Variable speed drives enable motors to run at variable speeds. Applied to fans and pumps, variable speed motors can be used to control flow rates without the use of mechanical means such as valves, dampers, and guide vanes. Energy savings are achieved by limiting flow to needed levels, and achieving flow rates more efficiently than a pump or fan operating at full speed with mechanical flow control.
This measure applies to small pumps and fans (up to 20 HP motors) where variable speed control is not required by code for the project. There are measure applications for both retrofit and new project. A retrofit is defined as a project in which the existing fan or pump is not replaced. A drive can be installed on an existing more or the motor can be replaced as part of the project, and the drive may be integrated with the motor. A new project is defined as a project where the fan or pump itself is new.
Savings for fans are based on usage estimates developed in the DOE rulemaking process for commercial and industrial fans and engineering estimates of power draw at various flow rates for different control methods. Savings for pumps are based on NEEA research: metered pump data and simulation of counterfactual systems (e.g., pump without drive where the existing pump has a drive).
This measure is categorized as “Planning” to reflect significant uncertainties in the savings estimates and the need for research on current practice VSD saturation and the pre/post hour of use and load profiles for the range of measure applications.