C018 -- Pump Right-Sizing and Flow Control Strategies to Improve Hydronic Building Space Heating Systems

Hydronic distribution systems account for approximately 20% of the world’s energy use per a study by US DOE and the Hydraulic Institute. Many existing pumps and motors are oversized in capacity by more than 20%, applied with a 100% capacity redundancy in the form of an extra pump, and operated at a constant speed throughout the heating season. Triple duty and balance valves are often implemented in design to throttle the pump flow to match design. Due to equipment oversizing, the actual operating point often does not position well with the pump’s best efficiency point. This leads to decreased pump efficiencies, higher motor electricity consumption, and increased maintenance and operational costs due to excessive wear of system components. Over pumping reduces boiler loop differential temperature resulting in more frequent boiler cycling, inefficiencies, and increased gas use. GTI Energy performed demonstrations of emerging space heating hot water distribution system improvements to generate electricity savings while minimizing capital investments and maintaining resiliency at two (2) Illinois Army National Guard (ILANG) Facilities. This demonstration sought to generate electricity savings by optimizing the pump selection process through a “right-sizing” approach, while also improving system operation through variable flow conversion and parallel pump controls. Application economics, lessons learned, installation best practices and commissioning processes to ensure success are also presented. Site A involved retrofitting an existing pump with a Variable Frequency Drive (VFD) to develop a system performance curve. A right-sized pump was then selected to provide the constant system flow rate of 250 gpm (15.8 lps) and achieved a significant reduction in power draw from 11.06 hp (8.25 kW) to 2.9 hp (2.16 kW) and reduced electric consumption of 74%. Site B’s oversized building loops pumps operated at constant speed with 100% capacity redundancy. These pumps were replaced with right-sized pumps, with on-board Sensorless Electronically Commutated Motor (ECM) Controls and operated in parallel to serve the building zones. The secondary loop flowrate was commissioned by ensuring the flowrate at the extreme end-of-the-loop coil matched the coil specifications during design day conditions. This demonstration at Site B decreased electric demand from 1.38 hp (1.03 kW) to below 0.67 hp (0.5 kW) and reduced electric consumption by 46%.