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HVAC  Service Glossary (A-Z)

This glossary is designed for frontline customer service agents supporting HVAC customers. It includes technical HVAC terms, refrigerants, service terminology, customer-facing language, equipment components, and common industry phrases.​

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  • Absolute Pressure: Pressure measured relative to a perfect vacuum.

  • AC (Air Conditioner): Equipment that removes heat and humidity from indoor air.

  • Accumulator: Component that prevents liquid refrigerant from entering the compressor.

  • AFUE (Annual Fuel Utilization Efficiency): Efficiency rating used for furnaces.

  • Air Filter: Device that removes dust, pollen, and contaminants from airflow.

  • Air Handler: Indoor HVAC unit containing the blower and evaporator coil.

  • Ambient Temperature: Temperature of the surrounding environment.

  • Auxiliary Heat: Backup heating system used when a heat pump cannot meet heating demand.

  • Balanced System: HVAC system operating within designed airflow, pressure, and temperature specifications.

  • Blower Motor: Motor that moves air through ductwork.

  • BTU (British Thermal Unit): Measurement of heating or cooling capacity.

  • Breaker: Electrical safety device that disconnects power during overloads.

  • Burner Assembly: Furnace component responsible for combustion.

  • Capacitor: Electrical component that helps motors start and run.

  • CFM (Cubic Feet per Minute): Measurement of airflow volume.

  • Charge (Refrigerant Charge): Quantity of refrigerant inside a system.

  • Compressor: The "heart" of an HVAC system that circulates refrigerant.

  • Condenser Coil: Outdoor coil that releases heat from refrigerant.

  • Contactor: Electrically controlled switch used to power HVAC equipment.

  • Cooling Cycle: Process through which heat is removed from indoor air.

  • Damper: Device that regulates airflow in ductwork.

  • Defrost Cycle: Heat pump operation mode used to remove ice accumulation.

  • Differential Temperature: Difference between supply and return air temperatures.

  • Ductwork: System of air distribution channels.

  • Discharge Line: Refrigerant line carrying hot gas from compressor.

  • EER (Energy Efficiency Ratio): Measurement of cooling efficiency.

  • Electronic Expansion Valve (EEV): Device controlling refrigerant flow electronically.

  • Emergency Heat: Manually activated backup heating source.

  • EPA Certification: Required certification for handling refrigerants.

  • Evaporator Coil: Indoor coil where refrigerant absorbs heat.

  • Fan Motor: Motor operating indoor or outdoor fan blades.

  • Filter Drier: Component that removes moisture and contaminants from refrigerant.

  • Float Switch: Safety device that shuts down equipment when condensate levels become excessive.

  • Freon: Common trade name often used to refer to refrigerants.

  • Furnace: Heating appliance utilizing gas, oil, or electricity.

  • Gauge Set: Diagnostic tool used to measure refrigerant pressure.

  • Gas Valve: Controls fuel supply in heating systems.

  • Grille: Decorative cover over air supply or return openings.

  • Heat Exchanger: Component transferring heat without mixing air and combustion gases.

  • Heat Pump: System capable of both heating and cooling.

  • HSPF (Heating Seasonal Performance Factor): Heat pump efficiency rating.

  • Humidity: Amount of moisture present in air.

  • High Pressure Switch: Protective device preventing excessive system pressure.

  • IAQ (Indoor Air Quality): Overall quality and cleanliness of indoor air.

  • Ignitor: Device that initiates furnace combustion.

  • Inverter Technology: Variable-speed compressor technology that improves efficiency.

  • Insulation: Material reducing heat transfer.

  • J-Load Calculation: Industry-standard method for determining HVAC sizing requirements.

  • Kilowatt (kW): Unit measuring electrical power consumption.

  • Kilowatt-Hour (kWh): Measurement of electricity usage over time.

  • Latent Heat: Heat involved in moisture removal during phase changes.

  • Line Set: Copper refrigerant piping connecting indoor and outdoor units.

  • Low Pressure Switch: Safety device protecting equipment from low refrigerant or airflow conditions.

  • Manifold Gauge Set: Equipment used to diagnose refrigeration systems.

  • MERV Rating: Air filter efficiency classification.

  • Mini-Split: Ductless HVAC system.

  • Motor Overload: Safety condition triggered by excessive current draw.

  • Negative Pressure: Air pressure lower than surrounding areas.

  • Nitrogen Test: Procedure used to locate refrigerant leaks and pressure test systems.

  • OEM (Original Equipment Manufacturer): Company producing original equipment or parts.

  • Outdoor Unit: Exterior HVAC equipment containing condenser components.

  • Overcharge: Condition where excessive refrigerant exists within a system.

  • Package Unit: HVAC system containing all components in one cabinet.

  • Plenum: Air distribution chamber attached to HVAC equipment.

  • PSI (Pounds per Square Inch): Common pressure measurement unit.

  • Purge: Removal of air, moisture, or contaminants from a system.

  • Quick Connect Fittings: Connections designed for rapid installation or servicing.

  • Quoted Repair: Technician's estimate for repair cost.

  • Refrigerants

    • R-11: Older low-pressure refrigerant previously used in centrifugal chillers.

    • R-12: Legacy refrigerant phased out due to ozone depletion concerns.

    • R-22: Older residential refrigerant phased out for new production.

    • R-32: Modern lower-GWP refrigerant increasingly used in air conditioners.

    • R-123: Refrigerant commonly used in certain chiller applications.

    • R-134a: Refrigerant used in automotive and commercial cooling systems.

    • R-404A: Refrigerant used primarily in commercial refrigeration.

    • R-407C: Replacement refrigerant for some R-22 applications.

    • R-410A: Common refrigerant previously used in residential HVAC systems.

    • R-438A (MO99): Retrofit refrigerant alternative for R-22 systems.

    • R-454B: New-generation refrigerant replacing R-410A in many residential systems.

    • R-513A: Lower-GWP replacement for R-134a.

    • R-717: Ammonia refrigerant used in industrial refrigeration.

    • R-744: Carbon dioxide refrigerant used in specialized systems.

  • Reclaim: Process of restoring used refrigerant to industry standards.

  • Recovery: Removal and storage of refrigerant from a system.

  • Refrigerant: Chemical substance used to transfer heat.

  • Return Air: Air brought back to HVAC equipment for conditioning.

  • Reversing Valve: Heat pump component that changes refrigerant flow direction.

  • Saturation Temperature: Temperature at which refrigerant changes state at a given pressure.

  • SEER2: Current industry cooling efficiency rating.

  • Service Call: Scheduled technician visit.

  • Subcooling: Amount liquid refrigerant is cooled below saturation temperature.

  • Supply Air: Conditioned air delivered to occupied spaces.

  • Superheat: Heat added to refrigerant vapor above saturation temperature.

  • Thermostat: Device controlling HVAC operation based on temperature settings.

  • Ton of Cooling: Equal to 12,000 BTUs per hour.

  • TXV (Thermostatic Expansion Valve): Device regulating refrigerant entering the evaporator.

  • UV Light System: Indoor air quality accessory designed to reduce microbial growth.

  • Undercharge: Condition where insufficient refrigerant exists in a system.

  • Upflow Furnace: Furnace designed to move air upward.

  • Vacuum Pump: Equipment used to remove air and moisture from refrigerant systems.

  • Variable Speed Motor: Motor capable of operating at different speeds.

  • Ventilation: Introduction of fresh air into occupied spaces.

  • Warranty: Manufacturer or contractor guarantee covering parts or labor.

  • Wet Bulb Temperature: Temperature measurement accounting for humidity.

  • Work Order: Document authorizing service activities.

  • X13 Motor: Electronically commutated blower motor commonly used in modern systems.

  • XR (Cross Reference): Process of identifying equivalent replacement parts.

  • Year-Round Efficiency: General term describing long-term HVAC performance.

  • Y1 Terminal: Thermostat connection controlling first-stage cooling.

  • Y2 Terminal: Thermostat connection controlling second-stage cooling.

  • Zoning System: HVAC configuration allowing independent temperature control of multiple areas.

  • Zone Damper: Motorized damper controlling airflow to a specific zone.

  • Zero ODP (Ozone Depletion Potential): Classification for refrigerants that do not deplete the ozone layer.

  • Zone Control Board: Electronic controller managing multiple HVAC zones.

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Customer Service Phrases Frontline Agents Should Know

  • No Cooling: Customer reports system is running but not producing cold air.

  • No Heat: Customer reports heating system is not producing warm air.

  • Short Cycling: Equipment repeatedly starts and stops before completing a full cycle.

  • Frozen Coil: Ice buildup on evaporator coil, often caused by airflow or refrigerant issues.

  • Leaking Unit: Customer observes water or refrigerant leakage.

  • System Down: Complete loss of HVAC operation.

  • Comfort Concern: Customer dissatisfaction related to temperature, airflow, or humidity.

  • Parts Availability: Status of replacement component inventory.

  • Dispatch Window: Time range when a technician is expected to arrive.

  • First-Time Fix Rate: Measurement of repairs completed during the initial visit.

  • Preventive Maintenance: Routine service intended to prevent equipment failure.

  • Service Agreement: Contract providing scheduled maintenance and other benefits.

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