Increase CFM with Multiple Fans: Building Advice

[jimbofoxman]

I built the unit linked below several years ago. I wanted to rebuild it to utilize a electrostatic filter and bag filter. Right now I just run 2 filters (11 merv) before the fans and 1 filter (11 merv) after the fans. I know things like design, filters, etc all work into the calculations of this, but I am wondering if I would be shooting myself in the foot by adding the electrostatic filter and bag filter.

Right now the filter sizes are 10"x24". Would be going to 12"x24"

Each fan is rated at 340 cfm...so to me all 3 running would be more CFM. One commercially available units run unrestriced at 1500cfm using a squirrel cage blower, then with the filters in place drop down to 1000cfm. Another one unrestricted runs at around 1000cfm and filtered 750cfm.

http://lumberjocks.com/projects/392

I have a big furance blower that I was thinking of using if this one doesn't cut it, but that would have to be on the ground and now mounted.

All I know right now is the unit as it stands sucks up a lot of junk and I can see the particles of dust heading towards the unit.

Thanks all!

 

[FredGarvin]

The addition of more filters means more flow restriction but the electrostatic unit should be a minimal blockage as compared to a membrane type filter element. Running all 3 fans does, in theory, triple the flow since they are in parallel. A squirrel cage fan will usually produce more head pressure so it would probably fare much better in the scenario with the extra filters. If you are smart about the placement and ducting to the unit, I would (without seeing the fan curves) put my money on the floor unit being your best bet for getting the best flow through the unit.

 

[oswaler]

I would recommend conducting some calculations and simulations to determine the potential effects of adding an electrostatic filter and bag filter to your unit. Factors such as design, filter efficiency, and fan power can significantly impact the overall CFM output. It would be helpful to gather data on the current CFM output with your current setup and compare it to the potential CFM output with the added filters.

Additionally, it is important to consider the potential drawbacks of increasing CFM. While it may seem beneficial to have a higher CFM, it could also lead to issues such as increased noise and turbulence, which could impact the overall effectiveness of the unit.

I would also suggest consulting with experts in the field, such as HVAC engineers, to get their professional opinion on the potential impact of adding the electrostatic and bag filters. They may have insights and recommendations based on their experience and knowledge.

Overall, it is important to carefully consider all factors and gather data before making any changes to your unit. This will ensure that you are making an informed decision and not potentially compromising the effectiveness of your unit.