Plain English
HVAC terms, demystified.
A pocket glossary so you’re never caught off guard by a technician’s vocabulary. Bookmark it.
AFUE
Annual Fuel Utilization Efficiency. The percentage of fuel a furnace converts to heat. 80% AFUE means 80¢ of every $1 in gas becomes heat in your home.
Capacitor
An electrical component that gives the compressor and fan motors the jolt they need to start. The #1 reason an AC won't start on a hot day.
Compressor
The heart of an AC system. Pressurizes refrigerant so heat can be moved from inside your home to outside. The most expensive single component.
Condenser
The outdoor unit. Where heat collected from your home is released into the outdoor air.
Evaporator Coil
The indoor coil (above the furnace, usually). Where refrigerant absorbs heat from your air to cool it.
Heat Pump
A system that can both cool and heat by reversing the refrigerant cycle. Often the most efficient option in DFW's mild winters.
Load Calculation (Manual J)
The proper engineering process used to determine the right AC or furnace size for your home. Based on square footage, insulation, windows, orientation, and more.
MERV
Minimum Efficiency Reporting Value. How well a filter catches particles. MERV 8–11 is typical residential; MERV 13+ catches allergens and viruses but needs proper duct sizing.
Refrigerant
The chemical fluid that absorbs and releases heat. Older systems use R-22 (no longer manufactured); newer systems use R-410A or R-454B.
SEER2
Energy Efficiency Ratio (updated 2023). How efficient an AC is over a cooling season. Higher = more efficient. 14.3 SEER2 is the current Texas minimum.
Short Cycling
When an AC turns on and off too frequently. Usually means the system is oversized, low on refrigerant, or has airflow issues.
Static Pressure
The resistance air faces moving through your ducts. High static pressure means weak airflow, hot rooms, and shortened equipment life.
Ton
A measure of cooling capacity. 1 ton = 12,000 BTU/hr. Most DFW homes use 2–5 ton systems.