filter size

[doneinnc]

got a question,
if a filter should be at least 1 square foot per ton, why does goodman have a filter holder in its unit, 5 ton air handler, 20 by 22 or 440 sq inches compared to the needed 720

[dan sw fl]

Originally posted by doneinnc
got a question,
if a filter should be at least 1 square foot per ton, why does goodman have a filter holder in its unit, 5 ton air handler, 20 by 22 or 440 sq inches compared to the needed 720

Do you mean
any other MFg may have a larger filter?

[amickracing]

One quick answer $$$

For what it's worth, most filters that come in a furnace (or AHU) will be marginal or undersized. Heck, a lot of the filters that are installed in designated filter racks are not exactly over sized! *sorry, you caught me on a bad day... I actually did a clean and check today on a 100,000 BTU furnace today with a 14x20 filter, and at least 2" of it was sticking out of the drop.

[doneinnc]

no but I wonder if the goodman unit will work properly

[fix_it_dude]

got a question,
if a filter should be at least 1 square foot per ton, why does goodman have a filter holder in its unit, 5 ton air handler, 20 by 22 or 440 sq inches compared to the needed 720

answer:
Hey dude
the filter size the unit bring will work properly.

besides how much space do you think the airhandler will take.
for 720 sq in. it will be king size filter 20 x 36 just what you need in your closet. J.K.

the 20x22x1 is good enough

[dash]

Originally posted by doneinnc
no but I wonder if the goodman unit will work properly

You should size the ducts and filter for the actual install,per Manual D ,from ACCA.

Factory supplied filters in the air handler aren't very restrictive ,us the fan data chart from the mfr. and Manual D.Don't use a 3M type one inch pleated in the air handler filter slot,it's too restrictive.

[wyounger]

Goodman specs typically show double the filter area for disposable filters as for "permanent" filters. The only permanent filter I know of has a hard time even catching hair, though, so it's not very restrictive.

For five ton furnaces their spec is 960 square inches of "disposable" filter, but 480 square inches for "permanent".

Hmm... if they stopped including those worthless internal filter racks, would hacks do better work, or would they just leave the filters off completely? :-D

Either way it takes a heck of a lot of filter area to stay under the typical 0.5"/0.8" ESP limit. Not many people ever measure that, though, to know that they're always over.

[iowa tech]

where does manuel d say what size filter to use?

[dash]

Originally posted by iowa tech
where does manuel d say what size filter to use?

It lists recommended velocities and you use the actual PD of the filter to determine the ASP and resulting Friction Rate to select ducts with the ductolator.

[iowa tech]

should you use same asp for supply and return

[duxinaroe]

Where did you get 1 sqft per ton? I have never heard of that. Thats not going to apply to the bottom of the unit, maybe to the grill size. Its all about static pressure and velocity not the size of the opening in the unit. Many manufacturers use the same cabinet for different btu units.

"Hey home depot you got any of those 27x38 filters in for my 4.5 ton yet?"

[dan sw fl]

Originally posted by duxinaroe
Where did you get 1 sq.ft. per ton?

Thats not going to apply to the bottom of the unit, maybe to the grill size.

400 Feet Per Minute ( FPM ) is
appropriate for filter GRILLE sizing.

A.K.A.
1 Square Foot / Ton
for Wall or Ceiling filters.

[dash]

Originally posted by iowa tech
should you use same asp for supply and return

The ASP is determined by Manual D,current method would yield the same ASP for supply as return.

If an existing and space for new or unable to enlarge ducts ,you could use a different ASP for return or supply.This would mean you'd have larger ducts on one,so space would need to be avalable for that.