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Zeke2112 11-19-2009 09:01 AM

Cold air return grill at furnace intake
Hello everyone. Long time lurker, first time poster :)

I have a grill on my cold air return duct right at the intake to the furnace, just before the filter. This intake is allowing basement humidity and odor (cat boxes, etc) to permeate the entire house. Can I seal this off without any problems? The rest of the house has plenty of cold air return, with large "5-port" grills in each bedroom and each large room.

Thank you for your advice!


beenthere 11-19-2009 10:43 AM

Its probably needed.

You may have a lot of return grilles. But that doesn't mean you have enough return air.

Temp cover the grille, and see if it reduces air flow from your supply grilles, and or increase noise at your other returns.

Zeke2112 11-19-2009 01:04 PM

Thanks and a follow-up
Thanks for the reply. I do have a follow-up question: from a fluid-flow perspective, wouldn't having a grille right at the intake overpower the cold air returns from the rest of the house? Seems that the blower would pull most of its air from that grille and reduce the pull from the rest of the house. This would account for the fact that the 2 rooms farthest from the furnace don't seem to have any air circulation in them - warm near the floor and cold near the ceiling.

It's also worth noting that this intake is about 5 feet from our sump pump. We have a major radon in our area and have a radon mitigation system in place, so I'm also paranoid that any radon that might escape into the basement is promptly going to be distributed throughout the house.

Thanks again for the reply. Will give covering it a try and see how it goes.


beenthere 11-19-2009 02:47 PM

The return in the basement. Has to pull its air from the basement. And unless the basement has supplies. Or a lot of fresh air infiltration. It can't pull anymore air, then what the basement is supplied with.

So the other returns will pull as much air as they need/can.

Are the rooms that don't heat right have doors that are under cut?
If not, do they stay warm when the doors are open?
If not. Then you don't have either enough supply to those rooms. or, the system on a whole doesn't have enough return air.

tinmanrob 11-19-2009 03:15 PM

If it's a natural draft furnace, the return air is illegal.
Should be minimum 6 feet away.

Marty S. 11-19-2009 04:28 PM

No return within 10' of any combustion appliance by our code.

Zeke2112 11-20-2009 06:41 AM

Thanks for the replies, everyone. I sealed off the grille last night and I don't feel any difference in supply. I do feel better intake at the far rooms' cold air returns. No additional noise except for a slight whistle at the filter slot.

Thanks again - appreciate the help.


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