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Grounding Question (alien.top)

submitted 11 months ago by [email protected] to c/[email protected]

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I recently had a lighting strike and lost about $1000 worth of equipment. I'd like to reduce the chance of that happening again so I'm looking for advice.

I have a UDM in my house, with a 125 foot run underground in conduit to my barn. In the barn, I have a POE switch that feeds 10 cameras and an Ubiquiti AP. I'd like to add a ground somewhere. I just purchased a surge protector with ethernet for the barn, since the switch is currently plugged in directly to an outlet and should be protected anyway. I also bought this from APC for my equipment in the house. I was going to install that between my UDM and POE switch in the house, then ground it to an outlet.

I'm reading so much information about how to go about this. My barn is powered with 220v from my house, so 4 wires go to the barn H/H/N/G. the ground on the barn is the same ground as the house. If I use both devices can that create a ground loop in the event of a surge? I'm also reading that I can use the APC at any point on my network to provide protection. Is this correct?

Please don't suggest fiber runs, as the cable is already run and I don't plan on redoing it. Thank you all in advance.

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[–] [email protected] 1 points 11 months ago

Fiber converters only do something useful when all other incoming wires (especially AC) have well proven protection as implemented over 100 year ago. If every other incoming wire is not properly earthed, then irrelevant is whether a data cable is fiber or copper.

Surges are not induced. Surges are (for example) lightning's current incoming and outgoing. A direct connection.

Lightning current (a connection from cloud to distant earthborne charges) is even incoming on buried wires. As this Tech Note clearly demonstrates. Even underground wires can be part of lightning's current path. As demonstrated in the 1950s when telcos did research for COs. That would be filled with germanium transistors.

Surges (including lightning) are always a direct current flowing in and out between two charges. For lightning, a path from charges in a cloud to charges (maybe four miles away) in earth. That path must not connect anywhere inside a structure. For surge protection to exist.

Concepts (also defined elsewhere by the IEEE) dictate a "single point" ground. And when properly earthed, the protection is 99.5% to 99.9%. From all surges - especially direct lightning strikes.

For example, lightning struck a tree. That electric current went 100 feet underground to the building's earthing electrode. Up into the house. Through appliances. Then out so earth via electrodes on the other side. Then that current flowed some four miles to distant charges.

Damage because a best path to those distant charges was up through appliances in that house. Damage because earthing was not single point.

Only wild speculation claims E-M fields at that tree caused damage 100 feet away. Surges are always a current that directly flows through a structure to cause damage. For lightning, damage is in the path that connects a cloud to distant earthborne charges.

Why were church steeples damaged? Even wood is an electrical conductor. But not a very good one. So wood is damaged. Franklin's lightning rod (like all surge protection) was only a more conductive path to distant earthborne charges. Protection is always and only about providing a better path, outside, so that surge currents are nowhere inside.

In another venue, they had Fios - fiber optics. Lightning struck cause damage to various networked appliances. Fios ONT also was damaged. How can this be? It is a fiber converter? They did not have properly earthed protection on every incoming wire. So a direct lightning strike out at the pole flowed destructively through the ONT (fiber optic box) and other appliances. To connect to distant charges.

Surge damage is always about the current path into and out of a structure. Protection only exists when that current has a path that need not go into the building.

Box (Fios ONT) "powered by an electrical source means protection is gone - compromised." Protection only exists when every incoming wire connects to the same earthing electrodes. Either directly or via a protector. Those connection to and earthing electrodes require most all attention. Virtually all professionals say that.

NEC only defines a barest minimal earthing.

Regarded as legendary are Polyphaser's application notes that discuss this extensively. In one note, lightning struck the manhole cover. Which connected lightning destructively underground into a communication building maybe hundreds feet distant. Not damage induced by induced fields as so many only wildly speculate. Damage is always about where that direct strike current flows. Its incoming and outgoing path. Even on underground cables.