Is that filter 2 or 5” width? If two, —-> FilterBuy

My apology - I should have explained - this is a 5" width

Those are odd sized so you will have to have them custom made and max width for a custom made is 4 inches wide which could pose an air flow restriction.

So to get these exact you probably have to go back to your HVAC contractor who installed this system. Then when buying filters buy several so you have them available to be changed.

"Those are odd sized so you will have to have them custom made and max width for a custom made is 4 inches wide which could pose an air flow restriction." As the OP stated, the filter is a 5" filter. That's the nominal thickness-- not the width (actual thickness is 4 3/8" plus gaskets.) Both of the filters are stocked as replacement parts for RUUD's XHF and XGF series media air cleaners; you don't have to have them custom made and you don't need to purchase them from your contractor

Any filter restricts flow, by definition. The MERV8 has a pressure drop of 0.09 in. w.c. at 1600 cfm; the MERV13 has a pressure drop of 0.24 in. w.c. at the same air flow rate.

I appreciate the information. I found a replacement with a Merv rating of eight. We do not have pets and our grandson visits a couple of times a year. I’m hoping that will suffice. Another question would be, can I replace the air filters in the returns and not have one at the unit? Currently, I only have the filter in the unit and nothing in the returns.

You'll probably get a variety of opinions on where to place a filter in your system. With regard to function, the filter is intended to remove particulates so you're not recirculating them or breathing them. It's also intended to keep the coil in your air handler clean. You can achieve those objectives with filters at the individual returns or at the air handler. In my former home, I changed from filters at the individual returns to a high-quality pleated air filter at the air handler which I changed every 4-5 months. It improved air quality, and I didn't notice any build up of dust or particulates in the return ductwork.

I found the filter you want on eBay. At $73 it is expensive and as Charles mentioned restrictive. I don't think a higher MERV rating will help with allergies, but I am not an expert.

Rheem 54-109477-02 MERV 13 Replacement Filter

You can get the MERV 8 filters at about half the cost.

Rheem PD540043 (2-Pack) - 21" x 28" x 5"

In my opinion one 5 inch filter at the furnace is better than a one inch filter at the return. If you have more than one return then you have to deal with more filters.

I cant thank you enough for the info. I am so annoyed at the company that did the install. We had outrold system go out on us last June when the temps were 90+ (of course). and I was recovering from a hip replacement. We picked a local company and left it to them to make recommendations for our home. I wonder now if we got the leftover unit sitting in the back room. My fault for not doing research - however, at the time I would have picked anything to get A/C. I think for now, I'll go with the 5" MERV at 8.

Knowledge is power so for your information in the event you want to up the game to more than just getting by. A simple device can be retrofitted which tells you when filter needs to be changed. There's many households where annually is more than often enough to change filter then of course there's some that monthly isn't enough. It's easily within an average handyman's ability to make fillers for your rack so that 20x25 filters fit perfectly.

As someone opined, filter near air handler has advantages over being located several feet upstream. If you already have filter racks at room intakes, those can be utilized to enhance Merv 8/12/15 at handler. By volume, 50-75% of what your Merve 8 catches would be caught by el cheapo merv 4. Therefore merv 4s in room intakes will significantly extend life of Merv 8 at handler. I've set many systems (including all my personal) up with dual filtration. If there's dogs, healthy boys, people with dirty jobs and such, dual filtration is a no brainer and benefit for tightwads is obvious.

All the best to you all and your grandson.

however, at the time I would have picked anything to get A/C. I think for now, I'll go with the 5" MERV at 8.

As long as it will fit the filter rack that should be fine... what was meant by restrictive is as the filter gains dust it will become restrictive. A Merv 13 is already restrictive -- as it has to be this way to filter more particles. (the builder has a chip on his shoulder as anything I say he has to counter act... he's a builder. So keep that in mind.)

A 4 inch wide filter has less "surface area" than a 5 wide inch filter--- if you buy the "specific brand of the filter" you most certainly pay more for the filter. These filter sizes dimensions can be "all over the place" some of these filters are 5 1/2 inches wide some are 4... some are 5.

Less surface area of a filter + higher merv rating = more restrictive = your AC works harder, more prone to breaking and so on.

-------- Putting filter at the unit -------

Dust = dust mites in the returns -- this will take time to develop but in time it will develop. Where do you think all those duct clean before and after pictures come from? People who think it's a good idea to put filters somewhere's else to generate more work? Remember it will be me or someone like me who does the work... not them. Why I often say: Bulders provide me work. Um yeah it's true... even on this thread. Thanks Charles.

A healthier home is to prevent dust from accumulating any where. So if you have a filter at the unit like a 5 in Merv 8 for example... placing cheap see thru kind of filter at each of the returns and then replacing those every 30 days or so isn't a bad idea. Why the cheap see thru kind? = restriction. Remember we have no idea from the internet how well your system was installed or not? (no one here knows what exactly you have -- I am not a psychic nor is the builder or anyone else)

I prefer multiple returns feeding back to the furnace and a decent quality filter pleated. If you don't have multiple returns. As a filter fills up it will eventually *if not changed* will start letting smaller particles thru.

"As a filter fills up it will eventually *if not changed* will start letting smaller particles thru." As mechanical filters become more occluded they actually become better at filtering out particles. However, that comes at the expense of increased pressure drop across the filter and an attendant reduction in the flow rate of filtered air. Air will often find routes which bypass an occluded filter, thus reducing the amount of filtration. For electrostatic air cleaners, accumulation of particles does reduce their effectiveness. Electrostatic units require frequent cleaning to operate properly which people rarely do in my experience.

(the builder has a chip on his shoulder as anything I say he has to counter act... he's a builder. So keep that in mind.)

See I told you....

Correcting the misinformation you spread on houzz. com is a full-time job, Ray.

I would verify the HVAC manufacturer’s recommended MERV range before moving from MERV 8 to 13, since a higher rating can increase airflow resistance. Fine Filters can be useful for comparing available 21x28 options and their MERV specifications. If allergies are the main concern, balancing filtration with the system’s airflow requirements is important.

A couple of practical steps that helped me when I was sorting out an odd filter size: first, keep a photo of the old filter frame showing all three dimensions, including the 5-inch depth, and the part number if there is one. That makes it much easier to compare options and to ask a supplier to match it exactly, rather than relying on the two face dimensions alone.

Second, before moving up to a higher rating, check the system manual or ask the installer in writing for the recommended MERV range for your unit. A thicker media filter does have more surface area than a thin one, which helps, but a higher rating can still add resistance, and a filter that is left in too long can be worse than a lower rating changed on time. For allergy concerns, regular changes, keeping return vents clear, and vacuuming soft surfaces often matter as much as the rating itself. If the installer supplied the original filter, I would also ask them to put the exact replacement specification on the service paperwork so the next visit does not default back to a different rating.

Daaaaamp what is that smell ? Oh it's only a "PRO" grave digging in hopes of getting their name out there.

I run Ocala Pro AC Repair here in Ocala, FL — we see this a lot in Florida heat, and the short answer is that a higher MERV rating is not automatically better for your system.

A MERV 13 filter will catch smaller particles than a MERV 8, which sounds ideal when allergies or asthma are a concern. The trade-off is airflow. A denser filter creates more resistance, and once it starts to load with dust that resistance rises further. In a home where the air conditioner runs for long periods, reduced airflow can mean weaker cooling, longer run times, higher bills, and in some cases a frozen indoor coil.

Before moving up in rating, check the manual or the rating plate for your air handler, or ask the installer to confirm the recommended MERV range in writing. That matters more than the number on the box. A 5-inch filter such as your 21x28x5 has more surface area than a thin 1-inch filter, so it usually handles a higher rating better, but it is still not a guarantee.

A few checks you can safely do yourself: confirm the exact size, fit it snugly with no gaps around the edges, and make sure the airflow arrow points towards the air handler. Check it monthly, especially in dusty or high-pollen periods, and change it when it looks dirty rather than waiting for a fixed date. Keep return grilles clear and do not stack a second filter at a return on top of the one at the unit, as double filtering can restrict airflow further.

For allergy concerns, regular changes, vacuuming soft furnishings, and washing bedding often help as much as the rating itself, and a filter cannot replace medical advice for asthma.

Call a professional if airflow stays weak after a fresh filter, the coil ices up, the system short-cycles, or you are unsure whether your system can handle MERV 13. A technician can check airflow and pressure drop and confirm the right rating for your set-up.