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A B C D E F
G H I K L
M N O P R
S T U V W
Z
A
AFUE: Annual Fuel Utilization Efficiency. A
measurement of a gas furnace's efficiency in converting fuel to energy - the higher the rating, the more
efficient the unit.
AGA: Abbreviation for American Gas Association,
Inc.
Air Conditioner: A device that can change the
temperature, humidity, or general quality of the air.
Air Cleaner: A 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).
Air Handler: An air moving and/or mixing unit.
ARI: Air Conditioning & Refrigeration
Institute.
ASHRAE: American Society of Heating, Refrigeration,
and Air Conditioning Engineers.
B
BTU: British thermal unit; the amount of heat
required to raise or lower the temperature of one pound of water one degree Fahrenheit.
BTUh: British thermal units per hour. 12,000 BTUh
equals one ton of cooling.
Burner: A device that uses fuel to support
combustion.
Burner Orifice: The opening through which gas flows
to the air/gas mixing chamber of the burner.
Burner (Sealed Combustion): A burner that obtains
all air for combustion from outside the heated space.
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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".
CFM: Abbreviation for cubic feet per minute.
Charge: To add refrigerant to a system.
Compressor: Mechanical device to compress
refrigerant gas.
Condensate: Water vapor that liquifies due to the
lowering of its temperature to the saturation point.
Condenser Coil (or Outdoor Coil): In an air
conditioner, a finned coil which dissipates heat from the refrigerant, changing the refrigerant from vapor to
liquid. In a heat pump system, the coil absorbs heat from the outdoors in the
heating cycle.
Condenser Fan: The fan that circulates air over the
air-cooled condenser.
Contactor: A switch that can repeatedly cycle,
making and breaking an electrical connection.
Crankcase Heater: An electrical resistance heater
installed on compressor crankcase.
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D
Damper: A movable plate installed inside ductwork
to control airflow.
Defrost: To melt frost.
Degree-day: A degree-day is equal to 65 degrees
Fahrenheit minus the mean outdoor temperature.
Dehumidifier: An air cooler that removes moisture
from the air.
Diffuser: A grille over an air supply duct having
vanes to distribute the discharging air in a specific pattern or direction.
DOE: Department of Energy.
Downflow Furnace: A furnace that intakes air at its
top and discharges air at its bottom.
Drain Pan: Also referred to as a condensate pan.
This is a pan used to catch and collect condensate (in residential systems vapor is liquified 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.
Ductwork: A pipe or conduit through which air is
delivered. Ducts are typically made of metal, fiberboard, or a flexible material.
DX: Direct expansion; a system in which heat is
transferred by the direct expansion of refrigerant.
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E
EER: Energy Efficiency Ratio (steady state)
Energy Star®: The U.S. Department of Energy,
Environmental Protection Agency (EPA), Energy Star labeled products are more energy efficient and help reduce our
whole earth's pollution problems.
EPA: Environmental Protection Agency.
Expansion Valve: A refrigerant-metering value with
a pressure or
temperature controlled orifice.
Evaporator Coil (or Indoor Coil): Located inside
your home in the indoor unit. This is a finned coil in which a volatile liquid evaporates and absorbs
heat. This is where the refrigerant evaporates as it absorbs heat from the
indoor air that passes over the coil.
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F
Fahrenheit: The temperature scale on which water
freezes at 32 degrees and boils at 212 degrees; designated by the letter F.
Fan: A device that creates air currents.
Filter: A device that removes impurities through a
straining process.
Flue: Any vent or passageway that carries the
products of combustion from a furnace.
Furnace: That part of the heating system in which
the combustion of fossil fuel and transfer of heat occurs.
Fuse: A metal strip in an electrical circuit that
melts and breaks the circuit when excessive current flows through it.
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G
GAMA: Gas Appliance Manufacturers Association.
Gas Furnace Heat Exchanger: Located in the furnace,
the heat exchanger transfers heat to the surrounding air, which is then pumped throughout
your home.
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: Heatinhg 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.
Humidistat: A humidity-sensing control that cycles
the humidifier on and off.
Humidity: The presence of water vapor in the air.
HVAC: Abbreviation for Heating, Ventilating, and
Air Conditioning.
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I
Ignition: The lighting of a fuel to make it burn.
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K
Kilowatt (kW): 1,000 watts.
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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.
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M
Media: The material in a filter that traps and
holds the impurities.
MERV:
Minimum Efficiency Reporting Value.
An expression of the filtering efficiency of an air filter that has been
evaluated using the ASHRAE Standard 52.2 test procedure. MERV values
range from less than 1 for disposable panel residential filters to as
high as 20 for HEPA filters used in Clean Rooms.
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N
NEC: National Energy Council / National Electric
Code.
NEMA: National Electrical Manufacturing
Association.
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O
OEM: Original equipment manufacturer.
Orifice: An opening or hole; an inlet or outlet.
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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.
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R
Reciprocating Compressor: A 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 and in the
United States by the Environmental Protection Agency. R-22 is scheduled to be in
production until the year 2020. It's used in approximately 95 percent of air conditioning
equipment manufactured in the U.S. today.
Refrigerant Charge: The required amount of
refrigerant in a system.
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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. SEER is the ratio of the BTU cooling in normal annual use to
the total amount of electrical power (watts) over the same period.
Self-Contained System: A refrigerating system that
can be moved without disconnecting any refrigerant lines; also known 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.
Setpoint: The temperature or pressure at which a
controller is set with the expectation that this will be a normal value depending on the
range of the controller.
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.
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T
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 lost 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.
UL: Underwriters Laboratories.
Upflow Furnace: A furnace in which air is drawn in
through the sides or bottom and discharged out the top.
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V
Vacuum: A pressure below atmospheric pressure. A
perfect vacuum is 30 inches Mercury (periodic symbol "Hg").
Variable-Speed Motor(s): A motor whose speed may be
varied.
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.
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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.
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Z
Zoning System: A method of dividing a space into
different comfort zones so each zone can be independently controlled depending on use and
need; an air conditioning system capable of maintaining varying conditions for various
rooms or zones.
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