Optimized Fan Control In Variable Air Volume HVAC Systems Using Static Pressure Resets: Strategy Selection and Savings Analysis

The potential of static pressure reset (SPR) control to save fan energy in variable air volume HVAC systems has been well documented. Current research has focused on the creation of reset strategies depending on specific system features. As the commissioning process has begun to require the prediction of savings, knowledge of the extent to which various SPR control strategies impact fan energy has become increasingly important. This research aims to document existing SPR control strategies and utilize building data and simulation to estimate fan energy use. A comprehensive review of the literature pertaining to SPR control was performed and the results were organized into a top-down flow chart tool. Based on the type of feedback available from a particular system, or lack thereof, this tool will facilitate the selection of a SPR control strategy. A field experiment was conducted on a single duct variable air volume system with fixed discharge air temperature and static pressure setpoints. Finally, an air-side model of the experimental system was created using detailed building design information and calibrated using field measurements. This model was used to estimate the fan energy required to supply the trended airflow data using fixed static pressure (FSP) and SPR control based on zone demand, system demand, and outside air temperature. While utilizing trend data from November 1, 2008 to February 12, 2009, the FSP control of the experimental system was used as the baseline for ranking the energy savings potential of nine different forms of duct static pressure control. The highest savings (73-74%) were achieved using zonal demand based SPR control. System demand based SPR control yielded savings ranging from 59 to 76%, which increased when the duct sensor was positioned near the fan discharge and under similar zone load conditions. The outside air temperature based SPR control yielded savings of 65% since the experimental system supplied primarily perimeter zones. Finally, increasing the FSP setpoint from 2 to 3 inWG increased fan energy by 45%, while decreasing the setpoint from 2 to 1 inWG decreased fan energy by 41%.