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HVAC
Terms & Definitions
Navigating heating, cooling, and refrigeration terminology shouldn’t feel complicated. Whether you are reviewing an equipment quote, scheduling preventative maintenance, or learning how your home comfort system operates, use our quick glossary below to understand the most common industry terms and acronyms. Have questions about your system? Call our Coolville office at (740) 667-6784.
Browse Terms by Letter
Air Handler
The indoor component of a split system that circulates heated or conditioned air through your home’s ductwork. An air handler typically consists of a blower motor, an indoor evaporator coil, and integrated heating elements or controls.
BTU (British Thermal Unit)
A standard unit of heat energy representing the amount of energy required to raise the temperature of one pound of water by one degree Fahrenheit. In HVAC sizing, BTUs measure how much heat a furnace provides or how much heat an air conditioner/heat pump extracts from your property per hour.
Capacity
The heating or cooling output a system can reliably generate, typically measured in BTUs per hour or in tons of refrigeration.
Carbon Monoxide (CO)
A colorless, odorless, and dangerous gas produced when carbon-based fuels (natural gas, propane, oil) burn incompletely. Routine heating inspections ensure heat exchangers and venting pipes remain intact and leak-free.
CFM (Cubic Feet per Minute)
A measurement of airflow volume indicating how many cubic feet of air pass a stationary point each minute. A standard residential cooling system requires approximately 400 CFM of airflow per ton of capacity.
Compressor
The core mechanical component of an outdoor heat pump or air conditioning unit. The compressor circulates and pressurizes refrigerant gas, driving the thermodynamic cycle that moves heat in and out of your building.
Condenser Coil
The outdoor coil in a central air conditioning system that dissipates absorbed heat into the outdoor air, cooling the pressurized refrigerant gas back into a liquid state. (In heat pump heating mode, this process reverses).
Condensing Unit
The entire outdoor assembly of an air conditioner or heat pump, housing the compressor, condensing coil, fan motor, and safety controls.
Damper
A movable internal valve or plate within ductwork that regulates, directs, or balances airflow to specific rooms or zones.
dB (Decibel Level)
A measurement unit used to quantify sound output. Modern high-efficiency heat pumps and inverter compressors operate at significantly lower decibel ratings for quiet operation.
Department of Energy (DOE)
The federal agency responsible for setting regional minimum energy efficiency testing and rating standards across HVAC heating, cooling, and water heating equipment.
Ductwork
The network of sheet metal, flex duct, or fiberglass channels that distributes conditioned air from your air handler or furnace to supply vents throughout your home, returning air back to the system.
Electronic Air Cleaner (EAC)
An advanced whole-home indoor air quality filter that uses an electrical charge to attract, trap, and eliminate microscopic airborne particles, pollen, dust, and dander.
Energy Star®
A government-backed program that awards certification to HVAC and refrigeration systems that meet stringent efficiency benchmarks established by the EPA and DOE.
Environmental Protection Agency (EPA)
The federal agency that regulates environmental safety, including certified technician handling, recovery, and recycling of refrigerants.
MERV Rating (Minimum Efficiency Reporting Value)
A scale ranging from 1 to 16 measuring how effectively an air filter captures airborne particles between 0.3 and 10 microns. Higher MERV ratings catch smaller particles, but require proper system sizing to maintain required blower airflow.
Micron
A unit of length equal to one-millionth of a meter (about 1/25,000 of an inch), commonly used to measure the size of airborne particulates, allergens, and dust.
Gas Furnace Heat Exchanger
The metal chamber within a furnace where fuel combustion takes place. It transfers thermal heat to circulating indoor air while safely directing combustion gases outside through the exhaust flue.
Indoor Coil (Evaporator Coil)
The coil located inside the air handler or mounted above the furnace. During cooling mode, cold refrigerant circulates through this coil to absorb heat and dehumidify warm indoor air passing across its fins.
Heat Pump
A versatile HVAC system that cools your property in the summer and reverses the cycle to provide heat in the winter by transferring thermal energy rather than burning fuel.
HSPF / HSPF2 (Heating Seasonal Performance Factor)
A standardized rating measuring the heating efficiency of a heat pump over an entire winter season. HSPF2 reflects updated, more demanding Department of Energy testing criteria. Higher numbers signify greater heating efficiency.
Humidifier
An indoor air quality accessory that adds controlled moisture to heated air circulating through your ductwork, preventing dry winter air, static electricity, and wood drying.
Humidistat
A control sensor that automatically monitors and maintains indoor relative humidity levels according to your preferred setpoint.
HVAC
An industry acronym for Heating, Ventilation, and Air Conditioning.
Odors / Chemical Contaminants
Airborne volatile organic compounds (VOCs) and gaseous household odors that standard particulate filters cannot capture without specialized carbon media filtration or UV air purifiers.
Packaged Unit
An all-in-one heating and cooling system where all major mechanical components (compressor, coils, blower, and heat source) are housed within a single exterior cabinet, typically installed on rooftops or outdoor concrete pads.
Particles
Solid or liquid airborne matter measuring less than 100 microns in diameter, including pollen, pet dander, mold spores, and soot.
Programmable Thermostat
A digital temperature control device that automates comfort schedules based on daily routines, preventing systems from running under heavy load when a building is unoccupied.
Refrigerant
The specialized chemical compound (operating under various trade designations) that cycles through an HVAC or refrigeration system, alternating between liquid and gas states to absorb and release heat. In a properly sealed system, refrigerant is never consumed and only requires service if a leak develops.
Refrigerant Line Set
Two insulated copper tubes that link the outdoor condensing unit to the indoor evaporator coil, carrying high-pressure liquid refrigerant in one direction and low-pressure suction gas in the other.
Scroll Compressor
An efficient, quiet compressor design that uses two interlocking spiral scrolls to compress refrigerant gas in a continuous circular motion rather than traditional reciprocating pistons.
SEER / SEER2 (Seasonal Energy Efficiency Ratio)
The relative measure of cooling efficiency for an air conditioner or heat pump across a typical summer season. SEER2 represents the modernized testing standard reflecting realistic external static pressure in ductwork.
Split System
The most common residential HVAC configuration, dividing components between an outdoor unit (compressor and condenser coil) and an indoor unit (furnace/air handler and evaporator coil).
Thermidistat
An advanced environmental controller that monitors both ambient indoor temperature and relative humidity, adjusting cooling cycles and auxiliary dehumidification/humidification to maintain precise comfort levels.
Thermostat
A wall-mounted control interface equipped with temperature sensors and relays that signals heating and cooling equipment to cycle on and off based on target comfort setpoints.
Ton (Cooling Capacity)
A standard unit of air conditioning capacity. One ton equals 12,000 BTUs per hour of cooling output—the amount of heat required to melt 2,000 pounds of ice over a 24-hour period.
Two-Stage Operation
Heating or cooling equipment featuring a compressor or burner that operates at two distinct output levels: low capacity for mild days (running longer, quieter cycles with enhanced dehumidification) and high capacity for extreme seasonal temperatures.
Upflow Furnace / Air Handler
An indoor system configuration that draws return air into the bottom or lower side of the cabinet and discharges conditioned air out through the top of the unit into overhead supply ductwork.
Variable-Speed Blower Motor
An electronically commutated motor (ECM) that automatically modulates its operating speed in gradual increments, delivering steady airflow, quiet startup, and consistent room-to-room temperature distribution.
Ventilator (Energy Recovery / Heat Recovery)
A dedicated mechanical system that expels stale indoor air while introducing fresh outdoor air, recovering thermal energy in the process to maintain indoor air quality without placing excessive demand on heating or cooling equipment.
Zoning
A method of dividing a property into independently controlled temperature zones using motorized duct dampers and individual thermostats, allowing customized comfort settings for distinct floors or living areas.