What is a Makeup Air Unit in an HVAC system?

A makeup air unit (MAU) is an air handler that conditions 100% outside air. Typically used in industrial or commercial settings, or in “once-through” (blower sections that only blow air one-way into the building), “low flow” (air handling systems that blow air at a low flow rate), or “primary-secondary” (air handling systems that have an air handler or rooftop unit connected to an add-on makeup unit or hood) commercial HVAC systems. Abbreviated MAU.

How does it work?

A makeup air unit takes in fresh outside air, mixes it with recirculated inside air, and then distributes the conditioned air throughout the building via the ductwork. The mixing of fresh and recirculated air can be controlled to maintain a desired indoor air quality (IAQ).

While the primary purpose of a makeup air unit is to provide fresh air for ventilation, it can also provide heating and cooling for the building as needed. The type of heat exchanger used will determine how the MAU can provide heating and cooling.

What are the parts of a make up air unit?

The main parts of a makeup air unit include:

  1. Fresh Air Dampers: To control the amount of fresh air being brought into the system.
  2. Recirculating Air Damper: To control the amount of recirculated air being mixed with the fresh air.
  3. Heating Coil: Used to heat the air being distributed throughout the building.
  4. Cooling Coil: Used to cool the air being distributed throughout the building.
  5. Filters: To remove contaminants from the air being distributed throughout the building.

Is make up air necessary?

A makeup air unit is one way to provide the required fresh air for ventilation. Other options include using an energy recovery ventilator (ERV) or supply fans. An ERV or supply fan can be used without an MAU, but a MAKEUP AIR UNIT IS REQUIRED when using an exhaust-only system.

What are the benefits of using a makeup air unit?

The main benefit of using a makeup air unit is that it provides fresh air for ventilation.

Other benefits include:

  • Can provide heating and cooling as needed.
  • The mixing of fresh and recirculated air can be controlled to maintain a desired indoor air quality (IAQ).

What are the drawbacks of using a makeup air unit?

The main drawback of using a makeup air unit is the initial cost. Makeup air units can be more expensive than other options, such as an energy recovery ventilator (ERV) or supply fan.

What is the difference between an air handler and a make up air unit?

An air handler is a device that circulates and controls the air in a building. The primary purpose of an air handler is to provide ventilation, but it can also provide heating and cooling as needed. A makeup air unit is a type of air handler that provides 100% outside air.

What is the difference between make up air unit and a rooftop unit?

A rooftop unit is a type of air handler that is placed on the roof of a building. A makeup air unit is a type of air handler that provides 100% outside air.

Commercial makeup air unit

A commercial makeup air unit is a type of air handler that conditions 100% outside air. Typically used in industrial or commercial settings, or in “once-through” (blower sections that only blow air one-way into the building), “low flow” (air handling systems that blow air at a low flow rate), or “primary-secondary” (air handling systems that have an air handler or rooftop unit connected to an add-on makeup unit or hood) commercial HVAC systems. Abbreviated MAU.

Make-up air unit for kitchen hood

A make-up air unit for a kitchen hood is a type of commercial makeup air unit that is typically used in restaurants. It provides 100% outside air to the hood and is connected to the exhaust system.

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