1404
Modern Refrigeration and Air Conditioning
compound refrigeration system. A multistage system that
has two or more compressors connected in series. (44)
compression rings. Piston rings that are designed to pre-
vent pressurized refrigerant vapor from blowing past the
piston and into the crankcase. (15)
compressor. A vapor pump that draws low-pressure refrig-
erant vapor from the cooling side of the refrigerant cycle
and squeezes or compresses the vapor, forcing it to the high-
pressure or condensing side of the cycle. Most compressors
are motor-driven, though some are engine-driven. (2)
concentrating collector. A solar collector that uses either
mirror-type concentrators or lens-type concentrators to
reflect or bend the light/heat into a collector. (39)
condensate pump. A pump designed to move condensate
from a system and into a drain. (46)
condenser. A component in a refrigeration system that
receives hot, high-pressure refrigerant vapor from the com-
pressor and cools the gaseous refrigerant until it returns to
its liquid state. (2)
condenser capacity. The amount of heat a condenser can
reject. (52)
condenser condensate line. A refrigerant line running from the
outlet of the condenser to the inlet of the liquid receiver. (49)
condenser pressure regulator. An open on rise of inlet pres-
sure (ORI) valve that opens when condenser pressure rises
to a proper level and closes to block the flow of refrigerant
from the condenser to the liquid receiver when condenser
pressure drops too low. Also called condenser holdback valve,
holdback pressure valve, head pressure control valve, and limiter
valve. (45)
condenser splitting. A method of head pressure control in
low ambient conditions in which a condenser is divided into
two separate spaces: one space that is used as a condenser
year-round (summer-winter condenser) and the other space
(summer condenser) that is evacuated during low ambient
conditions. (45)
condensing boiler. A boiler designed to condense combus-
tion gases, which allows the circulating water to absorb addi-
tional latent heat from the combustion gases. Condensing
boilers are over 90% efficient. (33)
condensing furnace. A high-efficiency furnace with an
annual fuel utilization efficiency (AFUE) rating above 90%.
Condensing furnaces use primary and secondary heat
exchangers to extract enough heat from the combustion
gases that they condense. (32)
conditioned area. A specific area in which an HVACR sys-
tem regulates conditions, such as temperature, pressure,
and humidity. (13)
conduction. The flow of heat between substances by molec-
ular vibration. (1)
conductor. A material or substance that allows electrons
to flow easily. Electrical conductors are typically made of
metal. (9)
connecting rod. A reciprocating compressor component
that connects the piston to the crankshaft. (15)
console air conditioner. An entire air-conditioning system
mounted in a stand-up cabinet. Also called vertical packaged
terminal air conditioners. (25)
contact point bounce. An unwanted effect that occurs when
contacts close through high amounts of pressure and then
rebound from each other due to the force. Contact bounce is
undesirable because it can create secondary arcs and reduce
contact life. (29)
contactor. A heavy-duty type of electromagnetic relay that
can handle high-current loads, such as motors. Contactors
can have a variety of contact configurations, from a single
set of contacts to five or six sets of contacts. (13, 45)
continuity. The condition that exists when there is an
un broken path between two points in an electrical circuit. (14)
continuous-cycle absorption system. An absorption system
operated by the application of a limited amount of heat. The
circulated refrigerant is evaporated by heat and subsequently
reabsorbed, displacing the need for a compressor. (27)
contractual agreement. A legal agreement that specifies the
terms of service, including initial repair work and follow-up
maintenance. (5)
control circuit. A circuit that uses electrical or electronic
devices to control current flow, causing loads connected to
the circuit to be either energized or de-energized. (11)
control point. The present condition as measured by a sen-
sor in a conditioned area. (13)
control system. A collection of interacting components that
work together to regulate the operation of an HVACR sys-
tem. The basic components of a control system include sen-
sors, controllers, and actuators. (13)
controller. A device that responds to changes in the signals
from sensors and issues signals to actuators. (13)
convection. The transfer of heat from one place to another
by means of a liquid or gas. (1)
conventional boiler. A noncondensing boiler that operates
at water temperatures above 140°F (60°C). (33)
cooling anticipator. In a thermostat, a high-value resistor
wired in parallel with the bimetal coil temperature-sensing
device that conducts current during the cooling system’s Off
cycle to produce heat that will trip the cooling system on
several minutes before the conditioned area reaches the cut-
in temperature. (29)
cooling tower. A structure that rejects heat from the cooling
water of an HVACR system using the evaporation of water.
(26, 45)
corrosion. A chemical degradation of metal. In a hydronic
system, corrosion occurs when the water is too acidic or
when certain gases are dissolved in the water. (33)
coulomb. The quantity of electricity transferred by an elec-
tric current of one ampere in one second. A coulomb is equal
to approximately 6.24 × 1018 electrons. (9)
counter electromotive force (cemf). The voltage induced
in a running motor by the rotor’s magnetic field that has a
polarity opposite of the voltage applied to the stator. (12)