses an air conditioner’s cooling capacity in Btu/hr for
each watt of power consumed. (41)
energy recovery ventilator (ERV). A mechanical ventilation
system that passes incoming fresh air and outgoing stale air
through a series of parallel passages. As each air stream
passes through the ERV, heat and humidity are exchanged,
so the incoming air is closer to the temperature and humid-
ity level of the outgoing air. (22)
Energy Star. A label given to buildings and appliances built
according to a set of US Department of Energy (DOE) guide-
lines that promote increased energy efficiency. (41)
energy utilization index (EUI). A calculation that shows
the relationship of Btu consumed per year for a given area.
The EUI is calculated by dividing energy consumption in
Btu by the square footage of conditioned space. (40)
enthalpy. Total amount of heat in a substance, calculated
from an accepted reference temperature. For water calcula-
tions, the reference temperature is 32°F (0°C). For refrigerant
calculations, the accepted reference temperature is –40°F
(–40°C). On psychrometric charts, enthalpy is the total heat
content in the air sample. (1, 21)
entrained air. Air in a hydronic system consisting of small
air bubbles that travel along with the circulating water.
Entrained air can be removed with air scoops and air sepa-
rators. (33)
Environmental Protection Agency (EPA). A US govern-
mental agency that enforces the rules for working with
refrigerants. All HVACR technicians must be certified by
the EPA. (6)
enzymes. Specific types of proteins in food that trigger
organic change. (17)
epoxy repair kit. A repair kit containing all the materials
(sandpaper, surface cleaner, resin, and hardener) needed to
patch a small hole in an aluminum evaporator. (20)
epoxy resin. A polymer substance used to repair small leaks
in a refrigeration system. One-part epoxies require the use
of heat to harden, while two-part epoxies come with a hard-
ener that is mixed with the epoxy at room temperature. (8)
equalizer. A small external tube connecting the suction line
at the evaporator outlet to a chamber inside the expansion
valve, just below the diaphragm. This tube is used to bal-
ance pressure and provide the correct refrigerant flow. (16)
equivalent temperature. Temperature that represents how
warm the combination of humidity and temperature feels to
the occupant of a space. (21)
eutectic plate. A thin, rectangular tank containing an evapo-
rator surrounded by a solution that freezes at a desired tem-
perature. Primarily used in truck or trailer refrigeration. (43)
eutectic salts. A combination of inorganic salts, water,
and various elements formulated to freeze at a desired
temperature. (39)
evacuated tube collector. An efficient type of solar col-
lector that uses tubes containing fluid contained within
slightly larger glass tubes. The glass tube is sealed and the
air between the tubes is removed, creating a vacuum. (39)
evacuation. The removal of all vapors, gases, and fluids
from a refrigeration system. The two main methods of evac-
uation are deep vacuum and triple evacuation. (8)
evaporative condenser. A condenser that uses drafts from
fans to aid in evaporating a water mist on and around the
refrigerant-carrying tubes of the condenser to condense and
subcool high-side refrigerant. (26, 45)
evaporative cooling. The natural cooling effect of evapora-
tion, used to cool a space or objects. (27)
evaporative humidifier. A humidifying unit that adds
moisture to the air through evaporation. (28)
evaporator. A component in a refrigeration system where
low-pressure refrigerant vaporizes and absorbs heat. (2)
evaporator pressure regulator (EPR). A valve that restricts
the flow of refrigerant coming out of the evaporator to main-
tain a set minimum pressure in the evaporator while the
refrigeration system is operating. Also called holdback valve,
two-temperature valve, and constant pressure valve. (44)