In 2015, Bonneville Power Administration contracted with SBW to develop an Advanced Rooftop Control (ARC) savings calculator. The methodology automated in the ARC calculator was tested against work done by Bill Koran for BPA to evaluate post install savings for VFDs.
The ARC calculator requires ex post power, speed, and temperature data to perform statistical calculations of savings. Ex ante performance is extrapolated by developing fan curves to back out energy use without the advanced rooftop unit controls. These calculations were all designed to be normalized with TMY3 data to predict savings for a typical year within the BPA service region. The calculator can estimate savings for up to 7 speed settings on a control unit, or a true variable speed control. Savings can be calculated for any gas heated or heat pump rooftop units.
To use the ARC calculator, download the zipped file from the Materials section and then decompress the folder on your computer or network. Open the document labeled ARC_V1-01 which was created in Excel 2010. Instructions are provided on each sheet. Sample data files are also included in the zipped folder.