Consulting-Specifying Engineer - January 2008 - (Page 52) AMCA standardizes induced flow fan rating How AMCA developed a new certified rating standard for induced flow fans. BY JOE BROOKS ir Movement and Control Assn. International Inc. (AMCA) Standard 260-07 “Laboratory Methods of Testing Induced Flow Fans for Rating” establishes a uniform method of laboratory testing for fans. The standard determines the aerodynamic performance in terms of inlet and outlet airflow rate, pressure developed, power consumption, air density, speed of rotation, and efficiency. This standard supports ANSI/AMCA Standard 210-99, “Laboratory Methods of A To ensure that a specified induced flow fan will have the expected performance, engineers should include language that the fan is in accordance with AMCA 260-07. Testing Fans for Aerodynamic Performance Rating” to accommodate the induced flow fan’s unique characteristics. To ensure that a specified induced flow fan will have the expected performance, engineers should include language that the fan is tested in accordance with AMCA 260-07. An induced flow fan is a housed fan whose outlet airflow is greater than its inlet airflow due to an induced airflow. An induced flow fan uses a nozzle and windband on the outlet to enhance induction (see Figure 1). Typically, this type of fan is installed as an alternative to a traditional centrifugal or axial fan that exhausts into a stack. Induced flow fans do not exhaust into a stack, but may or may not have ducted inlets. These fans generally are used in laboratory or hazardous atmosphere exhaust applications. Standard 260 and its corresponding Certified Rating Program were developed to answer questions such as, “What is an induced flow fan, how is its performance quantified, why does it need AMCA certified ratings, and what does the AMCA certified ratings program accomplish?” Recently, at the ASHRAE technical meeting, “Should Induced Flow Fans be Certified?” these questions were discussed. During the seminar, wind engineering and airflow analysis expert Ron Petersen, vice president and principal-in-charge of air quality services at CPP Inc., Fort Collins, Colo., presented examples of what products were marketed along with manufacturers’ performance claims. Specific needs of professionals in the laboratory or hazardous exhaust fields were presented in comparison to the performance specification made available by manufacturers. In some cases, the promotion of inadequate ratings occurred. The summary included a recommendation that said, “Vendors supply certified flows and exhaust diameter (or area) in their specifications for use in numerical or wind tunnel air quality assessments.” Accurate ratings are needed to enhance the health and safety of building occupants and for energy minimization assessments. Because the majority of manufacturers of these fans are AMCA members, and because AMCA has a great amount of certification experience, it was only natural for AMCA to lead the development of a new Certified Ratings Program. A standard is born AMCA previously certified the inlet air performance of induced flow fans using an AMCA 210/ASHRAE 51 airflow measurement setup on the inlet that measures the airflow through the fan only (see Figure 2). However, this did not totally satisfy the needs of the user, as Petersen’s seminar showed. Consequently, AMCA members that manufacture these products formed a committee that developed an initial certification program. The program’s goals were to meet the needs of the user, provide the information for input into numerical models, wind tunnel modeling for air quality assessment, and also provide a level competitive playing field for manufacturers’ products. This committee included manufacturers, engineers, and induced flow fan experts who discussed particular problems in the industry. The first key to developing a certified rating for induced flow fan performance is the determination of specific customer and industry needs. Petersen’s seminar and the expertise of the committee members were critical important parameters had to be resolved, including: • Outlet airflow • Outlet area • Thrust • Crosswind effects • Outlet velocity. 52 Consulting-Specifying Engineer • JANUARY 2008
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