2,400+ Definitions
HVAC GLOSSARY
Every HVAC term, acronym, and industry phrase — defined in plain English.
Liquid-Line Filter Drier
A serviceable or replaceable cartridge installed in the liquid line…
Lithium Bromide Chiller
A lithium bromide chiller is an absorption cooling system that…
Lithium Iron Phosphate Battery
Lithium Iron Phosphate (LiFePO₄) batteries are rechargeable energy storage systems…
Load Calculation
A load calculation determines how much heating and cooling capacity…
Load Duration Curve
A load duration curve is a graphical representation that ranks…
Load Forecasting
Load forecasting estimates the amount of electrical power that will…
Load Shedding
Load Shedding is the controlled reduction or disconnection of electrical…
Load Shifting
Load shifting is the strategy of moving HVAC energy consumption…
Local Exhaust
Local exhaust systems capture air contaminants directly at their point…
Location Based Control
Location based control is an HVAC technology that adjusts heating…
Locked Rotor Amperage
The steady-state current drawn by a motor when its rotor…
Locked Rotor Amps
Locked Rotor Amps (LRA) is the maximum current a motor…
Lockout Relay
A lockout relay is a safety device used in HVAC…
LonWorks
A networking platform developed by Echelon Corporation using the LonTalk…
Loop Field Manifold
The header piping assembly that connects multiple individual geothermal loop…
Loop Temperature Range
The acceptable span of entering water temperatures within which a…
Loss Coefficient
A dimensionless number that quantifies the pressure drop across a…
Low Ambient Control
Low Ambient Control refers to a set of strategies and…
Low GWP Refrigerant
Low GWP refrigerants are cooling fluids with global warming potential…
Low Pressure Category
The Low Pressure Category includes HVAC systems and large appliances…
Low Pressure Switch
A Low Pressure Switch (LPS) is a safety device installed…
Low Refrigerant
Low refrigerant indicates the system contains less than the manufacturer-specified…
Low Temperature Cascade
The low temperature cascade stage is the coldest circuit in…
Low Velocity Duct
A low velocity duct is an HVAC ductwork system designed…
Low VOC Adhesive
Low VOC adhesive contains fewer than 100 grams per liter…
Low VOC Paint
Low VOC paint contains fewer than 50 grams per liter…
Low-Loss Header
A hydraulic separator that uses a large-diameter vessel to decouple…
Lower Room UVGI
Lower room UVGI refers to ultraviolet germicidal irradiation (UVGI) systems…
LWT (Leaving Water Temperature)
The temperature of the fluid exiting the heat pump heat…
Machinery Room
A machinery room is a specialized, dedicated space housing refrigeration…
Magnehelic Gauge
A Magnehelic gauge is a differential pressure instrument that uses…
Magnetic Bearing Chiller
A magnetic bearing chiller is a type of centrifugal chiller…
Main Breaker
The main breaker is the primary safety switch that controls…
Main Trunk
The main trunk is the primary large-diameter ductwork that carries…
Maintenance Agreement
A maintenance agreement is a contractual arrangement between an HVAC…
Maintenance Checklist
A maintenance checklist is a standardized list of inspection and…
Makeup Air Kitchen
Makeup air in a kitchen is replacement air supplied to…
Makeup Air Unit
A makeup air unit (MAU) supplies fresh outside air to…
Manifold Gas Pressure
Manifold gas pressure is the regulated gas pressure measured at…
Manifold Gauge
A manifold gauge set is a diagnostic tool that measures…
Manifold Gauge Set
A manifold gauge set is a diagnostic instrument used by…
Manifold Station
A central distribution component in a radiant floor or zoned…
Manometer
A Manometer is a precision pressure measurement instrument using a…
Manual D
ACCA Manual D is the industry standard for residential duct…
Manual Damper
A manual damper is a hand-operated plate or blade installed…
Manual J
Manual J is the ACCA (Air Conditioning Contractors of America)…
Manual N
ACCA Manual N is the commercial load calculation procedure for…
Manual Q
ACCA Manual Q is the procedure for designing duct systems…