EXECUTIVE SUMMARY In many classrooms in Ontario, the heating and ventilation is provided by a fan system called a unitventilator. (See Figure #1 at the back of this report.) The unitventilator is a small fan system dedicated to only one room. Figure #1 is a drawing of the type of unitventilator, which is the subject of this report. They are very inefficient and, at times, have difficulty maintaining the comfort conditions in the classrooms. Over the years, during service, we have witnessed the symptoms of excessive energy use and discomfort in many buildings with unitventilators. This report graphically illustrates the problems with these units and a solution that improves both the energy use as well as the controllability. The problem, from an energy point, with this type of unitventilator is that the hot water flows continuously through the heating coil. A damper arrangement is used to allow the air to flow through the heating coil, deflect the air to bypass the heating coil or blend the air to various temperatures to select the amount of heat the room requires. Even when all the air is theoretically bypassing the coil, heat escapes into the air stream. This causes the unit to automatically bring in excessive fresh air to compensate for the unwanted heat. The problem, from a comfort point, is that often the amount of heat escaping is greater than the cooling capability of the unit, even when the unit is on full cooling. The room over-heats while it is actually ventilating with about 500% more cold fresh air than required by code. Figure #2, at the back of this report, is a drawing of the Energy Conservation Control Circuit that replaced the original heating supply water control circuit. The original circuit was reset based on only the outside air temperature. By modifying the controls to the Energy Conservation Circuit, the system saved: 81.7% on heating energy, on day operation, compared to a system supplied with 171°F supply water (boiler temperature) 58.4% on heating energy, on day operation, compared to a system supplied with water reset from the outside air temperature the unit used 247% more heat with the 171°F supply water on full cooling than the Energy Conservation Circuit used on full heating comfort levels are superior in the occupied space when using the Energy Conservation Circuit 8.129
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