AZ HVAC key terms

The Arizona state agency that issues contractor licenses, investigates complaints about contractors, and enforces the statutes and rules that govern construction work performed in the state.

A category granted by the Arizona Registrar of Contractors that defines the type of work and dollar limits a contractor may perform, such as residential, commercial, or specialty work.

A surety bond an Arizona licensed contractor must keep in force as a condition of licensure; it provides a fund from which a consumer may recover for certain violations.

A written notice that an Arizona subcontractor, laborer, or supplier may serve on the owner and lender early in a project to preserve the right to later record a mechanics' lien.

A statutory claim recorded against real property by someone who furnished labor, materials, or services for improvements, giving security for payment if the owner or general contractor fails to pay.

A written modification to a signed contract that changes scope, schedule, or price; it must be approved by the owner before the extra work is performed to be billable.

A percentage of each progress payment withheld by the owner until the work is substantially complete, held to protect against unfinished or defective work.

The number of degrees a refrigerant vapor is above its saturation temperature at the measured pressure. Measured at the evaporator outlet, it shows whether the coil is fully boiling liquid refrigerant.

The number of degrees a liquid refrigerant is below its saturation temperature at the measured pressure. Measured at the condenser outlet, it indicates how much solid liquid seal the condenser is holding.

The temperature at which a refrigerant boils or condenses at a given pressure. Technicians read it from a pressure-temperature chart and compare it with measured line temperatures.

Heat energy absorbed or released when a substance changes phase without changing temperature, such as when liquid refrigerant boils into vapor inside the evaporator coil.

Heat added to or removed from a substance that causes a measurable temperature change without a change of phase, such as air being warmed or cooled as it crosses a coil.

A cooling rate equal to 12,000 British thermal units per hour, about the heat needed to melt one ton of ice in a day; the standard unit for stating equipment capacity.

A metering device that controls refrigerant flow into the evaporator to hold a set superheat, moving its valve in response to bulb pressure, evaporator pressure, and spring force.

The indoor heat exchanger where low-pressure liquid refrigerant absorbs heat from the air stream and boils into vapor, cooling and dehumidifying the air that passes over its fins.

The heat exchanger where hot, high-pressure refrigerant vapor gives up heat to outdoor air and condenses into liquid, leaving the coil as a subcooled liquid.

The difference between the bubble point and dew point temperatures of a zeotropic blend at a given pressure, which shifts superheat and subcooling readings during charging.

A refrigerant made of two or more components with different boiling points, so it evaporates and condenses over a temperature range and must be charged as a liquid to avoid fractionation.

Removing refrigerant from a system into a recovery cylinder so it can be recycled, reclaimed, or destroyed, required before opening a system or disposing of equipment.

A federal credential required for technicians who service, repair, or dispose of equipment containing regulated refrigerants; it certifies knowledge of recovery, handling, and safe practices.

Annual Fuel Utilization Efficiency, the percentage of fuel energy converted to useful heat over a heating season; a higher number means a more efficient furnace or boiler.

Seasonal Energy Efficiency Ratio, the Department of Energy rating for cooling efficiency of air conditioners and heat pumps, calculated under updated test conditions that include blower and duct static pressure.

Heating Seasonal Performance Factor, the Department of Energy rating for heat pump heating efficiency over a season, expressed as BTUs of heat delivered per watt-hour of electricity used.

A four-way valve in heat pumps that changes the direction of refrigerant flow so the indoor coil acts as the condenser in heating and as the evaporator in cooling.

The indoor cabinet that holds the blower, filter, and often the evaporator coil and electric heat strips, and moves conditioned air into the duct system.

The relationship in which voltage equals current multiplied by resistance (E = I x R), used to predict amps, check voltage drop, and diagnose motor and control circuits.

An electrically operated switch whose low-voltage coil pulls in high-voltage contacts, starting and stopping compressors, fan motors, or electric resistance heaters.

A control device that runs on 24 volts, senses room temperature, and closes circuits to call for heating, cooling, or fan operation to hold a selected setpoint.

The resistance to airflow measured in inches of water column at the blower outlet and inlet, compared with the fan performance table to confirm the system is moving design airflow.

The resistance of a duct fitting expressed as a length of straight duct, added to the actual run length so friction loss can be estimated for the entire path.

ACCA's residential duct design procedure that sizes ducts from room airflows, available static pressure, and a selected friction rate for each run.

Adjusting dampers, registers, and blower speed so each room receives its design airflow, verified with a flow hood or pressure readings.

Joining tubing by heating the joint above roughly 840 degrees Fahrenheit so a filler alloy melts and flows into the gap by capillary action; stronger than soldering and used on refrigerant lines.

Flowing dry nitrogen through piping while brazing to push out oxygen and prevent internal oxidation, which would otherwise form scale that contaminates valves and filters.

A mechanical joint made by compressing a flared tubing end against a fitting with a nut, used where brazing is impractical, such as at some service valves and mini-split connections.

ACCA's residential load calculation method that estimates heating and cooling loads from construction details, windows, occupancy, and local design conditions.

The outdoor and indoor conditions selected for sizing equipment, usually a local winter and summer temperature paired with a target indoor comfort level.

Gloves, eye and face protection, respirators, and other gear worn to protect a worker from injury, burns, refrigerant exposure, and airborne hazards on the job.

Guardrails, harnesses, lanyards, and anchor points used to prevent or arrest a fall when working at heights where a fall could cause serious injury.

A procedure for de-energizing equipment, applying a personal lock and tag, and verifying zero energy so the unit cannot start while service work is being done.