An equipment shelter with AIRSYS WPUs recently installed experienced clogged filters that resulted in high temp alarms every 2 to 3 months. This was due to periodic excess airborne particulates being drawn in to the primary air filter during periods of Free Cooling.


Our goal was to find a way to extend the filter life well into the next scheduled Preventive Maintenance period which is typically scheduled for every 6 months.

Our solution was to add an AFPD to the HVAC system to temporarily shut down free cooling during periods of excess airborne particulate count. The concept is to preserve the useful life of the air filter by optimizing Free Cooling time during periods when the air is clean.


Once the AFPD was added to the HVAC system the useful filter life was extended from < 2 months to > 9 months while at the same time preserving Free Cooling operation for ~ 90% of the available Free Cooling time.  This eliminated the high temp alarms and the associated costs of responding to the alarms à emergency dispatch and replacing the primary air filters.  This also preserved a large majority (90%) of the economic benefit of using Free Cooling instead of Mechanical cooling.