Powering WS-12-250-DC

[jsmithkc0512]

I have a unique problem where I"m trying to power this switch at a datacenter rooftop. The facility will not allow me to run DC cable from my rack to the rooftop, but they will run CAT6 for me. What is the likelihood of being able to power the switch by bonding half the wires in the cat6 line for positive and the other half for negative, and connecting it 310 ft away at our rack and powering it with a Duracomm 48V Rack Mount power supply? The data connection to the switch would be provided by fiber.

The issue we are trying to avoid is having AC power ran to the roof (20amp Min) and having to pay an absolutely insane amount for it.

Thoughts, Ideas, Concerns? This is a new one for us..

-Jordan

[Dave]

Jordan

It is ok to do this, it is simply going to be a matter of how much is your POE load & to make sure you don't try & use more current than you can push out the 24 AWG lines in the ethernet cable.

Dave

[jsmithkc0512]

We are wanting to power (2) Mimosa B11's and a Mimosa A5-360.. thoughts?

[Dave]

Jordan

Sorry, CAT6 is 23 AWG, even better.....

Dave

[jsmithkc0512]

Would you recommend Cat6 or the Ubiquiti ToughCable Carrier? Everything will be in conduit to the roof and piped into a NEMA box..

[sirhc]

I do not feel that 300' of CAT6 wire using 2 pair (4 wires) for each polarity is enough and the wire could get hot.


What are the power requirements of those radios (how many watts do they use)?

B11 requires ?? watts at 48V - My guess is 40-50 watts @ 48V

B5 360 requires ?? watts at 48V - If it is similar to the B5C then say 25 watts @ 48V


Let's assume each B11 radio needs 50 watts at 48V and the B5 360 requires 25 watts and the switch needs 10 watts so you are talking about needing 135 watts @ 48V up there.

Personally I would run (3) CAT6 wires and power the radios from the switch in the data center. Ethernet communication is speced at 326' but I have pushed good cable beyond that. Normally I would tell someone to run 10AWG to power the switch at 100 meters away.

I guess you could run 3 cables, (2) CAT6 one for each polarity, and (1) Fiber for communications.

I am sort of busy at the moment and can not take the time to calculate if the CAT6 would be sufficient to carry the needed watts but I put this up there so Dave can take a peek or you could Google copper wire capacity as there are several online wire calculators.

[jsmithkc0512]

Thank you Chris. We will see exactly how long the run is once the cable is pulled. I'm going to have them pull 4 cat6 lines, so worst case scenario, I do what you suggested and use 1 cat6 line as positive and 1 as negative and test. Stay tuned.

[lligetfa]

I was contemplating suggesting pulling multiple CAT6 lines but didn't want to be Captain Obvious.

Also was going to suggest that you could dedicate one more pair to the (+) and steal it from the (-) since AFAIK the (-) is/should be bonded to the protection ground so that can carry much of the current.

[rebelwireless]

I do bonded CAT6 for power all the time. 4x 24AWG conductors = 1x 18AWG conductor..

This calculator does a good job:

http://www.calculator.net/voltage-drop- ... &x=39&y=13

just select DC, your input voltage, and 4 conductors per phase.

for example, a 24V5A draw would lose 6.5 volts over 100ft. As long as you use a DCDC converter, or a WS with that integrated, you're good. 5A is 10 AF5X! Run this over 2 cables and you only lose 3.25 volts over 100ft.. CAT6 is cheap, double or triple up.