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

ACCA Manual S — Equipment Selection — is the companion…

ACCA Manual T provides guidance on selecting and sizing air…

A commercially available fuel gas composed primarily of propylene, used…

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 is a standardized classification system for organizing construction specifications,…

Matter Protocol

Matter is an open-source smart home connectivity standard developed by…

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 subcooling

A dedicated refrigeration circuit used to cool the liquid refrigerant…

Mechanical Ventilation

Mechanical Ventilation uses motorized fans and ductwork to actively supply…

Media Adsorption

Media adsorption refers to odor and gas removal through the…

A megawatt (MW) is a unit of power equal to…

Meggering is a high-voltage insulation resistance test performed on motor…

A megohmmeter, also called a megger or insulation tester, measures…

MEP Coordination

MEP Coordination is the systematic process of designing and integrating…

MERV 11 (Minimum Efficiency Reporting Value) filters capture 40-65% of…

MERV 13 (Minimum Efficiency Reporting Value 13) is an air…

MERV 16 (Minimum Efficiency Reporting Value 16) is a high-efficiency…

MERV 8 (Minimum Efficiency Reporting Value) is a standard air…

MERV (Minimum Efficiency Reporting Value) is the standard rating system…

Metabolic rate is the rate at which the human body…

Metering Device

A metering device is a flow-restricting component in a refrigeration…

Microbubble Reabsorber

A high-efficiency air removal device that uses a coalescing medium…

Microgrid Controller

A microgrid controller is specialized software and hardware that manages…

Microgrids are localized electrical systems that can operate independently or…

A microinverter is a small inverter installed directly on or…

A micron gauge is a precision vacuum measurement instrument used…

A micron reading measures absolute pressure in a refrigeration system…

Mineral wool is a fibrous insulation material manufactured from molten…

A mini-split (also called a ductless mini-split or ductless heat…

Mini Split Installation

Mini split installation is the complete process of placing a…

Minimum Activation Flow

Minimum activation flow is the minimum water volume, typically 0.5-0.6…

Minimum Pipe Velocity

The lowest refrigerant gas velocity in a suction or discharge…

Minor losses are pressure drops occurring at fittings, valves, bends,…

Mixed Mode Ventilation

Mixed Mode Ventilation integrates natural and mechanical ventilation within the…

Mixed-Mode Ventilation

A ventilation strategy that combines mechanical systems with operable windows…