LA HVAC key terms

A required safety procedure in which the energy source feeding equipment is de-energized, isolated, locked, and tagged so it cannot be restarted while a technician services or repairs it.

Wearable gear such as safety glasses, gloves, respirators, and hearing protection that reduces a worker's exposure to hazards on the job site.

The distance from energized electrical equipment within which a person could receive a second-degree burn from an arc flash, establishing where shock and burn protection is required.

Practices for joining tubing with heat, including fire watch, shielding combustibles, purging with nitrogen, and ventilating fumes from flux and refrigerant decomposition products.

A tool with high-side and low-side gauges and hoses used to read system pressures, evacuate, and charge refrigerant. Hoses and manifolds must be rated for the refrigerant in use.

An electronic instrument that measures deep vacuum in microns during evacuation, confirming that moisture and non-condensable gases have been removed before charging a system.

The number of degrees a vapor is above its saturation temperature at a given pressure. Measured at the evaporator outlet, it indicates how well the metering device is feeding the coil.

The number of degrees a liquid is below its saturation temperature at a given pressure. Measured at the condenser outlet, it verifies the refrigerant charge and condenser performance.

A metering device that regulates refrigerant flow into the evaporator by maintaining a target superheat, responding to bulb temperature and evaporator pressure.

The indoor coil where low-pressure liquid refrigerant absorbs heat from the conditioned air and boils into vapor, producing the cooling effect.

The outdoor coil where high-pressure refrigerant vapor rejects heat to outdoor air and condenses into a liquid, completing the refrigeration cycle.

The heart of the refrigeration cycle; it raises refrigerant pressure and temperature, moving vapor from the evaporator to the condenser and driving the entire circuit.

An industry method for estimating a building's heating and cooling loads from envelope, orientation, occupancy, and climate data, used to size equipment correctly.

An industry method for sizing ducts based on available static pressure, friction rate, and equivalent lengths of fittings so each room receives its design airflow.

An industry procedure for matching selected heating and cooling equipment to the calculated loads, checking sensible and latent capacity at design conditions.

The friction loss of a duct fitting expressed as an equivalent straight run of duct, added to the physical run to determine total effective length.

The pressure drop per unit length of duct, usually inches of water per 100 feet, used to size ducts for a given available static pressure.

The fraction of total cooling capacity that removes sensible heat, calculated as sensible capacity divided by total capacity; important for humidity control.

The air supplied to a fuel-burning appliance for complete combustion; inadequate supply causes carbon monoxide production and unsafe operation.

Procedures for preventing and detecting carbon monoxide, including combustion analysis, flue inspection, and use of personal CO monitors during service calls.

A device on atmospheric gas furnaces that draws dilution air and maintains a stable negative pressure at the appliance flue collar, preventing spillage of combustion products.

The metal component separating combustion gases from supply air in a furnace; cracks or holes allow carbon monoxide to enter the airstream and require replacement.

The process of confirming correct refrigerant quantity using superheat, subcooling, or weigh-in methods, following manufacturer charging charts and system conditions.

An evacuation method using nitrogen and vacuum in alternating cycles to remove moisture and non-condensables from a system before charging.

Flowing dry nitrogen through tubing during brazing to prevent internal oxidation, and using nitrogen pressure for leak testing and evacuation support.

A DOT-approved, color-coded vessel used to store recovered refrigerant; it must not be overfilled and must be rated for the refrigerant recovered.

A test instrument measuring voltage, resistance, and current; used to verify power, check continuity, and diagnose electrical faults in controls and motors.

A capacitor that stays in the circuit during motor operation to improve torque and phase angle on permanent split capacitor motors; a failed one can prevent starting.

An electrically controlled switch that uses a coil to close heavy-duty contacts, supplying power to compressors, condensers, and other high-current loads.

The ordered steps a control system follows from a call for heat or cool through safeties, fan, and shutdown, used to diagnose where a system fails.

The pair of copper lines connecting indoor and outdoor units, consisting of the liquid line and the larger suction line, properly insulated and supported.

Cutting, forming, and joining galvanized steel duct using patterns, seams, and reinforcement to meet airflow and leakage requirements.

A water seal in the drain line that prevents air from being drawn into or blown out of the drain pan, ensuring condensate drains properly.

Local rules requiring permits and inspections for HVAC installations; work must comply with adopted codes and be inspected before being placed in service.

State and local requirements for contractors and technicians to hold the appropriate mechanical license or registration before performing or contracting HVAC work.

Adherence to adopted mechanical, fuel gas, and energy codes, including manufacturer instructions, which govern installation, ventilation, and safety requirements.

A written document signed by the owner and contractor that modifies the contract scope, price, or schedule before the additional work is performed.

A contractor's legal claim against property for unpaid work, subject to deadlines and notice requirements that vary by state and must be tracked carefully.

The complete set of drawings, specifications, addenda, and agreement forms that define the work, price, and obligations of the parties.