Ground antenna directly to outside electrical panel? - AVS Forum
Forum Jump: 
 
Thread Tools
post #1 of 22 Old 07-30-2012, 05:04 PM - Thread Starter
Member
 
wildgoose's Avatar
 
Join Date: Apr 2006
Location: San Jose, CA
Posts: 185
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Liked: 11
I know antenna grounding has been asked a lot of times but I can’t quite find the answer to my question so here it is.

Can I ground the antenna (coax and mast) to the main electrical service panel outside of my house? I am talking about making a connection to the outside of the box with those grounding screws and wires, not the inside of the electrical box.

This is how Comcast grounds their coax using a ground block, and how the phone company grounds their wires. Both are grounded to the service panel with screws on the panel’s hinges. I am just wondering if it’s safe to ground my antenna this way too.

My antenna and electrical box are all in the back of the house, but the ground rod is in the front of the house. So it’s pretty difficult to ground my antenna to the rod directly. The antenna sits directly on the ground (a concrete sidewalk next to the house), not on the roof.

I feel the setup is OK for removing static electricity from the antenna, but may not be good for lightening. Although chances of this happening here is very very low (never seen one near by in 20+ years), I’d rather be safe than sorry.

A related question, are there any grounding of the mast by having it sitting directly on the ground? (again, concrete, not soil). Lightening is usually associated with rain, so when it does happen, the ground will likely be very wet, won’t the wet concrete just act as a ground path directly?

Another idea I have is to ground the antenna directly to the #6 ground wire in the craw space between the service panel and the grounding rod. But I am not sure if it’s any different from what I have now.

The alternative is to install a new ground rod next to the mast (drive it through the concrete), and connect the new ground rod to the main electrical panel. But that is a lot of work and since I have to pay someone to do it, it might be cheaper to just run a #6 from the back of the house to the ground rod in the front… wink.gif
wildgoose is offline  
Sponsored Links
Advertisement
 
post #2 of 22 Old 07-30-2012, 07:04 PM
AVS Special Member
 
Colm's Avatar
 
Join Date: Aug 2002
Posts: 4,652
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Liked: 88
As always, check with your AHJ, but per NEC:
Quote:
Originally Posted by wildgoose View Post

Can I ground the antenna (coax and mast) to the main electrical service panel outside of my house?
Yes, if it constitutes service entrance equipment (where the electric company provides power to your house). Use a device listed for the purpose. Don't connect to an existing screw or just drive a sheet metal screw into the metal.
Quote:
...won’t the wet concrete just act as a ground path directly?
No, certainly not reliably.
Quote:
Another idea I have is to ground the antenna directly to the #6 ground wire in the craw space between the service panel and the grounding rod.
Yes, you can connect to the grounding electrode conductor. Exothermic welding would be the best way, and there are other approved ways. But why bother when you can just bond to the service entrance enclosure?
Colm is offline  
post #3 of 22 Old 07-30-2012, 08:11 PM - Thread Starter
Member
 
wildgoose's Avatar
 
Join Date: Apr 2006
Location: San Jose, CA
Posts: 185
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Liked: 11
Quote:
Originally Posted by Colm View Post

As always, check with your AHJ, but per NEC:
Yes, if it constitutes service entrance equipment (where the electric company provides power to your house). Use a device listed for the purpose. Don't connect to an existing screw or just drive a sheet metal screw into the metal.

What would be such a device? Currently it is connected to the outside screw. Where do such device make the connection inside the panel? Thanks.
wildgoose is offline  
post #4 of 22 Old 07-30-2012, 08:19 PM
AVS Special Member
 
Colm's Avatar
 
Join Date: Aug 2002
Posts: 4,652
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Liked: 88
Something like this. They don't connect inside. The enclosure is bonded to the grounding electrode conductor. The mounting screws bond the clamp to the enclosure.
Colm is offline  
post #5 of 22 Old 07-30-2012, 09:30 PM - Thread Starter
Member
 
wildgoose's Avatar
 
Join Date: Apr 2006
Location: San Jose, CA
Posts: 185
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Liked: 11
So essentially it is OKto ground the antenna to the case of the "service entrance equipment", in my case a 200amp electric panel with circuit breakers, etc.

If the lightening gets discharged to the electric box, it will escape through the big grounding wire to the ground rod, and not to the internal electrical wire of the house because those have higher resistance correct?

I am curious why grounding to the box surface is OK, but to the internal of the box is not. Based on my reading, isn't the surface of the box connected to the ground bar which the ground wire from the ground rod is connected, and isn't the neutral also connected to the ground as well at that location?

What's the advantage of the "Front Clamps for Ground Wire" vs a screw on the hindge of the panel? The screw will go into the inside of the panel, meeting unpainted surface, where as the front clamp will basically touch painted surface of the box?

Sorry for all the basic questions. The information I am getting is very very helpful. Thanks!
wildgoose is offline  
post #6 of 22 Old 07-30-2012, 10:03 PM
AVS Special Member
 
Colm's Avatar
 
Join Date: Aug 2002
Posts: 4,652
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Liked: 88
Quote:
Originally Posted by wildgoose View Post

So essentially it is OKto ground the antenna to the case of the "service entrance equipment", in my case a 200amp electric panel with circuit breakers, etc.
Yes, you can bond to the service equipment enclosure. Note that a panel isn't necessarily service equipment. A combination service entrance device that has both a panel and a meter would be though.
Quote:
If the lightening gets discharged to the electric box, it will escape through the big grounding wire to the ground rod, and not to the internal electrical wire of the house because those have higher resistance correct?
Well, this really isn't about shunting a lightning strike to ground. But hopefully, if you antenna is hit, having a low impedance path to ground will help minimize damage. FWIW just the EM field from a close strike can induce damaging voltages in your electrical system.
Quote:
I am curious why grounding to the box surface is OK, but to the internal of the box is not
I didn't say that. You can run a wire to the ground bus inside if you want.
Quote:
What's the advantage of the "Front Clamps for Ground Wire" vs a screw on the hindge of the panel? The screw will go into the inside of the panel, meeting unpainted surface, where as the front clamp will basically touch painted surface of the box?
The advantage of the former is that it is code approved, using an existing screw meant for another purpose is not. It is also simple and safe. The mounting screws scrape the paint away and make a good connection to the enclosure. Don't quote me on this, but, IIRC, at one time anyway, you could drill and thread a hole to accept a machine screw for the purpose, as long as at least two complete threads are in the metal. Likewise, I believe you could use a self-tapping machine screw. But you cannot use a sheet metal screw because they have never been tested and approved.
Colm is offline  
post #7 of 22 Old 07-31-2012, 04:03 PM - Thread Starter
Member
 
wildgoose's Avatar
 
Join Date: Apr 2006
Location: San Jose, CA
Posts: 185
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Liked: 11
Ok I am getting the front clamp. Thanks for the suggestion.

If I have 4 things to ground (comcast, OTA coax, OTA mast, phone), do I need 4 of these clamps, or one, and use some kind of things to combine the 4 ground wire to one wire and then to the clamp? (what would be such a thing? didn't see anything at solid signal's grounding section...)

One last question of the day. Can a dual grounding block be used for grounding wires from different signals (comcast cable and OTA)? Or should a separate grounding block be used to avoid interference?

Comcast is claiming I am leaking signal into their system when I do this, and the dual grounding block is the only connection between the comcast lines and my OTA lines. I don't quite understand why signals would be leaking through the grounding block, but I have since replaced it with 2 separate grounding blocks. But they are all connected to the same electrical panel close by, so I am not sure if two grounding block is really making any difference...
wildgoose is offline  
post #8 of 22 Old 07-31-2012, 06:00 PM
AVS Special Member
 
Colm's Avatar
 
Join Date: Aug 2002
Posts: 4,652
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Liked: 88
Quote:
Originally Posted by wildgoose View Post

...do I need 4 of these clamps...?
You do unless they are listed for more than one connection. Sucks, doesn't it? There is something new called an intersystem bonding termination that is starting to show up on new construction. You might want to consider that.
Quote:
Can a dual grounding block be used for grounding wires from different signals...?
I am not aware of any reason not to. FWIW cable companies typically blame any customer work before considering their own when they experience probems.
Colm is offline  
post #9 of 22 Old 08-01-2012, 05:03 PM
Advanced Member
 
fastl's Avatar
 
Join Date: Sep 2007
Location: Boston
Posts: 578
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 3 Post(s)
Liked: 11
...Can I ground the antenna (coax and mast) to the main electrical service panel outside of my house?....

Ideally, the antenna should be grounded using the shortest and most direct connection to a suitable grounding electrode. THAT electrode (the antenna ground rod) should be in turn connected to the ground electrode associated with the service panel, typically with a buried 6 AWG (or larger) cable. If the above noted antenna ground rod would be located within a few feet of the existing service ground rod, then skip installing it and just connect the antenna grounding conductor to the service ground rod. DON'T connect the antenna ground (or any other lightning conducting ground wire) directly to the service panel!
fastl is offline  
post #10 of 22 Old 08-07-2012, 12:45 PM - Thread Starter
Member
 
wildgoose's Avatar
 
Join Date: Apr 2006
Location: San Jose, CA
Posts: 185
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Liked: 11
Quote:
Originally Posted by fastl View Post

DON'T connect the antenna ground (or any other lightning conducting ground wire) directly to the service panel!

I was under the impression bonding the antenna ground (ground wire clamped to the mast, and ground wire from the coax grounding block) to the service equipment enclosure is allowed by the NEC. See the above replies.

Is the worry that if a lightening strikes the antenna, it's not good to have the energy directed to the service panel, since it's connected to all the equipment in the house? A dedicated grounding rod next to the Antenna is better? Or is connecting to the service panel not in compliance of the NEC?
wildgoose is offline  
post #11 of 22 Old 08-07-2012, 03:07 PM
AVS Special Member
 
Colm's Avatar
 
Join Date: Aug 2002
Posts: 4,652
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Liked: 88
According to the NEC, there have for many years been several places you can ground the antenna mast to, the service entrance enclosure being one of them. The latest editions, introduce the concept of an intersystem bonding terminal.

An antenna mast can be grounded to a separate grounding electrode. However, that grounding electrode still has to be bonded to the grounding electrode system of the structure.

FWIW lightning isn't the primary reason for grounding the antenna mast. It is to limit the voltage in case the mast comes in contact with a power line.

You might want to watch the Mike Holt videos about the subject on YouTube.
Colm is offline  
post #12 of 22 Old 08-07-2012, 06:31 PM
Advanced Member
 
fastl's Avatar
 
Join Date: Sep 2007
Location: Boston
Posts: 578
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 3 Post(s)
Liked: 11
...FWIW lightning isn't the primary reason for grounding the antenna mast. It is to limit the voltage in case the mast comes in contact with a power line...

You should read and study NFPA 780, REA Sections 80x, and other standardized grounding practices, particulary as employed in the Telecommunications industry. The primary reason for grounding an antenna mast above the roofline is lightning. It's basically illegal to run a powerline over a roofline where an antenna mast is mounted. You should know that. Even though NEC may say that it is ok to connect the antenna ground to the box, that doesn't mean that it is good grounding practice. I'm quite familiar with Mike Holt. Although he is very good at reciting the codes and regulations, like most electricians that I've run across, seems to have only a limited understanding of the more technical details of grounding systems and related phenomena. Most people confuse code requirements with good technical practice(s) - they aren't always one and the same.
fastl is offline  
post #13 of 22 Old 08-07-2012, 07:35 PM
AVS Special Member
 
Colm's Avatar
 
Join Date: Aug 2002
Posts: 4,652
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Liked: 88
Quote:
Originally Posted by fastl View Post

.
You should read and study NFPA 780...
NFPA 780 is about lightning protection systems, which are something quite different than grounding an antenna mast. We are talking about NFPA 70 (NEC from the same organization). That requires the antenna mast to be bonded to the house's grounding electrode system, and one of the approved ways is via the service entrance equipment enclosure.
Colm is offline  
post #14 of 22 Old 08-08-2012, 08:12 PM
Advanced Member
 
fastl's Avatar
 
Join Date: Sep 2007
Location: Boston
Posts: 578
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 3 Post(s)
Liked: 11
Yes, and what you don't seem to grasp is that just because it is "approved", doesn't mean that it is optimum, ideal or desirable. The antenna system that the OP is asking about obviously will be exposed to high frequency lightning strike currents, which require proper grounding techniques. NEC is primarily focused on power line frequency (50/60 Hz) safety grounding, not with lightning stroke protection grounding.

Given a choice of grounding connection points, the last place you would want to connect the antenna ground conductor would be a location exhibiting high inductance back to the grounding electrode (like a service entrance panel/box). That's why in commercial radio and telecommunications cell sites, antenna grounding conductors of the nature we are discussing, are NEVER bonded to system ground at high inductance locations such as described above. It's typically done the way I initially described.
fastl is offline  
post #15 of 22 Old 08-08-2012, 08:58 PM
AVS Special Member
 
Colm's Avatar
 
Join Date: Aug 2002
Posts: 4,652
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Liked: 88
Quote:
Originally Posted by fastl View Post

Yes, and what you don't seem to grasp is that just because it is "approved", doesn't mean that it is optimum, ideal or desirable..
And what you don't seem to grasp is that NFPA considers it adequate for the purpose of the NEC, which may not be the same purpose that you are entertaining. The OP is just trying to ground his antenna to code, not to protect against damage from a direct strike.

Per NEC, want to bond directly to the grounding electrode system? That is approved. Want a separate grounding electrode? That is approved, as long as it is bonded to the the main grounding electrode system. Want real lightning protection, well, that is quite something else again.
Colm is offline  
post #16 of 22 Old 08-09-2012, 04:29 PM
Advanced Member
 
fastl's Avatar
 
Join Date: Sep 2007
Location: Boston
Posts: 578
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 3 Post(s)
Liked: 11
....The OP is just trying to ground his antenna to code.....

Negative. I would suggest that you go READ what he actually posted. There is no mention or use of the word CODE, anywhere in his post!
fastl is offline  
post #17 of 22 Old 08-09-2012, 06:50 PM
AVS Special Member
 
Colm's Avatar
 
Join Date: Aug 2002
Posts: 4,652
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Liked: 88
Quote:
Originally Posted by wildgoose View Post

I was under the impression bonding the antenna ground (ground wire clamped to the mast, and ground wire from the coax grounding block) to the service equipment enclosure is allowed by the NEC....is connecting to the service panel not in compliance of the NEC?

If OP just wants to meet the requirements of the NEC, he should have enough information now, so I am done. If he wants effective protection against a direct lighting strike, you can explain air terminals, catenaries, ground rings, etc. to him, because simply grounding the antenna mast to a separate ground rod is not going to do it. In any case, the grounding electrode system used for lightning protection must be bonded to the grounding electrode system of the structure.
Colm is offline  
post #18 of 22 Old 08-09-2012, 08:34 PM
AVS Special Member
 
AntAltMike's Avatar
 
Join Date: Nov 2001
Location: College Park, MD
Posts: 3,569
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 15 Post(s)
Liked: 25
I don't have a copy of the 2011 NEC. My most current edition is the 2008 one, but I don't have the wherewithal to read it.

As I recall, recent editions of the NEC did not explicitly define the term "service panel" As I recall, a few decades ago, like, half a century ago, the service panel was the box that had the 100 amp cartridge fuses in it. It was separate from the fuse box, whereas the function of the box with the cartridge fuses and the function of the fusebox are now combined into one box. I think that most people regard that first, consolidated breaker box as the service panel, but I remember a decade or more ago some electricians here insisted that the service panel was the box that housed the meter, but neither side ever cited code section numbers in support of either of those interpretations.

In any event, you can't attach a ground wire to a service panel or to the box housing the meter by wrapping it around a screw that is used to attach a box cover. You need to use a thingie like Colm linked to in Post #4, or there also is a box corner clamp that may suit your fancy and circumstances.

Back in 1992, one electrical inspector told me that I could NOT run my ground wire from my antenna mast directly to the buss inside the main breaker panel where the white, common wires were connected, even though it was clearly at ground potential.

There are a number of reasons why people ground antenna systems. Some people do it to comply with the code. Professional installers attempt to comply with the code to minimize liability and to assure they are not penalized by their employer for failing to comply with the code. Some people install according to code in order to attain the degree of fire and shock protection that compliance with the code assures. When I am concerned with safety, I have no qualms about technically violating the code by connecting to a cold water pipe in violation of the code if I know that the pipe is continuous back to ground, because I am not creating a substandard performing ground path in doing so. It was permissible to do that until, I think 2005, but then the five foot limit was introduced out of concern that someone in the future might use plastic pipe for repair and disrupt the ground. As a home owner, I am not concerned about that possibility. In fact, in commercial buildings, it is still compliant to connect to a cold water pipe if the plumbing is professionally maintained and largely visible.

The code now allows you to connect the ground wire to something it calls the "raceway". Last I knew, that term was undefined, but there seemed to be a consensus that the raceway was whatever metal enclosure or conduit that goes from the meter housing box to the first or "service" panel.

Beyond that, lots of technical junkies denigrate the NEC as less than optimal for absolutely, positively minimizing lightning damage. The code does NOT mandate that the ground connection or even that the coax outer conductor ground actually be outside of the house even though common sense leads one to conclude it is better to make those attachments outside the house. The NEC even allows you to install supplementary ground rods that are not mandated if it lets you sleep better at night. And there are a lot of educated people who believe that grounding an antenna mast makes it a more inviting target for lightning, and some of those people have PhDs in physics.
AntAltMike is offline  
post #19 of 22 Old 08-10-2012, 06:45 AM
Advanced Member
 
fastl's Avatar
 
Join Date: Sep 2007
Location: Boston
Posts: 578
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 3 Post(s)
Liked: 11
....The code now allows you to...

The "code" doesn't "allow" you to do anything! The code is strictly advisory, meaning that it is a collection of recommended practices. Local government building codes and the electrical inspector are what permit/deny. Local codes and inspectors don't always agree with the code, although they commonly defer to it. Installing an antenna for broadcast reception purposes is a federally mandated privilege that usurps local codes and restrictions, and the NEC actually has no "say" as to what you do (or don't do) with your antenna, providing that you don't directly connect it to AC power. Not that I am advocating that you ignore proper grounding practices.

If you do install an antenna on the roof, in effect you've installed a lightning rod, whether that was your intention or not. There is a large amount of information available on the web that goes into detail as to how should PROPERLY deal with this sort of situation, and it isn't verbatim recitation (blather) of the NEC, either. Grounding techniques have been developed over many-many decades by the telecommunications industry, and the knowledge of how to effectively and safely deal with lightning effects are out there, if you want to spend the time doing the research (I certainly have).

It's really up to you, whether you do it the right way, or whether you just want to be code bozo that blindly runs around connecting up ground wires with no genuine understanding of what you are doing. That was the point of my previous posts.
fastl is offline  
post #20 of 22 Old 08-10-2012, 08:36 AM
AVS Special Member
 
AntAltMike's Avatar
 
Join Date: Nov 2001
Location: College Park, MD
Posts: 3,569
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 15 Post(s)
Liked: 25
One of the states for which I had researched the legal implcations of "the code" was Massachusets, where I did several commercial antenna installations in the 1990s and where one PITA electrical inspector made me get a class 2 (low voltage) permit.

Massachusetts General Laws generally "adopt" the NEC a year or two after each cyclical revision, with stipulated exceptions. Back when I read the Massachusetts statutory incorporation of "the code", I remember that they waived and rewrote the section on the ground requirements for temporary site facilities that were there to support the construction of a new building. And I have also seen that Arizona, they had more stringent standards to assure the conductivity of ground rods because of the commonly encountered dry, sandy soil. But as far as Massachusetts General Laws were concerned, they did not amend any of the 800s sections of the adopted 1990 edition of the NEC regarding communcations wiring.

One part of the code that was in force in Massachusetts in the 1990s said that the outer conductor had to be grounded with a solid insulated copper wire approximatly equal in current carrying capability to the coax outer conductor. This inspector said that since high frequency current traveled on the skin of a conductor, the ground wire would theoretically have to have the same outer diameter as the coax sield, but then, he reasoned that since the code had stipulated that a bonding conductor could be 6 gauge, then it would serve no purpose for him to require any other ground wire leading to a 6 gauge bonding jumper to be larger than 6 gauge since the bonding jumper would be the weak link, so I had to buy a short piece of 6 gauge solid insulated to get the job approved.
AntAltMike is offline  
post #21 of 22 Old 08-10-2012, 05:05 PM
Advanced Member
 
fastl's Avatar
 
Join Date: Sep 2007
Location: Boston
Posts: 578
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 3 Post(s)
Liked: 11
Ultimately, it's up to the discretion of the inspector as to what goes and, yes, it can be a real PITA, particularly when you have a personality conflict going on! To the 6 AWG issue, one of the REA specifications I cited above actually note that increasing the grounding conductor size above 6 AWG is a case of diminishing returns (with lightning) due to the inductance properties of the larger gauges. Despite that, telco standard wire size is 2 AWG, for outside grounding runs.
fastl is offline  
post #22 of 22 Old 08-12-2012, 12:01 PM
Senior Member
 
ernie's Avatar
 
Join Date: Mar 2001
Location: San Jose, Ca, USA
Posts: 232
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Liked: 10
The purpose of the NEC to prevent fires and injury to people. Its development was originally sponsored by fire insurance companies (National Board of Fire Underwriters). It is not designed to protect expensive electronic equipment from destruction.
Like TV stations and radio stations, ham radio stations have a need to be protected. There is some very good information about this topic at the ARRL (Amateur Radio Relay League) web-site: http://www.arrl.org/lightning-protection Most of the information seems to be available to non-members. (I was able to access the articles while logged out, but my apologies if you can't get to everything. The external links like this: http://www.lightningsafety.com/nlsi_lhm/IEEE_Guide.pdf should work fine.) So if your goal is to protect your equipment and not just satisfy a code requirement, then this should be enough information make the best choices.

Ernie/NE6D
ernie is offline  
Reply HDTV Technical

User Tag List

Thread Tools
Show Printable Version Show Printable Version
Email this Page Email this Page


Forum Jump: 

Posting Rules  
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off