2,400+ Definitions
HVAC GLOSSARY
Every HVAC term, acronym, and industry phrase — defined in plain English.
Roof Reflectance
Roof reflectance, also called albedo, measures the percentage of solar…
Rooftop Equipment
Rooftop equipment includes HVAC units, cooling towers, air handling units,…
Rooftop Unit
A Rooftop Unit (RTU) is a self-contained heating, ventilation, and…
Rooftop Unit (RTU) Heat Exchanger
The gas-to-air heat exchanger inside a packaged rooftop unit through…
Room Air Cleaner
A room air cleaner is a portable or wall-mounted device…
Room Air Distribution
Room air distribution describes the movement and mixing patterns of…
Room Condition Line
A line on the psychrometric chart connecting the room design…
Room Occupancy Detection
Room occupancy detection uses sensors to identify whether spaces are…
Rotary Heat Exchanger
A slowly spinning wheel or drum that transfers heat between…
Rotating Vane Anemometer
A rotating vane anemometer measures air velocity through a calibrated…
Roughness Factor
A parameter representing the surface texture of duct walls used…
Round Duct
Round duct is cylindrical metal tubing used to distribute conditioned…
RTD Sensor
An RTD (Resistance Temperature Detector) sensor measures temperature by monitoring…
Rubber Isolator
A rubber isolator is a resilient elastomer element that absorbs…
Run Capacitor
An AC electrolytic or film capacitor that remains in the…
Run-Around Coil System
A heat recovery system in which two separate coil-and-fan assemblies…
Runaround Coil
A runaround coil system consists of two heat exchanger coils…
Runway Damper
A runway damper is a fire damper engineered to compartmentalize…
Safety Switch Test
A safety switch test verifies that automatic shutoff devices function…
Saturation Pressure
Saturation pressure is the pressure at which a gas condenses…
Saturation Temperature
Saturation temperature is the temperature at which air becomes 100%…
SCADA System
SCADA (Supervisory Control and Data Acquisition) is an industrial control…
Schematic Design
Schematic Design is the initial phase of architectural planning where…
Schematic Diagram
A schematic diagram is a simplified, symbolic representation of an…
Schrader Valve
A Schrader valve is a spring-loaded poppet valve designed to…
Schrader Valve Core Remover
A tool that allows removal or installation of a Schrader…
Scope 1 Emissions
Scope 1 Emissions are direct greenhouse gas emissions produced from…
Scope 2 Emissions
Scope 2 Emissions are indirect greenhouse gas emissions generated by…
Screw Chiller
A screw chiller is a vapor-compression refrigeration system that uses…
Screw Compressor
A positive-displacement refrigerant compressor using two intermeshing helical rotors to…
Scroll Chiller
A scroll chiller is a vapor-compression refrigeration system that uses…
Scroll Compressor
A scroll compressor uses two interleaved spiral-shaped scrolls to compress…
SDHW
SDHW is the abbreviation for Solar Domestic Hot Water, representing…
Sealed Combustion Furnace
A sealed combustion furnace draws all combustion air directly from…
Seasonal COP
Seasonal COP (SCOP) is the ratio of total heating energy…
Seasonal Efficiency Standard
Seasonal Efficiency Standards measure HVAC equipment performance across an entire…
Seasonal Energy Efficiency Ratio
Seasonal Energy Efficiency Ratio (SEER) is a performance metric that…
Seasonal Energy Efficiency Ratio (SEER)
SEER (Seasonal Energy Efficiency Ratio) was the primary efficiency rating…
Seasonal Total Equivalent Warming Impact
Seasonal Total Equivalent Warming Impact (STEWI) is a comprehensive environmental…
Second Law of Thermodynamics
The Second Law of Thermodynamics states that entropy in an…
Secondary Air
Combustion air that enters the combustion zone around the outside…
Secondary Heat Exchanger
A secondary heat exchanger is an additional metal component in…
Secondary Refrigerant
A secondary refrigerant is a heat transfer fluid that carries…
Section 25C Tax Credit
Section 25C (formerly known as the Residential Energy Credits) provides…
Section 410
Section 410 of the Clean Air Act addresses stationary refrigeration…
Section 48 ITC
Section 48 of the Internal Revenue Code provides a federal…
Section 608
Section 608, part of the Clean Air Act, is the…
Section 609
Section 609 of the Clean Air Act regulates the servicing…