The information obtained from the chart gives a clear picture of the supply water temperature's impact on the energy use of a unitventilator as well as the effect on the comfort level in the room. ENERGY The building was running on the conservation circuit using the Energy Conservation Demand Signal when we got to the building. The rooms were all satisfied and the water supply temperature was 92.3°F. On full cooling the unitventilator was only losing 1.3F° of heat from the supply water as it passed through the unit. When the supply water temperature was raised to the original reset schedule control point of 121.7°F, the unitventilator, which was on full cooling, was losing 3.12F° of heat from the supply water passing through the unit. This is 240% more unwanted heat escaping into the air stream than on the conservation circuit. When the supply water temperature was raised to 171.5°F, to simulate a typical supply water temperature without a secondary loop, the unitventilator, which was on full cooling, was losing 7.1F° of heat from the supply water. This is 546% more unwanted heat escaping into the air stream than on the conservation circuit. The low limit branch pressure increased from 7.8 PSIG on the conservation circuit to 8.3 PSIG on the original reset schedule to 11.8 PSIG on the high temperature water supply. The damper motor has a spring range of five to ten pounds. The actual outside air temperature at the time of the readings was 27°F. While on the high temperature water the unit had to drive to 100% outside air and still could not get the supply air temperature below 64.9°F. The escaped heat caused a 37.9F° temperature gain in the supply air temperature with the unit on full fresh air. COMFORT The low limit branch signal had to gradually increase as the supply water temperature was increased to compensate for the greater amounts of unwanted heat escaping into the unitventilator. The low limit finally lost control in its attempt to provide cooling and the room over-heated while the thermostat and the low limit were both producing signals to demand full cooling. NOTE: When the thermostat was demanding full heat while on the conservation circuit the water differential was 2.8F°. When the thermostat was demanding full cooling on the high temperature water, the water differential was 7.1F°. The system used 247% more heat when on cooling with the high temperature water than it used when on full heating with the conservation circuit. 8.142
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