Cisco SG350 series fan replacement?

phil9878

New Member
Apr 2, 2021
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@geho10
I removed the tacho cable, which was not serving any purpose by the way.
It fixed the issue and no more overheating even while drawing 62W PoE and transferring data over two 10 Gb LAN cables at about 6 Gbps total bandwidth use.
After 45mn running:

Image1.jpg


Whith the tacho cable connected, the fans were properly spinning when the the system overheated. I guess at some point the voltage dropped to low levels and they were pushing less air !
I did not monitor the voltage all long the process, so not sure what is happening when the yellow cable is connected.

Thank you again for the feedback. I will post new photos with the proper connection
 

phil9878

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Apr 2, 2021
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Well, as soon as I put it in the final location, it gets hot
It is because i set it suspended vertically, fans down. The fans are not enough strong to pull hot air from top to bottom
 

geho10

New Member
Mar 3, 2021
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hmm ok, for a vertical positioned switch it's maybe better to switch the direction of the fans --> try to blow in fresh air the hot air should be blowed out on the sides.

mine is classically mounted in a self-made mini rack ;)

2021-04-08 16_42_41-Fotos.jpg

an other option would be to play with the position/direction of the fans: 2021-04-08 16_49_29-Fotos.jpg
 
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buri

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Mar 28, 2021
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buri.sk
I get my SG350X-24P two days ago and I did the same modification as @geho10 did because there is not 6V but 5.3V which is not suitable for Noctua fans. And I load my switch with PoE 38W and I connected one 10 Gb connection. My temperatures was stabilitzed after a few hours to this:
38Wload-heat.png

So everything OK. Maybe tacho cable is the reason in your situation.
 

phil9878

New Member
Apr 2, 2021
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I tried with two fans on the side, blowing outside. Passive intake. It is a no go with a vertical mount and LAN plugs on top. The fans just do not have enough pressure for such an orientation.
Lost enough time. I will install 2x 92 mm fans and never look at the temperatures again. Will post when done.
 

phil9878

New Member
Apr 2, 2021
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I drilled a hole and tested a Fractal Design R2 fan of 92x92 mm rated at 24 cfm
No more overheating in the vertical layout, cable plugs on top.

I ordered a Noctua NF-A9 FLX fan rated at 37 cfm, a grill and a sealing silicone frame.

I will post final setup images when done for anyone needing the vertical setup.

Notes:
- i could have tested 4x NF-A4-20 fans but i really think they do not induce enough pressure for such a large case
- the ground can be kept on the fan plug if the fan can spin at 6V. That gives the voltage regulation of 5 levels in the switch. The Fractal fan properly works in that setup. Hopefully the A9 too
 

phil9878

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Apr 2, 2021
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FAN setup for a vertical layout with LAN plugs on top:

Note: this will obviously void your warranty with no possible way of going back

The low speed 40x40 mm fans cannot drain heat from top of the case to the bottom (or even to the sides) in this orientation. Only the stock fans at near maximum speed (Level 4 to 5 in firmware, probable 10 to 12v) can properly evacuate all the hot air from top to bottom.

I tried many configurations, with up to 3 low speed fans on the sides without success. The board PCB overheats at +100° in a few minutes and the switch is turned off automatically. They probably do not have enough pressure to drain the hot air trapped in the top between the two PCB layers.

I fixed it in this way:

- Drilled a 93 mm (ideally should be 90-92 mm) hole in front of the motherboard and chip radiator (hardest part)
- Drille 4x 5mm holes for fan screws, at a 82.5 mm distance (try to be very precise !)
- Noctua NF-A9 FLX (92 mm with 3 pin plug) FAN
- A 92 mm FAN grill
- A 92 mm silicone FAN gasket
- a modded FAN cable converter: like previous posts images, the 12v is modified to the PCB fan plug layout, the ground is plugged into the case and the Tacho is disabled
- I tapped one of the two bottom fan holes to have more air drained from the sides. Tapping the two bottom fan holes causes a slight increase in temperature in the area of the electric cord, on the right of the PCB

Note: the NF-A9 FLX properly starts at 6V, so the cable modding is not needed. The fan will be adjusted by the Switch firmware in 5 levels from 6v to 12v depending on temperature. The mod is only needed if you want the fan to be always running at 12v for optimum temperatures and fan performance.

The temperatures are much better than with the stock two fans at maximum speed. Touching the case from outside is no longer hot, just a quiet non perceptible warm feel. Obviously the noise is completely controlled (I keep the switch in a dedicated downstairs room that was too noisy with the stock fans even with the door closed). The Switch logs show a maximum Level 2 voltage set by the firmware, probably a 7v output. With stock fans I was at least at 10-12v to be able to control the temperature in this layout.

I do not have a serial port available and I was too lazy to open my PC case to install it or buy a Serial to USB adapter. So I cannot get the exact temperature readings from the console. However, the logs and case temperature are an enough indication.

Below are the final setup pictures:

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20210409_183107.jpg



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20210414_180014.jpg

Image1.jpg

20210414_181955.jpg

20210415_124730.jpg

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Hope this can help other people that would need this orientation

Thank you and best regards
 
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