Air Conditioning - Air flow on air fliter

I replace my filter every 90 days. When I put my filter in.... which way should the air flow? ( arrows to unit or arrows to the duct work)

Some say the 90 day filters are not as good. They reccomend just using the inexpensive type and replace every 30 days. What is your opinon?

Not an HVAC Pro.....but....

The arrow points in the direction of air flow..so thats the way it should be installed. IAW the dust will collect on the base of the arrow, not the point.

I've always used the blue filters on a 30 day cycle. When I finally got the knowledge to know to clean my coil after living at the last house for 10 yrs, there was almost no dust or lint on it or in the air handler.

If someone had allergies or there was a dust control problem, I would move up to the pleated filters. There is a rating (MERV?)for the amount of restriction a filter puts in the line....I think most people say never go over an 8 (?).

Arrow points toward unit (which if the filter grille is in the wall is also towrds the duct) If the ductwork is properly sized for a more restrictive filter then you are ok to install a finer more restrictive filter. If the return duct is too small (and many of them are) you can kill your unit and increase operating costs by going with these filters.

I suggest the 3pack NaturalAire air filter that is sold at Home Depot.. They are MERV10, and I won't go any higher than that.

I tell my customer don't go by the 90 days unless your system don't run much, otherwise, change them 30 to 45 days..

I have to laugh at the cheap 50¢ filter, they are not even filled up with any thing at 30 days, that I can see 90 days getting by on that.