Replacing the Fans on a UniFi Switch 24 Poe 250w

May 10, 2020

I have two pieces of hardware with fans in my home networking rack. The first is a UniFi Dream Machine Pro which has never been audible. The second on the other hand, a UniFi Switch 24 PoE 250W, has fans audible from approximately ten feet away. Perhaps slightly less with the air conditioning running. This was highly annoying as this radius encompasses the couch in our living room, somewhere we frequently occupy. Armed with the knowledge that other people had done a fan replacement on this switch, I decided to do the same.

The first step was to find some replacement fans. The brand that immediately comes to mind when I think of quiet fans is Noctua, a company known for their silent fans and, well, unique color scheme. For this project, I was replacing the two 40x20 millimeter fans that come with the switch, which corresponds to Noctua’s NF A4x20 FLX model.

The process of disassembling the switch was fairly straightforward. Remove the seven screws from the sides and back of the switch. The shell can then be slid backwards to disengage the tabs at the front, and then lifted off to separate it completely.

So this is what the inside of a switch looks like…
So this is what the inside of a switch looks like…

Unfortunately the connectors on the Noctua fans were not long enough to reach the fan connectors on the main board, but Noctua accounts for this and provides the equipment necessary to splice the existing fan wires together with the included “OmniJoin” connector. While it did feel wrong to cut through the existing fan wires, I found joining the “OmniJoin” adapter to the existing wires as easy as the manual made it out to be.

One of the spliced connections.
One of the spliced connections.

The next obstacle I encountered was mounting the fans. The screws used to mount the stock fans were too small to attach to the Noctua fans, and the screws included with the new fans were too large to fit in the mounting holes. I decided to try the rubber anti-vibration mounts included with the fan kit, and after much struggling with a pair of pliers, I managed to pull the rubber mounts through the mounting holes that were clearly smaller than intended. Then I realized that the mounts would not be able to protrude from the side of the case, as the shell sits flush with the case. I ended up trimming the mounts down to about 1 millimeter which probably reduces the strength of the mounts, but I don’t foresee this being a major issue. If the mounts do end up failing, I will probably attach them with Velcro instead.

The fans mounted to pull air out of the case. Note the mounts protruding from the side of the case.
The fans mounted to pull air out of the case. Note the mounts protruding from the side of the case.

After sliding the shell back into place over the protruding fan mounts, I screwed it back into place. A tip here is to start with the screws at the back of the case which will align the holes on the sides.

With the new fans, the switch is inaudible until about two feet away. Mission accomplished. I do regret not getting temperature readings before doing the replacement, but right now the switch is sitting at 65° C while providing about 10 W of PoE power. While this seems to be a bit higher than average, it is still well within the standard operating temperatures.

RackSwitch-US.v4.0.80# swctrl env show
General Temperature (C): 65
Temp Sensor      Temp (C)     State            Max Temp (C)  Alert Temp (C)
===============  ===========  ===============  ============  ==============
TEMP-1           51           Normal           53            75
TEMP-2           38           Normal           39            75
PoE-01           57           Normal           59            80
PoE-02           65           Normal           65            75
PoE-03           65           Normal           65            75
PoE-04           63           Normal           65            75
PoE-05           61           Normal           61            70
PoE-06           59           Normal           61            70

Fan Duty Level: 100
Fan              Speed       Duty level  State
===============  ==========  ==========  ===============
Fan-1            0           100         Operational
Fan-2            0           100         Operational
Fan-3            0           100         Operational
Fan-4            0           100         Operational

If these temperatures become a problem, I will populate the two empty intake fan slots. Overall I’m very happy with the change, and more importantly, so are my roommates.