neutral, ground, bond.

[arkieguide]

If you remove the ground wire from all your radio connections. Then bond/ground, all your equipment to a copper grd. bar then from there, to your ground rod. Then how does stray current get to your electric ground system ? Either from lightning are short circuit. ? Your neutral goes to ground at the service entrance.

 

[RFI-EMI-GUY]

If you remove the ground wire from all your radio connections. Then bond/ground, all your equipment to a copper grd. bar then from there, to your ground rod. Then how does stray current get to your electric ground system ? Either from lightning are short circuit. ? Your neutral goes to ground at the service entrance.

The ground rod, or rods, should be bonded to the ground rod at the service entrance. The goal is to ensure that there is minimal or zero voltage differential in the ground system.

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[prcguy]

The National Electrical Code requires your antenna ground connects back to the ground at the electrical entry point of your house and any additional ground rods you put in must be bonded to the electrical entry point ground with no less than 6ga copper wire. That is because your question has been brought up before and that is the answer to the problem. You can look up NEC Article 810 that deals with antenna and radio grounding.

The main reason for the National Electrical Code is human safety and I have experienced putting in a ground rod on my property that was on the far side of the house from my electrical entry point but very close to my neighbors. I could measure about 90 volts AC between that ground rod and the third wire ground in the electrical outlets in my radio room at the time. Turns out my house and my neighbors house were fed from different power poles with different distribution and grounding.

Its nearly impossible to protect an existing house from lightning damage due to the complexity and cost of the grounding. One of the biggest things that happens with radio setups using a ground rod that is not bonded to the house main ground is when lightning hits the antenna or power lines, the difference between the neutral and ground can go many thousands of volts apart and anything plugged into the wall will usually not survive.

When all grounds are bonded together and lightning hits, the neutral and ground and even the hot might all rise together but the difference between them can still only be 120V between neutral and hot and ground will be close in potential to neutral.

If you remove the ground wire from all your radio connections. Then bond/ground, all your equipment to a copper grd. bar then from there, to your ground rod. Then how does stray current get to your electric ground system ? Either from lightning are short circuit. ? Your neutral goes to ground at the service entrance.

 

[elwood_blues]

The National Electrical Code requires your antenna ground connects back to the ground at the electrical entry point of your house and any additional ground rods you put in must be bonded to the electrical entry point ground with no less than 6ga copper wire. That is because your question has been brought up before and that is the answer to the problem. You can look up NEC Article 810 that deals with antenna and radio grounding.

The main reason for the National Electrical Code is human safety and I have experienced putting in a ground rod on my property that was on the far side of the house from my electrical entry point but very close to my neighbors. I could measure about 90 volts AC between that ground rod and the third wire ground in the electrical outlets in my radio room at the time. Turns out my house and my neighbors house were fed from different power poles with different distribution and grounding.

Its nearly impossible to protect an existing house from lightning damage due to the complexity and cost of the grounding. One of the biggest things that happens with radio setups using a ground rod that is not bonded to the house main ground is when lightning hits the antenna or power lines, the difference between the neutral and ground can go many thousands of volts apart and anything plugged into the wall will usually not survive.

When all grounds are bonded together and lightning hits, the neutral and ground and even the hot might all rise together but the difference between them can still only be 120V between neutral and hot and ground will be close in potential to neutral.[/QUOTE

Excellent answer! As a FF, I've been to many lightning strike calls going back to 1981 that left me scratching my head. I learned that lightning doesn't follow the NEC! I once went to a call where lightning hit the yard, jumped to the buried "Invisible Dog Fence" wire, traveled roughly 200' feet back to the house, blew the coontroller apart, and then proceeded to go to the main breaker panel and throughout the house! Quite impressive!

Here's my question: Why can't we just ground our antenna lead in to the Ground at the A/C outlet and be done with it? Regardless of where the antenna ground is bonded to, it still has the potential to backfeed the line IN to the house, unless you're fortunate enough to have a lightning arrestor at your main breaker panel.

 

[mmckenna]

Excellent answer! As a FF, I've been to many lightning strike calls going back to 1981 that left me scratching my head. I learned that lightning doesn't follow the NEC! I once went to a call where lightning hit the yard, jumped to the buried "Invisible Dog Fence" wire, traveled roughly 200' feet back to the house, blew the coontroller apart, and then proceeded to go to the main breaker panel and throughout the house! Quite impressive!

Good example.

Many years ago I was on a ship that was hit by a lightning strike.
-No damage to the radar.
-No damage to any radios.
-No damaged navigation lights or wiring.

Did blow out an engine management computer down in the engine room, below the water line.

I agree, Lightning doesn't follow the NEC, but we should!

Here's my question: Why can't we just ground our antenna lead in to the Ground at the A/C outlet and be done with it? Regardless of where the antenna ground is bonded to, it still has the potential to backfeed the line IN to the house, unless you're fortunate enough to have a lightning arrestor at your main breaker panel.

The standard ground in a home is going to be, at best, 14 gauge. That won't handle much. Plus, it's often daisy chained through multiple outlets/fixtures/appliances, which would all be charged in a strike.
Also, lightning has a bad habit of jumping off sharp bends in wire, and will find another path. Remember, that energy has traveled thousands of feet through the air. It'll jump off and find a path through water pipes, HVAC ducts, people, etc.
The outlet grounds are also going to be bonded to the neutral, which is going to create some issue.
You want it's own ground rod because you want to give that energy the shortest and easiest path to ground. Anything standing in it's way will be destroyed.

 

[RFI-EMI-GUY]

The National Electrical Code requires your antenna ground connects back to the ground at the electrical entry point of your house and any additional ground rods you put in must be bonded to the electrical entry point ground with no less than 6ga copper wire. That is because your question has been brought up before and that is the answer to the problem. You can look up NEC Article 810 that deals with antenna and radio grounding.

The main reason for the National Electrical Code is human safety and I have experienced putting in a ground rod on my property that was on the far side of the house from my electrical entry point but very close to my neighbors. I could measure about 90 volts AC between that ground rod and the third wire ground in the electrical outlets in my radio room at the time. Turns out my house and my neighbors house were fed from different power poles with different distribution and grounding.

Its nearly impossible to protect an existing house from lightning damage due to the complexity and cost of the grounding. One of the biggest things that happens with radio setups using a ground rod that is not bonded to the house main ground is when lightning hits the antenna or power lines, the difference between the neutral and ground can go many thousands of volts apart and anything plugged into the wall will usually not survive.

When all grounds are bonded together and lightning hits, the neutral and ground and even the hot might all rise together but the difference between them can still only be 120V between neutral and hot and ground will be close in potential to neutral.[/QUOTE

Excellent answer! As a FF, I've been to many lightning strike calls going back to 1981 that left me scratching my head. I learned that lightning doesn't follow the NEC! I once went to a call where lightning hit the yard, jumped to the buried "Invisible Dog Fence" wire, traveled roughly 200' feet back to the house, blew the coontroller apart, and then proceeded to go to the main breaker panel and throughout the house! Quite impressive!

Here's my question: Why can't we just ground our antenna lead in to the Ground at the A/C outlet and be done with it? Regardless of where the antenna ground is bonded to, it still has the potential to backfeed the line IN to the house, unless you're fortunate enough to have a lightning arrestor at your main breaker panel.

The ground on the AC outlet is really only for personal safety when equipment attached utilizes a three wire plug. The conductor for the outlet ground is too small and has too much inductance to sink the massive current applied by even a nearby strike.

Lightning is a high frequency discharge . It is a SPIKE of voltage. Not some benign slow rise in potential.

Lets say for example you have a radio connected to an outlet and you solely utilize the ground terminal to protect the radio and antenna.

For example I have an ASTRON SS-30M power supply and it has a three wire plug and it has the negative pole of the 13.8VDC output wired to the chassis and the ground terminal of the cord. If I wire an HF radio on that power supply and run a G5RV dipole antenna outside that is ungrounded, a nearby or direct lightning strike will charge that dipole and even if by some luck it does not damage the radio, the voltage SPIKE induced onto the ground wire will be induced as well into the hot and neutral wires in the circuit. So every device in the home that shares the breaker panel and service entrance will get the same SPIKE conducted into it. The wiring acts like a transformer when SPIKES are induced on it.

By bonding the equipment and antenna together and in turn bonding them to the ground rod at the service entrance the SPIKE bypasses the branch circuits in the house because the current sees less inductance in the ground system.

In practice, where you have equipment and antenna at a location on the far end of the house from the service entrance ground, you should install a ground rod at that far end and a series of ground rods around the house that bond a large conductor back to the service entrance ground. In commercial installations a ground ring will circle the building and will include many ground rods.

Your dog fence example is exactly why the outlet ground does not work.

 

[prcguy]

Yes, lightning doesn't always follow rules. A friend of mine was in his split level house in the basement, about 5ft below ground level and he was struck by lightning. He was working at a bench in the basement near a ground level window and lightning went through the window, through his head and chest on the way to something else. It didn't kill him but he was left really screwed up.

On the other hand, I helped replace a USCG fiberglass antenna about 75ft up a 100ft tower that was hit by lightning and it blew a chunk out of the fiberglass and burned some of the metal elements. The repeater connected to the antenna was unharmed due to the massive and proper grounding of the tower and all cable entry points that were also tied to the building AC entry point. This building on a 5,700ft mountain was designed from the ground up for lightning survival.

For amateur, CB, scanner antennas in homes I always tell people you can't protect against a direct hit and have a plan to disconnect all antennas if lightning is a possibility. Telling someone to buy a particular lightning arrestor and pound in a couple of new ground rods is only going to give false hope and will cost a lot of money if and when lightning hits. Otherwise always ground to NEC at the minimum and understand your limitations.

On your question of grounding to the house electrical panel, for satellite dish installers there is about a 25-30ft limit on running a 10ga ground wire from the dish ground block to the house electrical panel. That distance is taken in consideration when they are choosing where to mount the dish on your house. You can upsize the ground wire for a longer run or sometimes ground to a metallic conduit that has a home run to the building AC entry point in a commercial building, but every install is different and there are NEC limits on antenna ground wire sizes and lengths.

As someone else mentioned, for lightning grounding you need very short and very fat conductors that are very straight with no bends from the mast or tower leg to the ground rod(s) for starters. The last building I worked in was about 125ft X 275ft and had a ring of wire about 3/4" dia buried 4ft deep around the building bonded to 75, 10ft ground rods when it was built. After 15yrs of upgrades there were probably at least 200 ground rods and a couple hundred more ft of buried 500MCM ground cable around the building and antenna field.

We never had a direct hit on that building to test the system but there is a chance that millions of $$ of equipment could be damaged if we did.

The National Electrical Code requires your antenna ground connects back to the ground at the electrical entry point of your house and any additional ground rods you put in must be bonded to the electrical entry point ground with no less than 6ga copper wire. That is because your question has been brought up before and that is the answer to the problem. You can look up NEC Article 810 that deals with antenna and radio grounding.

The main reason for the National Electrical Code is human safety and I have experienced putting in a ground rod on my property that was on the far side of the house from my electrical entry point but very close to my neighbors. I could measure about 90 volts AC between that ground rod and the third wire ground in the electrical outlets in my radio room at the time. Turns out my house and my neighbors house were fed from different power poles with different distribution and grounding.

Its nearly impossible to protect an existing house from lightning damage due to the complexity and cost of the grounding. One of the biggest things that happens with radio setups using a ground rod that is not bonded to the house main ground is when lightning hits the antenna or power lines, the difference between the neutral and ground can go many thousands of volts apart and anything plugged into the wall will usually not survive.

When all grounds are bonded together and lightning hits, the neutral and ground and even the hot might all rise together but the difference between them can still only be 120V between neutral and hot and ground will be close in potential to neutral.[/QUOTE

Excellent answer! As a FF, I've been to many lightning strike calls going back to 1981 that left me scratching my head. I learned that lightning doesn't follow the NEC! I once went to a call where lightning hit the yard, jumped to the buried "Invisible Dog Fence" wire, traveled roughly 200' feet back to the house, blew the coontroller apart, and then proceeded to go to the main breaker panel and throughout the house! Quite impressive!

Here's my question: Why can't we just ground our antenna lead in to the Ground at the A/C outlet and be done with it? Regardless of where the antenna ground is bonded to, it still has the potential to backfeed the line IN to the house, unless you're fortunate enough to have a lightning arrestor at your main breaker panel.

 

[RFI-EMI-GUY]

Yes, lightning doesn't always follow rules. A friend of mine was in his split level house in the basement, about 5ft below ground level and he was struck by lightning. He was working at a bench in the basement near a ground level window and lightning went through the window, through his head and chest on the way to something else. It didn't kill him but he was left really screwed up.

On the other hand, I helped replace a USCG fiberglass antenna about 75ft up a 100ft tower that was hit by lightning and it blew a chunk out of the fiberglass and burned some of the metal elements. The repeater connected to the antenna was unharmed due to the massive and proper grounding of the tower and all cable entry points that were also tied to the building AC entry point. This building on a 5,700ft mountain was designed from the ground up for lightning survival.

For amateur, CB, scanner antennas in homes I always tell people you can't protect against a direct hit and have a plan to disconnect all antennas if lightning is a possibility. Telling someone to buy a particular lightning arrestor and pound in a couple of new ground rods is only going to give false hope and will cost a lot of money if and when lightning hits. Otherwise always ground to NEC at the minimum and understand your limitations.

On your question of grounding to the house electrical panel, for satellite dish installers there is about a 25-30ft limit on running a 10ga ground wire from the dish ground block to the house electrical panel. That distance is taken in consideration when they are choosing where to mount the dish on your house. You can upsize the ground wire for a longer run or sometimes ground to a metallic conduit that has a home run to the building AC entry point in a commercial building, but every install is different and there are NEC limits on antenna ground wire sizes and lengths.

As someone else mentioned, for lightning grounding you need very short and very fat conductors that are very straight with no bends from the mast or tower leg to the ground rod(s) for starters. The last building I worked in was about 125ft X 275ft and had a ring of wire about 3/4" dia buried 4ft deep around the building bonded to 75, 10ft ground rods when it was built. After 15yrs of upgrades there were probably at least 200 ground rods and a couple hundred more ft of buried 500MCM ground cable around the building and antenna field.

We never had a direct hit on that building to test the system but there is a chance that millions of $$ of equipment could be damaged if we did.

As far as lightning following rules. Here in Florida we get plenty of lightning and in turn we have many attic fires. YET unlike in the New England states, there is no local fire code requirement for rooftop lightning rods. It worries me that in my past two homes there is a metal fireplace flue that as far as I can tell is bonded to nothing at all. In my present home, grounding it would require driving an 8 foot rod through the living room floor or installing an extensive roof top system to reach it centered in the home.

Your friends situation may sound freakish, but probably lightning hit a downspout, jumped to a metal window frame and he was the next best thing to ground. Lightning was following the rules of seeking the path of least resistance.

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[K9DAK]

It worries me that in my past two homes there is a metal fireplace flue that as far as I can tell is bonded to nothing at all. In my present home, grounding it would require driving an 8 foot rod through the living room floor or installing an extensive roof top system to reach it centered in the home.

Excellent point! I'm guessing most fireplace flues are not grounded/bonded to anything; and furnace flues too, just grounded through their connection to the furnace itself and then through the home's AC system ground.

About 15 years ago a neighbor's house was hit (lucky me it was just after we moved in and I hadn't got around to putting up antennae yet)... we were lying in bed just waking up one Sunday morning, and the previously sleeping dog started whining... a few seconds later, BAM! Less than a minute after that I heard the FD dispatch go out for the lightning strike across the street.

Poor Cindy lost all her electronics and appliances, and there were dozens of .40 caliber size holes in the siding from the EMF actually blowing the siding nails out. The insurance investigator determined that the lightning hit the furnace flue.

 

[RFI-EMI-GUY]

Excellent point! I'm guessing most fireplace flues are not grounded/bonded to anything; and furnace flues too, just grounded through their connection to the furnace itself and then through the home's AC system ground.

About 15 years ago a neighbor's house was hit (lucky me it was just after we moved in and I hadn't got around to putting up antennae yet)... we were lying in bed just waking up one Sunday morning, and the previously sleeping dog started whining... a few seconds later, BAM! Less than a minute after that I heard the FD dispatch go out for the lightning strike across the street.

Poor Cindy lost all her electronics and appliances, and there were dozens of .40 caliber size holes in the siding from the EMF actually blowing the siding nails out. The insurance investigator determined that the lightning hit the furnace flue.

scary to think many of those fireplaces have a natural gas conversion as well.

 

[arkieguide]

I enjoy such discussions like this. I understand lightning protection - and have installed systems for this in many parts of our world. I still look for more & more thoughts and ideas. At my antenna base I have an 8' grd. rod. then 2 more rods around it, then go around my house, at about 70 feet i have another @@ grd rod and the then 40' later is my service grd.@@ this grd rod is where I had my gear back in the 60's & 70's, On 5, 6, floor or teller building's, the lightning down wire connects to the building grd. grid.i do see on U tube a man use's a 3 wire cord, use 2 wire's, with the grd outside the cord plug, to connect to your grd, grid & not carry the ground to the building service panel.After all the ground connects to the service grd rod.

 

[arkieguide]

A little more on grounds - my old CB base gear, only has a 2 prong end on it with a 2 wire cord. So I ground the radio to me ground grid. I could go inside the gear, and change to a 3 wire system ?
Thanks

 

[RFI-EMI-GUY]

You could, but if you bond the chassis of the radio to your single point grounding system you are in good shape.

A good reference is a document called Motorola R56. It is pretty detailed. The basics of single point grounding are the goal. You want all parts of the radio system to rise and fall at same voltage potential. If you prevent voltage differential you prevent damage.

A little more on grounds - my old CB base gear, only has a 2 prong end on it with a 2 wire cord. So I ground the radio to me ground grid. I could go inside the gear, and change to a 3 wire system ?
Thanks

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[n0iop]

Here's my question: Why can't we just ground our antenna lead in to the Ground at the A/C outlet and be done with it? Regardless of where the antenna ground is bonded to, it still has the potential to backfeed the line IN to the house, unless you're fortunate enough to have a lightning arrestor at your main breaker panel.

Well, you can if you want. It's your house, and it's pretty unlikely that it will be inspected or that the inspector will care. There are pros and cons to any grounding strategy.

The main rationale behind the requirement for #6 copper is that the ground resistance is high enough that you're unlikely to get a sustained current high enough to damage #6 copper even in the event of a fault. The purpose of the bond is not lightning protection but rather to make sure that the two grounds are kept at the same A/C potential even if there is a voltage gradient in the ground. Absent the bond, you could suffer an electrical shock when touching an antenna ground and also a surface connected to the building's electrical ground.

Part of the rationale is also to provide a path for fault current if the antenna structure falls onto a power line and becomes energized. The trend towards underground electrical service has reduced this risk somewhat but the requirement remains.