A
AC Abbreviation for alternating current, a type of electric
current in which the polarity is constantly reversing causing the electron
flow to reverse.
AC or DC Abbreviation for equipment capable of operating on alternating
or direct current.
A-Coil A heat exchanger consisting of two diagonal coils
that are joined together in a manner that looks like the letter "A".
Air Conditioner Any device that can change the temperature, humidity
or general quality of the air.
Air cleaner Any device that removes undesirable particles
from moving air.
Air flow volume The amount of air the system circulates through
your home, expressed in cubic feet per minute (cfm). Proper air flow depends
on the outdoor unit, the indoor unit, the ductwork and even whether the
filters are clean.
Air handler An air moving and/or mixing unit. Residential air handlers
include a blower, a coil, an expansion device, a heater rack and filter.
Heaters for air handlers are sold as accessories. In some models heaters
are factory installed.
B
BTU British thermal unit; the amount of heat required to
raise or lower the temperature of one pound of water one degree Fahrenheit.
The heat extracted from your home by an air conditioner is measured in BTUs.
BTUh British thermal units per hour. 3412 BTUh equals one
kilowatt-hour.
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C
Capacity The output or producing ability of cooling or
heating systems. Cooling and heating capacities are referred to in British
thermal units (BTUs) per hour.
Celsius The metric temperature scale in which water freezes at
zero degrees and boils at 100 degrees, designated by the symbol "C".
To convert to Fahrenheit, multiply a Celsius temperature by 9, divide by
5 and add 32 (25 x 9 equals 225, divided by 5 equals 45, plus 32 equals
77 degrees Fahrenheit).
CFM Abbreviation for cubic feet per minute, a standard
measurement of airflow. A typical system requires 400 cfm per ton of air
conditioning.
Charge To add refrigerant to a system. This is refrigerant contained
in a sealed system or in the sensing bulb to a thermostatic expansion valve.
Compressor This is the heart of a heat pump system. It
is part of the outdoor unit and pumps refrigerant in order to meet the cooling
requirements of the system.
Condensate Vapor that liquefies due to the lowering of its temperature
to the saturation point.
Condenser coil (or outdoor coil) In a heat pump, the coil dissipates
heat from the refrigerant, changing the refrigerant from vapor to liquid.
In a heat pump system, the coil absorbs heat from the outdoors.
Condenser fan The fan that circulates air over the air-cooled condenser.
Contactor A switch that can repeatedly cycle, making and breaking
an electrical circuit. When sufficient current flows through the A-coil
built into the contactor, the resulting magnetic field causes the contacts
to be pulled in or closed. COP Coefficient of performance
Crankcase heaterThis is the electric resistance heater
installed on compressor crankcases to boil off liquid refrigerant that may
have combined with compressor oil. Many newer cooling systems do not require
crankcase heaters, however heat pumps do require crankcase heaters.
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D
DC Direct current electricity. This type of electricity
(as opposed to Alternating Current, or AC) flows in one direction only,
without reversing polarity.
Defrost To melt frost; as in from an air conditioner or heat pump
coil.
Dehumidifier An air cooler that removes moisture from the
air.
Downflow furnace A furnace that intakes air at its top
and discharges air at its bottom.
Drain pan This also referred to as a condensate pan. This
is a pan used to catch and collect condensate (in residential systems vapor
is liquefied on the indoor coil, collected in the drain pan and removed
through a drain line).
Dry bulb temperature Heat intensity, measured by a dry bulb thermometer.
Dry bulb thermometer An instrument that measures air temperature
independently of humidity.
DX Direct expansion; a system in which heat is transferred by the
direct expansion of refrigerant.
E
EER Energy Efficiency Ratio (steady state)
Expansion Valve A refrigerant-metering valve with a pressure
or temperature controlled orifice.
F
Fahrenheit The temperature scale on which water freezes
at 32 degrees and boils at 212 degrees; designated by the letter F. To convert
Fahrenheit to Celsius, subtract 32 from the Fahrenheit number, multiply
by 5 and divide by 9 (77 -32 equals 45, times 5 equals 225, divided by 9
equals 25 degrees Celsius).
Fan Any device that creates air currents.
Filter Any device that removes impurities through a straining
process.
Fuse A metal strip in an electrical circuit that melts
and breaks the circuit when excessive current flows through it. The fuse
is designed to break in order to save more expensive electrical components.
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H
Heat Exchanger An area, box or coil where heat flows from
the warmer to the colder fluid or surface.
Heat Gain Heat added to the conditioned space by infiltration,
solar radiation, occupant respiration and lighting.
Heating Coil Any coil that serves as a heat source.
Heat Loss The rate of heat transfer from a heated space
to the outdoors.
Heat Pump A mechanical-compression cycle refrigeration
system that can be reversed to either heat or cool the controlled space.
Heat Transfer The movement of heat energy from one point
to another. The means for such movement are conduction, convection, and
radiation.
Hertz In alternating current (AC electricity), the number
of cycles per second.
HSPF Heating Seasonal Performance Factor. This rating is used in
measuring the heating efficiency of a heat pump. The higher the number the
more efficient the heat pump system.
Humidifier A machine that adds water vapor to the air to
increase humidity.
Humidity The presence of water vapor in the air.
Humidity, absolute Weight of water vapor per cubic foot
of dry air, expressed as grains of moisture per cubic foot.
Humidity, relative The amount of moisture in the air expressed
as a percentage of the maximum amount that the air is capable of holding
at a specific temperature.
I
Ignition The lighting of a fuel to make it burn.
K
Kilowatt (kW) 1,000 watts.
L
Latent Heat A type of heat, which when added to or taken
from a substance, does not change the temperature of the substance. Instead,
the heat energy enables the substance to change its state.
M
Media The material in a filter that traps and holds the
impurities.
O
OEM Original equipment manufacturer.
Orifice An opening or hole; an inlet or outlet.
P
Package Unit A heating and cooling system contained in
one outdoor unit. A package unit is typically installed beside, on the roof,
or sometimes in the attic of a home.
PSI Pounds per square inch.
PSIA Pounds per square inch, absolute.
PSIG Pounds per square inch gauge.
PVC Polyvinyl chloride; a type of plastic.
R
Reciprocating CompressorA compressor whose piston or pistons
move back and forth in the cylinders.
Refrigerant A chemical that produces a refrigerating effect
while expanding and vaporizing. Most residential air conditioning systems
contain R-22 refrigerant. R-22 is regulated under the Montreal Protocol.
R-22 is scheduled to be in production until the year 2020. It's used
in approximately 95 percent of heat pumps manufactured today.
Refrigerant Charge The required amount of refrigerant in
a system.
S
SEER Seasonal Energy Efficiency Ratio; a measure of cooling
efficiency for air conditioners and heat pumps. The higher the SEER, the
more energy efficient the unit.
Self-contained System A refrigerating system that can be
moved without disconnecting any refrigerant lines; also know as a package
unit.
Sensible Heat That heat which, when added to or taken away from
a substance, causes a rise or fall in temperature.
Sensor Any device that reacts to a change in the conditions
being measured, permitting the condition to be controlled.
Set point The temperature or pressure at which a controller
is set with the expectation that this will be a nominal value depending
on the range of the controller.
SF Side fan series
Split System The combination of an outdoor unit (air conditioner
or heat pump) with an indoor unit (furnace or air handler). Split systems
must be matched for optimum efficiency.
T
TF Top fan series
Thermostatic Expansion Valve A refrigerant metering device that
maintains a constant evaporator temperature by monitoring suction vapor
superheat; also called a thermal expansion valve.
Thermostat A thermostat consists of a series of sensors and relays
that monitor and control the functions of a heating and cooling system.
Ton A unit of measurement used for determining cooling
capacity. One ton is the equivalent of 12,000 BTUs per hour.
Two-stage heating / Two-stage cooling Two-stage heating
and cooling is considered to be more efficient, because it operates at low
speed most of the time. However, on days when more heating or air conditioning
is required, it switches to the next stage for maximum comfort.
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U
U-Factor The factor representing resistance to heat flow
of various building materials.
Up flow Furnace A furnace in which air is drawn in through the
sides or bottom and discharged out the top.
V
Vacuum A pressure below atmospheric pressure. A perfect
vacuum is 30 inches Mercury (periodic symbol "Hg").
Variable-speed motor(s) The fan motor is designed to vary
its speed based on your home's heating and air conditioning requirements.
Working in conjunction with your thermostat, it keeps the appropriate-temperature
air (e.g. warm air on cold days) circulating throughout your home, reducing
temperature variances in your home. It also provides greater air circulation
and filtration, better temperature distribution, humidity control, higher
efficiency, and quiet performance.
Volt The unit of measure used to describe a difference in electrical
potential; abbreviated by the symbol "v".
Voltage The force that pushes electrical current along wires and
cables.
W
Watt The unit of electrical power equal to the flow of
one amp at a potential difference of one volt.
Wet Bulb Thermometer A thermometer whose bulb is covered
with a piece of water-soaked cloth. The lowering of temperature that results
from the evaporation of water around the bulb indicates the air's relative
humidity.
Contact Solnet for pool heating and heat pumps systems.


