Where should returns go?

[21degrees]

One thing is we have to remember our design build can be different. Here in Canada we do not put fan coils or furnaces in attics much, usaually goes in basement and all supply grills are at floor level. So installing return grills high for cooling to me would be affective.

[adrianf]

A really cool and fun thing to do is get a source of smoke generation; no not puffers, a theatrical type they're cheap used at the music store. Now bypass the return grills but the smoke needs to enter through the return side of the unit so it can be distributed through the suppy duct system. Now if your supply velocities and throws are anywhere near correct the dang return can be right beside the supply grill but guess where the smoke goes, right out into the room.

Disclamer for my demo I didn't use the mechanical smoke generator I bought different sized ones that you have to ignite (they stink) available from a local suppler.

[adrianf]

They better get some trainning because central returns are good but in every room.

21

Down here in this neck of the woods most all our ductwork is in hot attics. What is best for our region is as KM noted. Central returns with minimum duct work in the attic which reduces my thermal gain according to Manual J. So now you need low resistance return paths out of your rooms back to the central return. This can be accomplished in any number of ways which most have been mentioned in this thread prior to this posting.

[beachtech]

anywhere but bathrooms and kitchens

i like returns in each room except the 2 above

[21degrees]

21

Down here in this neck of the woods most all our ductwork is in hot attics. What is best for our region is as KM noted. Central returns with minimum duct work in the attic which reduces my thermal gain according to Manual J. So now you need low resistance return paths out of your rooms back to the central return. This can be accomplished in any number of ways which most have been mentioned in this thread prior to this posting.

[B]I should have mentionthat earlier, I was thinking that, so I posted last post. You guys are totally right. I just did 4 fan coils in a huge house and top floor I ran through attic, had too put 2 " of foil insulation arround duct. Ran 16" spiral with 6" S.T.O and 6" Insulated flex. 18" spiral for R/A and did same for each R/A

[dash]

What would not be proper return path, All my returns are ducted and minimum 6"

"Originally Posted by 21degrees
I just think their are too many variables and should have 1 return in everyroom. How hard is it too do the job right. Isn't that why they call us professional. I can promiss you this that if you took a 15'x15' room and used bottom of door as return and someone came in and put 8"x14" return duct it will work better a faster for cooling because of stacking affect."

Relying on just the under door for a room that size,would not be a proper return path,it needs to be low resistance,< 2 pascals.


If the under the door was large enogh then a ducted return and it wouldn't work better or faster.

[21degrees]

Dash I didn't understand the post, but I sometimes forget that you guys are putting units in attics.

[kjander]

Had 2 contractors get back to me today. Their plans on the second level of my house that I plan to have be a seperate zonbe from the main level differed and I am unsure who is correct. They both measured and supposedly did calculations of some sort. My upper level sizes are as follows not including closets. All heights are 8 feet.

177 sqft bed
144 sqft bed
140 sqft bed
60 sqft bath
114 sqft stairwell, landing, and hall

Contractor one says

12 by 8 supply
14 by 8 return
6 in flex rounds supply each bed
5 in flex round supply for bath
7 inch flex returns in ceiling of beds
nothing in hall area

Contractor 2 says

14 by 8 supply
14 by 8 return
8 inch flex to bigger bed
low wall return (what size should these be and what size flex to the wall)
6 inch flex to other beds
low wall return
6 in flex to bath
6 inch flex supply to hall area
low wall return

[git-r-dun]

This may help you visualize what the techniques are in ducting

http://www.eere.energy.gov/consumer/.../mytopic=12730

[kjander]

As far as witch contractor is right or not in their size differences is there any way for me to figure out? They both seem professional and were concerned with getting everything sized right. yet they came up with different figures so I am a little concerned.

[dash]

My guess would be contractor 2,since the ducts are larger,plus manual D uses the same FR for supply and return,and he has the same size trunk for each.