I recently purchased a new Carrier HVAC system and had it installed. Everything went fine. The only hitch was that I asked them to put in a 1″ filter box rather than a 4″ box. Something got screwed up and the installers came out with a 4″ filter box. They said that to get a 1″ box, the install would have to be rescheduled. I did some quick math, looked up the filter prices and figured I could work with 4″ filters if I bought them in bulk.

Fast forward 6 months, when I go to put in my first replacement filter. I learn that my 16x25x4 filter box doesn’t take the most common size filter (90% of filters sold) but will only take a “Honeywell” size filter.  A Honeywell filter is less than 1/2″ larger than the most common size and the Honeywell filter box is designed so the common size filter won’t work. And, of course, Honeywell filters cost more.  Since I have a Carrier system I didn’t understand the reason for installing a box that didn’t take the most common size filter. I asked that question. 

Then I noticed that the filter box also has an obvious design flaw. The door of the filter box doesn’t touch the sides of the Honeywell filter (see photo). The door has a foam gasket along the edges to prevent air seeping around the filter. But the foam strips are 5 inches apart, while the Honeywell filter is only 4 3/8 wide. That means the foam doesn’t actually touch the filter along the entire vertical edge of the door. The metal of the door doesn’t touch the end of the filter so there is a gap of 1/4″ where air simply goes around the filter inside the door.

So in mid July I sent three questions to the installer, Nugent and Sons in Sterling, VA:

• Why did they use a non-common size filter box?
• How do I get this box to take a common size filter?
• Why is there a gap between the original filter and the filter box door?

I was told the questions would be passed along to the ‘install team’. I sent the same questions again in late July.  With no response I called their office and was asked to resend the information.  I sent it twice more in early August. No response was received. 

Update as of 2/22/2026:  Still no response from Nugent, but I have found a forum post that describes this design flaw in the Honeywell door.