Ductwork is found in every heating and cooling system, whether residential or commercial. They’re run through the ceiling, and each room contains a rectangular opening so that vents can be installed for efficient airflow.
For the most common parts found in a commercial heating and cooling system, check out Kaempf & Harris’ comprehensive list:
- An air handler (also known as an air handler unit or abbreviated as AHU) often attaches to the duct system. The AHU is usually a large metal box containing a blower, heating or cooling elements, filter racks or chambers, sound attenuators, and dampers.
The metal box made of galvanized sheet metal is responsible for regulating and circulating air as part of the ventilation system. An AHU can be designed for indoor or outdoor use. The latter is known as a package unit (PU) or rooftop unit (RTU).
- Dampers are installed to regulate air flow. Volume Control Dampers enable the volume of air flow to be adjusted, while Combination Smoke & Fire Dampers seal off a duct when they detect smoke and fire.
Other dampers for commercial use include Air Measuring, Thermal, Backdraft, Industrial/Heavy Duty, Tunnel Transit, Marine, Balancing, Low Leakage, Relief, and Zone.
- Duct fittings and configurations, including ells, tees, and reducers, are responsible for equalizing the duct pressure and balancing the airflow. For example, a reducer is a fitting that’s used when a change from one size duct to another size is needed.
Another ductwork fitting is a vent cap that provides protection for the open end of a ductwork vent stack. Each fitting and configuration helps the overall commercial ductwork performance.
- The outlets, including diffusers, grilles, and registers, divide the airflow in a truck-and-branch ductwork design. For example, diffusers are used to introduce conditioned air into a space to achieve even distribution and mixing with minimum noise.
Another outlet is a register box (also known as a floor box), which is a galvanized steel grille with moving parts that’s capable of being opened and closed with the airflow directed.
- Plenum is arguably the most important part of any commercial HVAC ductwork. It’s an air distribution box for the central distribution and collection air flow unit of an HVAC system.
You should recognize two types of plenum: The supply plenum directs air from the central heating and cooling unit to the rooms which the system is designed to heat or cool. The return plenum carries the air from several large return grilles to a central air handler.
- Take-offs are round, oval, or rectangular fittings that are carefully designed to take the correct amount of airflow from the main duct into each branch duct.
For example, a High Efficiency Takeoff (HETO) is a tap used on a rectangular duct that’s designed with an increase on the upstream side of the fitting. This design allows the maximum amount of air to flow downstream making the system much easier to balance and saves energy.
- Vents are typically placed in the ceiling with their edges corresponding to the opening in the above duct. As warm or cool air pours through the commercial ductwork, vents allow it to disperse into the rooms below.
The ventilation system is usually made of sheet metal, which can handle a variety of temperatures. According to an eBay buying guide on HVAC, “The vent is comprised of a rectangular edge or frame, within which is a series of thin, metal slats angled to channel the air downward. Some also include a manual control that lets users change the angle.”
For more information about the basics of commercial ductwork design, download Kaempf & Harris’ Commercial Ductwork Anatomy infographic by clicking on the button below. You’ll receive a labeled diagram of a simple commercial duct for on-the-job reference: