I’ve been running a Dell PowerConnect 5324 as my secondary switch at home that connects all the rooms together. The switch is rather loud in the location it’s sitting so I’ve decided to replace the fans in it to something quieter.
The switch uses 2 40mm high speed fans that exhaust air out of the enclosure. I had several 40mm fans that I could try to get the best noise/cooling ratio. I’ve used a digital multimeter with a thermal probe to measure the efficiency of the fans, my simple SPL meter to measure noise level and a simple Android app to measure the sound spectrum. The switch was ran for 30 minutes in each configuration to let the temperature of the switch settle.
Ambient Noise: 23.3 dbA
Ambient Temperature: 23C
What would happen if I invert the fans so that they blow air into the switch?
|Inverted Stock Fan
The new fans are significantly thinner and operate at lower RPMs. They do not move quite as much air as the original fans.
A quick note about the fan pinout on the Dell PowerConnect 5324. The fan pins are actually non-standard and have to be swapped around. The Dell PowerConnect fans use Positive-Sense-Negative pinout as opposed to the standard Negative-Positive-Sense pinout. Connecting the fans incorrectly doesn’t seem to have any detrimental effect on the fans themselves (as I found out) but the fans will simply not operate.
Once the fans were installed. I ran the test.
A 9.1 dbA drop is quite significant, that’s almost half as noisy as the original fans and the switch is now quieter than the ambient noise in the room the networking equipment is in. The temperature with the new fans running only went up a few notches.
Even though this was the configuration I was most likely stick with, just for kicks, I’ve went ahead and tried the inverted fan configuration.
|Inverted New Fan
In the end I ended up going with the smaller fans in the same configuration as the stock fans, blowing air out of the switch. While slightly louder than the inverted configuration, it was lacking the whine which was quite noticable.