HVAC Glossary

SEER2

SEER2 (Seasonal Energy Efficiency Ratio 2) measures an air conditioner or heat pump's cooling efficiency over a season under updated 2023 federal test conditions. Higher SEER2 means lower cooling energy use.Learn more

AFUE

AFUE (Annual Fuel Utilization Efficiency) is the percentage of fuel a furnace converts to usable heat over a year. A 95% AFUE furnace turns 95% of its fuel into heat; the rest is lost to exhaust.Learn more

HSPF2

HSPF2 (Heating Seasonal Performance Factor 2) rates a heat pump's heating efficiency over a season under the 2023 test standard. A higher HSPF2 indicates more heat delivered per unit of electricity.Learn more

Ton (of cooling)

A 'ton' of cooling equals 12,000 BTU/hour of heat removal. Residential systems are commonly 1.5 to 5 tons; correct sizing comes from a load calculation, not square footage alone.Learn more

Manual J Load Calculation

Manual J is the industry-standard method for sizing heating and cooling equipment based on a home's insulation, windows, orientation, and air leakage — not a rule of thumb. Oversized systems short-cycle and waste energy.Learn more

MERV

MERV (Minimum Efficiency Reporting Value) rates how well an air filter captures particles, from MERV 1 to 16. Higher MERV traps finer particles but can restrict airflow if the system isn't designed for it.Learn more

Heat Pump

A heat pump is an electric system that moves heat rather than generating it — cooling a home in summer and reversing to heat it in winter. Modern cold-climate models perform well in Indiana temperatures.Learn more

Ductless Mini-Split

A ductless mini-split is a heat pump that conditions individual rooms or zones through wall-mounted indoor units, with no ductwork — useful for additions, garages, and rooms with uneven temperatures.Learn more

A2L Refrigerant (R-454B)

A2L refrigerants such as R-454B are the lower-global-warming replacements phasing in for R-410A under U.S. EPA rules beginning in 2025. New systems increasingly ship with A2L refrigerant.Learn more

Variable-Speed

A variable-speed blower or compressor adjusts output continuously instead of running only at full blast. This improves comfort, humidity control, and efficiency compared with single-stage equipment.Learn more

Static Pressure

Static pressure is the resistance to airflow inside a duct system. Excessive static pressure — from undersized ducts or dirty filters — strains the blower and reduces both comfort and equipment life.Learn more

Short Cycling

Short cycling is when a system turns on and off too frequently. Causes include an oversized unit, a refrigerant problem, or a thermostat issue; it raises energy bills and accelerates wear.Learn more

BTU

A BTU (British Thermal Unit) measures heat energy. HVAC equipment capacity is often listed in BTUs per hour; one ton of cooling equals 12,000 BTU/h.Learn more

Dual-Fuel

A dual-fuel system pairs an electric heat pump with a gas furnace. The heat pump handles milder weather; the furnace takes over below a balance-point temperature — common and practical in Central Indiana.Learn more

Balance Point

The outdoor temperature where a heat pump's heating capacity equals the home's heat loss. Below that point, backup heat (electric strips or a gas furnace) is needed to keep up.Learn more

Defrost Cycle

In heating mode, frost can form on a heat pump's outdoor coil. A defrost cycle temporarily reverses operation to melt that frost — brief cool air at registers can be normal during the cycle.Learn more

ERV / HRV

Energy Recovery Ventilators (ERV) and Heat Recovery Ventilators (HRV) bring in fresh outdoor air while transferring heat (and, for ERVs, some moisture) to reduce the energy penalty of ventilation.Learn more

Load Calculation

A load calculation (commonly Manual J for homes) estimates how much heating and cooling a house needs based on construction, windows, insulation, and leakage — the basis for correct equipment size.Learn more

Refrigerant Charge

The measured amount of refrigerant in an AC or heat pump. An incorrect charge reduces capacity and efficiency and can damage the compressor — it is diagnosed with gauges and temperature/pressure readings, not guesswork.Learn more

Zoning

Zoning divides a home into separately controlled temperature areas using dampers, multiple thermostats, or ductless heads — useful when one thermostat cannot keep every room comfortable.Learn more

Combustion Air

Air that gas furnaces and water heaters need to burn fuel safely. Blocked or inadequate combustion air can cause incomplete combustion and elevated carbon monoxide risk.Learn more

Tankless Water Heater

A tankless (on-demand) water heater heats water as it flows through the unit instead of storing it in a tank. Sizing depends on simultaneous fixture demand and incoming groundwater temperature.Learn more

Capacitor

An electrical component that helps motors in an outdoor AC or heat pump start and run. A weak capacitor is a common cause of humming outdoor units that won’t start on hot Indianapolis afternoons.Learn more

Hard-Start Kit

An add-on that helps a struggling compressor start under load. It can be appropriate in specific diagnoses but is not a permanent fix for a worn-out compressor.Learn more

Relative Humidity (RH)

The amount of moisture in the air relative to what the air can hold at that temperature. Many homes feel most comfortable around the mid-40% RH range in summer — exact targets vary by household and building.Learn more

Whole-Home Dehumidifier

A ducted appliance that removes moisture from whole-house air, often running when the air conditioner isn’t. Useful in sticky Central Indiana summers when cooling alone doesn’t dry the air enough.Learn more

C-Wire

A common (C) thermostat wire that provides continuous power to smart thermostats. Many older Indianapolis homes need a C-wire adapter or new cable before a Wi-Fi thermostat will stay powered.Learn more

Anode Rod

A sacrificial metal rod inside many tank water heaters that corrodes instead of the tank steel. A depleted anode accelerates tank failure — one reason age alone doesn’t tell the whole story.Learn more

Evaporator Coil

The indoor coil where refrigerant absorbs heat from home air. If airflow is restricted or charge is wrong, the coil can freeze — a common muggy-season no-cool symptom.Learn more

Architectural Review (HOA)

Many planned communities require HOA approval for outdoor mechanical equipment placement and screening. Clearances for airflow still override decorative boxes that choke the unit.Learn more

Auxiliary Heat

Backup heat on a heat pump system — often electric resistance strips — that engages in very cold weather, during defrost, or when the heat pump can’t keep up. Misconfigured thermostats can overuse it.Learn more

Still have a question about a term on your estimate? Ask us directly — no obligation.