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Grounding Question (alien.top)

submitted 1 year 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] 2 points 1 year ago

You have assumed the word 'ground' without an always required adjective. Numerous grounds exist. For transient protection of appliances, only 'earth' ground matters.

The concept first demonstrated by Franklin over 250 years ago. Surges (lightning is only one example) are hunting for earth ground. How that current connects to earth defines damage.

A most common incoming path is AC mains. Once anywhere inside, then that transient hunts for earth destructively via appliances. A most common destructively path is into networked hardware on AC mains. Then out to earth via networking hardware.

Damage is often on the outgoing path - ie an ethernet or HDMI port.

If any wire enters without making a low impedance (ie less than 10 foot) connection to single point earth ground, then protection is compromised.

Protection only exists when a surge is not anywhere inside.

Ethernet must make that low impedance (ie hardwire has no sharp bends or splices) connection via a protector. Coax cable has best protection without any protector. Only a hardwire makes a low impedance (ie less than 10 foot) connection to same earthing electrodes. Every wire inside every incoming cable (without exception) must make that earth ground connection.

How good is protection? Defined by that connection to and quality of earth ground electrodes. Wall receptacle safety ground is all but disconnected - never is an earth ground. Number of electrodes may be dependent on factors such as geology.

Products from APC do not claim effective protection. One need only read specification sheets. How does its hundreds or thousands joules 'absorb' a surge that can be hundreds of thousands of joules? How do 2 cm protector parts 'block' what three miles of sky cannot?

Scams target consumers who ignore these and other numbers. No protector claims protection. Either it makes that low impedance (ie hardwire not inside metallic conduit) to single point earth ground. (All four words have electrical significance.) Or may give a surge more paths to earth via nearby appliances.

Type 3 (plug-in) protectors cannot be anywhere near earth ground. To not try to do much protection. To avert what tiny joules protectors do - fire.

Don't take my word for it. Professionals have been both saying and doing this stuff for over 100 years. Only recently have companies such as APC been selling magic boxes to consumers who ignore numbers and all this well proven science.