ASHRAE Journal - November 2009 - 44

ASHRAE59–2009 YE A R S JOURNAL concluSion Pump impeller trimming has several advantages, the first of which is a short simple payback (often the criteria driving project implementation decisions). the simple payback was discovered to be less than two years for most buildings. Another advantage is that the impeller trim balancing procedure is relatively simple to implement. it is based on well understood—albeit seldomly applied—engineering principles. the implementation requires commonly available pressure measuring instruments, such as a differential pressure gage or Bourdon pressure gages with pressure test plugs. the actual impeller trimming process involves two steps: trimming the impeller and balancing it, usually with a dynamic or static balancing apparatus. the necessary equipment is commonly available in machine shops. Finally, all of the systems in the study were found to have a 100% standby pump so that impeller modifications in a retrofit application could be carried out in mid-season without disrupting building operations or comfort. Pump impeller trimming could be economically beneficial to large endusers such as universities, school districts, and state and federal buildings, which have a large number of pumps in use. the operating efficiency of pumps can be improved in existing buildings and new construction projects. Existing buildings exhibit a potential for energy savings. in this study more than 90% of the 27 pumps studied showed a potential for saving energy and reducing pump operating costs. impeller trimming can also be used on new projects. in fact, the benefits in new projects may be greater than in an existing building, since the incremental cost of the impeller trimming will be lower than in a retrofit application. On new projects, the engineer can specify the balancing contractor to recommend the proper diameter impeller and specify that throttling the balancing valve is unacceptable. Specifications must require the impeller to be statically or dynamically balanced after trimming. it may be best to have the trimming done through the pump manufacturer to ensure quality for the pump’s performance. the manufacturer can also furnish an updated nameplate tag that reflects the as-built condition of the pumps. Management for his guidance in collecting the field data. Acknowledgments This study was conducted under the Demonstration of Energy-Efficient Developments (DEED) scholarship program of the American Public Power Association (APPA). The study was sponsored through Algoma Utility Commission, Algoma, Wis. The authors are indebted to the APPA and Algoma Utility Commission for making this study possible. They would also like to acknowledge Gil Sommer of ITT Bell and Gossett for his constructive comments on pump systems, and Kevin Corcoran of the University of Wisconsin Department of Facilities Planning and References www.info.hotims.com/25210-44 1. Energy Information Administration (EIA). 1995 Commercial Building Energy Consumption Survey. March 13 1997. www.eia.doe.gov. 2. ASHRAE. 1995. ASHRAE HandbookApplications: Chapter 34: Testing, Adjusting and Balancing, Atlanta: American Society of Heating, Refrigerating, and AirConditioning Engineers, Inc. 3. Nadel, Steve et. al. 1992. Energy-Efficient Motor Systems: A Handbook on Technology, Programs and Policy Opportunities. ACEEE. 4. Gladstone, John. 1995. Mechanical Estimating Guidebook, sixth edition, New York: McGraw Hill. 5. Madison Gas & Electric Company. 1995. Residential and Commercial Electric and Gas Service Rates (Effective January 1, 1995), MG&E Rates Brochure. 6. Commercial Electric Rates. 1996. Energy User News, May 1996. Radner: Chilton News Magazine. November 2009 ASHRAE Journal a s h r a e. o rg

ASHRAE Journal - November 2009

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