Description:

What Is This Measure?

Small circulator pumps (< 2.5 horsepower) propel fluid through closed-loop heating and cooling systems to regulate air or water temperature. Researchers evaluated new high-performance variable-speed circulator pumps with automated control that adjust pump speed to meet changing demand. They tested the technology in two common applications at the Denver Federal Center, a domestic hot water (DHW) recirculation system and an air handler unit (AHU). They found that the pumps reduced energy use 26% to 96%, with payback of less than 6 years. The new variable speed pumps should be considered as end-of-life replacements for all constant speed circulator pumps.

Special Considerations

Because differential pressure and accurate flow readings are not readily available for smaller constant-volume circulator pumps, use one of the following methods to right-size the pumps:

• Determine pipe sizes and lengths and then calculate actual head loss from the pipes to estimate the flow (GPM) and head required for the pump.
• Observe supply and return temperature differentials to make an educated guess about the existing pump’s suitability for that system. For example, if the Delta-T is extremely small (2°F to 5°F), the pump is most likely too big.

See GSA’s Green Proving Ground for more details on the field demonstration findings.