Whole house fan install tip?

[Fuddy1952]

Neighbor gave me a 36" whole house fan. He barely used it, his wife prefers ac!
It runs great, but I could see where the blades have been installed on the miter shaft in different positions. Where is the best air flow, blades in the venturi housing?
In the new barn I'll put it in the cupola since it has vents it would be great pulling air up and out cupola. As you see it will go between two rafters, I won't cut any purlins as that won't affect air flow much, of course I'll have to cut/remove insulation there.
My idea is make a box, 2 sides rectangle, 2 sides triangle to match roof pitch. I'll have it on switch, probably a thermostat.
Thanks any ideas. It's high up so hoping to make it easy!

 

[Fuddy1952]

Spellchecker. Miter shaft supposed to be motor shaft

 

[JerryK]

I think the best blade position for a fan is with them rotating close to the circular opening, which you may be calling the venturi position. Box fans that have this circular metal piece seem to pull/push air better than a cheaper one that is just square. I think you will really like how much hot air it pulls out of you under roof area.

 

[TnAndy]

We have a 48", two speed one mounted in an upstairs closet wall that vents out to the attic. That is our main 'air conditioner' Flip it on at night when the temps dip into the upper 60's or lower, and it will suck the bedroom curtains out to 30 degrees, and have you reaching for a blanket in the middle of the night. Love it !

 

[Fuddy1952]

I made a simple drawing looking at fan from edge. The blades can be moved forward away from motor or back. Right now it's halfway, like #2 sketch. Would it move more air like 1,2,3? Thanks.

 

[Fuddy1952]

Sorry...right now half way like #1.

 

[LS Tractor Owner]

Ours is like #1, ours works great! Like TnAndy said, we need to reach for a blanket.... It really won't matter in your situation / usage where the blades are positioned. What will matter is that the "exhausted air" actually gets exhausted through the cupola. Make sure the sides of the 'triangle' are closed off, also on the 'rectangle' sides up between the rafters and purlins. Basically a "shaft" for the air to go up into the cupola then outside. You will definitely notice a difference!

 

[MossRoad]

Neighbor gave me a 36" whole house fan. He barely used it, his wife prefers ac!
It runs great, but I could see where the blades have been installed on the miter shaft in different positions. Where is the best air flow, blades in the venturi housing?
In the new barn I'll put it in the cupola since it has vents it would be great pulling air up and out cupola. As you see it will go between two rafters, I won't cut any purlins as that won't affect air flow much, of course I'll have to cut/remove insulation there.
My idea is make a box, 2 sides rectangle, 2 sides triangle to match roof pitch. I'll have it on switch, probably a thermostat.
Thanks any ideas. It's high up so hoping to make it easy!View attachment 607382View attachment 607383View attachment 607384View attachment 607385View attachment 607386

Ours is set up like yours is right now, with the blades centered halfway in and halfway out like your picture.

 

[fitter1]

You may overload motor depending on this position of fan on shaft. Use an amprobe when setting this up.

 

[jfh28]

one of the things you are going to want to check is the net free air space of the cupola......in other words the sq inches of space that is not blocked and will allow the air to exit......if its wire meshed then you will need to look up the reduction factor for that number......match the net free air space against the required exhaust rating of the fan......it should be equal or larger......if its not there will be a backup pressure of air flow as more air will be entering the cupola then can exit......I've seen many fan motors prematurely burn out due to this situation......Jack