Buildings

Air Handlers Need Time Off

In an attempt to provide non-medicinal aids to patients, a notable number of allergists tell allergy sufferers to turn their air handlers on permanently, rather than letting the system cycle them on and off. The thinking is that constant filtering of the air can only help the patient. In reality, this practice can actually aggravate an allergy problem, in addition to driving up energy costs. Why?

If air ducts are not airtight, any mold or mildew that exists in the crawl space will now be continually pumped into the house, rather than just part of the time.
Even if air ducts are tight, many homes do not have enhanced media filtration systems. In such cases, running the air handler merely re-circulates air rather than cleaning it. Enhanced media filtration systems range from the low-end 1-inch pleated filters to 5-inch pleated filters, and on up to high-end HEPA (High Efficiency Particulate Air) filters. All filtration systems are not created equal. The MERV (Minimum Efficiency Reporting Value) is a good way to begin making comparisons, with higher values being better.
Even if ducts are tight and filtration is good, constant air handler use (fan set to ON rather than the preferred AUTO ) can still increase the allergy suffering. After the compressor turns off, the coil is still wet and water condensate is in the pan underneath. The air handler will continue to blow air across this water and send moisture vapor back into the house. If the system has not been properly serviced, the vapor can also be laden with mold or mildew. In addition, the air handler is now in constant need of an air supply. If interior doors are closed, and there are no return air paths, the air handler might satisfy that need by sucking more allergen-laden air through any gaps, holes, or orifices in the exterior shell of the house.

HVAC equipment does play an important part in indoor air quality (IAQ) for allergy sufferers. To effectively help with allergy control, the allergen sources and the house as an entire system need to be fully understood. Until that is done, allergy sufferers will fare better by giving the air handler a break, simply letting it cycle on and off as designed.

For More Information

Contact Advanced Energy at (919) 857-9000 or moreinfo@advancedenergy.org.