This free interactive 3D model walks you through the HVAC systems of a multi-story commercial building — air-handling units (AHUs), VAV terminal boxes, the chiller plant, boiler and hot-water loop, supply/return ductwork, and the BAS/DDC controllers that tie it together. Click any component to see what it does. It's a visual learning tool for HVAC designers, mechanical engineers, facilities staff, and students learning how commercial HVAC fits together.
The viewer covers the full air-and-water path of a typical commercial system:
• Air-handling units (AHUs) — filters, heating/cooling coils, supply and return fans, and an outdoor-air economizer. • VAV terminal boxes — one per zone, modulating airflow (and often adding reheat) to match each zone's load. • Chiller plant — chillers making chilled water, cooling towers rejecting heat, and chilled-/condenser-water pumps. • Boiler and hot-water loop — for heating coils and VAV reheat. • Ductwork and diffusers — primary trunks down to zone supply and return. • BAS / DDC controllers — the building automation that sequences it all.
A central plant produces chilled water (and hot water) and distributes it to coils in the AHUs and terminal units. Each AHU mixes outdoor and return air, conditions it across the coils, and pushes it through the duct system. VAV boxes then throttle the volume of air delivered to each zone based on its thermostat — saving fan energy versus a constant-volume system. The building automation system (BAS) sequences chillers, pumps, fans, dampers and VAV boxes for comfort and efficiency, typically following ASHRAE 90.1 and Guideline 36 control sequences.
1. Drag to orbit the building, scroll to zoom, and pan to move around. 2. Click any piece of equipment to highlight it and read what it does. 3. Follow the air path (AHU → ducts → VAV → diffusers → return) and the water path (chiller/boiler → pumps → coils) to see how the system connects.
A VAV system delivers air at a roughly constant temperature from a central air handler and uses VAV terminal boxes to vary the volume of air sent to each zone based on its load. Reducing airflow at part-load saves significant fan energy compared with a constant-volume system, and many boxes add reheat for zones that need warming.
An AHU conditions and moves air. It typically contains filters, heating and cooling coils, supply and return fans, and dampers (including an outdoor-air economizer). It mixes outdoor and return air, conditions it, and distributes it through the duct system.
A chiller plant produces chilled water that is pumped to the cooling coils in AHUs and terminal units. The heat removed is rejected to the atmosphere through cooling towers (for water-cooled chillers). Chilled-water and condenser-water pumps circulate the water between the chillers, towers, and coils.
A constant-volume (CV) system delivers a fixed airflow and varies the supply-air temperature to control a zone. A VAV system keeps the supply-air temperature fairly constant and varies the airflow instead, which is more energy-efficient at part load — the dominant operating condition for most buildings.
A BAS is the network of DDC controllers, sensors, and software that monitors and sequences the HVAC equipment — chillers, boilers, pumps, AHUs, and VAV boxes — to maintain comfort while minimizing energy use, often using standardized sequences such as ASHRAE Guideline 36.