Speaking on Deep Background, the Press Secretary whispered:
I have a bunch of cat5 buried about 1 ft below the surface connecting multiple
buildings on a campus (short runs) and lightning strikes nearby have caused
surges along one or more of the cables and burnt out switch ports. I would
like to protect the switch ports -- there seem to be lots of products on the
market.
Anyone have recommendations
A) Don't.
B) Don't
C)...
Surge protectors can not protect you from ground differential issues.
Your answer is
1) Pull fiber with that CAT5 pullrope.
2) If you REALLY, REALLY can't....
Put a fiber transceiver in building A. At least 10 foot away,
put in a 2nd transceiver and connect THAT to the CAT5 going to
building B. Connect A & B wallwarts to different breakers, with
surge protectors....and stock spares.o
{Extra help; power B from a small hospital-grade isolation
transformer -- low leakage, hi breakdown voltage.}
Hopefully, you'll merely lose transceivers & wallwarts on the
B-side, with nothing in building B being zorched.
David Lesher wrote:
Surge protectors can not protect you from ground differential issues.
True enough - but 10/100 Ethernet is normally isolated by the
transformer on the Ethernet transceiver. AFAIK there is not a
connection between the signal lines and ground. Isolation is 1500V for
the magnetics I checked.
Off course all bets are off when lightning strikes since the voltage
tends to be just a tad higher than 1500 volts.....
Mark Radabaugh
That's an amazingly expensive optoisolator.
Seriously, though, that's exactly what you're describing, and about what I'd
suggest in a no-other-option scenario -- but if it's possible to pull fiber
through the conduits, it would probably be far less expensive long term, or
even medium term if the physical fiber spools can be bought cheaply enough.
As everyone else has said, fiber is best, but if that is not an option…
We have had good luck using these:
http://www.hyperlinktech.com/web/hgln_cat6.php
Trancievers will work as well, but that is a more expensive option.
Nothing is going to protect you from a direct strike.
Jerry
Todd Vierling <tv@duh.org> writes:
Seriously, though, that's exactly what you're describing, and about what I'd
suggest in a no-other-option scenario -- but if it's possible to pull fiber
through the conduits, it would probably be far less expensive long term, or
even medium term if the physical fiber spools can be bought cheaply enough.
For those who haven't priced the stuff lately, in spools of 1000' the
per-foot prices of 2-strand MM tight buffered fiber suitable for
pulling in conduits like he (hopefully) has tends to be
price-competitive with cat5 on a per-foot basis. Extra strands are
cheap; the pricey part of fiber is the jacket and strength members;
even super-pure glass is not that expensive overall.
The expensive parts in the equation turn out to be the termination
trays and connectors.
---Rob