Cisco SG350 series fan replacement?

phil9878

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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

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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

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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

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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:

20210409_182910.jpg

20210409_183107.jpg



20210414_175914.jpg

20210414_180014.jpg

Image1.jpg

20210414_181955.jpg

20210415_124730.jpg

20210415_160726.jpg


Hope this can help other people that would need this orientation

Thank you and best regards
 
Last edited:

WisiM

New Member
Apr 30, 2021
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Based on what I found at Pack 2x leise Lüfter für Cisco sg350x-24mp stapelbar Managed Switch Geräusch | eBay I will give a try to built this on my own. I think it could be this fan which they use: 109P0412H601

Other fans which might work:

109P0412H601 8000rpm
109P0412F601 6500rpm
109P0412M601 5000rpm
9GA0412P6F001 8000rpm
109P0412H6D01 8000rpm

KDE1204PKV3

109P0412H601 has a tachometer so this could be the right one. This fan is also available for order with a PWM signal...

I don't think this company does something special... they just take the fan, solder the cable and sell it for a high price.

Maybe someone is in US and can order a sample for us?
 
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phil9878

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Apr 2, 2021
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Based on what I found at Pack 2x leise Lüfter für Cisco sg350x-24mp stapelbar Managed Switch Geräusch | eBay I will give a try to built this on my own. I think it could be this fan which they use: 109P0412H601



Maybe someone is in US and can order a sample for us?
Do not buy it.
I have two, if you really want I can sell them to you for half the price. LoL

They do not spin at all at 6v, so they do not work. You will need the trick to solder them at constant 12v. And they are more noisy than originals because of a wheezing low level sound

If you insist, I can sell them but really a bad idea

My review was never published by ebay because of the delay since I tested them +1 year after buying
 

phil9878

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Apr 2, 2021
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Which fans are in the pack? The one I posted?
They are the Sunon, the link you posted is exactly the same description / comparision
As you see, I have tested all the combinations in this thread.

  • PWM: do not order 4 pins fans, you need 3 pins fans, they also have the tacho
  • The tacho is useless because Cisco OS assumes the fan is faulty under some unknown RPM. So, any silent fan will fail the tacho test because of the RPM
  • If the fan can spin up at 6V, you don't need to solder it at the PCB as ground (it is easy by the way, just the screw, no real soldering). The Sunon fans do not start at 6V, they need 7V. So, they do not spin unless the 12V soldering with the ground trick is done
  • If you plan to put your switch horizontally or vertically with the fan exhaust on top (cables' plugs down), the Noctua NF-A4x20 FLX are the best solution: silent and can spin at 6V. So you just can invert the wires on the FAN. I advice to use 2 small extenders, cheap on ebay/Amazon like this:
c2g_27392_3_pin_fan_power_extension-2.jpg

The advantage is that you do not need to alter the sleeved fan cable and when you change fans, you only use the modded extension cable like I did in my images posted above.

To invert the pins on the extention cable, do it on the female side, it is very easy using just a metal tip like those provided with smartphones to insert the SIM card:
unnamed2.jpg
  • If you plan to put the switch vertically, cables on top and fans at bottom, forget any silent 40x40 fan. The Sunon maybe would work, but the noise is not much better than originals believe me. Unlike the Noctua, they need the 12V mod because they cannot spin at 6V (inverting pins on the plug will not be enough) and they could not be enough strong fot the heat (I did not test them in the vertical layout because of the noise they did in teh horizontal layout). Using 4x Noctua 40x40 fans will not be enough either. They do not have the pressure to suck hot air trapped on the top between the 2 PCB boards. Even the side fans were not enough. For this specific layout, you either survive the noise of original fans or you put a 80-120 mm FAN like I did. It is icy cold and so silent :)