HVAC glossary
The terms your technician uses, translated. Each one links to the guide or service page where it matters.
AFUE (Annual Fuel Utilization Efficiency)
The percentage of fuel a furnace or boiler converts into usable heat over a year. A 95% AFUE furnace turns 95 cents of every fuel dollar into heat.
Heating servicesAir Handler
The indoor unit that moves conditioned air through your ducts. It houses the blower motor and, in many systems, the evaporator coil.
Air conditioning servicesBTU (British Thermal Unit)
The energy needed to raise one pound of water by 1°F. HVAC capacity is rated in BTUs per hour — bigger homes and hotter climates need more.
Capacitor
A small electrical component that gives compressors and fan motors the jolt they need to start. Heat is its enemy — capacitor failure is one of the most common AC breakdowns in foothill summers.
Why capacitors fail in foothill heatCold-Climate Heat Pump
A heat pump engineered to keep full heating capacity well below freezing, using variable-speed compressors and enhanced refrigerant circuits — relevant from Grass Valley up to Truckee.
Cold-climate heat pumps explainedCompressor
The heart of an AC or heat pump: it pressurizes refrigerant so the system can move heat. The most expensive single component to replace.
Air conditioning servicesCondensate Drain Line
The pipe that carries the water your AC pulls out of the air. Clogs cause overflows, water damage, and safety-switch shutdowns.
Fixing condensate clogsCondenser
The outdoor unit of a split AC or heat pump. It rejects heat pulled from your home — and in the foothills it collects pine pollen and dust that choke performance.
How pollen and dust clog systemsDuctless Mini-Split
A heating-and-cooling system with an outdoor unit and one or more wall-mounted indoor heads, no ductwork required. Ideal for additions, older homes, and zoned comfort.
Ductless servicesEvaporator Coil
The indoor coil where refrigerant absorbs heat from your air. Dirty or leaking coils cause weak cooling and frozen lines.
Signs of a failing evaporator coilHeat Exchanger
The furnace component that transfers combustion heat to your air while keeping exhaust gases separate. A cracked heat exchanger is a safety issue that requires immediate attention.
Heating servicesHeat Pump
A system that moves heat instead of generating it — cooling in summer, heating in winter — often at 2–4x the efficiency of electric resistance heat.
Heat pump servicesHSPF2 (Heating Seasonal Performance Factor)
The updated efficiency rating for heat pump heating, measured under more realistic test conditions than the old HSPF. Higher is better.
Heat pump servicesHVAC
Heating, Ventilation, and Air Conditioning — the whole system that controls temperature, humidity, and air quality in your home.
All servicesIAQ (Indoor Air Quality)
How clean and healthy the air inside your home is — driven by filtration, ventilation, humidity, and, in Nevada County, wildfire smoke season.
Indoor air quality servicesLoad Calculation (Manual J)
The industry-standard math for sizing HVAC equipment to a specific house — square footage, insulation, windows, orientation, and climate. Skipping it is how systems end up over- or under-sized.
All servicesMERV Rating
Minimum Efficiency Reporting Value — how well a filter captures particles, from MERV 1 (basic) to MERV 16 (hospital-grade). Wildfire smoke calls for MERV 13+.
Filter changes in wildfire seasonRefrigerant
The working fluid that carries heat through an AC or heat pump. Low refrigerant means a leak — it is not consumed in normal operation.
Checking for low refrigerantSEER2 (Seasonal Energy Efficiency Ratio)
The current federal rating for cooling efficiency, measured with more realistic duct static pressure than the old SEER. Higher SEER2 = lower summer bills.
SEER2 and your energy billsShort Cycling
When a system starts and stops in rapid bursts instead of running full cycles — a symptom of oversizing, thermostat trouble, or failing components that accelerates wear.
Why AC short-cyclesStatic Pressure
The resistance your ductwork puts up against airflow. High static pressure strains blowers, starves rooms of air, and shortens equipment life.
Ductwork leakage issuesThermostat C-Wire
The 'common' wire that provides continuous power to smart thermostats. Many older foothill homes need one added during a thermostat upgrade.
Tonnage
AC capacity shorthand: one ton = 12,000 BTU/hr of cooling. A typical home system runs 2–5 tons; correct tonnage comes from a load calculation, not square footage rules of thumb.
Variable-Speed Compressor
A compressor that modulates output instead of running all-or-nothing — quieter, more efficient, better humidity control, and the core of cold-climate heat pumps.
Heat pump servicesZoning System
Motorized duct dampers plus multiple thermostats that let one system heat or cool areas of the house independently.
Mini-split zoning vs damper zoningStill translating a quote or diagnosis? Browse the Learning Center or ask us directly — no jargon, promise.
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