I've consulted several HVAC contractors on this subject and received
widely ranging answers so I've turned to you folks for some expert
opinion/help.

I currently use 3M's new 12 MERV 1" premium filter and my furnace fan
is set to 'auto'. I'm very satisfied with the filtering I'm currently
getting with this filter. I'm in the process of adding an HRV and will

be running the furnace fan on low at the continuous setting year-round.

Some contractors have suggested upgrading from a 1" media filter to a
5" media filter to improve airflow, theory being the 3M's I'm currently

using are too restrictive now that I'll be running the fan
continuously.

My concern is that the 5" media filters typically have a lower MERV
rating and I'll lose some filtering effectiveness.

Should I be concerned about airflow restriction with the 3M filters
based on continuous fan operation and is there any other benefit, aside

from reduced filter change frequency, to switch to a 5" media filter?

The one upside that I've considered is that if I add a 5" filter to my
system I can use the 1" slot for a charcoal/carbon filter to improve
odor/gas removal - any thoughts?

I appreciate your responses.
Regards.
Buzz

I have an april air media , its a good filter and it lasts, filter
efficiency goes up as they get dirtier a large media will do a better
job longer. Just dont get an April Air unit the casing design leaks air
past the filter housing, something an april air rep said cant be fixed.

m Ransley wrote:

I have an april air media , its a good filter and it lasts, filter
efficiency goes up as they get dirtier a large media will do a better

Huh? The better, the dirtier?

job longer. Just dont get an April Air unit the casing design leaks air
past the filter housing, something an april air rep said cant be fixed.

Just put him in your kill file like everyone else has done.

"Tony Hwang" wrote in message
news:zfBzf.382119$ki.274740@pd7tw2no...
m Ransley wrote:

I have an april air media , its a good filter and it lasts, filter
efficiency goes up as they get dirtier a large media will do a better

Huh? The better, the dirtier?

job longer. Just dont get an April Air unit the casing design leaks air
past the filter housing, something an april air rep said cant be fixed.

If you look long enough, you'll find people to tell you how great those
filters are, but I've seen them do more harm than good.

"Buzz" wrote in message
ups.com...
I've consulted several HVAC contractors on this subject and received
widely ranging answers so I've turned to you folks for some expert
opinion/help.

I currently use 3M's new 12 MERV 1" premium filter and my furnace fan
is set to 'auto'. I'm very satisfied with the filtering I'm currently
getting with this filter. I'm in the process of adding an HRV and will

be running the furnace fan on low at the continuous setting year-round.

Some contractors have suggested upgrading from a 1" media filter to a
5" media filter to improve airflow, theory being the 3M's I'm currently

using are too restrictive now that I'll be running the fan
continuously.

My concern is that the 5" media filters typically have a lower MERV
rating and I'll lose some filtering effectiveness.

Should I be concerned about airflow restriction with the 3M filters
based on continuous fan operation and is there any other benefit, aside

from reduced filter change frequency, to switch to a 5" media filter?

The one upside that I've considered is that if I add a 5" filter to my
system I can use the 1" slot for a charcoal/carbon filter to improve
odor/gas removal - any thoughts?

I appreciate your responses.
Regards.
Buzz

The April-Aire filters have a high MERV, 12 as I recall. They have
MUCH less restriction to air flow than the one inch pleateds. Up to
2.5 tons, the April-Aire filters are about the same pressure drop or
less as a properly sized fiberglass filter. The one-inch pleated
filters have about 2.5 times the pressure drop of a properly sized (or
same sized) fiberglass filter. This is according to my own testing
with an air flow hood and digital manometers and magnahelic gauges. If
you put a carbon filter in the 1" slot, plus have the Aprilaire filter,
your pressure drop will go sky high again. Typically, a 1" pleated
filter will drop air flow 10% to 20% vs. a standard fiberglass filter.
If you want all that filtration, have someonme measure your air flow
with a flow hood before you install the filters. If you have less than
400 CFM/ton, stick to a fiberglass filter OR upgrade to a variable
speed blower OR replace your duct system. Low air flow will reduce
your system capacity efficiency and capacity. It can also damage your
compressor.

Stretch

Learn bobb, go read the April Air site. Filters filter better the
dirtier they get, filter dirt better. A filters job is filtering dirt
while allowing suficient airflow required for proper furnace operation.
The % pass through of dirt continues to go down till they are
restrictive, needing replacement. April Air Media go up something like
9% as they approach needing replacement. Media filter different micron
size particles at different first time % pass through. First time % pass
is the important number I am refering to, not airflow which large media
are superior in compared to 1". As acumulations of dirt build on the
filter first time % dirt pass through efficiencies go up on media, less
dirt is passed though. It is what media do, nothing new. Airlow is not
comprimised enough requiring replacement till filter is dirty. This is
exactly the oposite of 120v powered electronic wire type, they need to
be clean to meet stated efficiencies.

So bobb learn a bit before you post a response.