Sealed Return Duct

oil2025

Apologies if this is in the wrong category of the forum. On the second floor of my house, I have ductwork that supplies heat and AC.

I have 4 returns on this floor and recently noticed that the hallway return had insulation in it. I pulled back the insulation and the return duct seems to have been sealed at some point with a spray foam. The other returns seem clear. With both the foam and insulation it certainly seems intentional.

I’ve always had less than ideal airflow on that floor, with high electric bills especially during cooling season, to the point where I had to drop down to a less restrictive filter just to get decent airflow.

The only reason I could think to do this was if that duct was abandoned but I took a quick look up in the attic and it seems at least visually that the return is connected to the main trunk.

Any idea why that would have been done?

HVACNUT

Its possible it once was one central return, then for whatever reason, returns were diverted to individual rooms. Do you know the model number of the air handler and the duct sizes of the 3 returns in use?

oil2025

Hey @HVACNUT thanks for the reply! The furnace is a Lennox ELO183UF68.

As far as I can tell, the other returns have the same size grille but I will open those up tomorrow and confirm the actual duct sizes for certain.

HVACNUT

https://forum.heatinghelp.com/discussion/comment/1849775#Comment_1849775

This is an oil fired furnace? Is there more to the model number, because from what I see, that model is an upflow. I don't see anything in the manual to covert to horizontal with the ELO. Unless you have a really tall attic.

pecmsg

static pressure readings? TESP

oil2025

https://forum.heatinghelp.com/discussion/comment/1849803#Comment_1849803

Sorry if this wasn’t clear, yes it is an upflow unit. The furnace is in the basement, connected to a long duct run that runs up through the house into the attic where the main supply and return branch off. I also misspoke earlier, there are actually five returns in total, with one sealed off as described. I do still need to get a measurement of the return duct size for you.

https://forum.heatinghelp.com/discussion/comment/1849843#Comment_1849843

Appreciate the help but unfortunately I don’t have a manometer so I have no way to measure these at the moment. I understand there’s a limit to what can be diagnosed without these but with my original post was trying to get some more education on why this would be done.

pecmsg

TESP will tell you where your short…..

Supply

Return

or

both!

Without that information no one can tell.

oil2025

https://forum.heatinghelp.com/discussion/comment/1849938#Comment_1849938

Understood, I will try to measure and report back! Thanks!