Wanted to give some info on swapping the fans in an ICX7250-48P. As fohdeesha's awesome original post says - it's quiet to start with, but this thing sits right next to me in my office so I wanted to go even quieter.
The 48P has 3 fans - in my case they're Nidec W40S12BGB5-52 T02. They're pretty whiney and I couldn't find any info about them on Nidec's site. I tried disabling one fan but the sound didn't decrease much, and the ASIC temperature went past 70 C (which made me uncomfortable).
https://i.imgur.com/lo5pTnw.jpg
https://i.imgur.com/JS3P3ok.jpg
Knowing the basic info about them (3-pin, 12V, 40x40x28mm, ~25 CFM, 18000 RPM, tach-controlled), browsed Digikey (their fan search tool is amaaaaazing).
DC Brushless Fans (BLDC) | Fans, Thermal Management | DigiKey
Narrowed my options down to a few different Delta fans that I've had good luck with in the past. There's a lot of choices that appear to meet the specs for the Brocade, I went with the
Delta FFB0412SHN-BF00 - they're slightly newer in design and quieter than its peers, coming in around 5 dB lower. They also run a max of 13000 RPM vs the Nidec's 18000 RPM (though I can't seem to manage to push it that high, ever).
The trick, apparently, with the ICX is that the pinouts are a littler weird - but the Deltas come without fan connectors, so you'll have to crimp them anyway. If anyone ever comes looking and isn't sure of the order, here it is:
PIN 1: Blue on Delta/Green on Nidec - Frequency
PIN 2: Red on Delta/Yellow on Nidec - Positive
PIN 3: Black on Delta/Black on Nidec - Negative
https://i.imgur.com/kBuMcNs.jpg
With the Deltas installed, the system is quieter - there's no whine, and less air noise. System controls the speeds and gives me speed/thermal data just like the stock fans. It has passed the wife-test noise-wise. Tinkering with the idea of trying out the Delta FFB0412VHN-BF00 - which runs at 9500 RPM but is another 6 or so dB quieter; significantly less air movement though.
Temperatures have remained in the mid-60s under decent load, which I'm quite happy with. Tried two fans vs three again, just for kicks, but again temps went higher than I was comfortable with, so sticking with three.
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Special thanks to all the other posters that have contributed about fans on this thread, including fohdeesha and Skud - you guys gave me the confidence to drop some money and try this out.