What are Make-Up Air Units and How Do They Work


As the name suggests, make-up air units are designed to “make-up” and replace the air in an interior space that has been removed by process exhaust fans. It is an HVAC unit which means that it deals with heating, ventilation, and air conditioning. These units have a variety of uses and technologies that enable them to control the temperature, humidity, as well as purity of the air in a building. It essentially works by pulling fresh air through the unit from the outside, tempering it, and replacing the air inside that could otherwise not be recirculated. They are an excellent solution for poorly ventilated buildings or those who have a great need for ventilation. This protects the health of those who work in such buildings. Let’s take a more in-depth look at how make-up air units work.

1. The Set-Up

The MUA unit is generally installed on the top of a building. It is located either in the mechanical room or outside and on the roof of the building. The function of the MUA unit is to “make up” air. In buildings with poor ventilation, it replaces the air that is no longer viable in the building. Air quality can get spoilt in a variety of ways. From people breathing in a poorly vented area to the use of a variety of exhaust systems, both affect the air quality. According to wesellmakeupair.com, MUAs can be “implemented across all industries” and come in a range of different shapes and sizes. Some companies even offer custom MUAs, designed to fit your specifications.

2. Temperature Control (H)

As we said, HVAC systems like make-up air units temper the air, which is just one way it can positively affect the health of those working or living in the building. Temperature control is important. Too hot and people won’t feel comfortable, will struggle to work and machinery could seize up. Too cold and you have a similar set of issues. In the winter the MUA system ensures that the ice-cold air from the outdoors isn’t sucked in directly from the outdoors as is as this would distribute icy air into the building. The cold air is heated to a comfortable temperature, ensuring that your occupants don’t have to wrap themselves in a million blankets to stay warm, and efficient work can take place in a workplace. Likewise, in summer the warm air is sucked in, cooled down, and pumped into the building.

3. Ventilation (V)

Buildings need to have sufficient ventilation in order to be up to code. High-bay warehouses and or distribution centers have typically been able to rely on natural ventilation, but more and more are making the switch to MUA systems. Mechanical ventilation is more efficient as it addresses temperature (covered in the point above) as well as air freshness. Big ventilation fans are often not enough as they simply circulate the existing air inside around, doing nothing for freshness. Fresh air improves comfort in the workplace

4. Air Balancing

Something that doesn’t get spoken about enough is the importance of the air balancing capabilities of an MUA. It is a complex and delicate system that requires calibration in order to work correctly in each space. If you have a complex system that is well integrated into your building, people might be able to mess with it on different floors, shielding vents because they make noise, or they don’t like where the air blows as it comes in. This isn’t an uncommon issue, but definitely something you need to look out for. When people mess with the diffusers, this can interrupt efficient airflow. In order to ensure that the system is working efficiently, hallway grills should be checked regularly. This will make sure that each floor and area in the building is receiving adequate, balanced airflow.

5. It Needs Regular Preventative Maintenance

Maintenance is important, but how much maintenance is necessary and when do things like filters need to get changed? Preventative maintenance stops any serious issues from occurring. MUA filters typically need to be changed once a month but doing preventative maintenance and checking them bi-monthly will ensure that you don’t run into unpleasant and unexpected issues. The rest of the components, including belts and the motor, be inspected, too. The inlet should be lubricated about twice a year to keep it in good running, condition. Lastly, the entire system should be given a thorough service at least once a year.

6. Making Use of Variable Frequency Drives

Variable frequency drives, or VFDs, are an important feature that most newer MUAs have or are sold alongside them. They are installed on your equipment to slow the operation of a motor or pump (whichever option you have) delivering less air during off-peak hours. The VFD is typically set up on a timer and reduces the output percentage. So how do you work out when machines should be producing more and less air? Well, this depends on the building. If we’re talking about an industrial building, peak hours are obviously during work hours when machines are in use and lots of people are in the building. This is when the MUA unit should be operating at optimum efficiency. If we’re talking about a residential building, peak hours are first thing in the morning and after people arrive home from work at the end of the day, and the building is once again filled with people. Things like dryers, showering, cooking, etc all take place at the end of the day, and without the system operating at its peak, the air quality will decrease pretty quickly. Making use of this technology not only puts less strain on the unit itself but keeps unnecessary costs down.

Whether it’s a residential building, commercial building, or industrial building, good quality air is important. Some buildings are better equipped for fresh air circulation, but many need a boost. Make-up air units are just the thing and the boost you need. Now that you know what it is and how it works, consider replacing the substandard ventilation system your building might have and enjoying improved air quality.


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