Openings in air intake duct on central HVAC system

Omegazz

Hi,

Our house has central air/heat with two separate systems for the upstairs and downstairs. I was in the process of sealing some the leaks in the ductwork in the attic when I noticed that an opening had been left in the return duct where it attaches to the furnace. The opening appears to have been intentionally left, and on inspection of the basement furnace I discovered that it also has an identical opening. I can't think of a good reason for leaving such an opening although it is obvious that the installer intentionally left them there. The openings would appear to allow unfiltered, unconditioned air to get into the system. Is there any reason why I shouldn't seal up the openings? Are they perhaps supposed to be openings to allow easy cleaning of the ductwork perhaps?

Does anyone have any ideas?

Cheers,

Sean

8 Ball

What kind of opening? Like a filter slot, or a square or rectangular opening with a diffuser? If its a filter slot...drop a filter in there. Should be a narrow cover lying around up there.

Omegazz

Its a rectangular gap in the in the return duct where the duct attaches to the furnace. There is no obvious way a filter could be slotted in. The duct itself leads to an opening in the conditioned part of the home which does have a filter.

8 Ball

I cannot think of any good reason there would be that type of opening in your ductwork, unless your return ductwork is undersized, or just an oversight by the installer.

If you are drawing return air from an enclosed space with other gas fired equipment, the negative pressure may cause a downdraft, which would not be good.Try covering it and see if it effects the performance of the AC.. Watch for frosting on the larger of the two pipes to the air handler, and see if it effects the airflow to the rest of the house.

That has to be costing you a fortune, drawing hot air from the attic...not good.

Look forward to hearing more.

Omegazz

Thanks for the feedback. I'll try covering it and see how the AC performs. I'll let you know the results after a couple of days trial.

Cheers

Sean

susancrook

In addition, Energy Star says you must cover/seal the furnace filter slot to prevent allergens and pollutants (including carbon monoxide and radon) from entering the duct system and spreading throughout the home (regardless of the type of filter) and eliminate air leaks. There's a brand new product, FilterLOCK, that magnetically attaches to the furnace. It’s simple to attach and inexpensive. It SAVES ENERGY, reduces utility bills, and increases the furnace and AC lifespan, but most importantly keeps our families safe and healthy. Thought you'd like to know! Thanks for all your great tips!