swapping out section of round duct for rectangular on gravity furnace


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Old 07-08-14, 07:52 PM
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swapping out section of round duct for rectangular on gravity furnace

I just purchased a 1927 home with a gravity furnace. While I'd love to replace the whole thing it's not in the budget right now. Anyhow.

One section of the duct work goes through a basement rec room. Because of the low ceiling, it's a perfect head smacking height.

Would it be good idea/safe to swap that section out for rectangular duct work so it's closer to the ceiling, of if I can, place it between the joists.

Thanks.
 
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Old 07-10-14, 01:52 PM
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Can anyone help out with this question?
 
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Old 07-10-14, 02:09 PM
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Gravity furnaces work on the principle that warm air rises. They require large duct area and a continuous rise from the furnace to the outlet register. If you can accomplish this, i.e. the same cross-sectional duct area and continuous rise, then it should be okay. If you decrease the duct area or have it go up and then down all bets are off.
 
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Old 07-10-14, 04:03 PM
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Thank you!!!

So basically I need to calculate the current area that I would be replacing and make sure I'm getting the same area from with width of the rectangular duct.
 
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Old 07-10-14, 09:59 PM
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That is correct. I'll add that while I rarely suggest duct fans this is one time that installing a duct fan may help and also allow you to use a somewhat smaller round duct.
 
 

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