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cramer
Premium
join:2007-04-10
Raleigh, NC
kudos:9
reply to jmich

Re: Cable Nazis... Grab a tissue

Interesting points. PoE would be a special case. Using the first chart google points out [link], 100m of 24AWG (worst case, cat6 is supposed to be 22) wire would have 8.41976ohms of resistance. (PoE uses 2 parallel pairs.) 802.3af specs 15.4W (350mA) and 802.3at 34.2W (600mA.) So, a max "af" device would have just over 1W in the cable, and "at" just over 3W. If you put 48 runs in one conduit, they were all pulling full power, and they were all 100m... (an unlikely case) that would be a 50W or 146W pipe. (31 and 92 for 22AWG) That'll get toasty if there's no air moving around it. (BTW, I've seen power conduits like that, but never any data wiring.)

[PS: It's worth noting your switch or midspan would need a 750W or 1700W power supply *just for PoE* to run such a setup.]

TheMG
Premium
join:2007-09-04
Canada
kudos:3
Reviews:
·NorthWest Tel
said by cramer:

If you put 48 runs in one conduit, they were all pulling full power, and they were all 100m... (an unlikely case) that would be a 50W or 146W pipe. (31 and 92 for 22AWG) That'll get toasty if there's no air moving around it.

That works out to 1.46W per foot, which is unlikely to create any problems. Might feel slightly warm to the touch but that's about it.


DarkLogix
Texan and Proud
Premium
join:2008-10-23
Baytown, TX
kudos:3
reply to cramer
said by cramer:

[PS: It's worth noting your switch or midspan would need a 750W or 1700W power supply *just for PoE* to run such a setup.]

BTW some POE switches do have that

The ones where I work have dual 930watt powersupplies
so in theory 1860watts, I think when one PS fails it cuts the available PoE power down to what one powersupply can do.

cramer
Premium
join:2007-04-10
Raleigh, NC
kudos:9
Yes, but they are exceedingly expensive, rather large, and generate far more heat than all the wiring in the building.

Hahausuck
Premium
join:2003-12-14
kudos:2
HIPOE is awesome, but you're right it is horribly expensive even in lower density options.


DarkLogix
Texan and Proud
Premium
join:2008-10-23
Baytown, TX
kudos:3
reply to cramer
I really don't foresee any issue with POE heating cables.

Ya the heat coming off the switches is far more than all the wiring in the place.

I was just pointing out that some switches do have that kinda wattage, though how much is for POE and how much is for the switches to do normal stuff I'm not sure but I'd bet the bulk is for POE.