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Old 12-18-2011, 10:26 PM   #1
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inconsitent air flow


i was walking around my place and noticed, some vents pump out air and others barely have any flow. i have a attic where they vent from, what can/should i do about this?

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Old 12-19-2011, 05:29 AM   #2
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Are any of the ones not moving much air, returns?

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Old 12-19-2011, 07:21 AM   #3
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inconsitent air flow


No, we only have 1 return and its attached the hvac unit.
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Old 12-19-2011, 10:56 AM   #4
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inconsitent air flow


The vents that are moving the least amount of air are usually the ones furthest from the unit. Also if the duct runs are Y'd off (one main trunk splitting into three) then that can be the issue as well.

Generally location on the plenum (where the duct takes off from the unit) is a big deal as well as being dedicated runs to individual vents.

For now you can check for any possible leaks and check to see if you have any dampers (air flow control doOrs in the duct's themselves), usually located at the plenum.
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Old 12-19-2011, 11:32 AM   #5
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inconsitent air flow


how would i check for leaks? crawl around and feel for air? or is there a scientific method?
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Old 12-19-2011, 11:38 AM   #6
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inconsitent air flow


incense candle stick thingamajig, very scientific. turn on the system and crawl around and feel for leaks as well as hold that lit incense stick at all connections. watch the smoke.

check the return as well.
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Old 12-19-2011, 11:56 AM   #7
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inconsitent air flow


Once you fix any leaks if you dont have enough air in certain rooms you can always close some other vents in closer rooms part way to force more air to other vents.
How many rooms dont have cold air returns?maybe try leaving the doors open on those rooms to help get some air back to furnace .
Has filter been changed?
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Old 12-19-2011, 12:44 PM   #8
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inconsitent air flow


its a small place and only has 1 cold air return.

we leave all doors open usually. ill try closing the vent and seeing, but the pressure between the one vent to the other is immense.

one vent you get showered with air, if you sit under it, the others you put your hand to the vent and barely feel any air.
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Old 12-19-2011, 12:48 PM   #9
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thats why you close the vents getting a lot of airflow part way to force more air to other vents
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Old 12-19-2011, 02:42 PM   #10
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inconsitent air flow


Closing off supply registers is not a good solution. Your duct system is designed to move a certain amount of air, and when you close off supplies, it can't do it. It will likely force air out the other vents, but will cause an increase in your static pressure, and not moving enough air can cause a host of other problems.
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Old 12-19-2011, 02:50 PM   #11
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sometimes you dont have a lot of other options
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Old 12-19-2011, 04:08 PM   #12
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inconsitent air flow


There are always options. Closing off registers is almost always a bad one. It sounds like he needs to make some duct modifications. Closing off registers is going to cause an unnecessary temp rise, which means high head pressure if it's a heat pump, or an over temp condition across the heat exchanger if it's a furnace. Both of those conditions WILL lead to bigger problems than poor air flow.
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Old 12-19-2011, 04:10 PM   #13
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inconsitent air flow


closing off, be it partial or completely, registers will hardly if at all affect sp. closing off dampers at the plenum will.
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Old 12-19-2011, 04:55 PM   #14
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inconsitent air flow


Remove the return grille, and see if you get more air out of any of the supplies.
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Old 12-19-2011, 05:50 PM   #15
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Quote:
Originally Posted by brandonmcginnis View Post
There are always options. Closing off registers is almost always a bad one. It sounds like he needs to make some duct modifications. Closing off registers is going to cause an unnecessary temp rise, which means high head pressure if it's a heat pump, or an over temp condition across the heat exchanger if it's a furnace. Both of those conditions WILL lead to bigger problems than poor air flow.
so make a suggestion!

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