If you need an easy way to implement a "quick-and-dirty" POE solution, you CAN
safely deliver 120VAC over most Cat-5 cable types.
(check your specs to be sure) Most are rated to 300V RMS, so the voltage
(Dielectric Break-down) is not an issue (the Phone
companies routinely run 140VDC power over all types of twisted pair to power T1
repeaters). The only thing you need to make sure
of, is that you PROTECT the cable from excessive current. I recommend TWO
fuses at the "bottom" end of the cable rated at 2A (one
on each side of the incoming AC line just to be sure), and use fast-blow if you
can. I use both wires in the Brown pair for "Hot"
(black) and the Blue pair for Neutral (white), as this happens to conform to
the European color code by some strange coincidence.
Also, I HIGHLY recommend you run the Cat-5 inside a metallic conduit of some
type (Seal-Tite, BX, etc is good) for not only safety,
but this also makes your cable environmentally hardened and shielded, and
provides a solid ground for your equipment. DO NOT EVER
USE PART OF THE CAT-5 AS A GROUND!
For safety and equipment protection, I don't advise you to use RJ-45s on the
cable carrying 120V, make direct connections on a
terminal block or something instead. Just "split out" the Orange and Green
pair and run it directly into the RJ-45, and attach the
Brown & blue pairs directly to a terminal block. Also, don't try to run the
Ethernet in 100Base mode if you do this, as it is more
reliable to run in 10Base. (Although tests confirm that 500 feet of Belden
1500A Cat-5E cable will still run at 100mBit reliably
while pulling a 1 amp load at 120VAC on the Blue/Brown pair. Don't "split" the
pairs, use both wires in a pair together for each
"leg". This is safer and will help reduce inductive coupling of the 120v into
the Ethernet.
You should be able to power most any 2.4Ghz radio equipment and even a couple
of Amplifiers with under 2 Amps of 120VAC (That's a
240 Watt capacity).
The only down-side is that this requires you locate the SMPS (Switch-mode Power
Supply) up on the far end of the cable, where it
could require a "climb" if it fails, but on the plus side it makes the
installation less likely to fail if lightning gets into the
equation. Lightning induced surge on a +5VDC cable going directly into a
Lucent AP-1000 is far more likely to kill it than the same
lightning induced surge going into the front-end of the SMPS. It's also a good
idea to put a cheap APC Back-UPS on the line at the
bottom to give you some extra protection.
Drop me an Email if you have any questions....
Phil Sadow
Ingineerix Communications Consultants
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