Manuf. recommended filter size REALLY wrong?

[fferd]

I'm stumped.

Last year I purchased an older ranch home with solid ducts and a 3-ton AC and gas furnace installed in 2007. The unit sits on a filter box made for 1" deep filters (can be 2" if some tabs are ripped off), sized for 14"x25" filters. Seemed very inadequate so I found the manufacturers online pdf and it recommends a 14x25x1 filter.

Compared to the advice given in this forum this seems way, WAY wrong. Am I missing something?! How can a manufacturer recommend a filter size thats, what, a whole third or fourth the size of current best practices?



Manual for Lennox G4OUH-36A-070-15 (1200CFM gas furnace)
http://www.lennox.com/pdfs/installat..._G40UH_IOM.pdf

Manual for Lennox C33-38A-2F-3 (1200CFM Coil, Dry .27, Wet .30)
http://tech.lennoxintl.com/C03e7o14l...7R/505060h.pdf

On top of that, (bad pics below) the unit sits in a hall closet on a raised platform along with the water heater, where a single return air is just 14x25 hole into said platform cavity to a opening under the closet door into the hall. The studs and floor plate only provide a return opening of a mere 28"w x 9.5"h to the hall.



I've come up with the following options:

1) Burn it all to the ground. Cost prohibitive.

2) At least make the filter box accept 2" filters and cut out some more drywall to the hallway and make a bigger grilled return. Filtered grill doesn't look to be an option with just 9.5 height restriction. All this still leaves the puny 14x25 hole in the platform.

3) Somehow raise the whole unit and replace the filter box with something bigger. Ducting into the attic is but a few feet so not a lot of wiggle room. I'm very handy, but no experience with HVAC, am I better off having a pro do this and so how much cost am I looking at?

4) Cut a hole in the hallway wall and side of the unit and side-mount some sort of filter/box/return grill? It's 6.25" from the unit to the closet drywall.

5) Yell obscenities at it until it fixes itself. Time prohibitive.

Any advice?

[Cooked]

First off I'm getting a bit older and it hurts my neck to look sideways so I rotated the pics for you.

According to manual that's all you need. It wouldn't hurt to enlarge the opening to the platform (in the hallway) as much as you can. Trying to raise the unit up by yourself is a really really bad idea.

Attachment 233201 Attachment 233211 Attachment 233221

[fferd]

Trying to raise the unit up by yourself is a really really bad idea.

Alright, I'll take your word for it even though where I'm from "bad idea" implies a dare.

Thanks for editing the pics for me.

[second opinion]

I'm stumped.

Last year I purchased an older ranch home with solid ducts and a 3-ton AC and gas furnace installed in 2007. The unit sits on a filter box made for 1" deep filters (can be 2" if some tabs are ripped off), sized for 14"x25" filters. Seemed very inadequate so I found the manufacturers online pdf and it recommends a 14x25x1 filter.

Compared to the advice given in this forum this seems way, WAY wrong. Am I missing something?! How can a manufacturer recommend a filter size thats, what, a whole third or fourth the size of current best practices?



Manual for Lennox G4OUH-36A-070-15 (1200CFM gas furnace)
http://www.lennox.com/pdfs/installat..._G40UH_IOM.pdf

Manual for Lennox C33-38A-2F-3 (1200CFM Coil, Dry .27, Wet .30)
http://tech.lennoxintl.com/C03e7o14l...7R/505060h.pdf

On top of that, (bad pics below) the unit sits in a hall closet on a raised platform along with the water heater, where a single return air is just 14x25 hole into said platform cavity to a opening under the closet door into the hall. The studs and floor plate only provide a return opening of a mere 28"w x 9.5"h to the hall.



I've come up with the following options:

1) Burn it all to the ground. Cost prohibitive.

2) At least make the filter box accept 2" filters and cut out some more drywall to the hallway and make a bigger grilled return. Filtered grill doesn't look to be an option with just 9.5 height restriction. All this still leaves the puny 14x25 hole in the platform.

3) Somehow raise the whole unit and replace the filter box with something bigger. Ducting into the attic is but a few feet so not a lot of wiggle room. I'm very handy, but no experience with HVAC, am I better off having a pro do this and so how much cost am I looking at?

4) Cut a hole in the hallway wall and side of the unit and side-mount some sort of filter/box/return grill? It's 6.25" from the unit to the closet drywall.

5) Yell obscenities at it until it fixes itself. Time prohibitive.

Any advice?

Your filter dimension is not the problem, the return air grill is too small.

[beenthere]

Most manufacturers use a filter size that meets or just barely exceeds the 500 FPM rating of the air filter. Yours is 494FPM at 1200 CFM.

[behappy]

There are a lot of things wrong with those pictures.

If I am not mistaken, that filter box will accept a 3" or maybe a 4" filter.
You would do yourself a favor by upgrading.

[catmanacman]

looks like a typical Texas install was probably furnace only when built and ac added later I would remove the slides and install a 2 inch filter. sometimes you can cut more return air vents into wall .I have installed many units similar to what you have

[fferd]

looks like a typical Texas install was probably furnace only when built and ac added later I would remove the slides and install a 2 inch filter. sometimes you can cut more return air vents into wall .I have installed many units similar to what you have

Hit it right on the head, it's in Texas and the space was originally made for just a furnace.

From everyone's advice it's nice to hear nothing too drastic has to change. Still don't quite understand how this 3 ton filter size "needs" is so different from other 3 tons discussed on this site.

[fferd]

If I am not mistaken, that filter box will accept a 3" or maybe a 4" filter.

Unfortunately a 3" (2 5/8" or whatever it really is) won't fit unless it's crushed and jammed in.

[RoBoTeq]

If nothing else, at least stop using those restrictive 1" pleated filters. Let the system breathe. 1" filters claiming to be better for your health are always going to be potentially damaging to your HVAC system.

As long as there are no air leaks around the filter or at the connections of the filter rack to the unit, the inexpensive fiberglass filters are best to protect they HVAC system while not restricting air flow.

There is no air filter that will make any significant difference in the healthiness of your air that will not cause too much restriction for the system without greatly enlarging the free area of air for that filter. Filters are there to protect the HVAC equipment, not so much for human health. If you need/want better filtration for cleaining up the air for health reasons, have a self contained by-pass HEPA filter, properly placed UV lighting or Bi-polar ionization units and outside air system installed.

[Sleuth]

.
2A)
Next filter change pick up the 2" pleated merv 8 filter and make the move,
simple effective and better than you have at this time.
..

[fferd]

Right, I get the "more Merv isn't better", currently using the cheapest 1" pleated.

My main concern is if a single 14x25(1" or 2") is anywhere near adequate and if not, just how far can I reasonably go to make the unit breath easier.

[Sleuth]

.
See Post #4.

Your return grille is too small / restrictive.

Possibly replace that grille with a custom plastic eggcrate grille.
..


It will prevent cats from getting sucked thru.

[Texas-Tech]

.
See Post #4.

Your return grille is too small / restrictive.

That is a problem for sure, but what is that gap in the flue pipe just above the 90?

[Sleuth]

.
Appears to be a 12" adjustable.
..

[Cooked]

It will prevent cats from getting sucked thru.

And who among us would consider that to be a problem?

[fferd]

And who among us would consider that to be a problem?

I'd pay extra for the cat-sucking feature. May need to clean the unit more often, though.

[RoBoTeq]

Right, I get the "more Merv isn't better", currently using the cheapest 1" pleated.

My main concern is if a single 14x25(1" or 2") is anywhere near adequate and if not, just how far can I reasonably go to make the unit breath easier.

1" pleated filters are restrictive, no matter the cost. There isn't really 1" of filter, but rather only a thin layer due to the pleating. Use regular 1" fiberglass or spun plastic filters that actually have 1" of media.

[behappy]

Use regular 1" fiberglass or spun plastic filters that actually have 1" of media.

With CATS!

[RoBoTeq]

With CATS!

I don't understand.

If this is supposed to be a question pertaining to having cats in the house, then what ever cat fur does to a 1" filter with 1" of media is going to be the same for any filter.