strong return?

I was Visiting the In-laws and noticed the return air filter was being bent and twisted as though it was soon to be swallowed by a hungry AC. The return is in the hallway (high) ceiling. Is this simply a cheap filter that needs to be replaced by a more rigid filter or is there something else going on? I’ve never seen or heard of something like this.

the cheapies do this all the time…especially if they’re dirty.

It may not be a cheap filter, but probably is. That being said, and based on my understanding of your discription, it sounds like the filter is located in a Filter Grille at the ceiling level.

I personally like centrally located F/G’s, if designed and located in the right location. I use to design them for convenience sake. People have a bad habit of forgetting to change the filter on a regular basis (out of sight out of mind thing).The F/G’s usually have a heavy duty track to hold the filter, are hinged for easy open/close function, and you usually get very little bypass effect.

I just wish they had located the F/G in a low sidewall, to make it just that more available to service. I do recommend getting a quality 3M or better disposable filter (A MERV rating of 11+). I avoid the washable type for filtering and maintenance sake.

Sounds to me like you will need to visit on a regular basis, and take along a ladder. Get’um a good filter.


I forgot, you may want the HVAC Contr. to check the Fan speed setting in the Furnace or H/P Air Handler. Make sure the setting is proper/adequate. Too much airflow is almost as bad as too slow an airflow.

I bet they didnt want to remove the last screw in the cover plate. So they held the grate with one hand, tried to push / guide / install the filter with the other hand…while balancing on a chair… Been there, done that…:mrgreen:

What is the size of the filter grill and what is the size of the a/c unit?

Is the return plenum panned just behind the filter or is it a large box?

Thanks for the replies. I figured it’s a cheap filter just never seen one bent, looking like it was being sucked into the unit.
I know, I’ll get’em a nice, strong filter as a Christmas gift!! :twisted: I’ll get a pic of their faces as they open the box and see what they got!

If the duct or grill is undersized, the return static pressure may get too high and cause compressor damage.

You should not have more than 500 ft/min through the grill either.

The 3M Filtrete filters are typically death to a climate control system unless the ductwork and filter area have been engineered to deal with the increased static pressure. The result could be damage to the compressor, heat exchanger or blower fan. You will be damaging equipment, paying more in energy costs, and not as comfortable in your home. I recommend the looser type filter, changed once per month, with the system serviced once per year.

Unfortunately, the cheaper spun fibergalss filters collects less than 40% (avg.) airbourne.

3M is a great filter, if properly installed and changed every 30 days or so, unless you live in a Kennel or Beauty Salon or other type of similar atmosphere.

There are lots of different filter Manuf’s. out there, that offer all types of filtering capabilities. Pick any you want, just monitor and replace as necessary.

Damage to Equipment, increased Energy Costs, Comfort ???

Typical locations of Filter Grilles make it easy to monitor and service.

Note: We will assume the system has been engineered to handle static pressures within standard paramiters. (See ASHRAE Std’s of Design)

Greg, I agree that the looser type filters do not protect the equipment from dirt as well as a filter like the Filtrete would. A Filtrete filter installed in a system that is not designed for the increase in static pressure will definitely make the system work harder. If the system works harder it costs you more money to operate and will fail sooner. Decreased airflow can cause the comfort level to go down, especially in the rooms furthest away from the air handler. I would never assume that the system has been engineered to handle static pressures within standard parameters. I’ve seen too many systems that appear to not be designed properly for a restrictive type filter. (little to no airflow at far registers, with a clean pleated filter, with a marked improvement after filter has been removed)
I recommend that a looser filter be used with periodic maintenance (cleaning the air handler components) due to the type of design work I’ve seen in my area. If my client has allergy concerns or concerns about the looser type filter, I recommend they have the external static pressure measured by a licensed HVAC contractor and/or have a 4" or 5" media type filter installed.

A sometimes useful rule of thumb is to have a return/grille size of about one s.f. for each ton of cooling. Substantially smaller returns tend to be noisy, and may tend to suck in the cheaper filters.

Another possible solution is a less restrictive pleated filter (MERV 6 or so), changed frequently. Although standard fiberglass filters obviously aren’t designed to clean the air for occupants, I always assumed that they were sufficient for equipment protection.

P.S. You know home inspection is in your blood when that starts happening … :wink:

That is absolutely correct I can not take a whizz at some one’s home without twisting the commode between my knees