Bests & Worsts Reviews from Amazon

I found this Amazon product page while looking for information on furnace problems and this filter. We've been using the red "micro" Filtrete filters for years. This was our first try with the purple "Ultra" filters. I tried one in December, and removed it today (January 3, 2010). It cut our heating ability by at least 40%! With the red Filtrete, we have at least 92 degrees of heating ability: if we set the thermostat at 72, the house maintains 72, even when the outside "ambient" temperature (the average of the day's low and high) is -20 degrees F. Yesterday and today, we lost the ability to maintain temperature. On a day with an average temperature of 10 degrees F (low of 5, high of 15) the house dropped to 65 degrees. So, instead of being able to heat the house to at least 90 degrees above the outside temperature, we are down to only 55 degrees. The FAQ on the 3M site glosses over this problem. "Do I have to worry about restricted airflow with Filtrete filters? Filtrete filters are designed to operate in most residential furnaces and air conditioning systems. If a Filtrete filter remains in use longer than three months, it may begin to restrict airflow or cause the system to malfunction. It also could restrict airflow in some higher efficiency/air conditioning systems. In this case, change the filter more frequently." Bull! Our furnace isn't "high efficiency", it's an older 125000 BTU Singer, with a 160 degree limiter on the heat exchanger. A 3 or 4 week (not month) old purple "Ultra" choked the furnace, but when I put the 2 month old red "Micro" back in, the temperature came right back up!