HOW TO GET MORE OUT OF YOUR FANS AND CIRCULATION SYSTEM There are many things that influence how well your circulation system performs and how efficient it moves air and we have listed some basic guidelines below. The electrical efficiency of the total system also needs to be a major consideration but there are other, sometimes forgotten, major benefits to be obtained from an air circulation system. Winter destratification could pay for the whole system in power savings alone! Please see below for more information. Using the right fan for the right job * Ventilation fans move large volumes of air over short distances at low speed while circulation fans move relativly small amounts of air over larger distances at high velocity. For people cooling you need air velocity. * Never position fans to blow towards each other – they cancel each other out. *Never blow air into a ‘boxed’ area where air cannot flow freely out or the area will pressurize. *Never position a wall or roof exhaust fan near an outside opening or “short circuiting” will occur. Designing the system *Balance the building with the right number of air changes. *Decide upon the required air velocity based on the type of work going on in the building. *Choose the size and type of equipment to produce that velocity. * Design the circulation system to bring fresh air into the building, circulate it at velocity throughout the building and to remove the heated, stale air out of the building. *Utilize existing ventilation and circulation equipment in the design as much as possible or re-position or turn off. Redco-USA can advise on system design so that you achieve maximum benefit. HOW DO YOU KNOW THE EFFICIENCY OF A FAN? Ventilation fans have always been measured by CFM – the volume of air that moved through the unit every minute – but until recently there was no impartial measurement of how power efficiently that air was being moved and there was certainly no standard for circulation fan efficiencies. Bioenvironmental and Structural Systems laboratories (BESS), part of the University of Illinois, are in the process of testing both circulation and exhaust fans to establish minimum power efficiencies and these results to date can be viewed, by manufacturer, on the following websites.
The following table represents the mimimum efficiency standards produced by this research. To compare fans not measured in this way, multiply motor amp requirement by operating voltage and divide into cfm of fan. As an example, a 24” dia fan delivering 5500cfm using 6.5 amps at 115vac would produce 7.35 cfm/watt.
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