Technical Note: Development and Testing of an Induction-Operated Current Switch for Monitoring Fan Operation

Abstract

Emissions of gaseous compounds and particulate matter are the product of the pollutant concentrations and air exhausted from the fans of mechanically ventilated animal confinements. Direct methods of monitoring exhaust fan operation (mercury tilt, limit/ whisker, and vibration switches) have been reported to have limitations due to mechanical failure and/or the effect of dust, wind, and moisture. The objective of this study was to find a reliable method of monitoring fan operation status. This article describes the development, lab testing, and field use of a fan monitoring system based on an induction-operated current switch (ICS). The ICS is unaffected by the environment and can provide direct measurement of real-time fan operational status by sensing the AC current drawn by the fan motor. A laboratory test of the ICS was performed to simulate a fan off/on duty cycle for a two-year field emissions monitoring study; no ICS failure was recorded. Three studies led by Iowa State University (Southeastern Broiler Gaseous and Particulate Matter Emission, Determining Ammonia and Particulate Matter Emissions from a Midwest Turkey Grow-Out Building, and Feeding DDGS and Other Altered Diets to Egg Laying Hens to Demonstrate Economically Viable Reductions in Ammonia Emissions) used a total of 28, 12, and 50 ICS systems for 24, 16, and 27 months, respectively, without a non-user error related failure. At a unit cost as low as $21.45 this method offers a reliable, accurate, and economical way of measuring the real-time operational status of ventilation fans – a critical component of any air emissions monitoring in a mechanically ventilated confinement.