HVAC Frederick, Maryland

To understand when to schedule maintenance and how a home is heated and cooled, you must know the parts of an HVAC system.

HVAC System Glossary

Air Conditioner

A unit that removes heat from inside of a home to improve the comfort of its occupants.

Air Filter

A device composed of fibers that remove dust, pollen, mold, and other allergens and pathogens from the air to improve indoor air quality.


An appliance that heats (and occasionally boils) water.


An appliance at the center of an air conditioning or heat pump system, it pumps refrigerant (a fluid that causes cooling) and maintains adequate pressure that causes refrigerant to flow in sufficient quantities to meet the cooling requirements of the system.

Condensor Coil

Located in the outdoor unit, the coil dissipates heat from the refrigerant, changing the refrigerant from vapor to liquid.

Condensing Unit

Inside a cube-shaped HVAC unit, a condensing unit exchanges heat with the air that passes over it and gives off heat.


A movable plate found in ductwork that opens and closes to control airflow and is used effectively in zoning between floors to regulate airflow to certain rooms.


A system of ducts that move air throughout a home. Air comes into the heating and cooling system through specific sections of the ductwork and is distributed to rooms through other sections.

Evaporator Coil

A coil that’s located inside of a furnace but isn’t part of it. Refrigerant runs through the evaporator coil, which absorbs heat from air passing over it. The now-cold air is blown through the air ducts throughout a home.

Exhaust Component

A part of an appliance in chimneys, stoves, and vents that clears gases away from controlled combustion.


An appliance that takes up a majority of space in an HVAC system and usually resides in the lowest level of a home. It moves air from the heat exchanger into the air ducts and is only used for high-temperature heating.

Heat Exchanger

An exchanger that’s located inside of a furnace but isn’t part of it. The heat exchanger adds heat to the incoming air from the combustion chamber.

Heat Pump

An appliance that takes heat from the inside to the outside during warm months and performs the opposite task during cold months.

Pilot Light

A small continuous blue flame that ignites a larger burner on a gas stove, furnace, or water heater.

Refrigerant Tubes

Metal tubes that connect an evaporator coil to a condensing coil, which ultimately connects a home’s indoor and outdoor HVAC units. These tubes contain cooling refrigerant under a wide range of temperatures.


A small appliance that’s placed on the wall in the main level of a home, and, depending on what temperature it’s set at, the thermostat turns on the air conditioning or heating system.


The entrance point in rooms as air travels through the ductwork. Most homes offer rectangular covers on the ceilings and floors that direct and take air.

If you need help identifying home heating or cooling problems or want to learn more about the parts of a residential HVAC system, contact a professional.

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