By-Pass Blending Station: An Innovative Secondary In-Building Pump System for District Heating and Cooling Systems

An innovative secondary in-building pump system called the By-pass Blending Station (BBS) has been developed to reduce building pump energy consumption and maintain the desired return water temperatures in district heating and cooling systems. This method applies where district systems provide sufficient pump head for in-building water circulation. The BBS moves only the returned by-pass flow. Therefore, it uses less pump energy than the ASHRAE recommended method, which moves the entire building water flow by using in-building pump. The pump in the BBS is smaller than that of the ASHRAE recommended in-building secondary pump system. The BBS can be used in both constant and variable flow secondary systems. This paper compares the ASHRAE recommended secondary in-building pump with BBS systems using chilled water systems. The BBS only applies to cases where the primary distribution systems provide sufficient pump head for in-building circulation, which are typically found in commercial district cooling and heating systems.