Disconnect fans on a 3550?

Hello all,

Probably a simple question, but I will ask anyways because I'm not 100% sure. I just picked up 2 x 3550s and just wanted to know if it is alright to disconnect the fans? They are noisy, but if I disconnect the fans it's not going to overheat and blow up on me is it?

Asif

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Comments

azaghul

I'll use the catch-all IT answer..."It depends"

In some cases it may not make a difference, but the environment you have them in will impact...ie: hot & humid conditions, heavy load vs air/con cool conditions, light load...

I also like to err on the side of caution, after all if they didn't need fans, they wouldn't have fans. If you do disconnect them, you'll also get constant fan failure messages on the console.

Jon_Cisco

I picked up a switch last week that is very noisy. I was considering the same thing. Right now I use them for very short time periods and don't think over heating should be a problem.

This is my first home lab so I have not played with any of the devices that much. My advice would be don't disable the fans unless you are willing to accept that it might damage the equipment.

Jon

Roguetadhg

These puppies get hot. If you sit in any server room that has a malfunctioned AirConditioner long enough you realize that cooling is needed.

Heck. I have to have my office lights turned off because of the heat my lab produces!

martell1000

assuming that the fans in these 3550 run full speed all the time no matter what the device is actually doing it might be worth a try. depending on the model a 3550 is designed to handle 48 ports stuffed with devices 24/7. if you are a daredevil open it up unplug the fan and constantly check if and which parts get hot.

https://www.dropbox.com/s/30n8cmqry2f6rp8/19vx535piqsjsmizan2y.jpg

found this image of an open 3550 - looks like the fans main job is to blow out the heat comming from the power supply, so you should keep an eye on that should you decide to remove the fan. another way might be to solder some resistors into the fans cable so it runs slower but you`ll need to do some research or ask an electrician to do it for you...

Asif Dasl

I opened it up and disconnected the fan and left it for half an hour or so, and eveything seemed to be OK. This is a 48 port version so I expected it to get warm pretty quick. It got warm but not too warm that I couldn't hold my hand to the bottom of the switch - albeit a very unscientific test and not under any type of load.

Very eerie, the sound of a completely silent switch! Curiousity got the better of me so I put a Kill-a-watt on it - 72W without the fan, 75W with the fan (it sounds like it's sucking up a 100W though!). I suppose I am prepared to let it die on me, I'd take a gamble on it like. Fingers crossed I don't have to make a "My 3550 died on me!" thread... Thanks for the replies everyone!

martell1000

interesting, did you close the switch during that test period or was it left open?

anyhow - if it dies on you it was in the name of science

Asif Dasl

I did one first and closed it back up, then took the power rating. Plugged in the other switch which wasn't done yet and took the power rating. I think at worst it'll cost me another €100 for another switch (maybe 2 if it all goes wrong!!), they are pretty cheap these days considering how much they were even a year ago.

Greenmet29

I have 3 2950 switches and a whole slew of routers that I have unplugged the fans on. When I am labbing, they are left on all the time and i've never had a problem. I do leave the covers off the routers, but my switches don't have an enclosed power supply and I'd rather my switches die then my kids, so I put the cover back on them just in case my kids got curious. haha... anyway, I doubt you'll have a problem unless you put a really high load on them.

Roguetadhg

Asif Dasl wrote: »

I did one first and closed it back up, then took the power rating. Plugged in the other switch which wasn't done yet and took the power rating. I think at worst it'll cost me another €100 for another switch (maybe 2 if it all goes wrong!!), they are pretty cheap these days considering how much they were even a year ago.

So when will you be Watercooling everything with this guy:
ERM-3K3UA Liquid Cooling System, Aluminum Rev1.1

Cyanic

I put resistors on most of my equipment to slow down the fans, but still have some air flow. You can get some here:

Amazon.com: Gino 5 Pcs 3" Fan Speed Reduce 3 Pin Power Cable Adapter for Desktop PC: Electronics

The pin outs matched for most of the Cisco gear, but I had to change the pins for something, maybe the 3550. They work very well and dropped the noise down considerably.

theodoxa

Asif Dasl wrote: »

I did one first and closed it back up, then took the power rating. Plugged in the other switch which wasn't done yet and took the power rating. I think at worst it'll cost me another €100 for another switch (maybe 2 if it all goes wrong!!), they are pretty cheap these days considering how much they were even a year ago.

That's still a bit expensive. 3550s are running half that ($65 = €48.84) on this side of "the pond". I hate to imagine what a 3560 or 3750 must cost over there.

martell1000

theodoxa wrote: »

That's still a bit expensive. 3550s are running half that ($65 = €48.84) on this side of "the pond". I hate to imagine what a 3560 or 3750 must cost over there.

just checked on ebay

:
[h=1]CISCO WS-C3560-24PS-S Cisco 3560-24PS-S Switch 24 Port FE PoE - 229€[/h]
but on the other hand its nice to see that my 3550s didn`t loose any of their worth since i bought em last year...
2950s are available for as low as 29€

Asif Dasl

Yeah we pay a premium for Cisco gear this side of the pond, that €100 included next day shipping from the UK though (not that I wanted next day!) I will order those cables Cyanic and try them out, I actually used something similar to that with my ReadyNAS when I changed the fans on that.

Corndork2

Dont disconnect the fan! Add a resistor!

Disconnecting the fan stops all the airflow that is not caused by convection. This can be bad for the equipment, especially if there are things racked above it.

Consider adding a resistor to the +V wire on the Fan (Usually the red wire. Red +V, Black GND, and Blue for RPM Sensing) which will cause it to slow down and make less noise. You will still have sufficient air flow.

I have a 3550-12G that had a very loud fan. I added a 25ohm 1W resistor, that slowed the fan speed down by more than half making it practicially silent, but still moving enough air to keep the switch cool.

Priston

What does show env or show env temp say without the fans installed?

Asif Dasl

Priston wrote: »

What does show env or show env temp say without the fans installed?

It's been on for about 2 hours and I did a "show env all"

Switch>show env all
FAN is FAULTY
TEMPERATURE is FAULTY
POWER is OK
RPS is NOT PRESENT

But this time after leaving it on for 2 hours it was too hot to touch the bottom of the switch, I'll get those cables to lower the fan speed failing that I'll get some new fans on eBay if I can...