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Author Topic: Grounding system & avoiding ground loops  (Read 996 times)
VK2FCMD
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Posts: 25




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« on: March 20, 2019, 12:42:08 AM »

Hi all,

I'm trying to find the best answer for my situation, I'm not a lightning/grounding expert. I'm putting together my shack again after some time off and I've got a question;

I'll be putting a box on the outside of the house with a copper plate inside. I'll have surge protectors bolted to the copper plate that will connect the coax from the antennas to the coax to the shack. The copper plate will be connected to the ground rod via some 3" copper strap.

Inside the shack all equipment will be connected to a copper bar with some copper braid.

I'll be using the same 3" copper strap to connect the shack ground to the outside. The question I have, is do I connect the shack ground bar directly to the copper plate inside the box on the outside wall, or do I connect the shack ground bar directly to the ground rod outside, or doesn't it matter. I'm trying to avoid ground loops.

Thanks for taking the time to reply Smiley
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AA4PB
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Posts: 15066




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« Reply #1 on: March 20, 2019, 06:00:47 AM »

It doesn't really matter which you connect to. In order to meet the NEC requirements, make sure you bond (permanently connect) your ground rod (or connecting wire) to the electrical system ground rod (or connecting wire) using at least a #6 wire. This ensures that both grounding systems remain at the same potential (i.e. no voltage difference between them).
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Bob  AA4PB
Garrisonville, VA
VK2FCMD
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Posts: 25




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« Reply #2 on: March 20, 2019, 06:20:41 AM »

Hi, thanks for that advice! I will be bonding this ground rod to the main ground rod, that part I'm sure of Smiley

I just wasn't sure if the in shack ground should tie to the ground rod or to the copper plate the surge protectors are mounted to - to avoid creating a ground loop.
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W9IQ
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Posts: 3553




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« Reply #3 on: March 20, 2019, 06:28:02 AM »

If you are using low impedance connections, such as your wide copper straps, it would be difficult to develop ground loops from either connection point provided these are relatively short connections.

If it were me, I would go directly to the ground rod so as to avoid a potentially common point of failure - the connection from the ground plate to the ground rod conductor. By going direct, you have some redundancy in your ground system connections.

You use the term copper strap - these should be a solid copper material. Using a braided material outside will allow for corrosion between the braid conductors which will eventually reduce its effectiveness as a low impedance conductor.

- Glenn W9IQ
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- Glenn W9IQ

I never make a mistake. I thought I did once but I was wrong.
VK2FCMD
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Posts: 25




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« Reply #4 on: March 20, 2019, 06:37:01 AM »

Hi,

Thanks for the advice. The material is 3" copper strapping - it's solid copper 3" in width .012" in thickness - I was only going to use braid inside the shack.

Cheers Smiley
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W9IQ
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« Reply #5 on: March 20, 2019, 07:12:33 AM »

It sounds like you have things well thought out. Enjoy.

- Glenn W9IQ
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- Glenn W9IQ

I never make a mistake. I thought I did once but I was wrong.
VK2FCMD
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Posts: 25




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« Reply #6 on: March 20, 2019, 05:13:55 PM »

One last question, I promise!

Can the copper strap be directly buried in the ground or does it need to remain above ground?

Cheers.
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SOFAR
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« Reply #7 on: March 20, 2019, 05:21:10 PM »

.012" thick?
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W9IQ
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Posts: 3553




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« Reply #8 on: March 20, 2019, 05:30:05 PM »

.012" thick?

If you are questioning that, you may want to calculate the skin depth in copper at 1 MHz.

- Glenn W9IQ
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- Glenn W9IQ

I never make a mistake. I thought I did once but I was wrong.
W9IQ
Member

Posts: 3553




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« Reply #9 on: March 20, 2019, 05:34:34 PM »

One last question, I promise!

Can the copper strap be directly buried in the ground or does it need to remain above ground?

Cheers.

You can do that but make certain it is protected from physical damage such as frost heave, rocks, shovels, etc. If your soil is acidic you may see continuous erosion of the copper instead of it forming protective oxides.

- Glenn W9IQ
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- Glenn W9IQ

I never make a mistake. I thought I did once but I was wrong.
VK2FCMD
Member

Posts: 25




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« Reply #10 on: March 20, 2019, 06:31:36 PM »

Thanks for your help! I think I'll just put them through some pvc to protect them.. cheap insurance.

Cheers!
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