Typically a commercial kitchen includes a stove or a cooking unit. Over the stove or cooking unit there is provided an exhaust hood. During the cooking operation, air is pulled over the stove and up through the exhaust hood where the air, laden with smoke, cooking aromas, etc. is exhausted from the kitchen and eventually the building. Because the exhaust system continuously draws air from the kitchen area, it is necessary to replenish air to the kitchen area. This is typically provided by what is often termed a makeup air unit. Makeup air units pull ambient air from the outside the building and disperse the air into the kitchen area. In moderate climates it is appropriate to disperse the makeup air in the vicinity of the exhaust hood. Consequently the dispersed makeup air is simply pulled over the stove area and out the exhaust system.
In cold and hot climates a problem can be presented. By simply directing ambient air into the kitchen area, it can be difficult to control the temperature within the kitchen at a comfortable level. Thus, it is known to condition the ambient air prior to the air being dispersed into the kitchen area. For example, in extremely cold environments it is beneficial in some cases to heat the makeup air before the air is dispersed into the kitchen. In extremely hot climates it may be beneficial to cool the air prior to the air being dispersed into the kitchen. However, conditioning the makeup air before dispersement into the kitchen can be an expensive undertaking. This is because some of the conditioned air will immediately be induced into the area over the stove and up and through the exhaust system. Thus, the energy required to condition that portion of the makeup air is not effectively utilized.
Therefore, to conserve energy and to provide a more cost effective make up system for commercial kitchens, it is desirable to provide a makeup air system that will provide two systems or streams of air, an untempered system of air and a tempered system of air. The idea is to provide a system where the untempered or ambient air is truly makeup air inasmuch as a substantial portion of that air stream is utilized to be recirculated over the stove and out the exhaust systems, while the tempered system or stream of air can be utilized to heat or cool the kitchen area. The problem is to devise a system where these two systems of air can be efficiently provided and controlled such that a majority or a substantial portion of the untempered air is utilized for exhaust purposes while a majority or a substantial portion of the tempered air is used for heating or cooling and generally making the kitchen area comfortable.