2,400+ Definitions

HVAC GLOSSARY

Every HVAC term, acronym, and industry phrase — defined in plain English.

All A B C D E F G H I J K L M N O P Q R S T U V W X Y Z
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…
Lower Room UVGI
Lower room UVGI refers to ultraviolet germicidal irradiation (UVGI) systems…
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…
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 S
ACCA Manual S — Equipment Selection — is the companion…
Mass Flow Rate
Mass flow rate is the amount of substance, measured in…
Massachusetts Stretch Code
The Massachusetts Stretch Code, established in 2009, is a voluntary…
Master Technician
A master technician is the highest level of HVAC professional,…
MasterFormat
MasterFormat is a standardized classification system for organizing construction specifications,…
Matter Protocol
Matter is an open-source smart home connectivity standard developed by…
MAU
MAU is the abbreviation for makeup air unit, a mechanical…
Maximum Power Current
Maximum power current (Imp) is the operating current at which…
Maximum Power Point Tracking
Maximum Power Point Tracking (MPPT) is an advanced control technique…
Maximum Power Voltage
Maximum power voltage (Vmp) is the operating voltage at which…
Mean Radiant Temperature
Mean radiant temperature (MRT) is the uniform temperature of an…
Mechanical Advantage
Mechanical advantage (MA) is the ratio of output force produced…
Mechanical License
A mechanical license is a state or local credential authorizing…
Mechanical Penthouse
A mechanical penthouse is a rooftop structure housing major HVAC…
Mechanical Plans
Mechanical Plans are detailed drawings showing the layout, routing, and…
Mechanical Refrigeration History
Mechanical Refrigeration History traces from theoretical physics in the 1800s…
Mechanical Room
A mechanical room is a dedicated space that houses HVAC…
Mechanical Shaft
A mechanical shaft is a vertical cavity that runs through…
Mechanical Ventilation
Mechanical Ventilation uses motorized fans and ductwork to actively supply…
Media Adsorption
Media adsorption refers to odor and gas removal through the…
Megawatt
A megawatt (MW) is a unit of power equal to…
Meggering
Meggering is a high-voltage insulation resistance test performed on motor…
Megohmmeter
A megohmmeter, also called a megger or insulation tester, measures…
MEP Coordination
MEP Coordination is the systematic process of designing and integrating…
MERV 11
MERV 11 (Minimum Efficiency Reporting Value) filters capture 40-65% of…
MERV 13
MERV 13 (Minimum Efficiency Reporting Value 13) is an air…
MERV 16
MERV 16 (Minimum Efficiency Reporting Value 16) is a high-efficiency…
MERV 8
MERV 8 (Minimum Efficiency Reporting Value) is a standard air…
MERV Rating
MERV (Minimum Efficiency Reporting Value) is the standard rating system…