In order for commercial kitchen fans to operate safely, it must replace air that is exhausted from the inside to the outside. As a result, the Uniform Mechanical Code, or UMC, mandates the use of make-up air for commercial kitchens. Make-up air is defined as air that is pushed or pulled into a building proportional to the amount of air exhausted by the kitchen fan. This make-up air helps prevent backdrafting from combustion appliances such as fireplaces or gas water heaters located in the restaurant. Make-up air is also used to help trap various kinds of emissions from cooking surfaces.

The installation of an efficient make-up air system ensures that the kitchen does not experience large amounts of air being drawn in from outside. Otherwise, diners could experience uncomfortable drafts. This make-up air can also be tempered (heated or cooled), to increase the comfort of your kitchen staff.

A kitchen ventilation system has to include a make-up air system, and this system must pass certain performance-based criteria to operate safely. If you are planning to install a new ventilation system, there are six steps you should consider concerning the design of your make-up air system.

Step No. 1 – Review the type  and size of hood and the type of cooking appliances that will be serviced by the hood.  This info will be one of the factors to help determine the size of the MUA unit.

Step No. 2 – Make sure you carefully consider where the make-up air will be introduced. Over the last several decades many exhaust systems were designed with a short circuit hood, supplying the air directly into the hood.  The recent trend has been to move away from short circuit hoods as they are believed to be less effective at capturing heat, grease, and smoke.  Many designs now utilize make up air that is introduced outside of the hood.

Step No. 3 – Determine the amount of make-up air that you need.  Ensure the make-up air system is properly engineered to work with the fan and hood it services.  Many engineers are sizing MUA systems to replace about 90% of the exhausted air.  This helps keep unwanted smells from entering the dining room enhancing the customers dining experience.

Step No. 4 – Determine whether or not you want to temper the make-up air. Unless you are located in a very mild climate, you will probably be required by code to do so – especially during very cold weather.

Step No. 5 – Develop a strategy for controlling the system. Your make-up air system is required to work whenever the kitchen exhaust is running. Additionally, installing advanced controls for Demand Control Ventilation can reduce the energy consumed by the system.

Step No. 6 – Review local codes and your buildings requirements.  Some applications will call for an indirect fired verses a more efficient direct fired system, or you may need to consider where the unit’s air intake is located to ensure it’s not located too close to the outlet on the exhaust fan.

 

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