exhaust fan

[dlaery]

i am looking for an exhaust fan for my homemade paint boot and this is one of the specs:

• CFM @ 0.000-In. SP1904
• CFM @ 0.125-In. SP1812
• CFM @ 0.250-In. SP1719
• CFM @ 0.500-In. SP1429

I know what cfm stands for but I don't know what the rest means or how to put this in perspective.

I am guessing it has something to do with pressure

I want to know if this sucks or not.

the fan I use now puts out 1000 cfm but I am sure that is with no resistance and it is not a paint booth fan, it is a ventilation fan. I have a filter in the booth and this fan fills the filter up pretty quick but I need a little extra pull when I am spraying epoxy and the fan I have has a little bit of over spray on it and it is not working as good as it use to. I am going to put a 2nd filter in to try to keep it off of the fan.

In reading about the fan in question it is a paint booth 12" tubeaxial fan. 

It looks like it would be a lot better than what I have now. I am assuming this would pull almost twice as much as what I have now. what do you think?

[Apdriver]

This is copied and pasted doing a search as I was interested also. There is a way to figure out the SP but you would need to research that.

Those are static pressure (SP) adjustments. Static pressure is a confusing sounding term for resistance to flow. For example, if you put a 90 elbow turn in the duct, that causes a resistance to flow.  

CFM @ 0.000-In. SP 1005 means: 0.000 static pressure, i.e., if there is nothing creating any resistance to the flow... then the fan can pull 1005 cubic foot of air through the pipe, per minute.

CFM @ 1.250-In. SP 480 means 1.250 static pressure (measured in inches -In.), ie., if there is that much resistance to the flow... the fan can pull only 480 cubic foot of air through the duct, per minute.

You would have to do a static pressure calculation based on duct size, material, turns radius and locations, reductions, and duct length -- and the result would be a The SP#... then look for the number on that table and it will tell you what to expect that fan to be able to pull through it, in CFM.

 

 

[dlaery]

thanks  that makes sense. 

I'll keep working on this. right now it makes 1-90, through a filter, then another 90. I checked on the resistance on the filter and it is next to nothing, what the tech said, so if I put 2 filters in line I get double next to nothing.

so I need to find out how much SP I get with 2 - 90's. If it is not more than 0.500-in, then this fan should work.

I just hate trial and error. you know what they say "at first you don't succeed, try, try, try, try, try, try, try...................again"