Posted by: William Geyer on February 15, 2004 at 17:15:16

I have a gas furnace that heats fine. But about 30 sec. after a heating cycle, the blower comes on for another 15 sec. or so. This started a few months ago when I put a HEPA filter in the return air. I tried a regular fiberglass filter and the symptom went away. Then it started again and I put in a new filter and things were back to normal again. The last time I changed filter it made no difference. So the real cause must be getting worse. Any ideas??

Answer:
Caught between ... Reducing air flow is the cause of the recycling. The HEPA has high resistance to slow air. Replacing it with a standard filter permits dirt to coat the fam blades and exchangers to slow air.

Have a REAL pro, (identified by air flow instruments and thermometers in several locations in the ductwork), check your air flow. It may be as simple as increasing fan speed, or as complicated as getting a bypass whole-house filter; but there is a solution.