A Better Way to Compare Pump Efficiency
/By Chad Edmondson
Comparing pump efficiency just got a whole lot easier thanks to a new rating system developed by the Hydraulic Institute (HI).
For the first time ever, pump specifiers or purchasers can go directly to an online tool where they can compare the numerical efficiency scores of any pumps that have been tested and shown to meet the latest baseline efficiency standard established by the Department of Energy (DOE).
The HI Energy Rating System is the product of several years of collaboration between the HI, DOE and various energy efficiency organizations to develop verifiable test procedures and infrastructure for rating pumps. The HI is an association of pump manufacturers in North America that develops and publishes pump standards and guidelines and serves as a comprehensive resource to the pump industry as a whole.
Over a thousand Xylem (Bell & Gossett, Goulds and Marlow) pumps, as well as other brands, have already been tested to the HI/DOE standard and are listed with their efficiency score in the HI’s online database. More brands and models are certain to follow.
Apples-to-Apples Pump Efficiency Comparison
The HI Energy Rating System is a significant development because it provides a straight forward apple-to-apples comparison of pump efficiency. Much like the nutrition label that now adorns packaged food (but far easier to read!), the HI label is a thoroughly standardized snapshot of a pump’s efficiency profile. Most importantly, it clearly distinguishes the efficiencies of constant and variable speed pumps, something that previous rating systems did not do.
Previously under the DOE pump efficiency standard, manufacturers could opt to have their pumps rated (and sold) based on constant speed, variable speed or both, while not taking into account that the user may be seeking a pump for constant speed operation only. Clearly, any pump is more efficient with a variable speed control, so it is vitally important that specifiers seek out pumps that carry a constant speed rating. This is the only way to ensure optimum efficiency regardless of operating mode. Furthermore, under the new efficiency standard, some pumps will not be allowed to be sold into the market unless they are supplied with a VFD because otherwise they do not meet the standard. This may very well confuse well-meaning specifiers who aren’t aware of this rather significant change and could easily result in errors in pump orders.
Fortunately, the HI rating label clearly distinguishes whether a pump is rated based on constant speed (“Bare”) operation or from variable speed (“Continuous Control”) operation. Notice the following HI Efficiency Rating labels for two Bell & Gossett pumps. The first label clearly shows that this is the efficiency of the pump at variable load, while the second label shows a rating for the pump at constant load. Both pumps meet the new efficiency standards, but the variable speed pump yields a significantly higher efficiency. So, if an engineer is looking for a constant speed pump, he or she can specifically compare the constant speed efficiency of pumps that are listed in the HI database and do the same for variable speed pumps.
Spend some time scanning the lists of rated pumps using the HI online tool and it won’t take long to discover the disparity between constant speed and variable speed ratings. You may also notice that not every manufacturer has HI labeled constant speed pumps. That’s simply because it is difficult to meet the DOE efficiency threshold with a constant speed pump.
