"Scott McDaniel" wrote in message
...
Agree with Steve - don't use an electrostatic or one of the 3M filters
unless you've had the system checked by a competent tech (and those can be
hard to find!) to ensure it can handle the decrease in airflow.

Maybe a cheap filter has less resistance to flow when first installed but
the pleated ones work better when the dust starts to accumlute. The cheap
ones only pick up "BIG" stuff when first put in; their effectiveness
increases as the clog up.

THE reason for the pleating is to increase the surface area to compensate
for the increased air flow resistance. The more pleasts, the greated the
area and the less net resistance for a given medium.


I can't tell you how many calls we get at this time of year where the
homeowner has purchased one of the 3M filters ... return isn't quite large
enough and those filters can be extremely restrictive, therefore not
enough
air moving across the evap coil and you get a freezeup. Had one
yesterday -
3.5 ton packaged heat pump system with a 10 x 20 (yes, 10 x 20) return and
a
3M white pleated filter. This system is about 5 years old and has already
had 1 heat exchanger and 2 compressors installed ... go figure.

Go figure? If a pleated filter cuases all those problems someone didn't
plan the system right. Ever think about putting in a larger capacity
blower or do you enjoy replacing the compressors.