2,400+ Definitions
HVAC GLOSSARY
Every HVAC term, acronym, and industry phrase — defined in plain English.
Refrigerant Oil Management
The set of design features and operational practices used to…
Refrigerant Piping Pressure Test
A field procedure performed after lineset installation and before system…
Refrigerant Pressure Check
A refrigerant pressure check measures high-side and low-side pressures in…
Refrigerant Purchase Record
A Refrigerant Purchase Record is documentation of all refrigerant acquisition…
Refrigerant Reclaim
Refrigerant reclaim is the industrial process of purifying used refrigerant…
Refrigerant Reclaiming
Refrigerant reclaiming is the process of reprocessing used or contaminated…
Refrigerant Recovery
Refrigerant recovery is the mandatory process of removing refrigerant from…
Refrigerant Recovery Cylinder
A refrigerant recovery cylinder is a specialized pressurized container designed…
Refrigerant Recovery Machine
A self-contained unit that removes refrigerant from a system and…
Refrigerant Recycling
Refrigerant recycling is the process of cleaning used refrigerant extracted…
Refrigerant Safety Classification
Refrigerant Safety Classification is a standardized labeling system established by…
Refrigerant Scale
A calibrated weighing device, usually electronic, used to measure the…
Refrigerant Tracking
Refrigerant Tracking is the systematic monitoring and documentation of refrigerant…
Refrigerant Weigh In
Refrigerant weigh in is the process of accurately measuring and…
Refrigeration Capacity
Refrigeration capacity is the maximum amount of heat that a…
Refrigeration Cycle
The refrigeration cycle is the thermodynamic process by which HVAC…
Refrigeration Cycle Efficiency
Refrigeration cycle efficiency measures how effectively a refrigeration system converts…
Refrigeration Effect
The refrigeration effect is the amount of useful cooling capacity…
Refrigeration Load
Refrigeration load is the total amount of heat that a…
Refrigeration System
A refrigeration system is a mechanical apparatus that transfers heat…
Regeneration Air
The heated airstream passed through a desiccant wheel or bed…
Regenerative Drive
A VFD capable of returning braking energy from a decelerating…
Reheat Coil
A heating coil located in a terminal duct branch downstream…
Relative Humidity
Relative humidity is the ratio of water vapor pressure in…
Relay
A relay is an electromechanical or solid-state switch that uses…
Relief Valve
A relief valve is a safety device that automatically opens…
Remote HVAC Control
Remote HVAC control allows users to adjust heating, cooling, and…
Renewable Energy
Renewable energy is power generated from naturally replenishing sources such…
Renewable Energy Certificate
A Renewable Energy Certificate (REC) is a market-based instrument that…
Reset Ratio
The ratio of the change in supply water temperature to…
Reset Schedule
A reset schedule automatically adjusts HVAC setpoints based on outdoor…
Residential Solar
Residential solar refers to rooftop or ground-mounted photovoltaic systems installed…
Resistance Hygrometer
A humidity sensor that measures moisture content by detecting changes…
Retro Commissioning
Retro commissioning is a systematic process of identifying and correcting…
Retrofit
A retrofit is the modification or replacement of existing HVAC…
Return Air Grille
A return air grille is a ventilation component installed over…
Return Duct
Return ducts transport air from occupied spaces back to the…
Reverse Cycle Defrost
A defrost method used primarily in heat pump systems where…
Reverse Return
A reverse return piping configuration routes the return water line…
Reverse Return Piping
A hydronic piping arrangement where the return path is routed…
Reverse-Cycle Defrost
The most common heat pump defrost method, which temporarily reverses…
Reversing Valve
A reversing valve is an electromechanical device installed in heat…
Reversing Valve Failure
Reversing valve failure occurs when the component that switches between…
Revit MEP
Revit MEP is Autodesk’s specialized BIM software designed for mechanical,…
Rigid Foam Board
Rigid foam board is a lightweight sheet insulation material manufactured…
Riser Diagram
A riser diagram is a vertical representation of piping or…
Rolling Brownout
A Rolling Brownout is a temporary, rotating reduction in electrical…
Roof Mount Solar
Roof mount solar refers to photovoltaic panels installed directly on…