Fan Performance Test and Evaluation Methodology: Addressing the Difficulties of Full and Partial Capacity Testing When the Specified and Site Conditions Don’t Match

For many years now, an increased emphasis has been placed on the energy requirements of electric motor driven equipment. For end-users footing monthly electrical bills, efficiency is important along with the assurance that the equipment delivers the specified output. With fans, it is now commonplace to put performance guarantees in place when purchasing new equipment which specify volume flow, pressure requirements and expectations for efficiency or power that have to be met. Test procedures suitable for conducting fan performance guarantee tests are available in many published AMCA, ASME, ANSI, BS and ISO performance test standards and codes. These procedures specify how to measure the fan performance at discrete operating points and provide uncertainty analysis methods to estimate the accuracy of the test. Some test standards are believed to provide more accurate field test results than others. It is generally recognized throughout industry that it is virtually impossible to have suitable correlation between the site and the specified design conditions for the purpose of a ‘guarantee test’. This is often due to differences in the actual system resistance compared to what was predicted by the original design calculations as well as difficulties of adjusting system resistance and maintaining system stability with a process operating on line. The method of fan volume flow control, whether variable speed or throttle control, influences the amount of time and effort required to get the test point as close as possible to the specified operating point. With possibly the exception of AMCA and BS, published test standards and codes generally do not provide methods for evaluating whether the performance guaranteed by the fan vendor has been verified by a performance test. This technical paper provides guidelines for how to approach the difficult problem of verifying guaranteed operating points on fans. It specifically deals with the following aspects: - Evaluation of both partial and full capacity operating points. - Data collection methodology for selecting the number and relative positions of performance test points that are required to verify a guaranteed operating point. - Evaluation methodology that will relate the test points obtained to the specified operating point; Single Point, Multiple Point Line and Multiple Point Box data collection and evaluation methods. - Potential acceptance tolerances for flow, pressure, power and/or efficiency of the guaranteed operating point. - Field test accuracy and the implications on acceptance tolerances.