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A makeup air unit is a specialized air handler designed to bring in 100% outside air, primarily used in industrial and commercial settings. It is crucial in environments where there is a need for “once-through” systems, which only blow air one way into the building, “low flow” systems that operate at a reduced air flow rate, or “primary-secondary” setups where an air handler or rooftop unit connects to an additional makeup unit or hood.
How Makeup Air Units Operate
These units work by drawing fresh air from outside, mixing it with air recirculated from inside, and then distributing the conditioned air throughout the building via ductwork. This process allows for the control of fresh and recycled air ratios to achieve optimal indoor air quality (IAQ). Beyond ventilation, makeup air units can also provide heating and cooling, depending on the
heat exchanger type utilized.
Key Components of Makeup Air Units
Fresh Air Dampers
Regulate the volume of fresh air entering the system
Recirculating Air Damper
Adjusts the level of recirculated air mixed with incoming fresh air
Heating Coil
Responsible for heating the air distributed inside the building.
Cooling Coil
Used to cool the air for distribution.
Filters
Essential for removing contaminants from the air before it’s circulated.
The Necessity of Makeup Air
Providing fresh air for ventilation is vital, and a makeup air unit is one effective solution. Alternatives include energy recovery ventilators (ERVs) or supply fans. While these alternatives can function without an MAU, an exhaust-only setup mandates a makeup air unit.
Benefits of Makeup Air Units
The primary advantage of using a makeup air unit is the provision of fresh air for ventilation. Additional benefits include the ability to heat and cool as necessary and the control over the mix of fresh and recirculated air to maintain desired IAQ levels.
Potential Drawbacks
The initial cost is a significant drawback of makeup air units, often being higher compared to other options like ERVs or supply fans.
Comparison with Other Systems
Air Handler vs. Makeup Air Unit
An air handler circulates and controls indoor air, providing both ventilation and climate control. In contrast, a makeup air unit delivers 100% outside air.
Rooftop Unit vs. Makeup Air Unit
While both are types of air handlers, a rooftop unit is located on a building’s roof, whereas a makeup air unit ensures the intake of all outside air.
Commercial Applications
In commercial settings, makeup air units are vital for conditioning 100% outside air, especially in “once-through,” “low flow,” or “primary-secondary” HVAC systems. These configurations are prevalent in industrial and commercial environments.
Makeup Air for Kitchen Hoods
A kitchen hood makeup air unit, often used in restaurants, supplies 100% outside air directly to the hood and integrates with the exhaust system, ensuring efficient ventilation
In conclusion, makeup air units are integral to maintaining indoor air quality and providing necessary ventilation in various commercial and industrial applications. Understanding their operation, components, and benefits can help businesses choose the right system for their needs.
