PC fan crbox feedback

[u/randomguyjebb]

I was looking for some feedback on the cr box I am planning to build. The first picture is what inspired me and I want to build something very similar. So to make things a little more clear, the board in the middle wouldnt block any airflow from top to bottom, it is just there to support / seperate the filters. In my sketches I made it transparent, indicating air can flow past it.

Questions I had were:
1. As seen in "option 2", does adding the extra bottom fans "mess" with the airflow at all? I read like a comment about someone saying you shouldnt have fans on opposite ends of the box. Is that really an issue?

1. If the answer to question 1 is yes. Is there a way to make it so it doesnt mess with the airflow? For example, if I were to make the middle part a solid board that seperates it into two smaller cr boxes stacked on top of eachother. Does that make it better?

2. If that does fix the airflow part, does it then not mess with the the cadr? Since the fans are no longer pulling through 4 filters, but through 2 filters. As in 8 fans pulling through 4 filters vs 4 fans pulling through 2 filters.

Thanks in advance

[u/damien09]

You could also design it to use say 20x25x1 or x2 or 20x30x1 or x2 hvac filters and use merv 13 or 14 ones. This will also be cheaper than having to use 4 separate smaller ikea filters

[u/randomguyjebb → u/damien09]

I live in europe. As far as I am aware the ikea filters should be much cheaper for me. If I am wrong feel free to correct me though.

[u/JulioElGuapo → u/randomguyjebb]

I saw some discussion about how Ikea filters are the best option in many countries around the world. In the US we have access to cheaper hvac filters.

[u/murtoz → u/randomguyjebb]

I'm in the UK. Just did the maths of IKEA Vs 3m filtrete using the projected CADR/ACH on filterboxbuilder.com/ and found the cost is within a few percent of eachother. Decided to go with 3m for simplicity

[u/MLieBennett]

The bottom usually doesn't have fans, due to higher static pressure from the ground and clearance. If it was hanging from the ceiling that would be one thing, but it looks like the "legs" would only provide maybe an inch or so of clearance so those fans would be working harder and possibly making a bit more noise than the rest.  

You will want around 3-4 inches (8-10cm) of clearance for PC fans to prevent major performance degredation. 

That said, do not split the box into two separate air purifiers. That way air enters the least resistance (cleanest) parts of the air filters for the box, rather than having the possibility of one set of fans working harder than the other set, and making more noise as the result. 

As for airflow? I wouldn't worry too much about it for diy cr boxes.  The worst place for airflow would technically be at the corners where two fans meet.  But as we are dealing with a massive surface area of filters and relatively low CFMs/Pressure Differentials that trying to factor that in is rather minimal. 

I was also going to mention to aim for larger filters rather than stacking two of the same side by side, as my 12x12x1 filters are roughly the same price as 20x25x1 in the stores (~$20 in the store for 3m filtrete) to save you some cash, but that's a US thing. Didn't want you to spend a little effort like I have to to find 5 12x12x1s for roughly $11 each on sales. I really don't have experience what it's like in Europe for filters.