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-   -   How many return vents needed? (http://www.diychatroom.com/f17/how-many-return-vents-needed-15052/)

tigerbalm2424 01-02-2008 12:07 PM

How many return vents needed?
 
Im working on finishing my basement, currently working on the HVAC ducts. How do I determine how many return vents are needed? Does it just equal the number/size of supply vents?

Thanks

(still waiting to hear back from City on these questions. So far they are not very helpful or responsive)

qnzkrew 01-02-2008 01:47 PM

hey tiger im also trying to run my own ducts, so as far as i know and have read you have to match or better surpass the amount of cfm you are supplying so the furnace doeesnt have to work harder to get the air. hope the other guys can help you out

tigerbalm2424 01-02-2008 02:00 PM

Quote:

Originally Posted by qnzkrew (Post 84797)
hey tiger im also trying to run my own ducts, so as far as i know and have read you have to match or better surpass the amount of cfm you are supplying so the furnace doeesnt have to work harder to get the air. hope the other guys can help you out


Yeah, thats what I just read too.

qnzkrew 01-02-2008 02:28 PM

are you doin the whole ductwork layout yourself?

bigMikeB 01-03-2008 12:04 AM

The return should be double the cfm size of the total of supplies to cut the velocity in half.

5kimprovements 01-04-2008 09:35 PM

duct
 
where i come from they tell us 20% larger on the return side is sufficient.

bigMikeB 01-05-2008 08:10 AM

Quote:

Originally Posted by 5kimprovements (Post 85700)
where i come from they tell us 20% larger on the return side is sufficient.


Wouldn't you say that a typical residential supply trunk is 24x8 and a typical return is 25x16?

biggles 01-05-2008 08:25 AM

if you had the unit just the other side of the wall in the basement and in a closet the return ducted or not out to that wall along the floor with a grill on the finished side is typical.keep the filter size in mind when extending it or just open the wall and size the hole the size of the fiter.you don't need the return to run the lenght of your supply ducts just nearest the unit and the stat location.

Spike99 01-05-2008 09:56 AM

Not too sure what the answer is. Perhaps the answer is between 20% - 50% "more" intake volume openings when compared to heat vents. Not too sure. If you can, target 50% more. If needed, you can always block off the intake vents you feel your basement doesn't need.

---------------

I do know that our basement's floor was always cool. Too cool. After our basement flood in 2005, a furnace guy installed 2 cold air intakes that now "suck air" off our basement floor. Since then, our basement floor and rooms have felt much warmer. When installing cold air intake vents, do ensure their vents are at bottom of basement floor. Their location dramatically helps...

.

biggles 01-05-2008 11:10 AM

just like in commercial HVAC we use the return to move some air back to the unit with the return pull(inthe false ceiling by adding return grill work),,so the discharge heat is supplied into th basement and the unit pulls the remaining heat acrossand into the cooler floor...you will know the return is good when you go to open the fan section with the unit running...should pop up and out easily


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