Notice that as the outside air temperature dropped this day, the supply water temperature would have risen, based on the original reset schedule. The energy conservation demand signal, from the coolest room, determined that the water temperature should have done the opposite, and reduce the hot water supply temperature to exactly match the heating requirement of the coolest of the sample rooms. ENERGY CONSERVATION DEMAND SIGNAL ACTUAL OUTSIDE AIR TEMPERATURE HOT WATER SUPPLY TEMPERATURE, RESET FROM COOLEST ROOM HOT WATER SUPPLY TEMPERATURE, BASED ON OUTSIDE AIR TEMPERATURE 106°F 98°F 88°F 107°F 5°F 120°F -152°F 58°F 110°F 155°F 60°F 49°F This graph illustrates the heating water temperature difference between resetting only from the outside air temperature and resetting from the coolest room of the area served. The red line illustrates the water temperature based on the actual outside air temperature, illustrated by the green line. This is the originally designed reset schedule. The red and green lines are symmetrical. The black line illustrates the water temperature based on the heating requirement of the coolest area served illustrated by the blue line. This is the conservation circuit. The black and blue lines are symmetrical. The coolest room’s signal “tells” the main reset controller that the outside air temperature is a warmer than the actual outside air temperature, causing the reset controller to produce heating water at exactly the correct temperature to keep the coolest room in the comfort zone. Note that the water temperature drops when the coolest school class becomes occupied in the morning: the water temperature rises at noon when the bodies leave the room: it drops when the bodies re-enter the room for the afternoon and rises again when the people leave for the day. HEATING WATER RESET 5.36
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