Hvac contractors glossary

Short, plain-English definitions of the terms you'll meet when choosing a hvac contractor provider in Phoenix, Arizona.

What is a BTU (British thermal unit)?: A BTU is the amount of energy needed to raise the temperature of one pound of water by one degree Fahrenheit, used to rate the heating or cooling capacity of HVAC equipment.
What is a capacitor in HVAC?: A cylindrical electrical component in air conditioning systems that stores charge to help start the compressor and fan motors, and commonly fails in Phoenix's heat.
What is a compressor in an AC unit?: The compressor is the pump inside an air conditioner that pressurizes and circulates refrigerant to absorb and release heat, often considered the central component of the AC system.
What is a condenser coil?: The condenser coil is the heat-exchange component in your outdoor AC unit that releases warm refrigerant and expels absorbed heat from indoor air to the outside.
What is a contactor in HVAC?: An electromechanical switch that controls electrical power to the compressor and condenser fan motor in air conditioning systems; repeated on-off cycling from summer heat causes contact pitting and eventual failure.
What is a dual fuel system?: A dual fuel system combines a heat pump for primary heating and cooling with a gas furnace that activates automatically during extreme cold or system demand.
What is a heat exchanger?: A heat exchanger is a furnace component that transfers warmth from hot combustion gases into circulating air, keeping the gases separated so they exit safely through the flue.
What is a heat pump?: A heat pump is a heating and cooling system that transfers heat from one location to another using refrigerant cycles, rather than burning fuel or using electric resistance to create heat.
What is a HEPA filter?: A HEPA filter is a high-efficiency air filter that captures 99.97% of particles 0.3 microns or larger, meeting a strict federal standard for residential and commercial air purification.
What is a Manual J load calculation?: Manual J is the HVAC industry standard method that calculates the heating and cooling load a home requires based on size, insulation, window area, local climate, and occupancy to properly size air conditioning and heating equipment.
What is a MERV rating?: MERV (Minimum Efficiency Reporting Value) is a standardized scale from 1 to 20 that rates how effectively an air filter traps dust, pollen, and other particles while measuring the resistance it creates to airflow.
What is a mini-split system?: A mini-split system is a ductless air conditioning unit with an outdoor compressor connected to one or more indoor wall-mounted air handlers, used to cool individual rooms or zones without requiring ductwork.
What is a package unit?: A package unit is an all-in-one air conditioning or heat pump system housed in a single outdoor cabinet, with the compressor, coils, and fan combined in one metal box rather than split between indoor and outdoor components.
What is a split system?: A split system is an HVAC configuration that separates the cooling condenser outdoors from the heating or air-handling equipment indoors, connected by refrigerant lines and electrical conduits.
What is a thermostatic expansion valve (TXV)?: A thermostatic expansion valve (TXV) is an automatic metering device that regulates refrigerant flow into the evaporator coil by responding to temperature and pressure changes, replacing fixed restriction points in air conditioning systems.
What is a ton in HVAC sizing?: A ton is a measurement of air conditioning cooling capacity equal to 12,000 BTUs per hour, used as the standard sizing unit for residential AC systems.
What is a UV air purifier?: A UV air purifier is a germicidal ultraviolet light system installed in HVAC ductwork or around AC coils to eliminate mold spores, bacteria, and other microorganisms that thrive in moist environments.
What is an AFUE rating?: AFUE (Annual Fuel Utilization Efficiency) is a percentage that measures how much of the fuel a furnace consumes is converted into usable heat, with the remainder lost through exhaust and other inefficiencies.
What is an air handler?: An air handler is the indoor blower unit that circulates heated or cooled air through a home's ductwork, commonly used in heat pump systems and split air conditioning setups.
What is an evaporator coil?: The indoor coil in an AC unit where cold refrigerant absorbs heat from air, cooling your home; located near the furnace or air handler.
What is R-410A refrigerant?: R-410A is a hydrofluorocarbon refrigerant blend used in the majority of air conditioning systems and heat pumps installed over the past two decades, now facing phase-down due to environmental regulations requiring transition to lower-global-warming-potential alternatives.
What is R-454B refrigerant?: R-454B is an A2L-class refrigerant with lower global warming potential that manufacturers are using to replace R-410A in new air conditioning equipment starting in 2025.
What is SEER2?: SEER2 is the revised federal efficiency rating standard for air conditioning and heat pump systems, introduced in 2023, that uses updated testing conditions to better reflect real-world performance than the older SEER metric.
What is static pressure in ductwork?: Static pressure is the resistance to airflow created by friction and obstruction within a duct system, measured in inches of water column (in. w.c.) at the return and supply sides.