Out of sight, out of mind.  Changing a furnace filter is easy to forget.  But a dirty one can cause problems.  In the heating season, air does not flow smoothly and could overheat the furnace leading to intermittent shutdowns.  Rooms don’t heat properly making a liar out of your thermostat.  With the cooling season ahead, similar AC problems could occur.

How often should the filter be changed?  Mechanical Extremes’ Harold Wilkes says that depends on the amount of dust in the air.  For example, airborne particles are more abundant in rural areas with open fields.  Filter changes should be made as often as every month, or up to six months.  The thermostat on many of the Carrier furnaces that Mechanical Extremes installs will alert you when it’s time for action.  Other units can be set to remind you on a time basis.

Now here’s where it gets a bit more complicated – choosing the proper filter for your situation.  These facts should help. Filters have Merv ratings which define the potential performance of the filter.  The higher the Merv number, the filter will capture more, and finer, dust.  But know this.  A larger number is not always the best solution.  Harold Wilkes says “if the Merv rating is too high, it can suffocate the furnace.”  That can lead to poor functioning and damage.

The recommended Merv rating will depend on your furnace.  For a one-inch thick filter, a rating of 5 to 7 is about right.  For 4-inch filters, 8 to 13 is appropriate.  Best to check manufacturer specifications to find what’s right for your equipment.

If you have questions, or would like to transfer this worry to a professional, Mechanical Extremes can help. (517) 812-2484.