How-to: Swap the fans on the USW-Enterprise-24-POE

It’s been a while since I’ve made any sort of a blog post, as an attempt to get back to that we are going to try something entirely different.

I recently added a Ubiquiti USW-Enterprise-24-POE switch to my collection so I could get PoE and 2.5GBe in one place. Right now it lives in a rack in my office along with some other devices. However nothing in the rack was nearly as loud as this new switch, and not only is it significantly louder, it constantly changes speed and the frequency change was just starting to drive me nuts.

A bit of research showed no one had actually attempted to swap the fans on this exact switch, though several had asked. There is a guide for the USW-PRO-24-POE which I suspected to be similar as it’s also a gen2 switch. Since I like voiding warranties I decided to give it a go and throw in some NF-A4x20’s and return some peace and quiet to my workspace.

Step 1. Remove the top cover

To remove the top cover we must remove a total of seven screws, 2 on each side and 3 on the back. You will need to remove the rack ears to reveal screws underneath, you will also need to remove a small security sticker on the back of the switch to reveal one of the three rear screws.

Depending on your region and whether or not you catch a particular Ubiquiti support employee on a bad day or not, this may cause them to deny any warranty claims.

Slide the cover back while also lifting gently from the back side. There is a lip that fits under the front plate you must clear, additionally the back must clear the power cable locking mechanism.

Step 2. Remove the fan shroud

A photo of the usw-enterprise-24-poe fan shroud with NF-A4x20 fans installed and outlines for where the screws and connectors are.

First we must disconnect the PCI-E like power connector labelled “POE”. We can put this cable off to the side.

Once removed you should see the 2x four pin fan headers, go ahead and disconnect those. Once disconnected we can unscrew the 6 screws holding down the fan shroud and wiggle it upwards. Be extra cautious to not touch any of the power supply components under this shroud.

Step 3. Swap the fans

With the shroud removed we can unscrew each of the fans. Once unscrewed we can slide them downwards to avoid pinching the cables.

Eagle eyed viewers might have noticed that the fan headers are slightly non standard. As such we must use a utility knife to cut the small plastic tabs off the connectors of the new fans. Now would be a good time to do that before they are installed.

a photo of a 4 pin PC fan connector (not from the NF-A4x20)

With the the connectors shaved down we can go ahead and slide the fans in, ensure that they are in the same orientation as the original. The fan grills should be facing inward towards the PSU.

Assuming you are using the NF-A4x20, the screws we removed from the old fans will not fit. We must use the screws that came with our new fans.

Step 4. Reassemble

With the new fans installed in the correct orientation we can reattach the fan shroud. Be extra careful not to pinch any cables while reinstalling, pay close attention to both the power cables at the back and the other cables near the front.

A bit of gentle wiggling should allow the shroud to sit flush again, reattach the screws, plug in the fans (be mindful that the “shaved” side faces outward away from the shroud), and reconnect the POE power cable. Do your best to use the existing tape for cable management.

Next reattach the cover by putting it on and sliding it forward. Screw in the 3 screws on the back and the 4 screws on the sides.

Step 5. Results

In my testing I noticed an immediate and marked improvement in noise. Over the period of 24 hours with an ambient temperature average of 23c. Thermals and fan speed percentage remained relatively similar. However due to the NF-A4x20 having a lower maximum RPM and higher CFM I am seeing a lower ~3500rpm vs ~5500rpm at 55% fan speed. Additionally cranking the fan RPM to 100% is still remarkably quieter than the 55% of the previous fans.

Snapshot of stock fan thermals:

(UBNT) (Config)#show environment

Temp (C)....................................... 50
Fan Speed, RPM................................. 5561
Fan Duty Level................................. 54%
Temperature traps range: -5 to 110 degrees (Celsius)

Temperature Sensors:
Unit     Sensor  Description       Temp (C)    State              Max_Temp (C)    Alert_Temp (C)
----     ------  ----------------  ----------  -----------------  --------------  ----------------
1        1       TA                40          Normal             42              80
1        2       PSU               39          Normal             42              80
1        3       TEMP-1            42          Normal             46              80
1        4       TEMP-2            42          Normal             44              80
1        5       MAC-1 (Local)     49          Normal             52              80
1        6       SPHY              50          Normal             52              80
1        7       SPHY              44          Normal             46              80
1        8       SPHY              44          Normal             46              80
1        9       SPHY              41          Normal             45              80
1        10      SPHY              43          Normal             47              80

Fans:
Unit Fan Description    Type      Speed         Duty level    State
---- --- -------------- --------- ------------- ------------- --------------
1    1   FAN-1          Fixed     5561          54%           Operational
1    2   FAN-2          Fixed     5678          54%           Operational

PSU and RPS status:
POE PSU Error Count............................ 0
PSU 12v PG     PSU 54v PG     RPS Present    RPS 12v PG     RPS 54v PG
------------   ------------   ------------   ------------   ------------
True           True           False          False          False

Snapshot of NF-A4x20 thermals:

Temp (C)....................................... 52
Fan Speed, RPM................................. 3492
Fan Duty Level................................. 55%
Temperature traps range: -5 to 110 degrees (Celsius)

Temperature Sensors:
Unit     Sensor  Description       Temp (C)    State              Max_Temp (C)    Alert_Temp (C)
----     ------  ----------------  ----------  -----------------  --------------  ----------------
1        1       TA                43          Normal             43              80
1        2       PSU               41          Normal             43              80
1        3       TEMP-1            44          Normal             44              80
1        4       TEMP-2            44          Normal             44              80
1        5       MAC-1 (Local)     50          Normal             52              80
1        6       SPHY              52          Normal             53              80
1        7       SPHY              45          Normal             46              80
1        8       SPHY              45          Normal             46              80
1        9       SPHY              42          Normal             45              80
1        10      SPHY              45          Normal             47              80

Fans:
Unit Fan Description    Type      Speed         Duty level    State
---- --- -------------- --------- ------------- ------------- --------------
1    1   FAN-1          Fixed     3492          55%           Operational
1    2   FAN-2          Fixed     3457          55%           Operational

PSU and RPS status:
POE PSU Error Count............................ 0
PSU 12v PG     PSU 54v PG     RPS Present    RPS 12v PG     RPS 54v PG
------------   ------------   ------------   ------------   ------------
True           True           False          False          False

Conclusion

If you don’t mind potential warranty issues and have this switch in a place where noise is a concern, swapping the fans is entirely feasible. I will note that my specific use case does not require a large number of PoE devices. As such your results may vary and I urge you to keep and eye on the thermals, especially that of the PSU. This can be done by logging into the switch with SSH, running telnet localhost to break out, then running show environment to access all the temperature sensors.

I hope this helps someone who was on the fence about attempting a fan swap on this switch.