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Author Topic: Quick question about bonding lightning ground rod to utility ground  (Read 1522 times)

Posts: 7

« on: September 27, 2018, 09:38:13 PM »

I'm putting a ground rod at the place where my coax will enter the crawlspace (for lightning arrestors, etc.).  I need to bond it back to the utility ground.  I'm using 6 gauge bare copper wire underground.  The run is 70 feet if I run all underground or about 30 feet if I send an insulated wire under my shed (my shed is sitting on concrete).  My questions are two:

1. Can I use a split bolt connector to connect the bare wire to the insulated wire on both sides?  I'll wrap it up in Teflex and then Super 33+ tape after making the connections.

2. Do I need to put another ground rod along the way?  Even if I don't need to, should I?  I think with an 8 foot ground rod and then 30+ feet of buried bare cable I'll have a good path to ground, but I'm not 100% sure.

Posts: 781

« Reply #1 on: September 29, 2018, 12:41:31 PM »

Lots of good ways to do this, some better than others.

I would:
Use the short path.
Use non-insulated 2" strap.
Bang in a 3rd rod, somewhere in the middle.
not use tape.  
Use the rod clamps sold by Geo. Copper.  

But, like I said, there are many ways to skin this cat.  Many would cadweld on solid round wire, and I don't disagree with that.  
« Last Edit: September 29, 2018, 12:44:01 PM by WB4SPT » Logged

Posts: 6164


« Reply #2 on: September 29, 2018, 01:03:57 PM »

I'm not sure strap is code compliant.  OK for surge grounds but maybe not for service grounds.

Mark K5LXP
Albuquerque, NM

Posts: 1057

« Reply #3 on: October 01, 2018, 11:09:03 AM »

Check with an electrician. Why? If you get lightning damage or if someone is injured and the insurance company finds that the installation isn't up to code then they won't pay out.

Peter DL8OV

Posts: 2522


« Reply #4 on: October 01, 2018, 01:01:42 PM »

Peter is correct, do everything to code...  It is safer, and insurance has less hassles...

Amateur Radio: RFI help, Reviews, Setup information, and more...

Posts: 1862

« Reply #5 on: October 01, 2018, 07:06:26 PM »

I would strongly suggest the use of  3 ground rods (if you can do it) spaced 10 ft. apart, for the lightning protection ground. One ground rod is generally agreed to be inadequate for effective lightning protection. Remember, if you are unlucky enough to get a sizeable hit, you are trying to take 10 to 20 THOUSAND amps to ground!! don't want much of that headed into your AC line ground and likely the house systems looking for ground ! The AC power line ground is not, and should not be, a primary part of your lightning protection system; that is simply a safety ground. Something to remember is that a VERY high percentage of residential lightning damage (estimates vary from 50 to 90%, depending upon the source) comes in OVER the AC Power line. i.e your neighbor gets hit, but that will still put a large transient on to the line to your house. To wit: You might want to consider running AWG #4 solid from the power line ground to your "radio ground" to provide additional grounding protection for stuff coming IN from the AC mains! If you do have a fair amount of lightning in your area, you also may want to seriously consider a "whole house" surge protector at the entrance distribution panel; they are not expensive and pretty simple to install. (I believe the Code requires solid wire for grounding.) Obviously, how much money and effort you put into a grounding system is related to how common and how bad lightning strikes are in your area. In my area (eastern Kansas) lighting is BAD and frequent in the spring severe weather season and summer so I have put a lot of time and effort into extensive lightning protection, however there are parts of the country where lightning is extremely rare, so the cost vs. risk on a big system in those areas would be pretty poor in my mind. I believe the NOAA has lightning probability charts and maps which could be helpful in deciding how extensive you want to get with grounding.

73,  K0ZN
« Last Edit: October 01, 2018, 07:09:21 PM by K0ZN » Logged

Posts: 27

« Reply #6 on: October 15, 2018, 06:59:45 AM »

I'm not sure strap is code compliant.  OK for surge grounds but maybe not for service grounds.

Mark K5LXP
Albuquerque, NM
Doesn't come under NEC for his lightning protection.  Strap has lower inductance but will be harder to install.  #1 Shortest, staightest path.  #2  With 8' ground rod, also place a rod every 8' along the way, if you can.  Suggest you consult locally as local experience counts a lot with lightning protection.
73, Greg

Posts: 57


« Reply #7 on: October 18, 2018, 02:11:01 AM »

HI,   I have read that [in the USA] it is recommended to connect Your shack ground/earth to the house [utility] ground earth... but everyone I asked in Australia, said that was a VERY BAD Idea.... They all said it was best to keep your Shack earth separate....  I did have My shack ground rod in the floor of My Shack years ago, when My antenna on My Tower was hit by lightning... so the lightning came inside the house [not a great idea] and melted a few N connectors and burnt out all My RG-213 cables which were all new.... Damaged all the antennas too...  It also took out My rotator and a computer.. but no radios were connected at the time...  I no longer use the floor ground rod.. Hi Hi.... I now have 2 ground stakes about 3 meters apart and all My cables have lightning arrestors or maybe spark arrestors ??, in the cables before they come into the house..  but I disconnect every thing if there is lightning about... it is a real pain, having to climb a ladder to disconnect all the cables...  You do need to use very thick cable for the ground/earth... I use a car battery cable at My tower ground..   Don't forget about static electricity that is in the air with storms...   The lightning arrestors I use are really static electricity arrestors....
Lee  VK2LEE   

28 years as VK2LEE - The 1st 3 letter L call ever issued - in 1986 -

Posts: 6

« Reply #8 on: November 07, 2018, 05:49:56 PM »

My recommendation is to equalize all grounds.  This means bonding all grounds together.

Posts: 15065

« Reply #9 on: November 07, 2018, 06:48:45 PM »

The National Electric Code (NEC) **requires** that all electrical grounding systems in a single building be bonded together with a minimum of #6 copper wire. The primary purpose is NOT lightning protection, but rather to ensure that even with an equipment leakage fault, all grounds in the building will remain at nearly the same potential. Think about the case where the power supply is sitting near the radio. The power supply metal case is connected to the AC system ground via the third wire in the power cord. The radio is connected to the radio system ground rod via the antenna coax. The power supply case is NOT connected internally to the negative 12V lead. Something on the AC circuit causes leakage current to flow in the AC circuit ground so that the case of the power supply and the case of the radio are at different potentials. You inadvertently have one hand on the power supply while the other hand is touching the radio. There is now a leakage current path through your body if the grounds are not properly bonded together.

Bob  AA4PB
Garrisonville, VA
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