Looking for a square (16" O/C) carbon filter exhaust fan

[lyfespan]

I have this mostly setup and I am tweaking everything.

Instead of venting into the joist area and the raceway, I am going to run a flex duck (or I could go rigid if it offered any advantage) from the fan output, down the raceway to a room nearby but separate. The run will be about 25 feet.

Since that is kind of a long run, I was thinking about using a 6" to 8" adapter after the fan and use an 8" flex duct for the run instead of a 6". I have read some bad things about using reducers with fans but I think the way I am planning is OK.

Would it be better just to stay with 6" or am I OK with sizing up to 8" with a reducer?

I will talk with my neighbor, he's and heating and air engineer, but I believe that the theory is, that if you are going to have a long run for intake or exhaust, you need to start large and taper down to the size you need. This is again to cut down on static resistance. I should be seeming him tomorrow morning, and will have all your answers.

 

[Hackerman]

My thinking behind going to an 8" was that the air could almost "dump" into the 8" from the 6", thus relieving any potential for back pressure in a 25' run. No?

It's a straight run, pretty much. And since the flex duct comes in 25' lengths, it would be stretched pretty tight. Even stretched tight, there are plenty of ridges in flex duct.

Still, if you think a rigid duct would be better than the flex stuff they have 8' x 6" rigid duct at the store pretty cheap..... it only costs a little more to go first class. LOL

Thanks, LS

 

[lyfespan]

I also would like to inquire about the distance of the fan blades from the cylinder body of the fan. Is about a 1/2 in, if so you have an opportunity to improve and quiet the fan with some spray adhesive and thin foam insulation. Just remove the blade assembly spray the body and sleeve it with the foam, this will make it quieter and improve air moving. I'm going to look for some air flow diagrams that will help people with these air moving issues.

Just remember good rule of thumb is to intake cold clean air and bring it into the room at the lowest point possible, and to keep the exhaust pick up as far away from the return(intake entry) and as high up as you can, heat rises as we all know.

 

[The Hemp Goddess]

You cannot insulate this kind of fan in that manner.. However, you can make an insulated box to put it in if noise is a problem. We had a DIY here somewhere at one time....

I don't think you are going to have back pressure problems unless you have a lot of sags or turns--straight runs with no bends makes for nice even air flow from the fan. I really don't see the need to go the extra expense of 8" ducting.

I will be experimenting with even longer fairly straight ducting runs. I am going to see if I can extend my ducting so that I can exhaust it into a small greenhouse I set up on my deck to help heat it at night. The temps here are still dropping down below the freezing mark. I was surprised last year when a late hard (unforecast) frost killed things even in the greenhouse. I think this will alleviate that worry.

I am always amazed at the difference in temperatures at floor level and ceiling level. Having a good oscillating fan helps to keep this air mixed up so that it does not stratify into heat layers. But the cooler air will always be at the bottom and the hotter air will always rise. So, it is quite important to do as lyfe mentioned with intake low and exhaust pulling from high as possible.

 

[Hackerman]

This is why the call it dope......

I go to the store and I buy 30 feet of rigid duct, some elbows and other assorted goodies to do this exhaust thing all the way from the grow room to my workshop across the basement.

I get home and I take down the ceiling to install everything and I notice that the cold air return is RIGHT above my room. LOL How could I have missed that all the times I looked up here. I don't know who first called it dope but..... they were right. LOL

So, I am going to exhaust right into my cold air return. The grow room uses a carbon filter plus the furnace has a filter so I don't think I'm going to have a problem with odor (I hope not).

Now, the current question is, what's the best way to cut a nice round hole in a sheet metal duct so I can install a tap. I was thinking one of those rotary cutters would work nicely.

Can't believe myself, sometimes. LOL Back to the store again tomorrow.

 

[Hackerman]

Well, that went amazingly smooth. I am anything but a handyman and jobs like this usually turn into a nightmare for me. LOL

Piece of cake. Cut the hole. Put in the collar. Attached the flex to the fan. Bingo, I'm exhausting into my cold air return. Can't believe I didn't do this years ago. LOL

Thanks again to everyone for the motivation and assistance. My room is upgrading nicely thanks to all of you.

 

[sawhse]

Awesome man. :48: