HVAC Glossary

Understanding a few key terms makes it far easier to compare quotes and avoid being sold something you don't need. Bookmark this page and jump back any time a technician uses a word you'd like defined.

AFUE (Annual Fuel Utilization Efficiency)

A percentage that rates how efficiently a furnace turns fuel into heat over a year. A 95% AFUE furnace delivers 95 cents of heat per fuel dollar; the rest is lost to exhaust.

AHRI Certificate

Documentation from the Air-Conditioning, Heating, and Refrigeration Institute confirming that a matched system (outdoor + indoor unit) was tested together at a rated efficiency. Rebate programs and manufacturer warranties typically require it.

Air Handler

The indoor component that moves conditioned air through your ducts. In a heat-pump or AC system it houses the blower and evaporator coil.

BTU (British Thermal Unit)

A unit of heat energy. Cooling and heating capacity is measured in BTUs per hour. The higher the number, the more a system can heat or cool.

Capacitor

An electrical component that stores and releases the jolt needed to start and run motors (compressor, fan). A weak capacitor is one of the most common, and least expensive, causes of a no-cool call.

Compressor

The heart of an AC or heat pump, located in the outdoor unit. It pressurizes refrigerant so it can release heat outside. Compressor failure is usually the most expensive repair, which is why correct charge and airflow matter.

Condenser

The outdoor coil and unit that releases the heat pulled from your home. Dirty condenser coils are a leading cause of high bills and overheating in our dusty, high-pollen climate.

Condensate Drain

The line that carries the water your system pulls out of the air to a drain. When it clogs with algae, water backs up. A frequent cause of ceiling stains and shutoffs in humid South Texas.

Ductless Mini-Split

A system with an outdoor compressor connected to one or more indoor units, with no ductwork Ideal for additions, garages, and older homes. Learn more on our ductless services page.

EPA 608 Certification

A federal certification required for technicians who handle refrigerant. It exists to prevent the release of ozone-depleting and high-GWP refrigerants.

Evaporator Coil

The indoor coil where refrigerant absorbs heat from your home's air. A frozen or dirty evaporator coil reduces cooling and can lead to compressor damage.

Heat Pump

A system that both cools and heats by moving heat rather than burning fuel. Efficient and a strong fit for San Antonio's mild winters. See our heat pump services.

HSPF2 (Heating Seasonal Performance Factor 2)

The current efficiency rating for a heat pump's heating mode. Higher HSPF2 means more heat delivered per unit of electricity. (The “2” reflects updated 2023 federal test procedures.)

Manual J Load Calculation

The industry-standard calculation that determines the correct system size for a home based on square footage, insulation, windows, and orientation. Skipping it leads to oversized units that short-cycle and undersized units that never keep up.

MERV Rating

A 1–16 scale of how well an air filter captures particles. Higher MERV traps more allergens but can restrict airflow if the system isn't designed for it. Balance matters.

NATE Certification

North American Technician Excellence. An independent certification that validates a technician's knowledge across installation and service.

Refrigerant (R-410A / R-454B)

The fluid that carries heat through the system. Newer equipment is transitioning to lower-global-warming refrigerants such as R-454B; older systems use R-410A. A system low on refrigerant has a leak that should be found and repaired, not just topped off.

SEER2 (Seasonal Energy Efficiency Ratio 2)

The current cooling-efficiency rating for AC and heat-pump systems. Higher SEER2 means lower cooling bills. The Southwest region requires a minimum of 15 SEER2 on new single-stage systems.

Short Cycling

When a system turns on and off in rapid bursts without completing a full cycle. It wastes energy, fails to remove humidity, and wears out components, often caused by an oversized unit, a refrigerant issue, or a dirty filter.

Static Pressure

The resistance air meets as it moves through your ducts. High static pressure (from undersized or restricted ducts) strains the blower and shortens equipment life, which is why we measure it during diagnostics.

Smart Thermostat

A programmable, Wi-Fi-connected thermostat that learns your schedule and can cut cooling costs. See our smart thermostat services.

TDLR / TACL License

In Texas, HVAC contractors are licensed by the Texas Department of Licensing and Regulation (TDLR) and carry a TACL number. AC American Air holds Texas HVAC license TACLA36546E.

Ton (of Cooling)

A measure of cooling capacity equal to 12,000 BTU/hour. A typical San Antonio home runs 2–5 tons depending on size and load. Sized by a Manual J calculation, not a rule of thumb.

Zoning

Dividing a home into independently controlled comfort areas using dampers and multiple thermostats, so you stop paying to cool rooms nobody is in.

Don't see a term? Ask us We're happy to explain anything on your estimate before you decide.