CC Retrofits and Optimal Controls for Hot Water Systems

Abstract

Boilers account for about 42% of space heating energy consumption in commercial and multifamily buildings in the U.S. Boilers are typically designed to be oversized, with redundant safety factors and without consideration of internal heat gains. Significant energy savings could be achieved by optimizing the selection of commercial boiler systems and utilizing proper operation and optimal controls. This paper presents a case study in which the boilers are significantly oversized. After implementing Continuous Commissioning (CC) technologies, three old boilers (13.39 MMBH each) were replaced by three new boilers (1.675 MMBH each) and hot water pumps. Optimal controls for the hot water systems included optimal hot water temperature reset, hot water pump speed decoupled control, and optimal enable/disable. Heating load and heating capacity were calculated based on EMCS recorded data and hourly measured water flow data. The measured hourly utility data show reductions in annual gas consumption and cost by 36% and 43%, respectively.