## Latest Discussions : HVAC

toddjk

12:52PM | 03/28/06
Member Since: 03/27/06
I know you can put a table, for example, on top of a return grille. But could you put, say, a speaker stand with 1-2" clearence on top of one? I have a small return grill in my family room and I'd like to do just that. Nothing will be directly on top of the opening to choke the air flow - but there would only be a small space for air to get through. Does this matter? There are two other returns on the system - a large one in the living room and one in the basement just off the furnace.

toddjk

05:40AM | 03/29/06
Member Since: 03/27/06
Thank you for your reply - and I hear what you are saying. As information, the furnace is 80,000 btu input (64,000 out), the A/C unit is 2.5 tons, and the return in question is a small one - maybe 9x6 (that's just a guess). The other two returns are 14X14 in the living room and one in the basement just off the furnace on the trunk line that's maybe around 8x8.

But given your comments and the fact that this is in an addition that hasn't been finished yet, I'm going to relieve any worries and just move the supply line over one floor joist and alleviate any concerns.

Thanks again.

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Lets' say the return is 20 x 20 for 400 square inches divided by 2 for the fin interference = 200 square inches of open return. Then put something on top of it restricting the flow to go through 2 inches high by 20+20+20+20= 80 inches long. 2 times 80 is 160 square inches. you've lost 40 square inches or 20% of the air flow area. It might or might not make a difference in killing the furnace or air conditioner. Your chance to take.

Now all you have to know is the btuh required for the furnace or the air conditioner, as you usually need more than that area for most. The answer can only be a guess, because air return size is based on heat flow required by the machinery - and you don't say what it is. If you have a 40,000 btuh furnace or a 1-1/2 ton air conditioner, you might be OK doing that.

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