General Technical & Safety Information

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The changing thinking and information and the "Correctness" of grounding.

There is and was a time when separate ground rods were the Correct action.

There is and was a time when cold water pipes were the correct action to take.

There is and was a time when connecting to the electric service ground was a Big No , do not do it.

The Correct thinking changes over time.

[GroundUrMast]

There is and was a time when separate ground rods were the Correct action.

Yes, then it was realized that fault current flowing in one grounding system could raise the voltage to dangerous levels relative to the separate ground system. So the current codes call for bonding to prevent dangerous voltage differences from occurring.

Examples:

250.4 General Requirements for Grounding and Bonding.
The following general requirements identify what grounding and bonding of electrical systems are required to accomplish. The prescriptive methods contained in Article 250 shall be followed to comply with the performance requirements of this section.
(A) Grounded Systems.
(1) Electrical System Grounding. Electrical systems that are grounded shall be connected to earth in a manner that will limit the voltage imposed by lightning, line surges, or unintentional contact with higher-voltage lines and that will stabilize the voltage to earth during normal operation.

FPN: An important consideration for limiting the imposed voltage is the routing of bonding and grounding conductors so that they are not any longer than necessary to complete the connection without disturbing the permanent parts of the installation and so that unnecessary bends and loops are avoided

250.50 Grounding Electrode System. All grounding electrodes as described in 250.52(A)(1) through (A)(7) that are present at each building or structure served shall be bonded together to form the grounding electrode system. Where none of these grounding electrodes exist, one or more of the grounding electrodes specified in 250.52(A)(4) through (A)(8) shall be installed and used.

(NEC - 2008 edition)

There is and was a time when cold water pipes were the correct action to take.

Yes, and in the case of metal pipe that is buried in earth for 10' or more, that is still a grounding electrode and needs to be bonded to any other grounding electrodes.

Example:

250.52 Grounding Electrodes.
(A) Electrodes Permitted for Grounding.
(1) Metal Underground Water Pipe. A metal underground water pipe in direct contact with the earth for 3.0 m (10 ft) or more (including any metal well casing bonded to the pipe) and electrically continuous (or made electrically continuous by bonding around insulating joints or insulating pipe) to the points of connection of the grounding electrode conductor and the bonding conductors. Interior metal water piping located more than 1.52 m (5 ft) from the point of entrance to the building shall not be used as a part of the grounding electrode system or as a conductor to interconnect electrodes that are part of the grounding electrode system.

(NEC - 2008 edition)

There is and was a time when connecting to the electric service ground was a Big No , do not do it.

Perhaps you can cite examples of that... was that an old version of the NEC, a local interpretation/modification by a city or state or a lay persons opinion?

[OTAFAN]

Quote:
Do not neglect the part about connecting the new ground rod to your service entrance ground. That insures that the two ground rods maintain the same electric potential and prevents some serious issues from occurring with voltage differentials that could cause significant problems.

Please explain specifically what "some serious issues" could be. And what you mean by "electric potential." Any past examples of what has gone wrong when you don't follow your recommendations above that you could think of, would be helpful too.

I think this would help many people understand better in "real time" what issues you are raising concern about here. It would help translate code issues into everyday life.

Thanks Tim and GroundUrMast for your input!

(The above quote was from a current thread on reception issues and I was directed by Moderator GroundUrMast to post it here along with my questions.)

[GroundUrMast]

OTAFAN, Thanks for inviting more discussion about this...

Electrical potential is simply the voltage difference between two objects or points in an electrical circuit.

The purpose of grounding is to provide a conductive path for current between the ‘grounded’ object and earth. In the early history of electrical distribution systems, grounding was not common. As a result, those early systems experienced problems with static build up and so would experience insulation break-down and the subsequent damage to distribution equipment and/or customer equipment when the static voltage rose too high. By connecting one of the distribution conductors to earth, the voltage difference can not rise to damaging levels on the rest of the system. An antenna system would be at similar risk if it's not grounded. The modern day electrical distribution systems in most parts of North America use the multi-grounded-neutral method which has a connection to earth at most if not every distribution station, pole, transformer and customer service entrance. This assures that even if there is a poor connection to earth at one or even many points in the system, overall, the system neutral conductor has a very low resistance (impedance) connection to the earth. As a result, there is very high confidence that static build up and the damaging effects of it can be prevented.

Bonding is not the same thing as grounding and grounding is not the same thing as bonding. However, they work together to reduce hazards. Bonding is simply connecting two or more conductive items with a conductor that has low resistance and that can safely carry current if one of the objects becomes energized through some fault or accident. If the source of fault current is from a circuit conductor, you would want the use a bonding conductor that could safely carry the current until the circuit breaker trips. This serves two purposes during the fault… First, the voltage difference between all the items bonded together remains very close to zero so if you were touching two bonded items during the fault, you wont experience a shock. Two, the fault condition generates enough current flow so as to ensure the breaker will trip and thereby disconnect what would have been a hazardous voltage on the item had it not been bonded.

The earth is a rather poor (high resistance) conductor in many areas. Here in the Northwest, we commonly encounter glacial-till (the deposits left by glaciers grinding mountains into sand and gravel). My property is pretty much glacial-till with a small amount of clay. The last time I drove a ground rod here, I applied 120 AC to it (before connecting it to any part of my existing electrical service) and then measured the current… and calculated the resistance of the rod. As I expected, that 5/8ths inch by 8 foot copper clad rod had about 1500 ohms of resistance. Pretty typical for this part of the country. That means that I would have to apply 1500 volts to that ground rod in order to make one amp of current flow. The method I used is dangerous and anyone attempting to duplicate some or all of the test just described could suffer serious injury or death.

If I were to rely on a ground rod with any significant resistance to protect my antenna system I would almost always have confidence that I was protected from static build up on the antenna system. Great… But if a nail of screw happened to be driven through a a power cable and my coax, the 120 volts shorted to my coax would not be able to force enough current into the earth to cause a fuse or circuit breaker to open… I could have 120 volts standing on the exposed part of my antenna system, including the TV connected to it. That would be an obvious shock hazard and it could remain there for an indefinite period of time.

By bonding my antenna system to the electrical service grounding system (which in turn bonds to the rest of the electrical system on my property), I can have high confidence that damaged Christmas lights or errant nails and screws can’t apply hazardous voltage to my antenna system.

For what it's worth, in my work over the years, I have encountered improperly boned/grounded systems in homes and businesses. One was a dentists office where an outlet receptacle had an open circuit neutral inside... rather than replace it, someone had connected the downstream receptacles to the the conduit in order to return circuit current to the panel. I found out when I was holding onto both sides of a loose conduit connection. Current traveled through both arms and my chest. I've also come across appliances that were wet inside and as a result, had enough leakage current through the wet insulation to make me 'wakeup'. Both examples demonstrated the danger of improper bond/ground connections. I would not have been shocked if the appliance ground had not been defeated or the conduit had not been used as a circuit conductor.

[OTAFAN]

Thanks for a thorough reply, GroundUrMast! I appreciate you taking the time to address this issue. And please accept my apologies, if you thought my previous post was out of place with new member John's thread. That was not my intention as I mentioned.

I'm rereading this entire thread again along with your above reply (several times now), so I can try to understand as clearly as possible this important issue better. I'll probably have more questions to ask you later as I think about this, so please be patient with my non tech background. But I think I have a grasp upon what you have written. We'll see, right?

Presently, I'm just glad you didn't turn into "Frankenstein" after the shock you received at the dentists office. Honestly, I don't know what people are thinking about when they try to "fix" such electrical issues as you mentioned. Obviously, they weren't thinking at all! I'm not a tech or electrician, but I've replaced enough outlets and such to know what not to do. And I have basic book sources to help me with related issues. And when an issue is out of my league, I call an electrician or other professional for proper help.

Anyway, I'm just trying to say that this grounding issue is too important to get into arguments over as one poster above obviously was. After some more rereading, I'll ask my questions and again, appreciate your very kind help and expertise, GroundUrMast.

[JoeAZ]

Lots of terrific information above. Thanks for the explanations and good detail.
I cannot help but wonder the following: If grounding as above is not feasible or
possible, would the following work??? Turn the power off to an outlet near the
tv and/or cable inside the home. Insert a grounding block or splitter if needed.
Run a 12 gauge or possibly a 10 gauge wire to the ground on the outlet. Turn
the power back on. Probably not the best scenario but would if help discharge
static electricity????

[rabbit73]

Originally Posted by JoeAZ

I cannot help but wonder the following: If grounding as above is not feasible or possible, would the following work???

Turn the power off to an outlet near the tv and/or cable inside the home.

Insert a grounding block or splitter if needed.

Run a 12 gauge or possibly a 10 gauge wire to the ground on the outlet.

Turn the power back on.

Probably not the best scenario but would if help discharge
static electricity????

That wouldn't be according to code, but it would connect the coax shield to the house electrical system ground if done properly.

However, it wouldn't connect the mast to the house electrical system ground to drain the static charge. The code requires two 10 gauge wires connected to the house electrical system ground, one for the coax shield using the grounding block and the other for the mast.

As a temporary (only) measure, I have connected the coax shield to the house ground using a spare 3-wire plug. Of course, the outlet must be a properly wired 3-wire receptacle. Using the plug avoids messing with the receptacle wiring.



I have had three close calls with electrical shock, so I think it is a good idea to connect the coax shield to the house electrical system ground, even for an indoor antenna.

The antenna coax is connected to AC operated equipment. All AC operated equipment has leakage current, even when operating properly. We can't feel it because it is below our level of perception. If the equipment has a 3-wire cord and is connected to a properly wired 3-wire receptacle, any leakage current will be shunted to ground.

If the equipment has a 2-wire power cord, any leakage current will go through you to ground. If there is a defect in the equipment, grounding the coax will protect you from shock.

When I was calibrating two converter boxes, I felt a tingle when I touched the coax shield and a grounded metal strip on the counter. The antenna system had not been grounded for the tests.



I wanted to find out why I was being shocked, so I made some measurements with my Simpson 229 Leakage Current Tester. The meter showed almost 200 µA (200 microamperes or 0.2 mA) of leakage current.



When I grounded the coax with the plug shown above, the leakage current went to zero.

Details of tests in attachment.

[RMinNJ]

So the ground block for the coax should;

a.) Not be up by the antenna or in the house?
b.) Should not be in series with the the mast ground wire ?

What that means for me is running more coax from the antenna down near the grounding rod and where my cable TV input already has a ground block. I had always thought the best way was to put the coax directly into the house from the antenna and keep it short as possible.

[GroundUrMast]

OTAFAN, I'm glad you asked about this and don't think you were wrong to pose the question in the help with reception area of the forum. Just trying to maintain some organization.

[GroundUrMast]

Originally Posted by RMinNJ

So the ground block for the coax should;

a.) Not be up by the antenna or in the house?
b.) Should not be in series with the the mast ground wire ?

What that means for me is running more coax from the antenna down near the grounding rod and where my cable TV input already has a ground block. I had always thought the best way was to put the coax directly into the house from the antenna and keep it short as possible.

There are often competing factors to deal with. Whether it's a family member that wants the antenna to be hidden from view or keeping costs under control...

While keeping coax length to a minimum makes sense in terms of signal quality, the safety of the installation may argue for a less than ideal length of coax.

To your points specifically,

I have concluded that placement of the coax ground block very near the electrical service ground makes very good sense in most cases. Should the coax be struck by lightning or get crossed up with power, I don't want the fault current to have to travel inside the building on it's way to the ground connection. Mounting the antenna away from power lines is an obvious step that will reduce the chance of ever getting crossed up with heavy power... But if that did occur one could expect the coax to act as a fuse which is why I would take steps to make that occur outside the building. After the ground connection, I want as little coax exposed to the outside as possible. The most likely source of fault current inside the building would be from electrical branch circuits which have a breaker or fuse to limit the time a high current fault can last.

I would keep the mast ground separate from the coax ground because the sources of fault current in contact with the mast are outdoors so likely not fused. If I connect the mast to my coax, the coax will be forced to conduct some of the current if a fault exists. I'd rather provide my mast a single path to ground, entirely outside the building and with no connection to the interior.

When the mast and coax grounds come together at the electrical service ground, there is a minimum amount of resistance between each part of the antenna system and ground... Therefor, if fault current flows the voltage drop will be as low as possible.

[Tim]

A large static discharge is always going to take the path to ground with the least amount of resistance. That is the reason for the large ground conductors going directly to the ground rod.

As far as using the ground connection on one of the outlets in your home, I would not recommend it. The wires connected to that outlet travel through the walls of your home on the way back to the service entrance and do not provide a low impedence path to ground. You would not want that large static discharge travelling through the walls of you home with the possibility of damaging other electronic equipment connected to the wiring or even starting fires.

We are dealing with two different ground systems. The ground for your electrical system and the ground for your antenna system.

The one for your antenna system should be kept outside as much as possible and connected to the electrical system ground only at the service entrance.

[OTAFAN]

GroundUrMast
OTAFAN, I'm glad you asked about this and don't think you were wrong to pose the question in the help with reception area of the forum. Just trying to maintain some organization

.

Thanks, GroundUrMast. But I get it. I wasn't aware of this thread before you directed me to it and as a Moderator you were doing your job--something I would not be qualified for and I appreciate your efforts in said position.

Details of tests in attachment.

Wow, I would really like to visit rabbit73s laboratory! May I come to Virginia and hang out with you, Bro???

Ok.....after rereading several times this thread plus today's additional posts by all you fine Techs, I think I have a better understanding of this rather complex or multifaceted subject. I would not debate the NEC since as Mr. Spock has said in the Star Trek movie franchise, "That would not be logical."

However, there appears to be some variance given for particular situations that just cannot match up with that pristine house antenna grounding diagram, that rabbit73 posted from the NEC. I wish all homes were set up to match the diagram. It would make things quite easy.

But many homes do not fit that easily into the diagram. And after reading many posts across the Net and discussions with neighbors and friends here locally, the preponderance of opinion seems to come down to, "follow the NEC as much as is practical, but if you have to make some variance do it."

For instance, you can peruse the comments from posters below on this Amazon link:

https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1

I think these folks probably represent many OTA enthusiast's across the country and for better or worse, we need to offer not only the law, or NEC in this case, but the smartest and safest options available, IMHO.

Now, there were several key points that GroundUrMast, Tim and others kept repeating in this thread. And BTW, I agree with them. Among them were keeping your antenna system grounded outside your home, separating your mast grounding from your coax and tying them both into your service entrance ground so as to keep the electrical potential resistance as low as possible. I hope I'm understanding this correctly guys, and I'm sure there was other important points too. Like I previously mentioned, I'm no tech or electrician but I think I have a fair amount of common horse sense, no offence to horses! LOL!

However, as previously mentioned above, not all if many home situations match up to the NEC. So, what is your best advice?

[GroundUrMast]

I suppose I've repeated myself several times in this thread...

After scanning through the comments you linked to, I came away with the impression that many people have the misconception that grounding without bonding is sufficient. It makes me recall a news item from a few years ago which reported the case of a dog being electrocuted when it touched a metal street light pole (sad situation but I'm glad that no person was injured or killed). In an effort to eliminate this hazard, the city tried installing ground rods at each of the poles in the area. However, they did not bond the metal light poles to the grounding system of the service supplying the lights. Therefor, the fault remained due to the high resistance of the new ground rods and no fuse or breaker would open due to the current to ground being lower than the fuse or breaker rating.

My take away from such examples is that any added ground rod that is not properly bonded to the rest of the system will leave people with a false sense of security. Assuming that the electrical service is already grounded correctly, additional ground rods do far less than one might expect. Bonding to the existing service ground will in almost all cases be far more effective protection from static buildup and faults to a source of power. The bottom line is, an isolated ground rod can never be depended on to do the job of of a properly sized bonding conductor... The resistance of a lone ground rod is nearly always too high for it to serve as an effective part of a bonding connection.

In the end, I'm not on a crusade to check everyone's antenna ground/bonding. I make references to the code because I believe it's based on sound reasoning and many real world case studies. My conscience wont alloy me to recommend grounding/bonding methods that don't meet the minimum standards specified in the code in your area.

[OTAFAN]

I suppose I've repeated myself several times in this thread...

Sorry for having you go back to the same well again, GroundUrMast. I'm not trying to get you to say something you just cannot do, especially in good conscience. I understand better now after having reread your thread several times.

Safety first cannot be overemphasized, especially when it comes to electricity. I think your observation that many people believe grounding without bonding is sufficient is spot on. And in the end, each person will have to judge their particular situation and assume "responsibility"--oh, that's a rare concept these days!

Thanks for taking the time again to answer my questions. Time is among the most precious things we have in this life and you have been gracious with your time.

Perhaps others will chime in with any creative ideas they have, but it appears that the NEC is there for a very good reason.

[rabbit73]

Originally Posted by GrounUrMast

After scanning through the comments you linked to, I came away with the impression that many people have the misconception that grounding without bonding is sufficient.

My take away from such examples is that any added ground rod that is not properly bonded to the rest of the system will leave people with a false sense of security.

The bottom line is, an isolated ground rod can never be depended on to do the job of of a properly sized bonding conductor... The resistance of a lone ground rod is nearly always too high for it to serve as an effective part of a bonding connection.

In the end, I'm not on a crusade to check everyone's antenna ground/bonding. I make references to the code because I believe it's based on sound reasoning and many real world case studies. My conscience wont allow me to recommend grounding/bonding methods that don't meet the minimum standards specified in the code in your area.

Well said; my feelings exactly on the subject of grounding.

[rabbit73]

Originally Posted by OTAFAN

Perhaps others will chime in with any creative ideas they have, but it appears that the NEC is there for a very good reason.

The National Electrical Code, produced by the NFPA, contains guidelines for electrical safety. It is the responsibility of AHJ (Authority Having Jurisdiction), who is usually the electrical inspector, to interpret the guidelines. His interpretation then becomes the local law that is binding on the electricians and homeowners in his jurisdiction.

If you have any doubts about the correct method of grounding, the electrical inspector should be consulted. However, since some inspectors are more friendly than others, you might want to ask a local electrician first what the inspector requires.

If you want to look at the NFPA 70®, National Electrical Code®, you should be able to find a copy of the 2014 or 2017 Code in the reference section of your local library. The Code is difficult reading because it uses special language aimed at electrical professionals. ARTICLE 810 is about Radio and Television Equipment (OTA) and ARTICLE 820 is about Community Antenna Television and Radio Distribution Systems (Cable).

If you want to learn more about the controversial topic of grounding, take a look at this reference:
Antenna System Bonding and Grounding Requirements in the USA
Whitham D. Reeve (© 2012 W. Reeve)

http://www.reeve.com/Documents/Artic...quirements.pdf

see also:
Satellite System Grounding
Part 2 - NEC Overview
Presented by Todd Humphrey
http://www.dbsinstall.com/diy/Grounding-2.asp

Todd Humphrey doesn't speak for the NFPA that publishes the NEC code, but he has some ideas that are helpful.

The latest device to make connections to the house ground is the ERICO IBTB. It has a lay-in clamp for the house ground wire which must never be disconnected when your electrical system is energized:





This Old House on PBS showed one being installed.

[OTAFAN]

Thanks for the above references, rabbit!

I've printed them off for my files. They will be quite helpful regarding these grounding issues, et al.

I'm very glad you fine Techs are here on TV Fool, so that many of us across the country can continue to enjoy OTA TV safely, save money and all that goes along with these matters!

All the best as always.....

[GroundUrMast]

Here is the 20017 edition of the NEC (NFPA-70). Chapter 8, Article 810 is the primary portion that deals with antenna systems used for TV and Satellite reception.

https://www.tooltexas.org/wp-content...NEC-Code-2.pdf (7.4 MB)

[rickbb]

One thing this post shows is, I've done it wrong and now get to correct it.

[OTAFAN]

Can an antenna ground stake be checked for resistance with a multimeter, or would one have to use the expensive test equipment with multiple leads as seen on various websites discussing ground testing?

And if one could use their multimeter, where would the leads be placed for resistance reading?

Thanks in advance for any kind help!