Make-Up Air Unit
A complete ventilation system consists of equal parts exhaust air and replacement air. Exhausting air is a simple concept and easily understood, however the corresponding replacement air, commonly referred to as make up air, is often misunderstood or overlooked.
The ill effects of an unbalanced ventilation system are widespread and have a significant impact on everything from personnel health to manufacturing processes.
For this reason we will be focusing this discussion on replacement air and the corresponding make-up air unit to provide it (aka MUA unit).
It is important to know that one cannot work without other. Simply put, for an exhaust fan to extract air it must have air to extract.
If enough air is depleted within a space one of two things will happen:
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Most buildings are not tight enough to result in the latter, so so replacement air is drawn into the building through cracks, seams and openings around the structure.
Left uncontrolled the air will enter through any opening it can find. Commonly referred to as “drafts”, entry can be found around doors, windows, cracks in walls, drains, roof openings, Flue pipes, etc.
The heaviest influxes of air enter through open doors and windows as these are large openings and serve as a path of least resistance.
You may have experienced heavy influxes of air through doors and windows on days with little to no wind, air traveling fast and far, disrupting everything in its path including both people and process.
This is a perfect example of air stampeding in an effort to balance the building pressure.
This unintended and uncontrolled method of replacing air is inefficient, dangerous and unhealthy. Because the air being introduced is at a lesser rate than the exhaust, the space remains under a negative pressure.
This negative pressure allows contaminated air, including viruses (learn how to kill germs in HVAC systems here), bacteria and products of combustion to remain in both the office and manufacturing spaces for longer than intended.
The decreased air exchange has damaging effects on the indoor air quality, (IAQ) which compromises the overall health of the building and places personnel at risk of getting sick. Additionally, the negative pressure demands that all exhaust and HVAC equipment work harder to reach the original design points resulting in more energy usage for a lesser result.
In summary, a building under a negative is dangerous, unhealthy and costs significantly more to operate.
Whatever your building, there is a solution. An Air Handling Unit (AHU) or Makeup Air Unit (MUA or MAU).
We are official distributors of top make up air unit manufactures in the USA. As official representatives, we’ll be happy to help explain the best make up air unit for your application. Contact us for a quote or if you have any questions regarding industrial & commercial MUA.
Make-up Air Unit Diagram
What Does a Make-up Air Unit Do?
Simply put, a make-up air unit provides replacement air. The purpose of a make-up air unit is to replace the air exhausted from a space by general ventilation, process equipment, heaters and other HVAC equipment. By replacing the air the building is brought to a neutral or pre-determined building pressure.
This balanced building pressure allows the building to operate as intended with HVAC systems, manufacturing processes, etc. performing at peak efficiencies.
The result is a healthy building with good indoor air quality (IAQ), a healthy staff and lower energy costs.
The costs of a makeup air unit are often recuperated through the energy savings made up from lesser HVAC demands, lower exhaust demand, higher production levels, increased production, decreased personnel sick leave and other corresponding factors.
Make-up air is a significant benefit to any space using exhaust.
What is a Makeup Air Unit?
A Make-up Air Unit is mechanical piece of equipment designed to provide a consistent and controlled solution to replacing the air within the space. This can be as simple as a fan blowing air into the space or a more engineered approach including tempered air, filtration as well as other options.
However it is conveyed, the system is designed to introduce fresh outdoor air back to the space. A make-up air solution is recommended for buildings where environmental conditions warrant a greater need for ventilation not only to improve the quality of air within the building, but also protect the health of those inside.
Benefits of Make-Up Air System
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Make Up Air Unit Features
To best understand a traditional makeup air system we should first start with its construction. In its most basic form, a makeup air unit is a fan within a metal box.
These fan boxes are often modular and can be built to accommodate many requirements.
A traditional makeup air unit typically includes:
This is the basic construction, but certainly not the limitation.
Types of Make Up Air Units
Additionally, there are many types of makeup air units that can be provided with a variety of heating and cooling options including:
Make-up air systems are utilized in commercial, institutional and industrial applications. As each segment is different they often serve a variety of functions.
Commercial Make Up Air Units
Commercial make up air units are able to offer fresh MUA fans for all types of exhaust hood sizes with various airflow rates up to 100,000 cfm (cfm Wikipedia).
There are many configurations involved with commercial MUA systems. They typically have filters made of powered coated steel and also heavy gauge galvanized steel. Most models have blower fans that are powered by belt-drive motors, which are enclosed in weather protected cabinets for year-round protection.
The focus of our discussion will be on the industrial marketplace.
Industrial Make Up Air Units
Industrial makeup air incorporates all of the concepts and options available to other markets but on a larger scale. Industrial grade materials are used in the construction of the unit.
Furthermore, industrial MUA can push in more air, which is typically a requirement for larger areas and structures.
MUA Mounting Options
An industrial makeup air unit can provide as little as a couple hundred cubic feet per minute and as much as several hundred thousand cfm. In addition, the industrial MUA unit provides several other mounting options and a significantly broader operating range.
Buildings with contaminated air, such as manufacturing or processing facilities, typically introduce 100% outside air (O/A) or fresh air. This ensures the process equipment and employees are delivered fresh clean breathing air.
This recirculation feature allows for large amounts of air to be conditioned at a low operating cost while still introducing enough fresh air to provide the air changes necessary to meet local codes.
In all cases the intent is to provide healthy, tempered air to the space. The fresh, conditioned air provided makes for a better working environment resulting in less complaints and greater production.
The industrial makeup air equipment also provides a wide offering of heating and cooling options that can be installed together or independently.
Make-Up Air Unit Systems
In many cases make-up air systems require conditioning. Most can be provided with heating and cooling options to accommodate the requirement of the space.
Direct Gas Fired Make-Up Air
Direct-fired make-up air heaters are used to introduce heated air into a building. Direct-gas fired heat is by far the most efficient form for MAU. This is due to 100% of the heat being generated is delivered into the space.
This efficiency leads to significant cost saving over other methods in both equipment costs and operating costs. This heat can be served by natural gas or liquid propane.
There are limitations using direct gas fired heat because a limited amount of gas byproduct is introduced to the space, however the safeties included within the equipment limit and protect the people within the building from any ill effects.
Direct gas fired MUA can be recirculated but is limited to a maximum amount of 85% recirculated air to maintain the minimum thresholds set by ANSI.
Compact low CFM Direct Fire Heater
Modular Direct Fired Heater
Horizontal Industrial Direct Fired Heater
Horizontal Industrial Direct Fired Recirculating Heater
Vertical Industrial Direct Fired Heater
Vertical Industrial Direct Recirculating Fired Heater
Indirect Gas Fired Heaters
Indirect gas fired heaters are similar to most home furnaces in the way they work. These heaters utilize a heat exchanger. The gas fired flame is contained within a system of metal tubes known as a heat exchanger.
The incoming air is then drawn across this heat exchanger and the air is heated.
The heat exchanger is connected to an exhaust flue that discharges the gas byproducts out of the building making the air 100% clean.
This system is ideal for residential, institutional and office spaces as it does not introduce any byproducts or additional humidity to the space.
Because the air is so clean and dry, this system is the perfect candidate to heat rooms where mold is a concern. The air using an indirect fired heater can be recirculated up to 100%.
This system of heat typically carries the largest footprint for makeup air as well the highest equipment cost.
Non-Gas Fired MUA
There are several other types of MUA units that can be configured without the use of gas. They can be configured using electricity, steam coils, or hot water. Depending on what your application needs.
Electric MUA commonly applied where there are frequent air changes. These heaters can be installed indoor or out.
Common applications are for kitchens, factories, and similar commercial & industrial environments. Electric Make up air units can be used as combination packages that include an exhaust and supply fans that are mounted on the same roof.
There are many variations of In direct gas fired make-up air systems such as:
Modular In Direct Fired Heater
Cooling Make Up Air Units
Packaged DX Cooling
The DX cooling module is similar to most HVAC systems.
The DX coil utilizes refrigerant running through a coil to remove humidity and deliver cool air to a space. The coil is supplied by a condenser that can be incorporated as part of the unit or set separately.
This is a very common design and often understood by most HVAC contractors. These units can be installed both indoors and/or outdoors depending on the application. DX air handlers can be used in combination with other modules, such as direct or indirect gas fired heaters.
Chilled Water Cooling
The chilled water cooling module is quite common in the industrial sector. The coil is mounted within the MUA housing and air is drawn over to provide a temperature reduction. The coil is fed by a stand-alone water chiller which delivers cold water to the coil.
An incredibly effective means of cooling, chilled water is most often used in larger air handlers. These units can be installed both indoors and/or outdoors depending on the application.
Chilled water air handlers can be used in combination with other modules, such as direct or indirect gas fired heaters.
The evaporative cooling module is designed to deliver humidified, cooled air for areas that are hot and dry. Mixing the cool moisture with hot dry air will provide a significant temperature drop.
These units can be installed both indoors and/or outdoors depending on the application. Evaporative air handlers can be used in combination with other modules, such as direct or indirect gas fired heaters.
Untempered (Fan Box)
A make-up air unit fan, also known as a fan box, brings in fresh outside air without a heating or cooling element. This provides the required air changes while maintaining, or possibly reducing, the building temperature.
Fan boxes are ideal for applications where specific operating conditions are not a requirement. They are great for summer cooling and can provide a clean replacement air solution at minimal equipment and operating costs.
We are official distributors of the manufactures listed below. As official representatives, we’ll be happy to help explain the best make up air unit for your application. Contact us for a quote or any information regarding their products.
Make Up Air Manufactures
We are official distributors of the top rated make up air unit manufactures in the USA. As official representatives, we’ll be happy to help explain the best make up air unit for your application. Contact us for a quote or if you have any questions regarding industrial & commercial MUA.
Setting the standard for leadership in direct-fired "total air management" systems. AbsolutAire is meeting today’s needs for cost-effective make-up air, as well as for efficient heating and ventilating.
Manufacturing quality products to meet the needs of the ventilation industry for 35 years. Continuing to invest into research and testing to improve the efficiency of our make up air units.
Moffitt Corporation designs, manufactures, and installs ventilation equipment. The Moffitt team serves facilities ranging from commercial and institutional to heavy industrial.
We’ll be happy to help explain which model and make is best for your application.
R. Williamson & Associates goal is to continually supply and distribute their ventilation equipment with fast turn around time and great service.
From product selection to providing installation solutions, R. Williamson & Associates is here for your industrial ventilation needs.
Please take the time and learn more about us.
We supply our systems to a variety of different industrial and commercial facilities. Make-up air systems improve facility air quality which is perfect for industries with greater ventilation needs. Some industries that often require make-up air systems include: