FL HVAC key terms

Residential load calculation method from ACCA that estimates heating and cooling loads using envelope details, windows, occupancy, internal gains, infiltration, and local design conditions.

ACCA procedure for selecting equipment that matches the calculated room-by-room loads while checking sensible and latent capacity, airflow, and manufacturer performance data.

ACCA method for designing duct systems by converting available static pressure into friction rate and sizing each run for the required room airflow.

Outdoor and indoor temperature and humidity values chosen for load calculations. In Florida, cooling design often uses a 1% outdoor dry-bulb and matching wet-bulb.

Heat that raises or lowers dry-bulb temperature without changing moisture content. In a building it comes from conduction, solar gain, people, lights, and equipment.

Heat absorbed or released when moisture changes phase, such as water evaporating or condensing. In cooling loads it comes from infiltration, occupants, showers, and cooking.

Ratio of sensible heat load to total heat load. A lower ratio means more moisture removal is needed, so equipment latent capacity must be checked.

Cooling capacity equal to 12,000 British thermal units per hour. It is a rate of heat removal, not a weight, and is used to compare system sizes.

Pressure resistance measured across a blower from return to supply. High external static pressure signals restrictive ducts, filters, or coils and reduces airflow.

Pressure loss per unit length of duct, usually inches of water per 100 feet. It is used with available static pressure to size duct runs.

A method of expressing fitting and component pressure losses as additional straight duct length so duct sizing can account for them.

Air pulled from conditioned rooms back to the air handler. Restricted return paths raise static pressure, reduce airflow, and can cause noise or coil freezing.

Fresh outdoor air brought into a building for ventilation or makeup. It adds sensible and latent load and must be accounted for in sizing.

Standard that sets minimum residential ventilation and exhaust rates to maintain acceptable indoor air quality. It addresses whole-house ventilation, local exhaust, and source control.

Seasonal energy efficiency ratio for cooling equipment under revised test conditions. Higher ratings indicate greater efficiency, but actual performance depends on installation and ductwork.

Heating seasonal performance factor for heat pumps under updated test conditions. A higher number means more efficient heating across the season.

Manufacturer-issued document showing matched system model numbers, capacities, and efficiency ratings. Contractors use it to verify equipment combinations for permits and customer records.

Refrigeration system that can reverse refrigerant flow to heat or cool a space. In heating mode it absorbs outdoor heat and rejects it indoors.

A valve that changes refrigerant flow direction in a heat pump, swapping the indoor and outdoor coil roles between heating and cooling.

Heat pump operating mode that melts frost from the outdoor coil. It may temporarily reverse the cycle or use electric heat and can cause cool air at registers.

The number of degrees a refrigerant vapor is above its saturation temperature at the same pressure. It shows how much liquid is boiling off in the evaporator.

The number of degrees a liquid refrigerant is below its saturation temperature at the same pressure. It indicates how much the condenser has cooled the liquid.

Thermostatic expansion valve that regulates refrigerant flow into the evaporator by opening or closing to maintain a target superheat.

Temperature at which a refrigerant boils or condenses at a given pressure. Technicians find it from a pressure-temperature chart to calculate superheat and subcooling.

Department of Transportation-approved pressure vessel for storing recovered refrigerant. It must be labeled, not overfilled, and used with properly rated hoses and scales.

Federal Clean Air Act rule requiring technician certification and setting refrigerant recovery, leak repair, and handling requirements for stationary equipment.

Refrigerant safety classification for mildly flammable fluids. Handling requires attention to ventilation, ignition sources, charge limits, and leak detection.

Evacuation test where the system is pulled to a deep vacuum and isolated; a rising pressure indicates leaks, moisture, or trapped refrigerant.

Dry nitrogen flowed through tubing during brazing to displace oxygen and prevent internal oxidation. It is also used for pressure testing.

Minimum circuit ampacity from the equipment nameplate. It is the smallest conductor ampacity allowed for the field wiring of that motor circuit.

Maximum overcurrent protection shown on equipment nameplate. It is the largest breaker or fuse permitted to protect the circuit.

Electronically commutated motor that uses built-in electronics to vary speed efficiently. It is common in variable-speed air handlers and furnaces and often has a programming module.

Electrically operated switch that closes a high-power circuit for a compressor, fan, or heater when its coil is energized by a control.

Electrical component that stores charge and helps start or run motors by shifting phase. A weak or failed capacitor can cause no-start, low torque, or overheating.

Safety procedure that isolates energy sources, applies locks and tags, and verifies de-energization before service to prevent unexpected startup or release.

Florida recorded notice before construction begins that identifies the owner, contractor, lender, and property. It affects lien rights and deadlines for project participants.

A contractor licensed by the Florida Department of Business and Professional Regulation to perform work statewide. A registered contractor is limited to specific local jurisdictions.

Insurance covering medical costs and lost wages for employee work injuries. Florida contractors usually must show proof or a valid exemption when pulling permits.

A legal claim against real property for unpaid labor, services, or materials. Florida has detailed notice and deadline rules that contractors must follow.

Written document that modifies contract scope, price, or schedule after signing. It should be signed by both parties before the changed work proceeds.