80% A.F.U.E. - 80% of the fuel burned is turned into heat delivered at the register. The U.S. government's established minimum AFUE rating for a furnace is 78 percent.
AC Alternating Current - A type of current where the polarity is perpetually reversing, causing the directional flow in a circuit to reverse at regular intervals.
A-Coil - A heat exchanger consisting of two diagonal coils that are joined together in the shape of the letter A.
Accumulator - A storage tank located in the suction line of a compressor.
ACH - Stands for Air Changes per Hour. It is the number of times in one hour that the air in your house is completely replaced with outside air.
Acid Condition - The presence of corrosive substances in a sealed refrigeration system.
Add On Heat Pump - Installing a heat pump in conjunction with an existing fossil fuel furnace. The result is a dual fuel system.
A.F.U.E (Annual Fuel Utilization Efficiency) - A rating that reflects the efficiency of a gas furnace in converting fuel to energy. A rating of 90 means that approximately 90% of the fuel is utilized to provide warmth to your home, while the remaining 10% escapes as exhaust.
AHU (Air Handler Unit) - The inside part of the A/C system that contains the blower, cooling (evaporator) coil, and heater. The part of an HVAC system responsible for moving air, which may also clean, heat, or cool the air. This refers to equipment used to provide conditioned air to a space. The air handler unit generally includes a blower or fan, heating and/or cooling coils, and related equipment such as controls, condensate drain pans, and air filters. Does not include ductwork, registers or grilles, or boilers and chillers.
Allergen - A substance capable of causing an allergic reaction because of an individual's sensitivity to that substance
Allergic Rhinitis - Inflammation of the mucous membranes in the nose that is caused by an allergic reaction.
Aluminum Fin - Attached to a sleeve around the coil and used to dissipate heat away from the coil.
Air Change - The amount of air required to completely replace the air in a room or building; not to be confused with recirculated air.
Air Conditioner - A device that modifies the temperature, humidity, cleanliness, or general quality of air.
Air Conditioning - The science of controlling the temperature, humidity, cleanliness or general quality of air. Abbreviated: AC.
Air Cooled - Uses a fan to discharge heat from the condenser coil to the outdoors.
Air Diffuser - Air distribution outlet or grille designed to direct airflow into desired patterns.
Air Duct - Pipes that carry warm air and cold air to rooms and back to furnace or air conditioning system.
Air Exchange Rate - The rate at which outside air replaces indoor air in a space. Expressed in one of two ways: the number of changes of outside air per unit of time air changes per hour (ACH); or the rate at which a volume of outside air enters per unit of time - cubic feet per minute (cfm).
Airflow - The distribution or movement of air.
Air Handler - The portion of a central air conditioning or heat pump system that moves heated or cooled air throughout a home's ductwork. In some systems, a furnace handles this function.
Air Pressure Control (Switch) – Used to detect air pressure drop across the coil in a heat pump outdoor unit due to ice buildup.
Air-Source - Air is being used as the heat source or heat sink for a heat pump.
Ambient Temperature - The temperature of the immediately surrounding air or area.
Amperage - The rate of electrical current flow in a circuit.
ARI - Air-Conditioning and Refrigeration Institute is a non-profit, voluntary organization comprised of heating, air conditioning and refrigeration manufacturers. ARI publishes standards for testing and rating heat pumps and air conditioners to provide you with a standardized measure of comparison. So, ARI ensures a level of quality within the industry.
ASHRAE - American Society of Heating Refrigeration and Air Conditioning Engineers
Auto-Ignition - A feature of newer gas furnaces that eliminates the need for a standing pilot light. The system shuts off completely when not in use.
Balance Point - An outdoor temperature -- usually between 30°F to 45°F -- at which a heat pump's output exactly equals the heating needs of the house. Below the balance point, supplementary electric resistance heat is needed to maintain indoor comfort.
Boiler - A sealed chamber in which water is converted to steam or is heated for circulation in a hydronic heating system.
Blower - An air-moving device; a fan.
Boot - A fitting that connects round to rectangular sheet metal or fabricated duct systems.
Breaker - A heat-activated electrical device used to open an electrical circuit to protect it from excessive current flow.
BTU ( British Thermal Unit) - In scientific terms, it represents the amount of energy required to raise one pound of water one degree Fahrenheit. One BTU is the equivalent of the heat given off by a single wooden kitchen match. For your home, it represents the measure of heat given off when fuel is burned for heating or the measure of heat extracted from your home for cooling.
BTUH - The number of BTUs in an hour.
Burner - The device that facilitates the combustion of air and gas.
Burner Orifice - The opening in the burner through which the gas or fuel passes prior to combustion.
Capacity - The output or producing ability of a piece of cooling or heating equipment. Cooling and heating capacity are normally referred to in BTUs.
Carbon Monoxide - A colorless, odorless gas resulting from the incomplete combustion of hydrocarbon fuels. Carbon monoxide interferes with blood's ability to carry oxygen to the body's tissues and results in numerous adverse health effects.
Celsius - A temperature scale that registers the freezing point of water as 0° and the boiling point as 100° under normal atmospheric pressure.
Central Air Conditioner System - System in which air is treated at a central location and carried to and from the rooms by one or more fans and a system of ducts.
Central Forced-Air Heating System - A piece of equipment that produces heat in a centralized area, then distributes it throughout the home through a duct system.
CFM - A standard of airflow measurement. Cubic feet per minute. A typical system produces 400 CFM per ton of air conditioning.
Charge - The quantity of refrigerant in a system.
Charging a System - Adding coolant, or refrigerant, to an HVAC system.
Chase - A groove in a masonry wall or through a floor to accommodate pipes or ducts.
Chimney or flue - A vent for the products of combustion.
Coefficient of Performance (COP) - A ratio calculated by dividing the total heating capacity provided by the heat pump, including circulating fan heat but excluding supplementary resistance heat (Btu's per hour), by the total electrical input (watts) x 3.412. (See Heating Seasonal Performance Factor, below.)
Comfort Zone - The range of temperatures, humidity and air velocities at which the greatest percentage of people feel comfortable.
Compressor - The heart of an air conditioning or heat pump system. It is part of the outdoor unit that pumps refrigerant. The compressor maintains adequate pressure to cause refrigerant to flow in sufficient quantities to meet the cooling requirements of the system.
Condensate/Condensation - Water vapor that liquefies due to the lowering of its temperature to the saturation point.
Condensate Drain - An outlet for the moisture collected on an evaporator coil.
Condensate Pump - A water pump that disposes of or recirculates collected condensate.
Condenser - A device that transfers unwanted heat out of a refrigeration system to a medium (either air, water, or a combination of air and water) that absorbs the heat and transfers it to a disposal point. There are three types of condensers: air-cooled condensers, water-cooled condensers, and evaporative condensers. The evaporative condenser uses a combination of air and water as its condensing medium. Most residential systems have an air-cooled condenser.
Condenser Coil or Outdoor Coil - Located in the outdoor unit, the coil dissipates heat from the refrigerant, changing the refrigerant from vapor to liquid.
Condenser Fan - The fan that circulates air over an air cooled condenser. (usually located outside)
Condensing Furnace - A high-efficiency, gas forced-air furnace that uses a second condensing heat exchanger to extract the latent heat in the flue gas.
Condensing Unit - A complete unit that includes the compressor and the condensing coil.
Conditioned Air - Air that has been heated, cooled, humidified, or dehumidified to maintain an interior space within the "comfort zone".
Configuration - This describes the direction in which a furnace outputs heat. A furnace may have an upflow, down flow or cross flow (horizontal) configuration.
Contactor - A switch that can repeatedly cycle, making and breaking an electrical circuit. When sufficient current flows through a coil built into the contactor, the resulting magnetic field causes the contacts to be pulled in.
Convertible Air Handler - An air handler that can be installed in either an upflow or a horizontal left configuration.
Cooling Capacity - A measure of the ability of a unit to remove heat from an enclosed space.
Copper Coil - Coils move refrigerant under high pressure and copper is known for its durability and efficient heat transfer.
CSA - Canadian Standards Association.
DC - Direct Current. A type of electrical current that only flows in one direction.
Data Plate - An equipment identification label; usually lists model and serial numbers and various unit ratings.
Damper - Found in duct work, this movable plate opens and closes to control airflow. Dampers are used effectively in zoning to regulate airflow to certain rooms.
Decibel (db) - A decibel describes the relative loudness of a sound. Some common sounds are fairly close to a typical air conditioner or heat pump's sound level: human voice, 7.0 decibels; blender, 8.8 decibels.
Defrost Cycle - The process of removing ice or frost buildup from the outdoor coil during the heating season.
Defrost Mode - During the heating cycle of a heat pump, frost may build up on the outdoor coil. To remove the frost and maintain efficiency, the system will automatically defrost itself. This usually only takes a few minutes, then the system automatically switches back to heating. It is normal to see steam rising from the outdoor unit when this happens.
Degree Day - The difference between indoor design temperature and each day's average outdoor temperature. Abbreviated: DD.
Dehumidification - The reduction of water vapor in air by cooling the air below the dew point; removal of water vapor from air by chemical means, refrigeration, etc.
Dehumidify - To remove moisture from air.
DOE - The Department of Energy. A federal agency that sets industry efficiency standards and monitors the use of various energy sources.
Downflow Furnace - A furnace that pulls in return air from the top and expels warm air at the bottom.
Disconnect - A switch box that cuts off electrical power to a machine being serviced.
Duct - A pipe or closed conduit made of sheet metal, fiberglass board, or other suitable material used for conducting air to and from an air handling unit.
Duct Heater - An electric-resistance or hot water heater mounted inside an air-delivery duct to provide supplementary heat to the delivered air.
Ductless Mini-Split System - A system where there is no ductwork involved, simply a single indoor unit (usually wall mounted) or two or more indoor units and a single outdoor unit (condensing unit/heat pump) Used to heat and cool areas where traditional ductwork is not feasible such as additions, workshops, warehouse offices, enclosed porches, etc.
Ductwork - Pipes or channels that carry air throughout your home.
Energy Efficiency Ratio (EER) - A ratio calculated by dividing the cooling capacity in Btu's per hour (Btuh) by the power input in watts at a given set of rating conditions, expressed in Btuh per watt (Btuh/watt). (See Seasonal Energy Efficiency Ratio,below.)
Efficiency - The amount of usable energy produced by a machine, divided by the amount of energy supplied to it.
Elbow - Any fitting that produces a bend in the duct or piping run it connects.
Electric Heat - A heating system in which the energy source is electricity and the heat is produced by resistance elements.
Electronic Air Cleaner (EAC) - A filter that uses electricity to create a slight magnetic charge to help collect smaller particles. The EAC then draws tiny particles that are magnetized, such as viruses and bacteria, to a collector plate to remove them from the indoor air in your home.
Electronic Leak Detector - A test instrument that detects the presence of refrigerants in small air samples.
Electrostatic filter or Precipitator - An air cleaning device that electrically charges foreign particles in the air and then collects them on positively charges plates.
Emergency Heat (Supplementary Electric Heat) - The back up electric heat built into a heat pump system. The same as an auxiliary heater, except it is used exclusively as the heat source when the heat pump needs repair.
Energy Star - EPA rating given to products that exceed a standard efficiency level of operating costs of H.V.A.C. equipment. When properly installed, Energy Star-labeled products can save consumers 10-40% on heating and cooling bills each year.
Enthalpy - Heat content or total heat, including both sensible and latent heat. The amount of heat contained in a refrigerant at any given temperature with reference to -40°F.
E.P.A. - Environmental Protection Agency
Evacuate - To remove, through the use of a vacuum pump, all moisture and noncondensables from a system.
Evaporator Coil - The coil that is inside your house in a split system. In the evaporator, refrigerant evaporates and absorbs heat from air passed over the coil.
Expansion Valve - A valve that meters the levels of refrigerant through a temperature or pressure control.
Fahrenheit - The temperature scale on which water freezes at 32 deg. And boils at 212 deg.
Fan Coil - Another term for air handler. Which is generally the indoor section of a heat pump system which is made up of a blower and refrigerant coil.
Fill-Type Insulation - Loose insulating material which is applied by hand or blown into wall spaces mechanically.
Filter - A device for removing dust particles from air or unwanted elements from liquids.
FLA (Full Load Amperage) - The current draw of a motor under full load, the current flow in a circuit when the load is at its rated peak.
Flexible Duct - A duct that can be gradually bent to go around obstacles.
Flue - A vent that carries the products of combustion from a boiler or furnace.
Forced Air - This describes a type of heating system that uses a blower motor to move air through the furnace and into the ductwork.
Fungi - Any of a group of parasitic lower plants that lack chlorophyll, including molds and mildews.
Furnace - That part of an environmental system which converts gas, oil, electricity or other fuel into heat for distribution within a structure.
Fuse - A metal strip in an electrical circuit that melts and breaks the circuit when excessive current flows through it.
Gas Furnace Heat Exchanger - Located in the furnace, the heat exchanger transfers heat to the surrounding air, which is then pumped throughout your home.
Gas Valve - A valve that controls fuel flow to the burner in a gas-fired furnace or heater.
- A cage-like panel
that covers the end of a duct, permitting the passage of air but not foreign
Head Pressure - High-side pressure in a refrigeration system; pressure from the compressor discharge to the metering device.
Heat Gain - The amount of heat gained, measured in BTU's, from a space to be conditioned, at the local summer outdoor design temperature and a specified indoor design condition.
Heat Loss - The amount of heat lost, measured in BTU's from a space to be conditioned, at the local winter outdoor design temperature and a specified indoor design condition.
Heat Pump - An electric air conditioning and heating system that captures existing outdoor heat and transfers or "pumps" this heat into your home. The most common type is an "air to air" meaning heat is captured from the outside air and transferred to the air inside your home.
Heat Source - A body of air or liquid from which heat is collected. In an air source heat pump, the air outside the house is used as the heat source during the heating cycle.
Heat Strip - The supplemental or primary heating "coil" that produces heat using electrical resistance.
Heating Capacity - A measure of the ability of a unit to add heat to an enclosed space.
Heating Degree Days - The number of degrees per day that the daily average temperature (the mean of the maximum and minimum recorded temperatures) is below a base temperature, usually 65 degrees Fahrenheit, unless otherwise specified; used to determine indoor space heating requirements and heating system sizing. Total HDD is the cumulative total for the year/heating season. The higher the HDD for a location, the colder the daily average temperature(s).
High-Efficiency Gas Furnace - A furnace that recycles combustion gases to obtain efficiencies of 85% to 95%.
High Side - A term used to indicate the high-pressure or condensing side of the refrigeration system.
Horizontal Furnace - A type of furnace most often installed in attics or crawl spaces. The furnace is installed on its side and draws air in from one side, heats it and emits warm air out the opposite side.
HSPF = Heat Pump Heating Efficiency - It stands for Heating Seasonal Performance Factor, or HSPF. The higher the HSPF rating, the more efficient a heat pump is at heating your home. The US government has established a minimum 6.8% HSPF.
Humidifier - A device that injects water vapor into heated air as the air is expelled from the furnace.
Humidistat - A device designed to regulate humidity input by reacting to changes in the moisture content of the air.
Humidity - The amount of moisture in the air. Air conditioners remove moisture for added comfort.
HVAC - Industry acronym for the general category of Heating, Ventilation, and Air Conditioning
ICM - Integrally Controlled Motor. A specially engineered, variable-speed motor used in American Standard's top-of-the-line indoor units. ICM motors are more than 90% efficient versus 60% efficiency for conventional motors. Continuous comfort, whisper-quiet operation and ultimate system efficiency are the benefits of the indoor products graced with the ICM motor.
Ignition - Elevating the temperature of a substance to the point of causing a combustion reaction.
Indoor Air Quality - The purity of indoor air or a lack of polluting gases or particles given off by equipment and furnishings in a space that can affect human health.
Indoor Coil - The portion of a heat pump or central air conditioning system that is located in the house and functions as the heat transfer point for warming or cooling indoor air.
Induced-Draft Furnace - A furnace in which a motor-driven fan draws air from the surrounding area or from outdoors to support combustion.
Insulation - Any material that slows down the transfer of heat.
ISO 9000 Standards - The International Organization of Standards (ISO) 9000 standards define a Quality System which ensures the quality of a product.
ISO 9001 - The model for Quality Assurance in Design, Development, Production, Installation and Servicing. ISO registration is just one of the building blocks for achieving world-class products.
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(K) Factor - The insulating value of any material. Also known as conductivity.
Kilowatt (Kw) - Equal to 1,000 watts.
Kilowatt-hour (Kwh) - A common unit of electrical consumption measured by the total energy created by one kilowatt in one hour.
Life Cycle Cost - The sum of all the costs both recurring and nonrecurring, related to a product, structure, system, or service during its life span or specified time period.
Lifetime Cost - The cost of something, including purchase, operation, maintenance, and disposal costs.
Limit Switch - A protective device used to open or close electrical circuits when temperature or pressure limits are reached.
Line Drier - An accessory that removes moisture from a refrigeration system.
Line Set - A term used for tubing sets furnished by the manufacturer for connecting parts of an air conditioning system.
Liquid Line - The refrigerant tubing extending from the condenser outlet to the metering device. Usually the small warm line.
Load Estimate - Studies performed to calculate heating and cooling requirements for a specific house, using the size of your home, size of your windows and doors, quality of insulation, and local weather conditions.
Locked Rotor Amperage (LRA) - The current drawn by a motor at start-up, before the rotor starts turning.
Louver - An opening with horizontal slats to permit passage of air, but excluding rain, sunlight and view.
Low Side - a term used to refer to that part of the refrigeration system that operates at the lowest pressure, between the expansion device and the compressor.
LP Fuel (Liquefied Petroleum) - A substance used as a gas for fuel. It is transported and stored in the liquid state.
Matched System - A heating and cooling system comprised of products that have been certified to perform at promised comfort and efficiency levels when used together, and used according to design and engineering specifications.
Media - The fine material of a filter that traps dirt, dust, mildew or bacteria.
Multi-Position - An indoor air handler or furnace that can be installed as an upflow (ductwork overhead or in the attic), downflow (ductwork in a basement or crawl space), or horizontal (air handler or furnace in a basement or attic) application, depending on individual need.
National Electrical Code (NEC) - Publication that sets the standards for all electrical installations, including motor overload protection.
Natural-Draft Furnace - A furnace in which the natural flow of air from around the furnace provides the air to support combustion. It also depends on the pressure created by the heat in the flue gases to force them out through the vent system.
Natural Gas - A fossil fuel formed over millions of years from dead vegetation and animals that were deposited or washed deep into the earth.
OEM - Original equipment manufacturer.
Operating Cost - The cost of running your heating and air conditioning system, day-to-day, based on energy use.
Orifice - An opening or hole.
Overcharge - To fill a system with refrigerant beyond its design capacity.
Package System - A piece of air conditioning and heating equipment where all components are located in one cabinet. Used occasionally in residential applications, the package unit is installed either beside or on top of the home.
Package Unit - Any system that is self-contained in an outdoor package - no indoor section is required. Typically used in rooftop or mobile home applications.
Payback - The amount of time required (usually in years) for positive cash flows to equal the total investment costs. This is often used to describe how long it will take for energy savings resulting from using more energy-efficient equipment to equal the premium paid to purchase the more energy-efficient equipment.
Payback Analysis - An overall measurement of the efficiency and value of your heating and air conditioning system. Payback analysis is used to measure the period of time required to add up the energy saving on higher efficient equipment against the purchase price of that equipment. Or to calculate the monthly energy savings against the monthly payments to purchase an upgrade.
Plenum - A chamber which can serve as a distribution area for heating or cooling systems, generally between a false ceiling and the actual ceiling. A sealed chamber at the inlet or outlet of an air handler. The duct attaches to the plenum.
Preventative Maintenance - The scheduled inspection and replacement of short-lived components in order to avoid untimely and expensive emergency repairs.
Programmable Thermostat - A thermostat with the ability to record different temperature settings for different times for your heating and/or cooling equipment. Programmable thermostats can be electronic, or mechanical.
Propane - An LP gas used for heat.
PSI - Pounds per square inch.
PSIA - Pounds per square inch, absolute.
PSIG - Pounds per square inch gauge.
Pump Down - To use the compressor to pump all of the system's refrigerant into the receiver and/or condenser prior to opening the system for service. This is also used in commercial systems to prevent refrigerant migration in the off cycle.
PVC - Polyvinyl chloride; a type of plastic.
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R Value - Term used to measure the level of effect of insulating products that lower temperature transfer.
Radiant Heat - Coils of electricity, hot water or steam pipes embedded in floors, ceilings, or walls to heat rooms.
Reciprocating Compressor - A type of compressor used in air conditioners that compress refrigerant by using a type of "piston" action.
Recirculated Air - Indoor air that is taken in from the conditioned space and sent through the HVAC system. It must be mixed with sufficient outdoor air to prevent the build-up of contaminants.
Reclaiming - The practice of returning used refrigerant to the manufacturer for disposal or reuse.
Recycling - The practice of removing, cleaning and reusing refrigerant.
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 by international controls under the Montreal Protocol and in the United States by the Environmental Protection Agency. It 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 Lines - Two copper lines that connect the outdoor air conditioner or heat pump to the indoor evaporator coil.
Refrigerant Recovery - The process of removing refrigerant from a system and placing it in a container.
Register - Combination grille and damper assembly covering an air opening or end of an air duct.
Relay - An electrical switch controlled by the flow of current in a separate or parallel circuit.
Remote System - Often called a split system where the condenser is located away from the evaporator and/or other parts of the system. See Split System.
Return - The ductwork through which air is returned to the source for re-conditioning.
Return Air - Air drawn into a heating unit after having been circulated from the heater's output supply to a room.
Return Intake - An opening through which air is exhausted from a conditioned space.
Reversing Valve - An electrical, four-way valve in a heat pump that diverts refrigerant flow according to whether cooling or heating is needed; also called a four-way valve.
Roof Top Unit - A HVAC unit located on the roof.
Running Time - The time a unit operates. Also called the on time.
Scroll Compressor - A specially designed compressor that works in a circular motion vs. an up and down piston action.
Seer - Seasonal Energy Efficiency Ratio - means the total cooling output of a central air conditioner in British thermal units during its normal usage period for cooling divided by the total electrical energy input in watt-hours during the same period as determined using the ARI-specified test procedure. This rating is only for units with cooling capacity less than 65,000 Btu/hr. The higher the SEER, the more efficient the unit. The more efficient the unit, the lower the operating cost.
Sensor - A device that reacts to a change in conditions.
Setback Thermostat - A state-of-the-art electronic thermostat with a built-in memory that can be programmed for different temperature settings at different times of the day. A device, containing a clock mechanism, which can automatically change the inside temperature maintained by the HVAC system according to a preset schedule. The heating or cooling requirements can be reduced when a building is unoccupied or when occupants are asleep.
Short Cycling - Continual starting and stopping of a system over a shorter-than-normal time period, due to a malfunction.
Single Package - A central air conditioner which combines both condenser and air handling capabilities in a single packaged unit.
Sizing - Refers to the procedure you go through to determine how large a furnace (measured in btuh) is needed to heat a house efficiently. Too small a furnace won't deliver enough heating; too large a furnace increases energy costs and can have an adverse effect on comfort. Sizing depends on the square-footage of the home, the amount of ceiling and wall insulation, the window area, use of storm doors, storm windows, and more.
Solar Heat Gain - The amount of energy that a building absorbs due to solar energy striking its exterior and conducting to the interior or passing through windows and being absorbed by materials in the building.
Sound Rating Number (SRN) - Sound is measured in bels (a bel equals 10 decibels). The SRN of a unit is based on ARI test, performed at ARI standard rating conditions. Average sound rating range from 7.0 to 8.0 decibels. The lower the SRN rating, the quieter the unit.
Sound Ratings - Although sound does not affect the efficiency of a unit, it will certainly affect your comfort. If your unit has a low sound level, you will hardly notice it is operating. But if it has a higher sound level, it may mean your good night's sleep is disturbed every time it runs!
Split System - A central air conditioner consisting of two or more major components. The system usually consists of a compressor-containing unit and condenser, installed outside the building and a non-compressor -containing air handling unit installed within the building. This is the most common type of system installed in a home. Refers to a comfort system configuration consisting of components in two locations. Common examples include an outside unit, such as an air conditioner and an indoor unit, such as a furnace and coil.
Static Pressure - Condition that exists when an equal amount of air is supplied to and exhausted from a space. At static pressure, equilibrium has been reached.
Suction Line - The refrigerant piping from the evaporator outlet to the compressor inlet. (It is the larger, cold insulated refrigerant line.).
Superheating - Creating a rise in temperature by adding heat energy to a refrigeration vapor.
Supplementary Heat - The auxiliary or emergency heat provided at temperatures below a heat pump's balance point. It is usually electrical resistance heat.
Swamp Cooler - A type of cooling equipment that turns air into moist, cool air by saturating the air with water vapor. It does not cool air by use of a refrigeration unit. This type of equipment is commonly used in warm, dry climates.
Switchover Valve - A device in a heat pump that reverses the flow of refrigerant as the system is switched from cooling to heating. Also called a reversing valve or four-way valve.
Temperature Drop - The amount of supply air (outlet air) temperature under the return air (inlet air) temperature.
Temperature Rise - The amount of supply air (outlet air) temperature over the return air (inlet air) temperature.
Therm - Another measurement of heat. One therm equals One hundred thousand (100,000) British thermal units (1 therm = 100,000 Btu).
Thermostat - A temperature sensitive switch for controlling the operation of a heater or furnace. Typically found on a wall inside the home, that consists of a series of sensors and relays that monitor and control the functions of a heating and cooling system. A device that allows you to control the temperature inside your home by telling the heating or cooling system how much air to produce. An automatic control device designed to be responsive to temperature and typically used to maintain set temperatures by cycling the HVAC system.
Time Delay - Usually refers to a device that will not allow the condenser to restart for an average of 5 minutes.
Ton or "Ton of Cooling" - A cooling unit of measure. Each ton equals the cooling effect of 12,000 Btuh. Heat pumps and air conditioners are generally sized in tons. Typical sizes for single family residences are between two and five tons. It is important to note that actual capacity is not constant and will change based on outdoor or indoor temperatures. The published capacity rating of air conditioners and heat pumps is based on performance at the ARI standard temperature levels of 95 F outside, 80 F inside, and 50% relative humidity. The number of tons a system has is the total BTU capacity of the system. The size of the area to be cooled will determine the correct size of the system in tons. While an air conditioner may be called a three ton unit, it may not produce 36,000 Btu/h in cooling. There is a wide variety of actual capacities that are called "three tons." It is important to note that actual capacity is not constant and will change based on outdoor or indoor temperatures.
Total Home Comfort System - The ultimate solution to providing you with consistent, customized home comfort, despite the ever-changing weather.
Transformer - A set of coils that increases or decreases voltage by induction.
TXV (Thermostatic Expansion Valve) - A valve that controls the flow of refrigerant. It is operated by evaporator temperature and pressure.
UL - Underwriters' Laboratories
Unconditioned Space - A space that is neither directly nor indirectly conditioned space, which can be isolated from conditioned space by partitions and/or closeable doors.
Undercharged - A refrigeration system that is short of refrigerant.
Universal Replacement Part - A part that can be used as a replacement part for many different models, including equipment of different manufacturers.
Upflow - Provides upflow horizontal circulation of warm air, return air blower at bottom of furnace pushes air up over heating elements.
Upflow Furnace - A heater in which air is drawn in through the sides or bottom and discharged out the top.
UV - Ultra Violet Light. Tested and proven to be excellent source of air purification.
Vacuum - Any pressure below atmospheric pressure.
Vacuum Pump - A vapor pump capable of creating the degree of vacuum necessary to evaporate moisture near room temperature.
Vapor Barrier - A moisture proof covering to prevent condensation.
Variable Air Volume System (VAV) - Air handling system that conditions the air to constant temperature and varies the outside airflow to ensure thermal comfort.
Voltage - The force pushing electrical current along wires and cables.
Water-Source - Water is being used as the heat source or heat sink for a heat pump. Sources of underground water are wells and sources of surface water are lakes, large ponds, and rivers.
Weather Stripping - Specially designed strips, seals and gaskets installed around doors and windows to limit air leakage.
Weep Hole - A small hole in a wall which permits water to drain off.
Whole House Fan - A system capable of cooling a house by exhausting a large volume of warm air when the outside air is cool.
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Year-Round - Air Conditioner which uses gas or oil for heating.
Zonal Control - A method of designing and controlling the HVAC system of a residence so that living areas can be maintained at a different temperature than sleeping areas using independent setback thermostats. If specific requirements are met, zonal control may earn a credit towards compliance with whatever building energy efficiency standards are applicable.
Zone - A conditioned space in a house under the control of a thermostat. A space within a house with a distinct pressure compared to other pressure zones. Also see Buffer zone. or in the context of an HVAC system: a space or group of spaces served by an HVAC system or portion of an HVAC system controlled by a single thermostat or other control device. A space or group of spaces within a building with sufficiently similar comfort conditioning requirements so that comfort conditions can be maintained throughout by a single control device.
Zone Heat - A central heating system in a building, designed to allow different temperatures to be maintained in two or more parts of the building.
Zoning - A method of dividing a home into different comfort zones so each zone can be independently controlled depending on use and need. A process of dividing a home into different areas or zones so each has its own heating and cooling comfort levels. For example, you may prefer to keep the kitchen cooler than a bedroom. Zoning allows you to control different temperature settings for each area, room or zone.