Installing A Ground In This Unusual Case

Zeigh

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I could use some suggestions for how to ground an outdoor network camera in an unusual case.

In 2017 I lost a camera mounted to a corner of my home due to a lightening strike close by. It was my own fault for not using shielded cable or proper grounding. So, I designed a new location away from the house. Unfortunately the contractor that built the block wall where the mount sits missed the memo on establishing grounding into the rebar, so it is up to me to find a workaround.

The camera is an Axis Q6115-E PTZ unit and mounted atop a 20 foot metal pole with their pendant kit. There is a small ground wire that bonds the camera to the inside of the mount. The bottom of the pole is bolted upon a six foot high concrete block wall column filled with cement. The 12” mounting screws were simply placed in the concrete when it was poured and sadly not bonded to any internal rebar. The Cat6 shielded PoE communication wiring goes through the center of the pole and routed through the wall into a utility box, where a surge suppressor unit (Ubiquiti ETH-SP-G2) is, then traveling through 92 feet of mostly buried conduit before entering the home. There is a secondary surge suppressor on the inside wall and grounded to the main home grounding system.

What I am lacking is the grounding of the pole and/or first surge suppressor. My home is built upon a granite rock hillside and simple trench digging is usually quite cumbersome because of this. I suspect that driving a standard copper grounding rod would be the same (regardless of various installation orientations that are acceptable). So, here are the questions that I have:

1. Does the pole itself need to be grounded in this case? The utility box mentioned is just eight inches away from the pole base, so I hope to just start the grounding there. If it would be worth it, I could string a 10 AWG wire directly through the pole to the camera housing for grounding and tie in the first surge suppressor along the way.

2. There is another utility box about 26 feet away that has a 10-3 AWG wire in it for AC electrical use. Would accessing the ground in that wiring be acceptable?

3. If I do have to drive a ground rod, is a shorter length acceptable for this application? Solar panels were recently installed and the contractor that drove the ground rod for that went through three of them before he was able to sink a rod at least six feet, then cut it off. (Yes, the resistance readings were satisfactory.)

HA, maybe my OCD is taking over here and I am overthinking (as usual). Still, I want to do what I can to reduce the chance of another expensive lightening strike.


Peace,
Dr. Z.
 

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SpacemanSpiff

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<uneducated perspective>

Attach a separate ground the pole. I would think that anything that will help minimize the chances of the discharge using the the CAT 6 cable will be a good thing.

I would not tie into the ground of an electrical circuit. The ground rod installed by the solar folks is appealing, how far from the camera location is it?

</uneducated perspective>

How effective will a ground rod be in a granite hillside??
 

sebastiantombs

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Love your view!

I'd do whatever it take to get a ground rod in eight feet given your soil conditions. I have to ask what the conditions were like when the resistance was measured on that six foot ground rod. Had there been any rain in the previous week or less?
 

Zeigh

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Just like excavation or drilling for a well, you never really know what you are dealing with until the metal hits the dirt. The first day digging for the foundation of the home produced three boulders 3'x3'x3' from a hillside that was relatively smooth with desert plant life.

The solar panel array ground rod is much too far away to be worth the trouble. Regardless, that ohm reading still falls within parameters. Another luck of the draw.

I'll let this post mature a bit before making a firm plan. In the meantime, I ordered another ground rod attachment for my rotary hammer.

As for the comment on my home location view, thanks! It only took 35 years of hard work and good saving habits to finally afford. They will have to drag me out of here in a pine box! I'll try to remember to make my camera feed public with my last breath so everyone can watch.


Peace,
Dr. Z.
 

Griswalduk

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You can get long drill bits which may help installing an earth rod. You can use multiple rods at multiple points connected together to improve impedance. Depending on the ground they don't necessarily have too be driven in vertical.

You can also get earth mats and mesh that can be used instead

I'd recommend a bare earth tape used as a lightning conductor clipped down the outside of the camera pole and wall. Running from probably a little beyond the top of the pole so it "attracts" the lightning and down the wall leading to the earth rods / mats / mesh. What's left of the roll of earth tape could also be laid / left in a trench and act as the earth rod. In the UK there's usually a disconnection point for testing purposes. In this instance somewhere at bottom of the pole.

Instead of going directly underground at the bottom of the pole you could instead clip the tape horizontally along the wall 12" from the ground. From this horizontal run you could "Tee" off at numerous points to the earth rods until you get a suitable earth impedance reading.

Thankfully in the UK the climate is milder and lightning is nowhere near as prevalent as it is in the U.S so I would recommend a having a look at your local electrical codes or regulations they could be a lot stricter.

Earth tape


Clips


Info / examples

 
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TVille

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Grounding is more art than science, I'm afraid. Ham radio guys argue about this all the time. The only thing they agree on is the solution that won't work for you. Unplug the coax and throw it outside. Seriously, that is about the only way to keep it out of your house. Assuming you have POE, I would get a surge suppressor for each end of the cable, and drive a ground rod out there. Even if the rod is a few feet away. If you get a lightning strike, you can't protect it anyways, don't try. You are really protecting from induced voltages from "nearby" strikes. I don't think electrical codes will have much impact if you are low voltage (POE). I would ground the pole. It could very well attract/pickup static enough to cause a problem. Grounding it eliminates that issue.
 

Griswalduk

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As mentioned keep the earthing of the pole separate from the house / solar array etc and use surge protection. If lightning strikes I'd want it to hit the tape ( lightning conductor ) go down the pole and dissipate to earth using the earthing system at the pole.

Fault current will take the easiest route and if you start linking things up goodness knows where it will find. You will be introducing paths for it to get to other equipment.
 
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