Arkansas HVACR NewsMagazine September 2019

S tate, National, Chapter News Tech News

Filters

Fundamentals Tom Turner, Air Evangelist

Challenge- Proper filter application remains one of the biggest mysteries in the HVAC industry for good reason. There are so many filter choices with so little information; it is difficult to match filter performance with system requirements. Consumers yield to flashy marketing not understanding the mechanics of the selection process, the contracting community unknowingly gives up early sacrificing performance, and the overall industry suffers the consequences. Restrictive, undersized filter selection generally ranks high on the list causing underperforming HVAC systems. There have been effective electronic air cleaners around for many years but for our conversation within this article we will focus on media or fabric material filtering. Each furnace or air handler has some sort of filter housing and filter correct? So what’s the problem? Manufacturers must provide some type stop gap filtering to protect the equipment on initial start-up where air flow instructions or requirements are forgotten or ignored. The integral filtering has little to do with real life HVAC performance. Manufacturers must depend on installing contractors

“..it is difficult to match filter performance with system requirements.”

to navigate road blocks the structure brings to the table. Each job must be analyzed and viable solutions employed to insure the equipment is protected and the system flows sufficient air. If we read the manufacturer’s instructions thoroughly, it becomes apparent that one inch filters on anything but the smallest air handler or furnace are inadequate. Why? When we look at the dimensions provided for air to find its way to the blower wheel through the appliance chassis, we find the required cfm arrives at velocities that exceed filter manufacturers specifications. A 2 ton (nominal) furnace or air handler with a chassis opening of 16” by 20” must flow approximately 720 to 800 cfm to fill the duct system with performing air. When we calculate the required velocity, we