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Old 12-12-2010, 10:26 AM   #1
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holes in return duct -- why?


While running some electrical wire in the joists in the basement, I found that in the top of the return ducts for both the upstairs and downstairs heaters there are openings. These are in the top of the ducts so they are not visible unless you stick your head between the joists in the right place, maybe 6 to 8 feet from the heater. They are the width of the duct and about 10 to 12 inches long, so when the heater runs there is quite a flow into them.

Can anyone explain why they are there? It seems to me that they defeat the purpose of having a duct going into the rooms upstairs, since it must be pulling most of the air through this hole. Should I close them up? Is it possible they were added because there was not enough flow to the heaters to support good combustion?

The heaters are oil burners, installed about 5 years ago ina 35 year old house.

Thanks for your help.

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Old 12-12-2010, 12:08 PM   #2
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holes in return duct -- why?


Quote:
Originally Posted by ductnovice
While running some electrical wire in the joists in the basement, I found that in the top of the return ducts for both the upstairs and downstairs heaters there are openings. These are in the top of the ducts so they are not visible unless you stick your head between the joists in the right place, maybe 6 to 8 feet from the heater. They are the width of the duct and about 10 to 12 inches long, so when the heater runs there is quite a flow into them.

Can anyone explain why they are there? It seems to me that they defeat the purpose of having a duct going into the rooms upstairs, since it must be pulling most of the air through this hole. Should I close them up? Is it possible they were added because there was not enough flow to the heaters to support good combustion?

The heaters are oil burners, installed about 5 years ago ina 35 year old house.

Thanks for your help.
If you can send a pict. You should never take return air from attic or crawl. It sounds like you may have had a air flow problem and the installing contractor tried to cover it up

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ductnovice (12-12-2010)
Old 12-12-2010, 12:16 PM   #3
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holes in return duct -- why?


Installers probably found out that their wasn't enough return air for the furnaces. So they cut those in to get more return air to the furnaces.

Try closing them off, and see if you have enough air or not.

What you have can be dangerous. Its possible for both furnaces to run at the same time, and pull combusted vapors from the chimney.
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Old 12-12-2010, 02:05 PM   #4
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holes in return duct -- why?


Check the joist bays where the holes are and see if their are any returns in the bays. Maybe duct was never finished or the ceiling was intended to be finished to complete the returns.
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Old 12-12-2010, 04:49 PM   #5
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holes in return duct -- why?


This attached picture shows the hole cut into the top of the duct. It measures 6 inches wide. I was mistaken in my earlier post, the only opening I find is in the downstairs heater return duct. I must have found it twice, not reallizing it was the same one I already saw.
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holes in return duct -- why?-pc121171a.jpg  
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Old 12-12-2010, 04:51 PM   #6
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holes in return duct -- why?


No return in the bays, and it is in a utility room where there are no finished ceilings.
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Old 12-12-2010, 05:33 PM   #7
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holes in return duct -- why?


Measure the air temp from your closest supply with that return open. Then cover it and see how much hotter that supply temp gets.

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