Resource
HVAC Glossary
The heating and cooling trade is full of jargon. Here is what the common terms actually mean, in plain language, so a conversation with a technician makes sense.
- SEER2
- A cooling-efficiency rating. Higher is more efficient. Oklahoma is in the DOE hot-humid Southeast region, where new split-system air conditioners must meet at least 14.3 SEER2.
- AFUE
- Annual Fuel Utilization Efficiency — how much of a furnace's fuel becomes usable heat. A finalized federal standard raises the minimum to 95% AFUE, effective in late 2028.
- MERV
- A filter rating from 1 to 16 measuring how well it captures particles from 0.3 to 10 microns. The EPA suggests at least MERV 13 for particle filtration — but a denser filter raises resistance, so it has to suit your system.
- Tonnage
- The cooling capacity of a system, in tons. It is about capacity, not weight, and bigger is not better — an oversized system short-cycles and handles humidity poorly.
- Short cycling
- When a system turns on and off in quick bursts instead of running full cycles. It wears equipment and hurts comfort, and it often points to sizing, airflow, or a control problem.
- Heat pump
- A system that both heats and cools by moving heat rather than burning fuel. Oklahoma City's mild winters make it a strong option here.
- Dual fuel
- A heat pump paired with a gas furnace. The heat pump handles mild weather efficiently and the furnace takes over on the coldest days.
- Condenser
- The outdoor unit of a central air system. It rejects heat from your home to the outside air.
- Evaporator coil
- The indoor coil where refrigerant absorbs heat from your home's air. Ice here usually means an airflow or refrigerant problem.
- Static pressure
- The resistance the blower fights to push air through the ducts and filter. Too high, and airflow and comfort suffer — which is why a "better" filter can backfire.
- Load calculation (Manual J)
- The ANSI-standard method for sizing a system to a home based on its size, insulation, windows, and orientation. It is how sizing should be done, rather than copying the old unit.
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