so i dont know about the rest of you guys. But i hate summer now. Everytime i hear on the news a thunderstorm is rolling through i cringe. It seems after every storm we have a crapload of customers that there NICs are blown, or just as common the ethernet port on the radio is shot. It powers up but wont register an ethernet link. Any of you guys see this frequently too? I mean we ground block each radio, plug the poe’s into surge strips but it still happens. It seems all it takes is a fair amount of static in the area from a near strike and the units are pretty much useless. Is there anything that can be done to stem the tide?
We’ve also seen a lot of damage this year. We’ve spent as much time on repairs as installs this summer. Pretty tiring.
Often the outlet ground that the PC is plugged into is not the same ground potential as the ground you use for the radio. The difference might be 1/2 ohm or more. This difference is enough to allow induced current to flow across the Cat5 data lines and pop the NIC. An AC surge suppressor is not going to help with this as it’s ground reference is still the house ground.
A 600SS + APC supressor for the PC is your best protection. Ground both devices to the house ground rod using #10 solid wire.
http://apc.com/resource/include/techspe … ku=PNET1GB
This is a great article on DSS grounding - all the rules apply:
http://www.mikeholt.com/mojonewsarchive … 020303.htm
Where do you put the APC?
Put the APC at the PC
Ground the APC at the nearest plug receptacle?
Both the Canopy and the APC need to be grounded to the house ground rod, or at the least the same ground point.
You need to eliminate the difference in ground potential between the radio and the PC NIC.
Jerry Richardson wrote: Both the Canopy and the APC need to be grounded to the house ground rod, or at the least the same ground point.
You need to eliminate the difference in ground potential between the radio and the PC NIC.
So you are locating the PoE protector just outside the house, with the ground lug attached to the rod (or the wiring running to the rod) AND you are running out a #10 from the APC to the same point? I take it the APC is just inside the dwelling unit opposite the wall of the rod?
Let’s back up.
Lightning is a release of charged electrons trying to find their way back to earth. In a ground strike, most of that energy (but not all) makes it’s way to earth via the bolt and the rest is dissipated through the surrounding air. In a non-ground strike the energy is released into the air. Those electrons are still trying to get back to earth.
A section of unshielded Cat5 between the SS and the SM acts like a receiver of ambient energy. The longer the section, the more energy it will pick up. You want to have as short of a section of Cat5 between the SS and the SM as possible.
If you have a short section of Cat5 between the SS and the SM, chances are good you will have a long section between the SS and the PC. Putting the APC at the PC and bonding both grounds together ensure the excess energy is shunted to ground before it can get to the Ethernet port.
Rather than running the ground lead form the APC all the way back to the SS, you could use the drain wire in shielded Cat5.
amd phreak wrote: [quote="Jerry Richardson":1e66docx]Both the Canopy and the APC need to be grounded to the house ground rod, or at the least the same ground point.
You need to eliminate the difference in ground potential between the radio and the PC NIC.
So you are locating the PoE protector just outside the house, with the ground lug attached to the rod (or the wiring running to the rod) AND you are running out a #10 from the APC to the same point? I take it the APC is just inside the dwelling unit opposite the wall of the rod?[/quote:1e66docx]
Ideally you would want to ground the POE/600SS to the house "common" ground, assuming the house is properly grounded of course. Now the APC surge prot. could ground to your pc chassis or a nearby wall outlet. This will also prevent ground loops.
If you cannot locate the common house ground then it would work as you've described above.
Gotcha,
We use those same APC’s on the fiber side of the house, they seem to work very well.
Our demark is the 600SS, the customer is responsible for the inside stuff. I wanted to be clear on the best reccomendation for the customer.
As always, thanks for your ideas
Reay
The problem with grounding to the PC chassis is that you don’t really know the quality of that ground and the impedance (not resistance) to ground relative to the SS impedance to ground.
Recall:
Resistance is DC
Impedance is AC (Spikes are AC)
Grounding to the PC chassis or outlet ground is risky as you don’t know
a. The quality of the PC chassis ground
b. The quality of the wire in the PC power cord
c. The condition of the outlet prongs
d. The condition of the ground connection on the outlet
e. The condition of the wire and other ground connections between the outlet and the ground you used for the SS.
I can guarantee you with 100% certainty that the impedance from the SS to earth is lower than from the PC chassis or wall outlet to earth. The difference is impedance magnifies the current flow and consequently the voltage created. Get the voltage high enough and you’ll pop the Ethernet port.
A common ground point is the key but not all commons are truly common. The only way to now for sure is to put it in yourself.
If your home is properly grounded, the 600SS is grounded at the common house ground, your pc is using a standard grounded power cord, then the APC can be grounded to the pc chassis.
http://www.apcmedia.com/salestools/EALN … _R1_EN.pdf
Most new homes here in TX do not have a visible ground rod since the builders tend to put them inside the wall behind the main service panel. I see some cable and dbs techs grounding to the meter. Others cut corners by not grounding anything at all.
If your home is properly grounded
And there's the rub.....