Commercial HVAC refers to anything involved with heating and cooling large properties, such as business buildings, restaurants, rental properties, hospitals, schools, and more. Because of the scale, commercial HVAC heavily differs from its residential counterpart in terms of size, capacity, and operational complexity.
The main difference between commercial and residential HVAC is that commercial systems are designed to operate continuously at full capacity over long periods of time.
Residential systems are generally sized for peak use—when everyone is home at once—and then shut off when nobody's home.
Commercial systems need to be set up differently: they must be able to run all day long without failure.
Commercial HVAC systems also tend to be larger than residential ones: commercial buildings often require several units or zones (areas) for heating and cooling, whereas most houses only need one or two zones total. And because commercial buildings tend to be larger than homes on average (think Wal-Mart versus your house), you may even need multiple units per zone!
Because of the increased scale and complexity of commercial HVAC systems compared with residential ones, they require professional installation by trained technicians who know how to customize the system for each building's unique needs.