In the operation of commercial or institutional kitchens (e.g., restaurants, hospitals, schools), a substantial amount of the heat generated by the cooking equipment is wasted and lost with flue gases which are vented to the exterior of the building. In fact, due to the relatively large generation of heat, smoke and the like by such cooking units, a substantial problem is caused through the necessity for removal of these materials in the wintertime, particularly in more intemperate climates, where exhausting relatively large volumes of air from such a kitchen requires replacement with air which must be heated to bring it up to room temperature. Thus, for example, in the eastern and northern portions of the United States in the wintertime, external temperature can be quite low, and, therefore, makeup air brought into the kitchen from the outside may have to be heated more than 50.degree. F. to achieve the usually desired 70.degree. F. temperature. Moreover, throughout substantially the entire United States, during wintertime night-time hours of operation, makeup air must be heated.
In addition, the usual commercial or institutional kitchen has considerable need for hot water, and, in the past, this has only been met by the use of a separate source of energy, either fuel gas or electricity. Of course, the requisite energy for heating water to use in the kitchen or elsewhere in the facility is in addition to any other energy required for heating the makeup air already referenced.
As used herein, and in regard to which the subject invention is especially advantageous, the term "cooking equipment" shall preferably mean a gas-fired cooking stove or range, typically used in a commercial or institutional kitchen, and usually including a plurality of different heating sections, with open burners in certain sections, griddles in others, deep frying sections and ovens in still further sections. It is also contemplated that the term can embrace other gas-fired cooking devices such as enclosed broilers, steam cookers, steam generators and the like which are typically found in commercial and institutional kitchens.