Electrical Code vs. Good RF Grounding
Charles (KC8VWM)
on
November 21, 2003
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Forum Readers,
Grounding is probably the source of the greatest confusion in the understanding of electrical power distribution. The National Electric Code does little to clear this fog of misunderstanding.
The best way to ground your equipment is not only determined by, "Earth" grounding in itself, but also should be done in accordance to Electrical Code.
While it may be true in our radio world that you can never have enough grounding for your equipment, The National Electrical Code might not agree with the philosophy of installing a seperate ground rod at your home for your radio equipment.
According to the National Electric Code, the telephone service, cable TV, satellite, and other antenna grounds must be connected to the same ground point of the incoming electrical service to provide proper protection. Many times this is not done correctly.
Power surges can enter the house through the electrical, cable TV (or satellite dish cable), or telephone services. According to the National Electrical Code, when designing and building a new ham shack, you should locate the cable TV service and telephone service entrance into the house near the electrical service entrance. This will help in two ways:
It is very important that each of these systems be grounded to the same physical ground point as the electrical service. In all cases, the cable TV and telephone grounds must be physically connected to the ground of the electrical system. A ground wire must be run from the telephone and the exterior cable TV boxes to the electric service ground point.
While in cable TV, and service utility land, having these services enter the house close together shortens the ground wires, thus increasing the systems' protection. In Ham radio world this might contribute to further RFI problems.
Please share your experiences about station grounding, Electrical Codes, RF problems and ground, Insurance Claims etc...
73
Charles Bushell - KC8VWM
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Electrical Code vs. Good RF Grounding
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by K9KJM on November 21, 2003
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While I do not have the latest copy of the National
Electric Code, You have not mentioned anything in it
that would not be consistant with a proper RF ham
shack ground system.
You do NOT want a "separate" ground system for a
ham shack! All grounds need to be bonded together!
For good information on proper grounding, See the
series of articles in QST magazine last year, And/or
see the "Tech notes" on the Polyphaser website:
http://www.polyphaser.com/ppc_pen_home.asp
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Electrical Code vs. Good RF Grounding
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by WB2DCV on November 21, 2003
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The NEC deals only with 60 Hz grounding issues related to electrical distribution supply and service. It does not cover RF grounding.
Some suppliers of RF protection equipment offer advice on their web sites (Polyphaser, e.g.), but one of the best overall reference sources (and an industry standard) is: Motorola Quality Standard R56.
One area that most hams overlook involves problems related to loose or open neutrals. Residential power supply from utilities typically is via a center-tapped transformer providing 120/120/240 vac. If the neutral is open either in the utility plant or within the residence, voltage imbalances can occur when high current devices are powered on or off. Obviously, the open or loose neutral condition should be repaired; however, overvoltage damage can occur to sensitive equipment before the condition is even recognized.
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RE: Electrical Code vs. Good RF Grounding
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by AA4PB on November 21, 2003
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I think you are misintrepreting the NEC. It does not say that you must have one and only one ground. What it says is that all grounds must be bonded together. Thats so that a fault in the 60Hz power system cannot cause the various grounds to be at different potentials.
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RE: Electrical Code vs. Good RF Grounding
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by W3JJH on November 21, 2003
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The copy of the NEC that I have in front of me does deal with RF grounding. Article 810 of the NEC is "Radio & Television Equipment." It also deals with lightning protection systems. The Polyphaser ap note is consistent with NEC Article 810 and Article 250 ("Grounding").
While one of the purposes of the NEC is protection from electric shock, it is primarily an extention of the National Fire Protection Code. Indeed, the proponent agency of the NEC is the National Fire Protection Association. See www.nfpa.org. The NEC deals with any sort of wiring that could be the source of a fire.
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RE: Electrical Code vs. Good RF Grounding
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by WB2DCV on November 21, 2003
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Folks, I'm dealing with AMATEUR RADIO issues, not consumer electronics issues. The NEC radio/TV articles deal only with consumer electronics. There is not NEC article applicable to FCC licensed facilities where RF energy is both transmitted and received.
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Electrical Code vs. Good RF Grounding
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by KC0NYK on November 21, 2003
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I am a master electrician with a degree in Electrical Engineering who serves on the National Electrical Safety Code main committee for the IEEE. That being said, it is important to remember that the National Electrical Code is designed for the SAFEST installation method. It is not designed as a 'how to' book for the non-professional installer. Several of the comments relate to the SINGLE GROUND requirement of the code....it is there for a reason;that being that experience has shown us that multiple grounds tend to be extremly dangerous. There exist on the market today several very good devices for grounding your gear...my best suggestion is to use them and use them exactly per the manufacturers instructions. As for insurance claims from lightning strikes, I have never known a carrier to deny payment to anyone with a properly installed system.
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RE: Electrical Code vs. Good RF Grounding
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by AA4PB on November 21, 2003
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Better look again. The NEC has several references to radio transmitting and receiving devices and antennas. An FCC license does not exempt you from those requirements.
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RE: Electrical Code vs. Good RF Grounding
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by N8FVJ on November 21, 2003
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I follow the NEC for grounding 60Hz AC power distribution. My radio shack is somewhat different. I remove the power supply output negative post ground bond wire to the power supply chassis. I do not want AC power distribution noise to enter my radio shack. I view it as creating a possible ground loop. The power supply case is still connected to the 120vac ground. I use a seperate ground rod & #6 wire just outside my radio shack for the radio station ground. I do not measure any ground potential difference between the AC ground and my radio station ground and that is very important.
My antennas and tower are connected to a seperate pair of ground rods. This is for lightning protection. So far, I had three lightning strikes within 75 feet of my antennas over the last ten years. Two hit the ground and the other hit the power pole just outside our house. I lost a VCR & microwave on the last strike, but never ham equipment. If a lightning storm is forthcoming, all coax cables are removed from entering my house.
I believe the NEC is the best guide for electrical power distribution in the world. I have built power generation plants and power distribution systems for many large manufacturing facilities.
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RE: Electrical Code vs. Good RF Grounding
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by W3JJH on November 21, 2003
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WB2DCV:
If the NEC is not applicable to ham radio, why does Article 810-52 deal with amateur transmitting and receiving antennas?
73 de W3JJH
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Electrical Code vs. Good RF Grounding
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by K0RGR on November 21, 2003
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There was a provision in the FCC rules and regs stipulating that amateur installations must follow "good engineering practice". Failure to meet the recommendations of the NEC would never be "good engineering practice".
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Electrical Code vs. Good RF Grounding
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by WA0ZZG on November 21, 2003
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Grounding for RF and Lightning protection is a rather
strange science. The best information source is
a text published by Polyphaser called "The Grounds
for Lightning protection". I believe it is in its
second edition. If you have a tower, I suggest you
read it. Cost is around $20. The really best source
is a school put on by the Univ. of Wisconson. Cost
is around $1500 plus transportation. The reference
binder given to you is about 5 inches thick. When
it comes to lightning protection, look at it this
way: You can pay me now, or you can pay me later.
Dave....
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Electrical Code vs. Good RF Grounding
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by KG4IPO on November 21, 2003
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Two big issues stand aside good 60 HZ AC power grounding.
1. RF Grounding of equipment that needs to be protected.
2. Lightning Countermeasures.
In Florida, one thing you want is the energy from a direct or nearby strike to go straight to ground outside.....NOT come into your home or shack, I'm more concerned about myself and my house cathing on fire than a $ 400-600 rig. At my station, I have employed what I believe to be good engineering practice when addressing these issues.
When I speak of Lightning Countermeasures, I'm talking about air terminals and cabling on a home or building and tower grounding techniques.
Any opinion on these items would be appreciated.
To be honest, I stay away from the tower base and out of the shack during an electrical storm.
Thanks
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RE: Electrical Code vs. Good RF Grounding
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by KD5UJX on November 21, 2003
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I just sat through a grounding presentation put on by WA5MPA in Corpus Christi. Bill has extensive experience in this area. He stressed one thing, all grounds must be interconnected. The idea being that if there is a lightning strike on or near your shack/house, that the EMP would be uniform throughout the system. There would be no "low impedance" ground that would direct the charge one particular way. The entire system would rise and fall at the same rate, thereby minimizing damage to any one device.
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Electrical Code vs. Good RF Grounding
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by KG6AMW on November 21, 2003
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If you have a surge control device plugged into the wall socket (to protect electronic equipment from power line surges), then the only ground that device will bleed surges off too is the ac house ground. The ham shack ground you create for grounding equipment chassis doesn't even come into play in a typical power line surge scenario. Lightning of course is a different matter.
KG6AMW
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Electrical Code vs. Good RF Grounding
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by W5GNB on November 21, 2003
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As a professional engineer in the broadcasting business for many years, we have found that it is very important to ground the antenna structure at its base and also ground the feedline at the point of entry to the building. We also ground the feedline at several points down the tower from the antenna and at the base of the tower. These grounds must be very good, The ground rods should be at least an 8-Foot rod for amateur applications. This requires Two ground points for your antenna system but it will drastically reduce the possibility of lightning damage (Not strikes) to the system.
The power system will have it's own ground within itself and if by the NEC codes, that will be a Single ground point at the point of power entry to the facility or building. Hopefully all AC power supply points will lead back to this point of POWER ground. This will NOT be a good RF ground.
The only way to get a good RF ground is to ground the antenna structure at its base. By grounding the feedline upon entry to the house, you are reducing the chance of lightning damage from reaching your equipment through either strike or induction on the feedline or antenna system.
This will protect you somewhat but remember, lightning is unpredictable and there is still a GREAT chance for damage to occur even with all the protection you can muster up....
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Electrical Code vs. Good RF Grounding
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by KG4IPO on November 21, 2003
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I like to post this related site once in a while.
http://order.waytekwire.com/cgi-bin/lansaweb?procfun+wordpr01+webfunc+m36
Check it out
Thanks
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RE: Electrical Code vs. Good RF Grounding
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by KB1GMX on November 21, 2003
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NEC has been a sorce of constrnation for me.
As a VHF op RF ground is often not a concern, as a result of resonant antennas and yagis. However, lightening protection and the sometimes annoying problem power system neutrals and grounds keep me aware that the "tower ground" and entrance (phone, cable, power) ground must be one. NEC wants to avoid ground loops as far as I can figure out. Single point ground system do this for DC and low frequencies. As the frequecy goes up this can be problematic.
Here's the yabut for me. Long ranch house, entrance is the far end from the station. Only solution was
to run a LONG (over 100ft) perimeter wire from the tower grounds (that are also default radio ground)
around the outside of the house to the entrance ground.
It had to be fat wire (#6 cu minimum). Meets code but I really wonder if for lightining it does anything useful. I know for RF it doesnt even show
and to help this there is an additional ground rods
along the way to break the 100ft resonance and assure mechanical support.
The other yabut is the tower here is short compared to the trees. All lightning hits here have come in via the phone lines.
Since the power for the radio system is solar and battery the local tower ground is it the ground point by virtue of the pannel mounted to the tower. Nothing runs off ac mains for the station as a general rule.
Allison
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Electrical Code vs. Good RF Grounding
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by WB2JKM on November 21, 2003
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There is a lot of VERY dangerous "advice" being shared here. The NEC speaks quite clearly to the subject of protecting personnel and property from injury/damage by ensuring that electrical equipment and systems are properly grounded. Follow the NEC. Period.
Now, if you want to add more grounding and protective devices to help protect equipment from lightning and other surge sources -- a very good idea for hams to do -- then follow the NEC and the manufacturer instructions to the letter.
Question for our "professional engineer":
You said--
"The only way to get a good RF ground is to ground the antenna structure at its base." And, you went on to tell how to do it...
Questions --
WHAT? HUH? What exactly is an "RF ground" as it applies to a tower? What good is an 8' ground rod as a sink for a lightning induced surge? What about the COMMUNICATIONS INDUSTRY standards of single point ground systems and the proper ways to cable and connect to it and the ground field associated with an effective and protective ground system?
As for the use of "air terminals" and such, there is a lot of debate as to their effectiveness. Some swear by them and others frequently replace the charred remains of these devices and the equipment they were supposed to protect. As soon as someone can find a way to predict if/when lightning will strike in the same way at the same place two or more times, perhaps some science will happen to prove/disprove the effectiveness of air terminals. Until then, they are just "feel good" devices in my book.
Nothing ---- NOTHING ---- takes the place of a properly designed, constructed, and TESTED grounding system when it comes to lightning. If you don't figure out a way to measure/test the ground you are connected to you are only wishing and praying that you really do have an effective ground.
The Polyphaser book mentioned here is one excellent primer on the subject of lightning protection grounding. If you have a Motorola shop nearby that is "ham friendly" you might also see if they will loan you a copy of the latest grounding and lightning protection engineering standards documents. Both are very good info sources.
I hope nobody ends up hurt or has damage resulting from following some of the advice given here that is in direct conflict with the NEC and/or common sense.
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RE: Electrical Code vs. Good RF Grounding
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by KD5UJX on November 21, 2003
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Part of the problem here is, if you follow (to the letter) the NEC and the Comminications industry standards, you will have to have a second mortgage on your house just to pay for the copper! NOBODY (Bill Gates maybe) can afford a "proper" grounding system. What can us "regular folks" do to maximize our safety for the dollar.
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RE: Electrical Code vs. Good RF Grounding
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by KF4WXD on November 21, 2003
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I suggest a good reading of Section 800 of the NEC. It covers grounding requirement of communications systems. It stresses (again) that all grounding systems are to be bonded together. Another source is the Erico Corporation and A. J. Surtees, one of their engineers. He wrote a definitive article in a 1998 edition of "Power Protection" that details grounding and lightning protection of telecom systems. As an amateur radio operator, I don't need to be working during electrical storms. As a telecom engineer, I need to know that my systems are working and protected. Use flat strap, mechanical connections (or CAD welded), plenty of grounding rods and some common sense. And don't forget to bond all ground systems together!
Russ
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RE: Electrical Code vs. Good RF Grounding
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by KG5JJ on November 21, 2003
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ARRL (newer) handbooks have good grounding suggestions. Consists of a common ground buss buried around the entire perimeter of your house, tied-in with the Mains ground, and all equipment needing grounded tied-in to this main buss.
Other specifics in the handbook...
73 KG5JJ (Mike)
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Electrical Code vs. Good RF Grounding
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by WA0ZZG on November 21, 2003
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Just happened to check the Polyphaser web site. They
have a paper published about grounding an Amateur
Radio Station. Looks very readable. Check it
out at:
http://www.polyphaser.com/datasheets/PEN1016.pdf
I've got Polyphaser all over the commercial towers
I maintain. Noticed that many others do too.
Dave...
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RE: Electrical Code vs. Good RF Grounding
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by IX4NT on November 21, 2003
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Amazing! The discussion has gotten way off topic from the original post. I think the first few people to respond attempted to respond only to the original posting.
If you are running a radio station, amateur or private land mobile, I think DCV's suggestion about adhering to Motorola QS R56 is well advised. The R56 standards are conservative and univerally applied in almost all PLMRS applications where professional engineering/consulting services have been engaged.
In my experience, no municipality in which we've installed radio stations or equipment uses the NEC beyond the AC power aspects. In fact, if NEC only were used, most stations would not be properly or adequately grounded.
RF grounding and AC power grounding are separate issues. Their only connection is a common ground point. Othewise, you cannot do better than R56.
The R56 standard is available from Motorola via CD ROM. If you have a friend in the 2-way business, he also might have a copy. R56 covers lightning, electrical and ground potential rise protection.
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RE: Electrical Code vs. Good RF Grounding
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by IX4NT on November 21, 2003
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This place reminds me of a hens-only gossip column. It's no wonder that American hams lose battles with the FCC. You can't even be collegial. And when you find an issue that unites you, you file cookie-cutter comments.
Sorry I signed up for this site.
73
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Electrical Code vs. Good RF Grounding
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by K0ZN on November 21, 2003
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This is kind of fascinating (all the opinions, etc.) What becomes obvious if you step back and look at the big picture is, is that there are several combinations of practices that generally are beneficial and can provide cummulative protection if used. The important thing is to do SOMETHING to protect your station/home.
As a good friend of mine, KB0UH - SK, said once, "After lightning has been able to go through a couple of MILES of AIR.... do you really think you are going to totally control it??! It could care less about the last 50 feet!!"
You can TRY to control it with some common sense practices, but that is about all. Anyone who has been around the utility industry, communications or ham radio for a number of years can usually tell you SEVERAL stories of lightning doing stuff "it couldn't or shouldn't do...but DID!" I personally know guys who have been on the air for years with "terrible" ground systems and had Zero problems and other guys with "really good", "well designed grounds" who have been just hammered. Like one of the postings said, essentially, if you "throw money at it", you can build a copper house with 40 deep well grounds around it and, yeah, that would work pretty good, however, that is just not reality for most of us. Which leaves "common sense" ground systems for most hams with just large conductors binding as much "stuff" together as is cost effective, to a "good ground"....and hope you don't get hit by a Mega-bolt!
Personally, I take lightning strikes very, very seriously and totally disconnect all coax and transmission lines and ground them outside a good distance from the house in the spring and summer. Regardless, I don't hold any illusions that a Code is going to flat out guarantee Zero problems from lightning. The stuff IS unpredictable no matter what you do. However, ignoring the hazard and basic grounding practice IS foolhardy, no doubt.
73, K0ZN
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RE: Electrical Code vs. Good RF Grounding
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by K9KJM on November 22, 2003
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RF ground, AC "Safety ground" (NEC) and Lightning
ground, ALL have different requirments!
While one ground system MIGHT satisfy all of them,
then again, it might not.
NEC refers to "safety grounding" only.
RF ground requires "radial" type ground wires to
be effective. (Ground rods do close to ZERO to
help RF ground)
A proper ground "system" will be ALL bonded together.
Those who advocate "separate" ground systems are living
way back in the past for proper grounding.
While the procedures as presented by Polyphaser if
all purchased "new" at retail price, and hired done
would about break the bank for most all hams, The same
effective system can be installed for MUCH less money
if care is taken spending money. Chemical ground
systems as explained by STH and others do work!
"Cadweld" type connections can be done at home almost
as well by true "Silver Solder" with Mapp gas in a hand held torch. USED components can be used. No need to rush out and buy brand new wire! Old used copper grounds just as good as brand new store bought stuff!
Commercial radio stations, Police, Fire, Ambulance,
etc. DO NOT disconnect antennas at every storm. And
if they were properly protected, They do not suffer damage from lightning.
Those who say "nothing will withstand a direct lightning strike" are very misinformed.
My towers take direct lightning hits most every big
storm. So do most all tall commercial towers.
With NO damage!
Those old wives tales of damage are for the most part
over 50 year old tales of woe from improperly grounded/
protected stations. (Or more recent stories of stations
that were grounded with 50 year old technology)
Power companies learned many years ago that number
6 copper wire was heavy enough to withstand over
98 percent of direct lightning strikes. So number six
copper became the size to use for lightning protection...... HOWEVER, The power companies did this for economy, NOT total protection! It is cheaper
for them to go out and replace blown up parts once in
a hundred "hits" than it is to use number 2 or heavier
wire on EVERY power pole..... Check out a power company
electric substation...... number 2/0 ground wires....
For protection around 99.9% or so........ Same with
commercial towers, Those who only used number 6 or so
wire years ago would sometimes have damage..... Nowadays proper grounding involves several 6" wide
copper straps cadwelded to a very extensive ground
system. Around here where the soil conditions are
poor, Many now drill deep wells with steel case
that are then filled with bentonite clay just for
a lightning ground! Big bucks for sure. But it works.
Extensive use of copper radial wires and rods will also work, But is much more labor intensive.
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RE: Electrical Code vs. Good RF Grounding
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by IX4NT on November 22, 2003
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In my travels around the US consulting on various public and private land mobile projects, I've found many discrepancies between code and practice.
What should we take away from this discussion?
Codes! Codes are 'good practice' obligations that are enforceable by some entity that can impose a penalty for violation. Codes are minimum standards and generally reflect wide-view practices, compromises if you will, from standards body members all over the jurisdiction. Most codes are national or statewide, but one need only comply with codes that are legally adopted and enforceable.
Codes by construction! These are codes or practices that have not been adopted by a body able to enforce through punishment. These are practices adopted by a vendor or provider of services that affect service provisioning if they are not followed. A good example of this is IEEE 487. Many wireline carriers have adopted IEEE 487 and will require adherence to this network protection standard for telco installs at locations where a voltage potential of 1000 volts or greater exists between conductors/equipment and ground. The customer does not have to adhere to the standard, but service will be denied within a specified distance from the cutomer premises.
Good engineering practice! GEP often exceeds code requirements. GEP can take into account local anomalies and can be specific to a particular segment of the population. Motorola's QS R56 is an example of this. It provides technical and experiential guidance for proper electrical and lightning protection for the land mobile community. The NEC and other codes I've encountered do not adequately address protection for lateral runs of transmission line underground or inside PVC duct. Yet, experience and good engineering practice indicates installation of copper ground bus at the end of the vertical run, solid ground along the lateral run with periodic cadwelding to driven grounds, and grounded lighting arrestors before entering the shelter and another common copper ground bus inside the shelter, etc. The NEC does not adequately address stresses imposed on lateral runs of transmission lines due to ice loading. The NEC does not adequately differentiate between different wireless services: AM broadcasting, FM broadcasting, microwave, VHF, UHF, PCS, cellular, etc.
We recommend to clients that by following R56, they exceed requirements imposed by local codes.
Certainly, if a local code exists it must be followed or one risks enforcement action. However, I have not seen any code that exceeds the requirements of R56. I'm not aware of any local jurisdiction that requires permits and inspections for installation of amateur radio equipment that you buy, plug in, and put on the air. I see local inspections for 'mechanicals': tower footings, grounding system, etc. But I see no inspections for transmission lines, microwave dishes, land mobile antennas, or even for FAA hazard marking/lighting.
As for cost of compliance? If a code mandates specific requirements, it must be done anyway. I don't think that code compliance is voluntary. It is mandatory. But why risk damage to one's home and equipment by not following good engineering practice?
I've been in the RF business for too long! I was not really aware of the risk to equipment from open neutral conditions. I appreciate that information.
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Electrical Code vs. Good RF Grounding
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by WA1RNE on November 22, 2003
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Wow, talk about opening up a can of worms...and let the "sparks" fly......
Folks, let's not over-react. The number of catastrophies suffered by the ham community has got to be pretty low so we've probably been doing most of the right things.
A quick, "approximate" electrical analysis can be done on a sheet of paper. Sketch out your home and create a schematic showing where all the utilities enter the house and where the electrical service main ground is located and how they all connect together. Include the length of the service entrance ground, the wire size, etc.
Then draw in the ham station location, the line voltage feeds and cable lengths and antenna feed line entrances. Then last but not least, add the antenna/tower RF ground scheme and how it connects to the station.
Now, use this schematic to make a couple of quick calculations of the ground impedances:
1)The earth ground running from the service/breaker-fuse panel to the station - which may take multiple paths depending whether the station feed(s) power other things in the home like lighting or runs outlets in other rooms, etc.
2) The station's RF ground scheme.
The objective is NOT to end up with an impedance in the ground scheme that allows lightning currents to flow into the ground scheme of the home - or your shack via antennas like verticals with elaborate counterpoise schemes - and develop large voltage drops, etc. You want the lightning currents to drain AWAY from the service entrance ground, utilites (cable, phone, etc.) and the home's ground system - and your shack.
Again, this is not intended to be at the safety level of a commercial radio station - and all the expense that goes along with it -, nor is it a substitute for state/federal elctrical codes, etc. but it should give you a decent idea of how to create a reasonably safe ground scheme for the "average" ham station.
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Electrical Code vs. Good RF Grounding
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by W3DCG on November 22, 2003
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I think for me, reduced it all to two important aspects.
One was to tie all ground points together, so that all grounds are at the same potential. Otherwise, even a relatively nearby strike may have energy that travels on the ground, and if your equipment is connected to grounds of different potential, current may flow between, and given the voltage of lightning, it could be enough to render your equipment irrepairable.
Two, was to keep the ground run from rig to ground as short as possible, then running wire to several short stakes, surrounding the shack if possible, if not, have several short staked grounds- avoiding 1/4 wave lengths if at all possible, or o d d multiples of 1/4 wavelengths for the highest operating frequency, particularly from the first run from rig to 1st rod.
I haven't gotten around to implementing this myself yet, but I'm moving in that direction!
Nope, not very technical here, not every ham in the world is a E.E. or Physicist.
So don't take my word here, check your own references.
If you have a tower like I don't, then obviously, there would be more to it than this, and you've already researched the subject adequately.
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Electrical Code vs. Good RF Grounding
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by N6PYF on November 23, 2003
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Something I observed while recently staying with a relative in the Black Forest region of Germany:
I asked the relative why he didn’t have lightning protection on his relatively new home, since the majority of the houses in the area had lightning protection. His response was that in almost every case where a house was hit by lightning and caught fire, the insurance company would decline payment because they claimed there was a problem with the lightning protection system, whether or not there actually was. By not installing a lightning protection system the insurance company couldn’t reject his claim in the event his house was hit by lightning, there was no defective lightning protection system involved.
What this says is that while you might have the best grounding system in the world designed for your antenna system and ham shack, if it isn’t up to the letter of the NEC, your insurance company might have the loophole to decline a payment for damaged caused by a lightning strike or power line failure.
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Electrical Code vs. Good RF Grounding
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by K9YC on November 23, 2003
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Most of the folks commenting here seem to have a good grasp of what makes a safe installation, but a few do not. NEC is structured to provide the framework for a SAFE installation. The basic requirement at all grounds be tied together is based on real physics relating to BOTH lightning and protection from power system faults. This are based on inviolable laws of physics, whether legislated by codes or not, and the physics is WHY it is required by virtually ALLL codes.
At least one poster correctly noted the wisdom of tying ground electrodes together OUTSIDE the premises.
Think of NEC and other codes as a MINIMUM requirement. There is NO conflict between electrical codes and good RF grounding! Nothing in NEC prevents us from adding 500 ground electrodes and 100 km of copper around our premises as a ground system AS LONG AS WE BOND ALL GROUNDS TOGETHER. And, as another post wisely noted, the geometry of how those bonds are made should take the discharge paths for potential lightning hits into account.
Likewise, the poster who noted that the impedance of each ground path is important is right on target. IEEE studies have shown that the peak of the energy spectra in a lightning hit is roughly centered in the AM broadcast band, so it is the impedance IN THAT SPECTRUM that is important. Big copper is not the issue -- SHORT copper with MULTIPLE PARALLEL PATHS will lower the inductive and resistive components of the impedance, and it is likely that the inductance will dominate most paths. Yet another good reason for bonding all the grounds together.
Yes, FCC rules may supercede code from a point of law, but that does not change the physics, and the physics is that all grounds should be bonded together in a well thought out way. And if you think you need a SEPARATE ground (i.e., not connected to other grounds)for your shack, don't invite me to visit.
Jim Brown
K9YC
BSEE, Vice Chair AES Standard Committee Working Group on EMC
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RE: Electrical Code vs. Good RF Grounding
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by N8MMZ on November 23, 2003
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Might I recommend a good grounding and bonding seminar from Mike Holt? We viewed him as a pretty good authority on practical grounding issues back in my days as a consultant (commercial building design). He's got a lot of pretty good plain english stuff on grounding and bonding issues as ity pertains to the NEC (the short answer). He's got a lot of good stuff on the web.
If you prefer the long answer, IEEE has a series of "colored" books - I think the grounding book is the "Green" book - it's been a while since I picked those up though! Those were some pretty good books on grounding, among other things, but took a while to really understand.
In this case, the NEC is concerned about the protection of YOU from electrocution, and the protection of your house from fire (some claim that there is an electrolosis type of effect from improperly grounded systems that utilize metal raceways and wood studs - they claim that this leads to carbonization of the wood and then, of course, fire). You'd better have everything bonded back at the service entrance, or you are asking for trouble if any part of your RF system is energized with 60Hz (#6 copper is going to provide far less resistance than YOU).
I would argue that the NEC is more concerned here about keeping anything metal at an equipotential level, or at least well below tingle voltage, so that you don't get zapped when you touch the chassis of electrical apparatus (and so that if an overcurrent or ground fault condition exists, then faults can be properly cleared). I don't really think they care as much about lighting protection, since there is another section of the NFPA codes that covers that. As far as stuff away from the service riser, that would point you to NESC.
You are looking for a pretty good RF ground as well, so ditto what the other folks said about the Motorola pubs. I would bet that those prob. show how the ground connection is "made" back at the service entrance.
Better follow that NEC though. If you have an electrical fire for any reason, an unscrupulous adjuster might claim that it was due to improper grounding, and he would have pretty good evidence to support that point. Also, you might not like the potential of having a "random" defibrillator waiting to reach out and grab you in a poor electrically grounded system.
Good Luck and 73's
N8MMZ
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RE: Electrical Code vs. Good RF Grounding
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by W9WHE on November 24, 2003
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N6PYT writes:
"....while you might have the best grounding system......if it isn’t up to the letter of the NEC, your insurance company might have the loophole to decline a payment....."
Only one thing more dangerous then taking your grounding advice from an online BBS, and that is getting your legal advice from an online BBS!
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RE: Electrical Code vs. Good RF Grounding
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by N8MMZ on November 25, 2003
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W9WHE - Actually in the business I used to be in, there were plenty of Professional Engineers that were in litigation - we called them by a rather derogatory form of the noun "harlots". The insurance companies refered to them as "Forensics Engineers". I was on the recieving end a time or two from one of those nuts.
According to the Louisiana State Fire Marshal's Office, "Electrical fires are the number one cause for fires." I imagine that a lot of other insurance commissioners share his opinion. If you have an installation that is contrary to the NEC in conjunction with an electrical calamity, and you get an unscrupulous forensics engineer, then you will have some difficulty in resolving your casulty claim.
Remember that insurance companies are in the business to satisfy their shareholders. If there is a plausible way to deny a claim - they will prob. go that route (especially since they have taken a lot of losses in fires, hail, hurricanes, and "toxic mold" (which isn't that toxic - but that's for another thread)).
Here's another tip that would help us all sleep safe - take about $200 and find you an old, retired PE and let him sketch out a quick grouding scheme for you - give him a quick look at your loadcenter and mains and tell him what you plan on doing. That would certainly indemnify you and ensure that you have a good setup if you follow his advice.
If your bent on doing it all yourself, take a look at the NEC handbook, the IEEE Green Book, and NFPA 780 for the lightning protection stuff - these all should be at your local library - the most current books are dated 2002, 1992, and 1997, respectively.
73's
N8MMZ
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RE: Electrical Code vs. Good RF Grounding
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by AB8RU on November 25, 2003
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Well Polyphaser is good on their documents and all of these other companies like Motorola, and NEC has some very good ideas, I can say as my electrical insturctor once told me " When in doubt Ground it ! " period.
I used a glass canning jar to shove my PL-259 once upon a time into when it knew a storm was coming, the antennas had built in lighting protection.
also I read a book on two way towers, this was interesting for thought they sugguested a CONE of protection for the antenna mostly omni-directional a rod that proturded at some x amount of distance and was higher than the antenna it self, it was a direct ground sort like a lightning rod. I recalled it from the 1960's I was a teen and had libary privledges at a College.
I suppouse there is different ideas experimented with that worked, and did not.
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Electrical Code vs. Good RF Grounding
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by K2JX on November 27, 2003
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I am an electrician for the 9th largest police department in the U.S. We maintain a 25 channel Motorola trunking system covering 954 sq miles.
All electrical, electronic, and mechanical work is done "in house".
Referencing the comments about grounding and bonding according to Motorola's R56 handbook,we follow it to the letter. One of the biggest problems in the communications industry is getting that information into practice.
If you read that manual you will quickly come to the page advising strict adherence to the NEC.
Most ham shacks that I visit are positively scary. In some there is no attempt to ground and bond anything !
I guess some have been very lucky during electrical storms and power surges. Vhf'ers seem to be in first place when it comes to lack of proper grounding techniques.
73,Jack K2JX
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RE: Electrical Code vs. Good RF Grounding
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by K1CJS on November 28, 2003
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I have read here references to a "single ground" and statements that "multiple grounds" are extremely dangerous. I too have been around electrical installations and transmitting/receiving equipment for most of my life and have also worked with power company installers, linesmen and electricians. I have heard the same points debated again and again.
I can't offer an 'expert' opinion, but am wondering, however, about the veracity of some of the 'expert' comments posted here. For example, if a "single ground" is the so called requirement, how come almost every telephone pole has a number 6 ground wire running from the "common" line to ground? Why is almost every service ground also bonded to the cold water pipe coming in from either the street or a well? (It is understood that some water "inlets", especially in newer construction are non-metallic piping.)
Is it clearly understood that a 'RF' ground must be at the same potential as the 'service' ground because the two are almost always connected by any co-ax braid that runs from the tower to the shack through the chassis and power connections of the radio equipment?
From almost everyone I have spoken to on the subject, a single ground 'potential' is the real goal. However, I admit I'm not an expert, and would very much like to see comments about the questions I have asked. Thanks!
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RE: Electrical Code vs. Good RF Grounding
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by KD5UJX on November 28, 2003
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Posted By K1CJS
From almost everyone I have spoken to on the subject, a single ground
'potential' is the real goal.
I too believe this is what we strive for in a grounding system. I have three 8' ground rods at my tower, the coax is bonded to the tower and bonded to the inlet pannel (plexiglass with a copper pannel and bulkhead fittings) that is grounded just below it with a 2 1/2" wide copper strap and the "RF" ground for all my equipment is attached to that pannel. That ground rod is tied to the three at the tower and then runs around the house (with more ground rods every 16 feet) to the service ground and the telco connection. All my ground rods are tied together so any EMP that it "sees" is spread out all around. BTW all the "tie" wires are buried 3" below the surface.
If this is wrong, sue me.
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Electrical Code vs. Good RF Grounding
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by W7CYA on November 29, 2003
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W7CYA
About 3 months ago the phone company came to my door
and wanted to redue my phone drop and at the same time
ground it to my house ground. I told him yes he could,
but only if he also provided a ground rod.
We I had just built a new hamshack and the phone drop
was only 8 feet from the hamshack and then only 10 more feet to the new circuit box I had put in the new
shack. The phone man not only put in the ground rod
but left me with a 30 foot role of grounding wire.
My cable service is about 25 feet from the ground point
and was just installed about a year ago so it will be sometime before I can get them to change it. My have to run separate ground for it for now.
Tom
W7CYA
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Electrical Code vs. Good RF Grounding
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by W7CYA on November 29, 2003
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W7CYA
About 3 months ago the phone company came to my door
and wanted to redue my phone drop and at the same time
ground it to my house ground. I told him yes he could,
but only if he also provided a ground rod.
Well I had just built a new hamshack and the phone drop
was only 8 feet from the hamshack and then only 10 more feet to the new circuit box I had put in the new
shack. The phone man not only put in the ground rod
but left me with a 30 foot role of grounding wire.
My cable service is about 25 feet from the ground point
and was just installed about a year ago so it will be sometime before I can get them to change it. My have to run separate ground for it for now.
Tom
W7CYA
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Electrical Code vs. Good RF Grounding
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by N8PZD on November 30, 2003
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I have only been licensed about 13 years but have been an electrician over 25 with mostly commercial and industrial experience and a bit of residential. I watched down the thread and it seemed many were losing sight of the original question relating to electrical service entrance and equipment grounding and the choice location for a RF ground - they are really two scenarios here but they share the same trouble, fault currents and how to take them away.
The electrical service and equipment grounds are handled by the NEC 250, this is primarily to protect human life when a item connected to the electrical system fails enough to allow fault currents to pass to the equipment ground, this 3 wire system in newer homes is designed to protect the occupants from ground fault currents as well as provide a path for the load center/service entrance in the even of electrical fault. The minumum 6AWG copper is sufficient for this task with a 100 amp entrance, 4AWG is used for the stronger load centers in residential applications.
Now RF grounding is a slightly different scenario although the common name grounding is shared by both, never connect your transmitting equipment to the electrical ground inside that room, you force the RF inside the walls and it will radiate at some predetermined frequency, this will likely send RF thru most of the house and act as a great antenna for the radio station, your spouse may not like the results on the tv screen or in the telephone set. How to take this nuisance away? RF grounding, and this can be done in various ways, however a simple rule applies from NEC 810 - this ground must be bonded to that which serves the electrical load center and service entrance, you will use 6 or 4AWG to accomplish this connecting with split bolts to the outer most segment of your ground, do not cut and/or splice the electrical ground wire!! If you home does not have a ground electrode (8ft copper clad 5/8 rod minumum) then you are faced with adding this and whatever length of copper wire needed to get outside without any splicing, this was abolished in 93, no splices anywhere between the base of the water meter and the outdoor electrode (drive the rod about 2 ft away from the foundation so you don't break into the footer drains, also if you take a direct hit and the soil explodes it wont destroy the wall, just bend it a little), you should now have continuous copper to the load center, if you have a 9 inch wide load center you will need to change that to a 14 inch to allow room for the grounding wires to come in and connect to the ground bus, at least ground your refrigerator outlet and window A/C units so when they fail you won't get killed leaning over washing the window or raiding the fridge during a contest. If you have a tower you should get it grounded also with 4AWG to an electrode for each leg, don't cut the wire - roll it around the whole tower and fold the wire into the acorn shaped electrode clamp or use the erico cad welding mentioned earlier, it only cost about 8 bux per connection and they last a long time and don't come lose - never. If you just want to ground your station use flat copper strips or a length of copper pipe 1/2 with the ends flattened so you can drill and connect with short stainless bolts and nuts, this makes a quick method for grounding, once folded refrain from reforming the corners as they will break off. When you get to the inside of the radio station you can connect to the end of the copper pipe with bolts and nuts on your equipment grounds, and also in the middle if needed for multiple radio desks, fastening this to the outside is kinda quick and easy, just run galvanized or stainless deck screws thru it and into your house once you have the pipe straight or level as you can, use plastic anchors if you have brick or block walls. If you flatten it inside and drill several holes you will have a great place to connect everything. Having this bonded will prevent ever changing currents in the soil from causing an incomplete path to earth or ground as we call it, you will not get a tingle or anything like it.
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RE: Electrical Code vs. Good RF Grounding
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by W4WA on November 30, 2003
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Living in the South, we have our share of electrical storms. I have used 5 towers for many years and found that grounding them with at least two 8 foot ground rods seem to do the trick. A second ground rod in the shack from the main electrical service may help reduce RF but can cause dangerious lightning to enter the shack looking for a better ground during a strike. I do not use a second ground rod near the shack for this reason.
W4WA
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RE: Electrical Code vs. Good RF Grounding
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by KC8VWM on December 1, 2003
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Should one drive an 8 foot copper ground round at the base of their tower and connect the tower ground together with the home's "utility" service ground?
(Does NEC discourage the use of multiple grounds at a residential dwelling?) or should one only connect the ground wire from their tower to a single "utility" service ground source?
Can you have a separate ground and RF ground at your antenna for RF purposes, or is there an NEC requirement that all grounds should all tie in together?
73
Charles - KC8VWM
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RE: Electrical Code vs. Good RF Grounding
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by KC8VWM on December 1, 2003
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What is meant by the term "RF" ground and how is this seperated from the term "Electrical" ground.
(Besides the obvious answer that one ground is for "RF" antenna signal gain and one is for electrical safety.)
For example, describe an "optimum" RF grounding system and how it might affect "eletrical safety" ground.
Do they have to connect together or can they be seperated? Hence the two terms RF ground and Eletrical Ground.
What are NEC's requirements?
Why do cell phone towers have a ground rod connected at the base of the tower and yet the electrical signalling equipment is connected to seperate ground rods at the same site?
Shouldn't they all tie in together?
KC8VWM
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RE: Electrical Code vs. Good RF Grounding
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by KC8VWM on December 1, 2003
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Can running a seperate ground for you antenna that is better in conductivity than your "utility" ground cause lighning to take another path though your home through your radio gear if your grounds are seperated?
KC8VWM
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RE: Electrical Code vs. Good RF Grounding
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by KD5UJX on December 1, 2003
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It still comes down to one thing: you want ALL grounding systems bonded together so (theoretically that is) all grounds have the same "Potential" to ground. If you take a close by hit, the voltage in the entire system rises and falls at the same time frame. If you take a direct hit, your gonna get fried. Most hams cannot afford the kind of system that commercial radio stations use. But, you can do the best with what you have.
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RE: Electrical Code vs. Good RF Grounding
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by WB8YFL on December 1, 2003
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My house was struck by lightning and by no means did it do anything predictable. It ignored the 70 foot wet trees and any antenna I had, it went entered at the front corner of a wall covered in vynal siding. Then it followed the wall and garage roof transistion (metal flashing) when it could not find an adequate exit it punched a whole in the wooden sheething part of it got on the ac wiring not sure how (inductive coupling?) then wiped out alot of stuff, a lot of stuff. The other path was down the eavestrough, and downspout, it burned small holes in all that aluminum, it made a good sieve after that. Then it went towards a stump cut off at the ground and blew a hole in the dirt to get to it. I am still scratching my head over that strike.
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Ground Rods vs. Equipotential Network
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by AC7GO on December 1, 2003
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Ground rods don't do much. A single ground rod has a resistance of about 25 ohms (depending upon soil). 5 amps of current into such a ground rod is all it takes to raise its potential to 125V - the level of common household line voltage. Even a large array of many ground rods doesn't reduce the resistance that much.
The relevant concept (well presented in prior posts) is to create an interconnected network of ground conductors such that all points which should nominally be at ground potential are close to the same potential in the event of a lightning strike or other fault condition. That way, if lightning strikes your flagpole, and raises (or lowers, I can't remember which way lightning drives things) the voltage of the earth around your house to 1000V, your phone lines and your coax lines and your ham equipment and other equipment - and you and the floor you stand on - will also momentarily rise to 1000V potential. This as opposed to getting raised only part way up to 1000V and being fried by the difference.
This thread is a good revival of "old time religion" that serves us all well.
tnx & 73
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Electrical Code vs. Good RF Grounding
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by K2JX on December 1, 2003
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I would like to follow up on my first comment about this article. Some hams may not realize that thier local power company is exempt from the National Electrical Code.
One should remember this when comparing the power companies wiring methods to what is written in the NEC. In addition, the NEC (in general) does not apply when the system voltage is less than 48 volts. The reason for this was to accomodate the telephone company.
There are several other areas in which the NEC does not apply, and these are listed in the NEC. My additional comments are for information only.
73, Jack K2JX
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Electrical Code vs. Good RF Grounding
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by W4PQK on December 6, 2003
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What do the experts say relative to bonding gas pipelines to ground?
I have always heard NOT to ground equipment to a gas pipeline (makes sense).
But what about bonding the gas pipeline to all the other grounds? In particular, how about a propane gas system with buried (and therefore grounded) 500 gal tank? Obviously, the copper propane fuel line is connected electrically to the furnace, water heater, fireplace log and possibly clothes dryer by the copper supply tubing. Each of the gas appliances should be tied to the electrical system ground if electrically operated.
Thanks, Jess,w4pqk
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Electrical Code vs. Good RF Grounding
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by WD259 on January 5, 2004
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Interesting thread. On topic, I work ground issues daily. Code and a good RF ground arent the same animal. My opinion is do both to a common point (to avoid ground loop). Off topic, I have worked with lightning testing on aircraft structure and equipment for many years. FAA certified the equipment via actual testing. There are too many variables to protect 100% against with lightning. OAT, humdity, water droplet size, soil content, path etc. I've seen it all, 50KVA, 100KVA & Grand Mauls. I have never seen equpiment survive the big one, we design to fail in safest manner or provide a protected backup system. In a nutshell, lightning will take the path of least resistance to high Impedence ground most of the time. You can try and direct it by creating the path but the other variables are too out of your control to be even 70% effective. Luck plays a part as well. Sorry for the long post but one of my interests. 73 Dave
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Electrical Code vs. Good RF Grounding
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by KI4CFS on August 17, 2005
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The more I talk to ham's about RF ground the more confused I get.
"You must connect all groung's together but have a ground rod outside your ham shack that is connected to the house ground or you will have a dangerious difference due to the differenc ground potential"
or
"Under no condition should you connect the ground out side your shack to the house ground for you will create a ground loop"
or
"many grounds are good, one at the radio, one just below the antenna, etc. Just connect them all together"
WHAT IS IT!! COME ON!!! As a newer ham knowing how long ham radio has gone on, their can not be this many conflicting comments?? WHY IS THAT?
What is the truth, this is simple physics not pholosophy!!
I have a dipole and am putting in a second 6 meter Yagi on the roof. I have my radio on the second floor. What is the best RF ground and DC ground.
I know I am opening a can of worms for more conflicting explinations but I am foolishly wishing that this posting will lead to clarity.
Thanks (grins)
KI4CFS, the one with 1000 questions..
Also, I put up a web link with new ham tips and welcome suggestions of things to add. I send people who are interested in ham radio to it:
http://www.toinquire.com/ham
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RE: Electrical Code vs. Good RF Grounding
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by AD5TD on August 17, 2005
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I also am somewhat perplexed at the multitude of answers I get to this question. There are THREE types of grounding; Safety, Lighting, and RF. All three should be tied together.
Lighting will follow the path of least resistance. What you want is (ideally) have all your grounds at the same potential. This is unachievable in the real world, so you get as close as you can.
Some basics remain; Ground your tower for lighting (obvious to most). That's three ground rods with connecting bare wire of at least 4 ga. sloping at a slight angle. Tie all three of them together also. No turns, no pigtails, or bends. Ground you coax at the top and bottom of the tower. Ground it at the house where it comes in to the house. Put Polyphasers on all coax. Have a ground rod as close to the operating position as possible. Tie this to the cabinets of your rig, amp, etc. Run a connecting wire to this rod from the antenna grounds. Now run a wire from your "service ground", the rod that grounds your electrical service to the house, to the rod that grounds your rig. Tie in the one for the phone while you are at it. Sink ground rod (8' at least) every 16' along the way.
The idea is, if you get hit on the antenna tower, it goes to ground right there. If you get hit on the phone, it goes to ground right there, etc. The electricity does not find a better way through your radio or phone or TV. ALL your grounds have the same resistance or potential, therefore the electricity has no reason (as if it needs one) to go anywhere else except to the closest ground rod. When your house gets hit ALL points rise in voltage and sink in voltage at the same time. Theoretically if all voltages are the same, your equipment will be OK. (I said, Theoretically that is)
Above all, buy the Insurance from the ARRL! It's cheap compared to your gear.
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