CT HVAC key terms

A safety procedure in which energy sources are shut off, isolated, and marked with a lock and tag so equipment cannot be started while someone is servicing it.

Gear worn to reduce injury risk on the job, such as safety glasses, gloves, hard hats, respirators, and hearing protection, selected for the hazards of the specific task.

The process of removing refrigerant from a system and storing it in an approved container rather than venting it, so it can be reused, recycled, or reclaimed.

A federal EPA credential required for technicians who service, maintain, or dispose of equipment containing regulated refrigerants; passing a proctored exam proves the required knowledge.

An odorless, colorless gas produced by incomplete combustion that can cause illness or death; testing flue gases and ensuring adequate venting guards against dangerous levels in a building.

A tool with two gauges and hoses that connects to a system's service ports to read high-side and low-side pressures and to add or remove refrigerant.

A pump used to evacuate air and moisture from a refrigeration system before charging, lowering the internal pressure far below atmospheric so trapped water boils off.

An electronic instrument that measures very low absolute pressure in microns, used to confirm that a system has been evacuated to a moisture-free level.

A handheld meter that measures voltage, resistance, and often current and capacitance, used to troubleshoot electrical circuits and components in HVAC equipment.

A meter whose jaws wrap around a single conductor to read current by sensing the magnetic field, letting technicians check compressor and fan amp draw without disconnecting wiring.

An instrument that measures gas or air pressure, often in inches of water column, used to read duct static pressure, gas supply pressure, and vent draft.

The number of degrees a vapor is above its saturation temperature at a given pressure; measuring it at the evaporator outlet shows whether the metering device is feeding properly.

The number of degrees a liquid is below its saturation temperature at a given pressure; measuring it at the condenser outlet indicates how much liquid refrigerant is stacked in the condenser.

Heat that changes a substance's state without changing its temperature, such as the heat absorbed when liquid refrigerant boils into vapor in the evaporator.

Heat added to or removed from a substance that changes its temperature and can be felt or measured with a thermometer, as when air is warmed or cooled.

The temperature at which a refrigerant boils at a given pressure; it changes with pressure and is the reference point from which superheat and subcooling are figured.

The fixed pairing between a refrigerant's pressure and its boiling point, which lets a technician use gauge readings to determine the refrigerant's saturation temperature.

The rule stating that voltage equals current multiplied by resistance (E = I × R); it lets a technician predict one electrical value when the other two are known.

An electrically controlled switch with a low-voltage coil that closes higher-voltage line contacts to start a compressor, fan motor, or heater element.

A component that stores electrical charge and provides a phase shift or starting torque for motors; a weak or failed one causes hard starting and high amp draw.

A device that changes one alternating voltage to another, commonly stepping 240 or 120 volts down to 24 volts for control circuits and thermostats.

A safety device, often a bimetal disc or internal thermal element, that opens the motor circuit when current or temperature gets too high and resets when it cools.

The resistance to airflow in the duct system connected to a blower, measured in inches of water column across the unit to judge whether the air path is restricted.

A number from 1 to 16 rating how well an air filter captures particles of a given size; higher ratings stop more particles but add more airflow resistance.

The percentage of moisture the air holds compared with the maximum it could hold at the same temperature; it affects comfort, coil condensation, and mold risk.

The temperature to which air must be cooled for water vapor to condense; duct surfaces below this temperature will sweat and can support mold growth.

The metal component in a furnace where combustion gases transfer heat to the circulating air without the two streams mixing; cracks can allow carbon monoxide into the building.

A fan mounted at the furnace outlet that pulls combustion products through the heat exchanger and pushes them up the flue, often proving its operation with a pressure switch.

The pipe or passage that carries combustion gases from an appliance to the outdoors; it must be properly sized, sloped, and sealed to prevent spillage into the building.

A temperature-actuated safety control that shuts off the burner or heating element if the air in the plenum gets too hot, preventing damage or fire.

Annual Fuel Utilization Efficiency, the percentage of fuel energy a heating appliance converts to useful heat over a typical year; higher numbers mean lower operating cost.

A metering device that regulates refrigerant flow into the evaporator by sensing evaporator temperature and pressure, holding a steady superheat across changing loads.

A device in the liquid line that traps moisture, dirt, and acids from the refrigerant stream to protect the compressor and prevent ice or restriction in the metering device.

A four-way valve in a heat pump that switches refrigerant flow direction so the coil that was the evaporator becomes the condenser, changing the unit between heating and cooling.

The temperature difference between return air entering the equipment and supply air leaving it; measuring it helps confirm that airflow and refrigerant charge are in a reasonable range.

The superheat value a system should show at a given indoor wet-bulb and outdoor dry-bulb condition, used when charging a fixed-orifice system in the field.

The process of verifying that a newly installed system is adjusted, balanced, and functioning as designed, including measurements of airflow, charge, and controls before handover to the owner.

Testing flue gases with an electronic analyzer to measure oxygen, carbon dioxide, carbon monoxide, and stack temperature, so the technician can confirm safe and efficient burner operation.

Measuring the cubic feet per minute of air moving through the equipment or ducts, using tools such as an anemometer or a traverse, to confirm the blower delivers the designed amount.

An adjustable plate inside a duct that changes its free area, used to direct air to the right rooms and set the desired airflow split during air balancing.