Development and Testing of a Fan Monitoring System Using Induction Operated Current Switches

Emissions of gaseous compounds and particulate matter are the product of the pollutant concentrations and air exhausted from the fans of mechanically ventilated animal confinement buildings. Direct methods of monitoring exhaust fan operation (i.e., mercury tilt, limit or whisker, and vibration switches) have been reported to have limitations due to mechanical failure and/or the effect of the environment (dust, wind, moisture). Another method involves monitoring the control relay status at the fan system control box. A problem could occur at the fan but not in the signal at the control box, thereby giving a false operational signal. The objective of this project was to find a more reliable method of monitoring fan operation status. This paper describes the development, lab testing, and use of a fan monitoring system based on induction operated current switches (ICS). ICSs are unaffected by the environment and can provide direct measurement of real-time fan operational status by sensing AC current. A laboratory test of the ICS was performed to simulate a fan off/on duty cycle in a two-year emissions study; no ICS failure was recorded. The Southeastern Broiler Gaseous and Particulate Matter Emission study led by Iowa State University has been using 28 ICSs for over 190 days without a failure. At a unit cost as low as $19.50 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 system