First post here, so please feel free to redirect if required
I’ve just received my CRS328-24P-4S+RM which looks excellent; however, as others have noted here the “typical” fan noise is not “house” friendly. I’m therefore planning to replace the existing two fans with Noctua NF-A4x20 PWMs.
The installed fans are Sunford AD4028V12BLBGF’s. I’ve not been able to find the exact specs for this fan, but from what I can deduce from the Sunford AD4028GF series specs the closest match is the AD4028V12_LWGF with 11.61 CFM airflow and 12.15 mmH2O static pressure. By comparison, the Noctua NF-A4x20 PWMs have 5.5 CFM airflow and (only) 2.26 mmH2O static pressure.
The static pressure is my main concern here, as my PoE usage will be limited and with low wattage requirements. Accordingly, I’m planning to replace the existing Sunfords and install two further fans (4 in total) in the fan3 and fan4 slot.
My question regards the direction (push or pull) that I should install fan3 and fan4. fan1 and fan2 as currently configured are operated in pull mode (air pulled from inside the case to outside). My inclination is therefore to install fan3 and fan4 in push mode, so that they draw cool air into the case, and in general the airflow is maintained right to left across the unit.
Does anybody know in which direction fan3 and fan4 are intended to operate?
If you do that, you could create a ‘circling’ path for the air: fan3 and fan4 suck air in, it passes from right ot left, fan1 and fan2 push it outside, where (part of it) passes from left to right and fan3 and fan4 suck it in (again) …
The problem can become serious if space behind the RB is not really open (e.g. inside some smaller equipment rack or if router is mounted between longer servers) which makes harder for hot air to move away from the back side.
Most of gear I’ve seen maintains single direction of air across the device and usually that’s front-to-back (most of rack installations assume cold zone in front and hot zone at the back). So if you find additional fans necessary, I’d go for the same air flow direction (front to back).
Thanks for the reply. The fans in the CRS328-24P-4S+RM are located on each side of the unit, so the airflow is right to left (when looking at the front of the switch). There are no rear fans or vents, so no “circling” I think.
I had a response from Mikrotik support which corroborates my intent;
“you should put them in “reverse” mode. Since 1&2 push air from the case, 3&4 fans should push air into the case.”
Can you tell me if it worked? Is it better?
I have to peaces in house but one of them made a lot of noise. So i will replaced the fans but my question is wich fan did you use? And where did you get it?
What version are you using and can you post screenshots of /system health?
As @elbob2002 have said - in latest versions there were improvements which affects fan speed based on temperature.
It certainly operates well and is quiet. By placing my hand next to the fan there is good air flow through the unit, but I haven’t carried out an exhaustive flow/temperature survey within the unit
The fans I used were Noctua NF-A4x20 PWMs. I used four in total as set out above; also see the attached pics for orientation of the fans to keep the wiring tidy(ish). I purchased the fans through Amazon, here https://www.amazon.co.uk/gp/product/B07DXRNYNX. Frankly they’re not cheap, but they are quiet.
I’m currently running 6.45.6 (stable) and the system health is:
I’m guessing you don’t have something that measures decibels, do you? I’m considering this instead of a Ubiquiti equivalent, but need it to be “near-silent” as it’s going in a rack in a bedroom. I appreciate that this is nearly a year later than your thread
@SolidProfession - I can take a reading with a decibel meter on my iPhone to give you an idea. Will need to isolate the switch so will have to shutdown the remainder of my comms cabinet. Do you need it urgently?
I appreciate your reply, and no it’s not urgent at all. I’m looking to essentially consolidate what I currently have (A fanless Cisco switch that does PoE, that’s connected into a HP switch) Eight of those ports are providing PoE to access points, IP cameras, and a SIP base thing
May I ask what you’ve got plugged in, that requires PoE and how many devices use PoE from the Mikrotik switch you have? If this switch is near silent, then that definitely makes it a contender and not having to swap out for a Ubiquiti one instead!
Hi @SolidProfession, I currently have two UniFi AP-nanoHD’s connected and the rest of my used ports (0-7) are non-PoE devices. I will also connect a UniFi AP-AC-Mesh, but I need to run some further cabling for that (running SWA Cat 6 through an old farmhouse is non-trivial).
The current draw is as follows:
/interface ethernet poe monitor numbers=0,1,2,3,4,5,6,7 once
name: eth1 eth2 eth3 eth4 eth5 eth6 eth7 eth8
poe-out: off off auto-on auto-on off off off off
poe-voltage: auto auto auto auto auto auto auto auto
poe-out-status: disabled disabled powered-on powered-on disabled disabled disabled disabled
poe-out-voltage: 52.2V 52.2V
poe-out-current: 124mA 97mA
poe-out-power: 6.4W 5W
So, not masses! One thing I noted is that internally (see pictures earlier in this thread) the PoE is split into three banks for ports 0-7, 8-15, 16-23, so I’ve consolidated “all” my devices into the first bank. I hadn’t really considered whether splitting the devices across the banks would be beneficial from a thermals perspective.
I’ll get back to you with the dB readings in due course - I assume measured at 1m would be appropriate?
Thanks. That’s rather something. I’ll be changing my Arubas for UnIFi too. I largely just wanted to “learn Aruba” but once I get the UnIFI controller hosted in Azure, then I’ll swap them out for UniFis . Also, it’d reduce the electricity bill!
Thanks for that, regardless. A “worst case” would certainly be good, but even without that, that’s still pretty good! Makes me want to actually go ahead and buy one, given that it is ultimately cheaper than other stuff and also lower power than equivalent equipment
Thought you (and the rest of the community) may like to know that I’ve managed to get even better results with Noctua’s new fans. They’re about half the size of the ones you have, which probably helps. I’ve likely got a later version of the Mikrotik switch AND a later version of the Noctua fans (That much I can say for sure, given the tiny size of these)
You can see my “progress” , and my temperatures here:
Another thing I really like about this switch is the metal thing at the back of the switch, where the power goes. It makes it impossible to pull the power lead!
Mine has been behaving itself with all recent updates.. The nosiest things in my room now are a couple of HP Proliants. Not much I can do about them though!
