Any benefit to adding 5-inch media filter when new system is installed?

[Florida Joy]

I've been using 3M Filtrete Filters to help with my dust/pollen sensitivity, either their MPR 1000 (Merv 11) or MPR 1500 (Merv 12), depending on what's on sale at BJ's or Sam's Club. Current system is 3.5 ton Rheem, 12 years old, struggling to maintain t-stat temps since the condenser bottom rusted and fell out and the coil fins have extensive corrosion. I'm looking into replacing the system with either an inexpensive 3.5 ton single compressor system, or going with the top of the line Trane XL20i.... 3 or 4 ton depending on Manual J load calc.

My question is this: Is there any benefit to adding a 5-inch media filter to the a/h?

One quote I received offers a "free" 5-inch media filter as part of the Trane installation. The extra 7 inches required to install the filter cabinet will require lowering the stand that my a/h sits on, which may require patching drywall or adding 2x4's or some such to repair the wall above the new, lower a/h stand. Without the media filter cabinet, there's enough space for the new a/h without changing the stand. This contractor's quote included the Trane 900 t-stat. I've since seen the Trane 950 t-stat and it's AMAZING to a geek like me! I'm thinking about asking if he'd consider dropping the "free" media filter and including the 950 t-stat instead.

Besides, if I use the media filter, I suppose I'd have to change it every so often and I understand replacement filters are quite expensive compared to the paper filters.

What do you all think?

[RoBoTeq]

A 5" pleated filter is much better than any 1" filter, especially the so called "high efficiency" ones for a couple of reasons.

For one, the 5" filter is way better for the overall operation of your entire HVAC system because it will not restrict airflow the way a 1" filter will do. At the same time, because of how much more surface area there is, a 5" filter will capture more airbourne contaminants due to a slower air flow rate across the filter.

Just make sure the contractor has a good air seal around the perimeter of the filter, the filter has a well sealed door/panel over it and that there are absolutely no openings whatsoever between the filter and the system blower wheel. That means screw holes, connections....anywhere that any amount of air can enter the system without being filtered.

[Joehvac25]

There is more surface area on the filters so they help with static pressure issues. That also means they should take longer to plug up, I personally would take the filter.

[Joehvac25]

I guess roboteq hit enter first lol

[jtrammel]

If duct is not sized properly for a 3m 1" filter or any restrictive filter for that matter it raises the blood pressure of the entire system (ESP!!!!) can cause harm to entire system. The 5" filters require less frequent changes due to the surface area of the media usually only once or twice a year.

[Florida Joy]

If duct is not sized properly for a 3m 1" filter or any restrictive filter for that matter it raises the blood pressure of the entire system (ESP!!!!) can cause harm to entire system. The 5" filters require less frequent changes due to the surface area of the media usually only once or twice a year.

I guess i should have included additional info regarding the air return and the Filtered Grill/Grills feeding the return. The return is a ductboard sealed space directly under the a/h stand measuring 36 wide x 30 high x 26 deep which currently is fed by a 20 x 20 filtered grill through the hall wall. They will add another 20 x 20 filtered grill through the foyer wall.... the a/h sits in the corner of my laundry... the hall wall meets the foyer wall at a 90 degree angle and the a/h is directly on the other side of the wall in that corner.

Wouldn't the planned 2 filter grill returns obviate the need for the media filter? They'll remain filtered regardless... would that be a problem?

[jtrammel]

I guess i should have included additional info regarding the air return and the Filtered Grill/Grills feeding the return. The return is a ductboard sealed space directly under the a/h stand measuring 36 wide x 30 high x 26 deep which currently is fed by a 20 x 20 filtered grill through the hall wall. They will add another 20 x 20 filtered grill through the foyer wall.... the a/h sits in the corner of my laundry... the hall wall meets the foyer wall at a 90 degree angle and the a/h is directly on the other side of the wall in that corner.

Wouldn't the planned 2 filter grill returns obviate the need for the media filter? They'll remain filtered regardless... would that be a problem?

No its not a problem if you don't want it. I recall in another thread that you were concerned your ducts wouldn't be sufficient for a larger ton system if you couple that with the 3M 1" filters then your external static pressure is going to be too high for design. Unless your duct system is designed for a 3M filter it is going to raise your esp on system and cause premature failure. A 5" filter will be much less restrictive. They also make 5" filters that fit into filter grilles.

[Florida Joy]

If duct is not sized properly for a 3m 1" filter or any restrictive filter for that matter it raises the blood pressure of the entire system (ESP!!!!) can cause harm to entire system. The 5" filters require less frequent changes due to the surface area of the media usually only once or twice a year.

But I see a problem in lowering the a/h stand... perhaps as much as 10 inches to fit the filter cabinet and provide "working space" during shortening of the plenum above the a/h to accommodate the extra height of the new a/h. Lowering the stand that much would cover a few inches of the 20 x 20 grills and reduce airflow.

[jtrammel]

i agree, i would ask if instead of the filter at the furnace to put two 5" filters in the filter grilles themselves.

[RoBoTeq]

Filters in filter grilles need to be larger than do filters located directly onto the unit due to the static pressure of the ducting between the filter grill and the blower section. There is also a reduction of free air area with the filter grill louvers. As long as there is enough free area of filter grill and all air passages from the filter grills and the blower section are completely sealed, filter grills are fine.

No matter what, 5" filtes are going to be much better than 1" filters. If you use 1" filters, it is best to use the least expensive fiberglass filters and make sure there is a good air seal around them.

[Florida Joy]

No its not a problem if you don't want it.

What I meant was, would having all 3 filters be a problem... the 5" filter in the Trane cabinet AND two 20 x 20 Filtrete paper filters?

I recall in another thread that you were concerned your ducts wouldn't be sufficient for a larger ton system if you couple that with the 3M 1" filters then your external static pressure is going to be too high for design. Unless your duct system is designed for a 3M filter it is going to raise your esp on system and cause premature failure. A 5" filter will be much less restrictive.

'T'wasn't I who was concerned... I still feel confifdent they'd be sufficient... it was the pro's in this forum who insisted my duct system couldn't possibly be adequate and recommended that I hire the services of an air balancing specialist to confirm their suspicions. I'll continue my efforts to have that done before opting for a 4 ton replacement... but the decision on 3 versus 4 ton hasn't been made yet.

They also make 5" filters that fit into filter grilles.

I guess that would require changing out my 1" filter grill to a 5" filter grill. Didn't know that... I'll have to look into it. Thanks!

[jtrammel]

What I meant was, would having all 3 filters be a problem... the 5" filter in the Trane cabinet AND two 20 x 20 Filtrete paper filters?
Yes of you use filtrete filters in the grilles. If you use cheap fiberglass in grilles probably not



'T'wasn't I who was concerned... I still feel confifdent they'd be sufficient... it was the pro's in this forum who insisted my duct system couldn't possibly be adequate and recommended that I hire the services of an air balancing specialist to confirm their suspicions. I'll continue my efforts to have that done before opting for a 4 ton replacement... but the decision on 3 versus 4 ton hasn't been made yet.
Sorry, my mistake


I guess that would require changing out my 1" filter grill to a 5" filter grill. Didn't know that... I'll have to look into it. Thanks!

no the 5" filters are made to fit in a regular filter grille

[Florida Joy]

no the 5" filters are made to fit in a regular filter grille

Hey, thanks jt! I just did some googling and found out how that works. There are a number of mfg making the 1-inch flanged 5-inch deep filters that fit a standard filter grill, for example:

http://www.ventingdirect.com/smart-f...ilter/p1816562

So.... I've decided against the "free" 5-inch media filter and the 7-inch Trane cabinet that it slides into.