Central air return filter grate size is just barely too small?

[allergyman]

My location: Oklahoma City, OK
My home build year: 2004
Home size: ~1900 square feet, single story, abundant 10' ceilings

This summer I moved into a "new" home that was built in 2004. The home has a carrier heat pump and furnace and all ductwork up in the attic. There are 2 return air grates on opposite ends of the house on the ceiling.

Based on my measurements, the furnace filter grate size is probably 14"x24"x1", but I have yet to find a commercially produced filter in this size that actually fits.

I know the dimensions are actually something like 13.7"x23.7"x.75" but the only way I can get ANY filter to fit is by bending 2 of the edges so it'll flex enough to fit in the space. In my opinion, this means the filter is not fitting flush against the edges and unfiltered air is bypassing into the air handler.

It may only be cosmetic, but it drives me nuts. My last house, which was half the size of this one, had a single 20x30x1 return and every filter I bought fit perfect every time. This surely isn't so complicated that the ones in my new home just won't work, right?

Could this be an issue with this particular size, such that it's hard to get the manufacturers to agree? Can I or should I increase the size of the returns and in the process hopefully get a fitting pair with the furnace filter?

Thanks.

[Krzyd]

Custom size filters are easy to get through your favorite contractor or supply house, they won't be much more than standard sizes if you order a couple cases.

Boomer Sooner

[Sleuth]

.

Are you saying the 14 X 24 X 1 filters are slightly too big?

And where are you buying the filters? I presume they're disposable pleated.

The return boxes and grills were probably jammeed into a spce too small. It's usually the other
way around where the filters fit too loosely.

Can you post a picture?
..

[54regcab]

Locke Supply (Metro OKC supply house) has just about all the sizes in stock.
14x24x1 isn't uncommon, they should have plenty in stock. The Glassfloss pleated are an excellent value.

[allergyman]

.

Are you saying the 14 X 24 X 1 filters are slightly too big?

And where are you buying the filters? I presume they're disposable pleated.

The return boxes and grills were probably jammeed into a spce too small. It's usually the other
way around where the filters fit too loosely.

Can you post a picture?
..

That is correct. The filter itself is right around 1/4" too large by length and width. I have so far used filters that I purchased at Lowe's -- brands are Flander's and 3M.

It's almost like the opening in the metal frame is 13.5"x23.5", which means I have no choice but to go with custom fit...

[54regcab]

Does your grate have "clips" than allow the filter to be unhinged? Or do you have to unscrew to install filter? Is the "filter rack" bent in any way?

[Sleuth]

.

The pleated filter from Locke Supply do tend to be smaller. Take a tape measure and visit them.
..

[vstech]

I'd like to see a picture with your tape measure in the opening of the filter grill. I've NEVER seen a filter grille too small for a filter. My bet is you have an opening in the ceiling, and a simple grille screwed to it.

[vstech]

if you have an actual filter grille with handles to open the grille for filter placement, then someone special ordered a 13/24 grille, and you will have to either take your filters apart and shorten them 1/2" or order custom filters from your a/c supply technician.

[54regcab]

I'd like to see a picture with your tape measure in the opening of the filter grill. I've NEVER seen a filter grille too small for a filter. My bet is you have an opening in the ceiling, and a simple grille screwed to it.

+1

[allergyman]

Pictures as requested.

Looking up at the return in the hallway


Closer look


Opened the grill


Here you see how the edge had to be crushed to make this fit


My best try at showing the measurement the short-way


This one was hard to do with 2 hands. Trust me, the other end of the tape measure was touching the inner edge


Filter removed, shot of the inside



On a side note, I've noticed quite a bit of allergy irritation while at home, but only at home. I've had indoor air quality tests done (no mold), humidity remains right around 50% since this is Oklahoma and it's fall, and I've had the furnace and ducts cleaned (rotobrush). (Long story behind this that I may need to create another thread to discuss.)

Is it possible that that the fiberglass insulation in the ductwork is starting to degrade and let fiberglass dust blow into my living space? I feel like this would explain the problems I'm having (skin irritation, itchy dry eyes, sinus congestion, diminished sense of smell). Is it possible to NOT have any fiberglass in the ductwork -- like possibly put it on the outside of the metal instead of in the airstream path? I went into a dark room with a flashlight and could see all sorts of stuff glittering in the air and I was careful not to have disturbed anything in the room.

Hope the pictures explain the problem. I stayed up late to take these for you guys.

[Sleuth]

.

Pretty much average install around here. I've seen much worse.
Check out the filters from Locke.

I doubt the fittings have been sealed with mastic and you're likely pulling in
lots of attic air / crud due to poor air sealing. The fittings they used were cheap
and I prefer to use angled return boxes so the takeoff collars don't leak like yours
surely do.

What size a/c do you have? There's a good chance the returns are undersized.

If you look at the blower motor it should look clean. If it's loaded with dirt and
lint the returns are leaking & pulling in attic air. The particles you're seeing
suspended in air (insulation?) can be coming from the supply or return from poorly
installed, leaky fittings and it's not right. IMHO The Fall and Winter are the best time
to fix the problems in the ductwork.
..

[allergyman]

.

Pretty much average install around here. I've seen much worse.
Check out the filters from Locke.

I doubt the fittings have been sealed with mastic and you're likely pulling in
lots of attic air / crud due to poor air sealing. The fittings they used were cheap
and I prefer to use angled return boxes so the takeoff collars don't leak like yours
surely do.

What size a/c do you have? There's a good chance the returns are undersized.

If you look at the blower motor it should look clean. If it's loaded with dirt and
lint the returns are leaking & pulling in attic air. The particles you're seeing
suspended in air (insulation?) can be coming from the supply or return from poorly
installed, leaky fittings and it's not right. IMHO The Fall and Winter are the best time
to fix the problems in the ductwork.
..

Is mastic the stuff that looks like gluey cement? Up in the attic I see plenty of this used where the flex duct meets the vent/return boxes or where it attaches to the ahu plenum.

I will snap some pics tonight to share.

The model of the AC unit outside is 38ykc048. Not sure if this tells you much. Remember that there are 2 returns on opposite ends of the house. It seems like it does an adequate job of cooling as I can actually set the thermostat a few degrees higher in this house than my last. I almost wonder if it is removing too much moisture?

I will also try to look at the blower motor and snap some pics tonight. I had some company out here last week that cleaned my furnace but I'm not entirely sure they removed and cleaned the blower wheel.

I can't wait until I get all these issues resolved with the air quality in my home. This isn't exactly how I expected to be living when I purchased the home back in the summer.

[Shophound]

Ducts can "look" sealed, but until you test them for leakage, there is not a consistent way to verify how tight they are via eyeballing.

90° elbows, such as shown in your photo of the return with the filter removed, are notorious for leaking around all of those "ribs" you see on that elbow. Seldom are they sealed during installation; if any sealing on ductwork is done at all it is typically where the flex connects to collars, elbows, plenums, etc. Which is good when they do that, of course. But if the elbow joints (ribs) are not also sealed, you can well be pulling attic air into the return ducting and distributing same, unfiltered, through the entire house.

Two questions about your house, if I may:

• Are there pull-down stairs to the attic inside the house? If so, is there any weatherstripping where the hatch meets the ceiling?
• Do you have any recessed light fixtures in the ceiling that penetrate into the attic? When you are in the attic, can you see light (given the fixture is not illuminated and any attic light is also off) entering the attic from the house below through the fixtures (provided they are not buried in insulation)?

I mention these two items (which are only two among several related matters) that could be contributing to your health problems. The overall idea is to get an attic as isolated from the house as possible. Many builders have not yet grasped why this is so important, as in spite of technological advances, we keep building houses very similar to how they were made fifty years ago. Only styling and size has changed, with perhaps modest technical gains and technique changes in construction, such as better windows, composite materials, etc.

[allergyman]

Ducts can "look" sealed, but until you test them for leakage, there is not a consistent way to verify how tight they are via eyeballing.

90° elbows, such as shown in your photo of the return with the filter removed, are notorious for leaking around all of those "ribs" you see on that elbow. Seldom are they sealed during installation; if any sealing on ductwork is done at all it is typically where the flex connects to collars, elbows, plenums, etc. Which is good when they do that, of course. But if the elbow joints (ribs) are not also sealed, you can well be pulling attic air into the return ducting and distributing same, unfiltered, through the entire house.

Two questions about your house, if I may:

• Are there pull-down stairs to the attic inside the house? If so, is there any weatherstripping where the hatch meets the ceiling?
• Do you have any recessed light fixtures in the ceiling that penetrate into the attic? When you are in the attic, can you see light (given the fixture is not illuminated and any attic light is also off) entering the attic from the house below through the fixtures (provided they are not buried in insulation)?

I mention these two items (which are only two among several related matters) that could be contributing to your health problems. The overall idea is to get an attic as isolated from the house as possible. Many builders have not yet grasped why this is so important, as in spite of technological advances, we keep building houses very similar to how they were made fifty years ago. Only styling and size has changed, with perhaps modest technical gains and technique changes in construction, such as better windows, composite materials, etc.

The stairs into the attic are actually on the ceiling of the garage, which is a good thing because the hinge is ever so slightly crooked that the "door" doesn't close flush with the frame.

There are quite a few recessed lights in the home. At least 5 in the main living area/kitchen, and then another 3 in the master bathroom. I have not checked if these are sealed well because there is quite a bit of insulation in the attic covering up the recessed cans. I'm honestly not even sure if the lights are the style that can be buried in insulation, and it's something I need to check out some day to know they're not a fire hazard.

[Shophound]

Yes, that's a good thing to check..."can" lights that are compatible with insulation surrounding them should be labled "IC", which means "insulation contact". If it says "ICAT", that's really good, in that it means "insulation contact air tight". Which is what you really want up there.

[54regcab]

OG&E will do an energy Audit for $50 which includes a HVAC system checkup.
If you are concerned about utility bills look into Smarthours.

[allergyman]

OG&E will do an energy Audit for $50 which includes a HVAC system checkup.
If you are concerned about utility bills look into Smarthours.

Funny you mentioned this. I actually work for OG&E so I hear about this stuff quite often.

The only thing is I don't have OG&E as my utility provider (I'm down south where we have OK COOP), so I need to check if I still qualify.

[54regcab]

Funny you mentioned this. I actually work for OG&E so I hear about this stuff quite often.

The only thing is I don't have OG&E as my utility provider (I'm down south where we have OK COOP), so I need to check if I still qualify.

I doubt it, but you work there so you can find out for sure

[allergyman]

One last question for anyone still reading this. I really do appreciate all the responses so far.

Comparing my current home to the last one, I am noticing that I am able to set the thermostat in this house much higher and remain just as comfortable.

What was 77*F AC in the last home is probably equivalent to 80*F in this house. I have 2 independent thermometers I'm using to gauge the accuracy of the wall mounted Carrier-branded thermostat and the temperature is true.

Would this simply be a matter of humidity? The last house had an AirCycler hooked up to the AHU and the fan would circulate on its own clock...maybe every 15 minutes regardless of the system being on or not. I think this was part of the design of the home, which was built by a company here called Ideal Homes that is big on energy efficiency so they also use those louvered openings above the room doors to try and stabilize temperatures.

The current home doesn't have this so the fan only kicks on when the AC needs to run. My hygrometer is currently reading 52% humidity at 77*F and this feels actually almost chilly. Unfortunately I don't have a humidity % comparison for the old house.

In a way, I'm split. As a lifelong allergy sufferer I prefer it a bit more humid since it keeps my sinuses less congested, but at the same time it is nice that I can save on my electric bill a little by not having the thermostat set cooler.