HVAC glossary · plain English

HVAC Terms, Decoded.

Name: Air Solutions Heating & Cooling
Address: 1410 US-98 Suite N, Daphne, AL, 36526, US
Telephone: +1-251-300-9817
Price range: $$

30 HVAC terms explained the way we'd explain them at your kitchen table — what the term means, why it matters in coastal Alabama, and (where helpful) the next page to read for deeper context.

AFUE: Annual Fuel Utilization Efficiency. The percentage of fuel a furnace converts into usable heat over a year. A 95% AFUE furnace turns 95% of its fuel into heat; the remaining 5% leaves through the flue. Modern condensing furnaces hit 95–98% AFUE; older atmospheric units run 70–80%.
Air Handler: The indoor unit that contains the blower motor and (usually) the evaporator coil. It moves conditioned air through your ductwork. In a heat pump system the air handler also houses the auxiliary heat strips for cold-snap backup.

BTU: British Thermal Unit. The unit of heating or cooling capacity. One BTU is the energy needed to raise one pound of water by 1°F. A 36,000 BTU/hr (3-ton) AC removes that much heat from your home each hour. Sizing matters — oversized AC units short-cycle and dehumidify poorly.

Capacitor: An electrical component that stores and releases the surge of energy needed to start the compressor and fan motor. Capacitors are the single most common AC failure in coastal Alabama — humidity and heat both shorten their life. A weak capacitor causes hard starts, hums, or no-start conditions.
Compressor: The heart of the AC system — sits inside the outdoor unit. It pressurizes refrigerant to enable heat transfer. Compressor failure is the most expensive AC repair (often $1,500–$3,500); when it goes on a 10+ year-old system, replacement usually wins on the math.
Condensate Drain: The PVC line that carries water away from the AC's evaporator coil. Clogged condensate drains are the #1 cause of summer water damage from HVAC systems in Baldwin County — Gulf Coast humidity dumps gallons of water into the drain pan daily during peak season.
Condenser: The outdoor unit. Contains the compressor, condenser coil, and condenser fan. Releases the heat absorbed from inside your home into the outside air. Coastal condensers need salt-air corrosion protection — Air Solutions installs coastal-grade equipment within ~5 miles of the Gulf.
Cool Club: Air Solutions' annual maintenance membership. Covers two professional tune-ups a year (spring AC + fall heat pump), priority scheduling on repairs, 15% off all repairs, and 5% off new system installs.

Defrost Cycle: When a heat pump runs in heating mode below ~40°F, the outdoor coil ices over. The system periodically reverses to defrost it. You'll see steam off the outdoor unit; this is normal. Faulty defrost boards are a common heating-mode complaint in Baldwin County's mild winters.
Ductless Mini-Split: A heat pump system that uses individual indoor units mounted on the wall or ceiling instead of central ductwork. Ideal for additions, garages, sunrooms, and historic homes without ducts. Each indoor 'head' is its own zone with independent temperature + humidity control.

Evaporator Coil: The indoor coil where refrigerant absorbs heat from your home's air. Sits above or below the air handler. Frozen evaporator coils (low refrigerant or restricted airflow) are a common AC repair call. Coil cleaning is part of every Air Solutions tune-up.

Heat Pump: An HVAC system that both heats and cools by moving heat (rather than burning fuel). In summer it works like an AC; in winter it reverses to pull heat from outside air into your home. The most common system type in coastal Alabama because our winters rarely get cold enough to need a furnace.
HSPF / HSPF2: Heating Seasonal Performance Factor. The heating-mode efficiency rating of a heat pump. HSPF2 (post-2023) is the updated test method — the numbers are slightly lower than the old HSPF for the same equipment, not because it's worse, just because the test changed. Higher = more efficient.
HVAC: Heating, Ventilation, and Air Conditioning. The umbrella term for the equipment that controls the temperature, humidity, and air quality in your home. In residential coastal Alabama, 'HVAC' usually means a heat pump or AC + furnace combination.

Indoor Air Quality (IAQ): The collective health of the air inside your home — humidity, particulates (dust, pollen, mold spores), VOCs, and CO. Gulf Coast homes face chronic humidity that tips into mold territory if dehumidification isn't sized right. IAQ solutions: whole-house dehumidifiers, UV coil sterilization, MERV upgrades.

Manual J: The HVAC industry's standard load-calculation method for sizing equipment. Accounts for square footage, ceiling height, insulation R-values, window orientation, infiltration, and local climate data. Air Solutions runs a Manual J on every install — sized to your actual house, not a ductwork-area shortcut.
MERV Rating: Minimum Efficiency Reporting Value. The filtration rating scale (1–16). MERV 8 catches dust + pollen, MERV 11 adds pet dander + mold spores, MERV 13 adds bacteria + smoke particles. Higher MERV = better filtration but more airflow restriction — the system has to be sized for it.

R-410A: The refrigerant used in most US residential AC + heat pump systems installed 2010–2025. Being phased out in favor of R-32 and R-454B (lower global-warming-potential refrigerants). R-410A repairs are still standard but new installs in 2026+ increasingly use R-32 or R-454B.
R-32 / R-454B: The next-generation low-GWP refrigerants replacing R-410A in new installs. Both are mildly flammable (A2L classification) — modern equipment is engineered around this safely. Lower environmental impact, comparable performance.
Refrigerant: The fluid that absorbs heat at the indoor coil and releases it at the outdoor coil. AC and heat pump systems are sealed — they don't 'use up' refrigerant. If you're low, there's a leak that needs to be found and fixed before recharging. Top-offs without leak repair are bad practice.
Reversing Valve: The component that lets a heat pump switch between cooling mode and heating mode. When it fails, the heat pump gets stuck in one mode (usually cooling — bad in January). Reversing-valve replacement is a meaningful repair, around $700–$1,200.

SEER / SEER2: Seasonal Energy Efficiency Ratio. The cooling-mode efficiency rating of an AC or heat pump. As of 2023, SEER2 replaced SEER (updated test method, slightly lower numbers for the same equipment). New residential systems run SEER2 14–22; higher = more efficient + lower utility bills.
Short Cycling: When an AC turns on and off rapidly without completing a full cooling cycle. Common causes: oversized equipment, low refrigerant, dirty coil, faulty thermostat. Short cycling shortens equipment life and prevents proper dehumidification — a real problem in humid Baldwin County.
Static Pressure: The pressure pushing against the blower motor as it forces air through your ductwork + filter. High static pressure (undersized ducts, dirty filter, kinked flex) makes the system work harder, raises bills, and shortens motor life. Air Solutions checks static pressure on every install + tune-up.
Subcooling: A diagnostic measurement (in °F) that tells a tech how much refrigerant is in the system. Combined with superheat, it's how a competent HVAC tech actually verifies a system is properly charged — not just by guessing or topping off.
Superheat: The other diagnostic measurement (in °F) used alongside subcooling to verify refrigerant charge. Wrong superheat = compressor damage over time. Any tech recharging a system without measuring both is guessing.

Thermostatic Expansion Valve (TXV): The valve that meters refrigerant flow into the evaporator coil based on cooling demand. Modern systems use TXVs for efficiency. Failed TXVs cause poor cooling, frozen coils, or short cycling. Repair is moderate cost (~$400–$700).
Ton (HVAC): The traditional unit of HVAC capacity. 1 ton = 12,000 BTU/hr. Most Baldwin County homes need 2–5 tons depending on size and insulation. 'Ton' has nothing to do with weight — it dates from when AC capacity was compared to the cooling effect of a ton of melting ice.

Variable Speed: Equipment (compressor or blower) that runs at multiple speeds instead of just on/off. Variable-speed systems run quieter, dehumidify better, and use less power. The premium tier in residential equipment — strongly worth it in humid Gulf Coast climates.

Zoning: An HVAC setup with multiple thermostats controlling separate areas of the home via dampers in the ductwork. Lets you cool the bedrooms at night without freezing the unused first floor. Mini-splits have native zoning; central systems can be zoned with retrofit dampers.