Browse Categories

AHU

Air Handler Unit AHU Air Handling Units HVAC Equipment

Term of the Week: 
AHU

An Air Handling Unit (AHU) is one of the most essential components of modern HVAC systems—often described as the “lungs” of a building because it draws in, filters, conditions, and distributes air throughout occupied spaces. This blog breaks down what an AHU is, the key components you’ll find in commercial air handlers, and how they impact comfort, efficiency, and system performance. It’s a great primer for anyone new to HVAC terminology or looking to brush up on core fundamentals.

What is AHU?

HVAC 101 AHU, VAV, PIU, FCU — lots of three-letter acronyms.

What Is an Air Handling Unit (AHU)?

An air handler (AHU) is like the lungs of a building—pulling in air, filtering it, heating or cooling it, and distributing it through the duct system.

Key functions

  • Draws in air, filters it, conditions it, and delivers it to occupied spaces.
  • Sized based on airflow (CFM) and capacity (tons of heating/cooling).
  • Ranges from small residential units to large commercial AHUs the size of a room.
AHU Components

Common Parts Found in a Commercial AHU

  • Coils that require valves to control media flow (hot water, chilled water, or refrigerant).
  • Air filters and air flow switches used to prove airflow (the AFS-222 is a common example).
  • Fans, often paired with variable frequency drives (VFDs) to control fan speed and energy usage.
  • Temperature, humidity, and pressure sensors that monitor air quantity and condition.
  • A central controller (thermostat or BAS controller) to coordinate operation.
Bonus Term

What Does “A Ton of Cooling” Mean?

A ton of cooling is a unit of measurement used to describe how much heat an air conditioning system can remove over time.

  • Definition: 1 ton of cooling equals 12,000 BTUs per hour.
  • Origin: The term comes from the amount of heat required to melt 1 ton of ice (2,000 lb) over 24 hours.

Real-world examples

• A 1-ton unit can cool a small apartment or office.

• A 10-ton unit is common for large retail spaces.

• Large commercial AHUs can exceed 50+ tons to serve entire floors of a building.

Valves

Control • balancing • isolation

Air Flow Switches

Proving air movement

Variable Frequency Drives

Pump & fan speed control

Temperature • Humidity • Pressure

Sensors for HVAC & BAS

Controllers

BAS • VAV • unitary
New to the Industry?

A Simple Rule to Remember

It’s not about weight — it’s about cooling capacity.

Have questions? Contact us

Tags

bas networking distech building automation iot ot jace control valves hvac systems industrial valves eclypse tosibox jci bas network 8000 9000 dwyeromega remote display hvac pumps hydronic systems commercial hvac centrifugal pumps chilled water systems heating water systems boiler safety boiler components industrial heating equipment heating systems chiller Pneumatic Electro-Mechanical and DDC systems maintenance calibration remote bacnet n4 automation honeywell control panels network configuration port security network control smart buildings energy management ethernet based bas network guidelines managed switches optimizer commander johnson controls sma device count points Gas Meters Diaphragm Rotary meters gas trains fuel train gas supply commercial boiler burner ief transmitters Gas Valves for boilers Vent Valves Pilot Gas Valves switches for boilers a temperature sensor honeywell i4006 honeywell l6006c honeywell l91b temperature limit switches gas pressure limit switches pump selection pump sizing hydronic pump design pump fundamentals gpm flow rate total dynamic head tdh head pressure closed loop systems open loop systems glycol systems pump control strategies vfd pumps ecm pumps bas integration pump configuration inline pumps end suction pumps split case pumps redundant pumping lead lag pumps npsh hvac fundamentals industry terms pumps in hvac hydronic pump basics boiler systems hvac pump operation gpm and head pressure ahr boiler control Low Water Cut off Air Handler Unit AHU Air Handling Units HVAC Equipment york compressor tp valve temperature and pressure relief valve water heater safety domestic hot water systems plumbing safety devices pressure relief valves thermal expansion protection potable water systems water heater components mechanical code compliance plumbing code requirements boiler vs tp valve hot water storage tanks safety valves facility maintenance boiler relief valves ief electromagnetic flow transmitter optional lcd AI future pressure class belimo gas monitor air quality training certification atrius cloud platform fireye burnlogix yb honeywell q tosi n5 bacnetsc sc niagara fx heating season checklist tc500 promo chart recorder industrial cxc customer center dcv sensor network security cyber ul508a industrial solutions engineering solutions panel assembly custom control panels commercial panels gas regulator sizing gas safety inlet pressure outlet pressure flow rate natural gas propane regulators subnet it managed ip switch vlan setup quality of service qos spanning tree protocol stp routing configuration network management lldp setup energy efficiency ethernet managed network switch benefits ot network energy savings building solutions connected power building management bms transformers din rail transformer functional devices transformer in a box ai in real estate cybersecurity data integration realcomm ibcon sustainability sensors controllers interfaces
Show All

Posts

2026 2025
December November October September August July June May April February January
2024
November October September August July June May April March February January
2023
December November October September August July June May April March
2022