Questions about cfm...

Walterwhiter

Walterwhiter

Well-Known Member
So I have ×2 250cfm 150 Cfm airflow I believe it said. One pushes one pull on either end. I'm getting an air cooled hood and filter. It a negative pressure set up. Pull through the filter-hood-fan#1-about 20' of ducting-and out of the building. So now for the question how do I figure out what cfm my filter needs to be. Do I just go off the max cfm of one fan #1. Or do I factor in both and adjust for some loss through the almost 20' haul.
Thanks
 
bgmike8

bgmike8

Well-Known Member
Walterwhiter said:
So I have ×2 250cfm 150 Cfm airflow I believe it said. One pushes one pull on either end. I'm getting an air cooled hood and filter. It a negative pressure set up. Pull through the filter-hood-fan#1-about 20' of ducting-and out of the building. So now for the question how do I figure out what cfm my filter needs to be. Do I just go off the max cfm of one fan #1. Or do I factor in both and adjust for some loss through the almost 20' haul.
Thanks
Click to expand...
I'm confused by the numbers. You have what?

So when your looking for a filter you want it to be rated at least what your max air flow will be through or into the filter.
When in doubt go with a higher rated filter so that you don't move to much air and let smell escape.

That being said, I think you could probably google a calculator for duct loss. It's very common in hvac for installation of equipment. You're probably using flexible ducting which is even more of a loss.
 
bgmike8

bgmike8

Well-Known Member
I'm also not quite understanding where your filter will be in relation to your hood and exhaust.
The reason I'm curious is that if you pull through a sealed hood you could still get smell.
 
Walterwhiter

Walterwhiter

Well-Known Member
bgmike8 said:
I'm also not quite understanding where your filter will be in relation to your hood and exhaust.
The reason I'm curious is that if you pull through a sealed hood you could still get smell.
Click to expand...
2 259 cfm fans. My room is a closet the filter in the in the back top of the room.

Pull into the filter through the light. The first fan will directly connect to the hood then through 18+ feet of ducting too the second fan and exhausted out
 
Michael Huntherz

Michael Huntherz

Well-Known Member
Walterwhiter said:
I bet buy at that price it's the most expensive thing I've bought!
Click to expand...
The iPower filters work okay, I bought that exact 4" for my little drying tent, it is working absolutely fine. I'm not sure you want to run the 250cfm fans full speed with it, it will wear out faster, just get a little fan speed controller, $15 or so. I have a 150CFM fan on my 4" The Phresh filters last longer but I don't feel like they are more effective out of the box, speaking from experience. I think two cheapies is a better deal than one phresh, but your mileage may vary, I've read the same things about cheap filters, but my personal experience differs. Disclaimer; I'm not a lawyer or a doctor, but I have an extremely sensitive nose, and my sister is a straight-edge Marine, she didn't smell a thing.
 
Walterwhiter

Walterwhiter

Well-Known Member
Michael Huntherz said:
The iPower filters work okay, I bought that exact 4" for my little drying tent, it is working absolutely fine. I'm not sure you want to run the 250cfm fans full speed with it, it will wear out faster, just get a little fan speed controller, $15 or so. I have a 150CFM fan on my 4" The Phresh filters last longer but I don't feel like they are more effective out of the box, speaking from experience. I think two cheapies is a better deal than one phresh, but your mileage may vary, I've read the same things about cheap filters, but my personal experience differs. Disclaimer; I'm not a lawyer or a doctor, but I have an extremely sensitive nose, and my sister is a straight-edge Marine, she didn't smell a thing.
Click to expand...
I thought about wiring up a dimmer switch same thing right? I have some bends in the duct but the least amount possible. Man I this point I kinda wish I had some more balls in the beginning and made this easier on my by buying a 1500 dollar everything and one kit! Thanks man.
Those phresh filter higher than me brother lol
 
Michael Huntherz

Michael Huntherz

Well-Known Member
Walterwhiter said:
I thought about wiring up a dimmer switch same thing right? I have some bends in the duct but the least amount possible. Man I this point I kinda wish I had some more balls in the beginning and made this easier on my by buying a 1500 dollar everything and one kit! Thanks man.
Those phresh filter higher than me brother lol
Click to expand...
As far as I know those speed controllers are just potentiometers, so yes, dimmer should work, but I'm not an electrician. I ended up buying everything twice because I refused to do it right the first time, so I get how you feel. Cheers.
 
You must log in or register to reply here.
Top