PoE and 36 AWG patch cables ?

[hmw]

I have a network rack where I use Cat 6 36AWG patch cables from Monoprice: Micro SlimRun Patch Cable. The run from the patch panel to the switch is 2 feet. Monoprice specs these cables at < 87.6 ohm/km, I've seen some 26 AWG cables at 90 ohm/km

Would these cables be safe for PoE? I have 3 * 802.3af and 1 * 802.3at PoE devices. The 802.3af devices consume 1.5W, 4.5W and 7W - and the 802.3at device consumes 8W. I've checked the cables and none of them are getting warm. Checked network speeds and the cables perform as expected. Some of the runs are at 10 GbE and I do get 10 GbE.

How unsafe is it to use these cables? Do I risk the cables overheating and catching fire and/or destroying the switch and server?

 

[blinkenlights]

I have a network rack where I use Cat 6 36AWG patch cables from Monoprice: Micro SlimRun Patch Cable. The run from the patch panel to the switch is 2 feet. Monoprice specs these cables at < 87.6 ohm/km, I've seen some 26 AWG cables at 90 ohm/km

Would these cables be safe for PoE? I have 3 * 802.3af and 1 * 802.3at PoE devices. The 802.3af devices consume 1.5W, 4.5W and 7W - and the 802.3at device consumes 8W. I've checked the cables and none of them are getting warm. Checked network speeds and the cables perform as expected. Some of the runs are at 10 GbE and I do get 10 GbE.

How unsafe is it to use these cables? Do I risk the cables overheating and catching fire and/or destroying the switch and server?

Cannot (and will not) speculate whether they will cause your switch and server to go up in flames, but I would not choose to use them for PoE. I purchased 23 AWG plenum rated cable for something that I am planning to install in my attic. Then again, I always overengineer things like this.

Reference: https://www.nexans.no/eservice/Norway-no_NO/fileLibrary/Download_540223405/UK/files/PoE+_2013_1.pdf particularly section 2b.

 

[randman]

Two weeks ago, I switched to using 2’ Monoprice Slimrun Cat6a cables between my patch panel and POE+ switches. No issues so far. I really like how they make working with my switches so much easier.

 

[gregsachs]

This document has some calculations;

https://oberoninc.com/images/WebDocs/Partner_Resources/IEEE%20802_3af%20PoE%20document.pdf

Typical cat 5 is 100ohm/1km,
Power=i^2 * R, and we can figure the current at 200ma based on 8w device, 50 volts.
so .2*.2=.04 A^2 *R= watts in cable.
90 ohm/1km~90 ohm/3300 ft= ~90/1600 ohms /2ft=0.05625 ohms for the patch cable.
so power disappated in the cable is .04*.05625=.002 w.
I wouldn't worry about it.
Note that based on resistance/meter, this is closer to 29 AWG than 36 AWG, which is rated for over 1a. I don't know that I'd use those cables for a 60w PoE device, but for an 8w no issues.

 

[hmw]

This document has some calculations;

https://oberoninc.com/images/WebDocs/Partner_Resources/IEEE%20802_3af%20PoE%20document.pdf

Typical cat 5 is 100ohm/1km,
Power=i^2 * R, and we can figure the current at 200ma based on 8w device, 50 volts.
so .2*.2=.04 A^2 *R= watts in cable.
90 ohm/1km~90 ohm/3300 ft= ~90/1600 ohms /2ft=0.05625 ohms for the patch cable.
so power disappated in the cable is .04*.05625=.002 w.
I wouldn't worry about it.
Note that based on resistance/meter, this is closer to 29 AWG than 36 AWG, which is rated for over 1a. I don't know that I'd use those cables for a 60w PoE device, but for an 8w no issues.

hah, I was using the same calculations for 2 feet and reached the same conclusion

 

[blinkenlights]

Okay, can someone who promotes use of these ultra-slim cables answer a question? Why?

No, really, I am being serious - is it just about the aesthetics? I like to have an extra buffer available, whether we are talking about power or network infrastructure. Why these Ethernet cables that look as thin as USB 2.0 cables?

 

[randman]

I use 2' Monoprice Cat6a SlimRun cables for my POE cameras. Normally, they use less than 5 watts each. A couple of them are PTZ, which can theoretically use 16 watts max, but only when positioning the PTZ cameras. But moving the cameras via PTZ is rare, and when positioned, only takes a second or so. Normally, they use 5 watts or less.

I used to have about 30 CAT 6 cables in my equipment closet going to 3 switches. Switching to the SlimRun cables makes it so much easier managing the cabling to the 3 switches. Plus, I had the bonus of going from CAT 6 to CAT 6a (I'm transitioning to Multi-gigabit in this equipment closet).

 

[blinkenlights]

Thanks, @randman. I can see where that makes sense. I guess I've just had bad luck with slim/flat Ethernet cabling over the years. I do have some flat cables.. but only used for low-speed serial console access

 

[hmw]

Thanks, @randman. I can see where that makes sense. I guess I've just had bad luck with slim/flat Ethernet cabling over the years. I do have some flat cables.. but only used for low-speed serial console access

Me too, which is why I looked at the spec sheet (pdf here) from Monoprice and made sure they were up to spec. The patch panel used to use normal cables before and it's made a huge difference - even with just 20 odd cables. It's just better organized and much easier to pull cables out etc. Not to mention the rack door can actually close now ...

 

[Evan]

For home I am a huge fan of slim cables, just makes cabling so much easier. at work it’s all cat6a/cat7 which is horrible and that’s even using the quality stuff.
i tend to use POE rated cable for POE devices though but thy are higher power at 20+ watts. (Access points)

 

[blinkenlights]

i tend to use POE rated cable for POE devices though but thy are higher power at 20+ watts. (Access points)

Correct. The 23 AWG plenum cable referenced above is feeding from an injector to a Ruckus R720 that consumes 36+ watts in at+ mode.

I also understand the comments about it being easier to work with the thin cables.. but I always add "as long as it works." Previous owners of my house ran el-cheapo Cat 5 all over the place, which I've been replacing with Panduit Cat 6A as I have time. Not planning for 10Gbps at the moment, but do not want to be repeating the same cable pulls once I upgrade. And all you people with fiber drops at home can just stay quiet