Gound Rod Question

[charlesrshell]

Is there a rule in the NEC that allows for a second ground rod for homes? My two dishes or on the complete other side of the house. If I ran a ground wire from the dishes to the main home ground rod that is by the electric meter, the wire would be about 150 feet long. If I had a second ground rod by the dishes I estimate the direct distance from rod to rod would be about 70 feet. It seems to me that if the ground rods are far apart from each other there would be less chance of ground loops, etc.

 

[RandallA]

Take a look at this PDF file, slide 12 (exception):

It makes a good reading for grounding too.

 

[charlesrshell]

Got it printing now. Thanks RandallA

 

[RandallA]

Here's the link for the Power Point and the PDFs files. The Power Point file is over 6.0 MB so I didn't think it was worth posting it.

http://rweb.echostar.com/departmental_content/TechPortal/content/zips/20060520_SystemGrounding.zip

 

[charlesrshell]

Wow, thanks RandallA. Good info. So if understand it correctly I will have to install a ground rod by the dishes within 20 feet and then bond that ground rod to the main house ground rod? That is going to be tuff running that long of ground wire. Guess I better use a #4 gage too for that long of distance.

 

[webbydude]

To the OP, any chance of just connecting to a secondary ground, such as circuit breaker panel or a properly bonded coldwater pipe?

 

[charlesrshell]

CB panel is on the other side of the house around where the main house ground rod is. From everything I have read if I understand it correctly, cold water pipes are out of the question unless you are within 5 feet from coming in the house. I though all copper cold water pipes were bonded to the main house ground rod, but I guess I am wrong.

 

[highdefjeff]

Is there a rule in the NEC that allows for a second ground rod for homes? My two dishes or on the complete other side of the house. If I ran a ground wire from the dishes to the main home ground rod that is by the electric meter, the wire would be about 150 feet long. If I had a second ground rod by the dishes I estimate the direct distance from rod to rod would be about 70 feet. It seems to me that if the ground rods are far apart from each other there would be less chance of ground loops, etc.

Charles, in your case, there are two issues:

1. System ground to NEC standards, and
2. The grounding of your dish units specifically.

The current ground situation you are discussing about the water pipes is related to the NEC electrical safety of the system, while the grounding of your dishes, themselves, is about proper functioning of your system.

NEC doesn't care about a messenger line to the dishes, they care about the electrical safety and the system ground.

A second ground rod for your dishes would not need to be tied to the main house ground. The purpose of the ground line to the dishes is to "drain" static electricity and such, and to avoid lightning.

http://www.wowvision.tv/why ground.htm

 

[charlesrshell]

Would there be any ground loop problems not connecting to the home main grounding rod?

 

[highdefjeff]

Remember that the dish units are essentially metal "houses" for an LNB and the wires coming through it, but they are insulated by the plastic yoke and the insulation on the cables. They are sort of "free standing" in terms of electrical conductivity.

A ground loop would be established, or not, through the main ground, the one the NEC is concerned with, that deals with the electrical current in the house. Grounding just the dishes themselves, separately, could not cause a ground loop.

 

[charlesrshell]

Remember that the dish units are essentially metal "houses" for an LNB and the wires coming through it, but they are insulated by the plastic yoke and the insulation on the cables. They are sort of "free standing" in terms of electrical conductivity.

A ground loop would be established, or not, through the main ground, the one the NEC is concerned with, that deals with the electrical current in the house. Grounding just the dishes themselves, separately, could not cause a ground loop.

OK, gotcha.

 

[charlesrshell]

Jeff, can you analyze the following from the NEC when you have a chance or if anybody else would like to jump in and let me know what you think? Thanks

250.52 Grounding Electrodes

(A) Electrodes Permitted for Grounding

(1) Metal Underground Water Pipe A metal underground water pipe in direct contact with the earth for 3.0 m (10 ft) or more (including any metal well casing effectively bonded to the pipe) and electrically continuous (or made electrically continuous by bonding around insulating joints or insulating pipe) to the points of connection of the grounding electrode conductor and the bonding conductors. Interior metal water piping located more than 1.52 m (5 ft) from the point of entrance to the building shall not be used as a part of the grounding electrode system or as a conductor to interconnect electrodes that are part of the grounding electrode system.
Exception: In industrial and commercial buildings or structures where conditions of maintenance and supervision ensure that only qualified persons service the installation, interior metal water piping located more than 1.52 m (5 ft) from the point of entrance to the building shall be permitted as a part of the grounding electrode system or as a conductor to interconnect electrodes that are part of the grounding electrode system, provided that the entire length, other than short sections passing perpendicular through walls, floors, or ceilings, of the interior metal water pipe that is being used for the conductor is exposed.

I wonder why a homeowner can’t declare themselves as the supervisor of their own home to ensure that only qualified persons service the interior metal water piping and not have to worry about the 5 ft limitation. It appears to me the home’s water pipe is a good ground conductor if it is good enough for commercial buildings. Is there a way to test a water pipe to see if it is still a good bond to the home’s grounding rod? The installer that tested my water pipe by the headend area took a multi-meter reading between a water pipe and the electrical plug ground. The reading was 00.2. So I guess that met that water pipe at that location was a good ground. The water pipe I want to test is on the other side of the house by the dishes. Not close to an electrical outlet. Thanks again.

 

[highdefjeff]

Remember that the NEC code is written for the electricians who are wiring your entire house.

Here's a key point: Actually, we are not even grounding. We are just "bonding" to the ground system of the house. We just need to be tied in at a reasonable place, we are not grounding the house. I'm confident that with an added ground block, and a "drain" for your dishes, you are well within Dish Network standards, and not compromising any codes. Your water pipe ground will work fine for the job. Don't worry, Charlie!

 

[charlesrshell]

Remember that the NEC code is written for the electricians who are wiring your entire house.

Here's a key point: Actually, we are not even grounding. We are just "bonding" to the ground system of the house. We just need to be tied in at a reasonable place, we are not grounding the house. I'm confident that with an added ground block, and a "drain" for your dishes, you are well within Dish Network standards, and not compromising any codes. Your water pipe ground will work fine for the job. Don't worry, Charlie!

OK, thanks for the info

 

[red hazard]

Charles,

As previously recommended, connect the new grounding rod to the main grounding rod. It's not just a ground loop issue, it's a safety issue. I work out at the base and conduct evaluations of telecommunication facilities in CONUS with two electrical engineers and write reports for the Commander's signature. We use Mil-HDBKS, Mil-STD, and the NFPA 780 (Standard for the Installation of Lightning Protection Systems) for references. Your self-recommendation to consider #4 AWG is a good idea considering the substantial distance involved. I can give you a more detailed explanation if you PM me. As you are aware, we get plenty of lightning around here and you want to insure that both grounds are at the same potential when there is a nearby strike to prevent flash-over through your coax and house wiring.

Your northern neighbor

 

[Bob Haller]

yeah bond those grounds!! its a safety issue

 

[vegassatellite]

You want both ground rods to be at equal grounding potential. The way to do that is to bond them together with a low resistance conductor (read: large ground wire) such as #6 or #4 is better. Electricity prefers the path of least resistance so if the path to your satellite ground proves to be better than the path to your house main ground, its gonna go there. Equalizing the two via a common bond ensures that won't likely happen. You get ground loops when the path of least resistance ends up being across your signal wires and the result is you end up hearing the 60hz noise produced by electricity. Audio hum in that situation can easily be the least of your problems.

 

[charlesrshell]

You want both ground rods to be at equal grounding potential. The way to do that is to bond them together with a low resistance conductor (read: large ground wire) such as #6 or #4 is better. Electricity prefers the path of least resistance so if the path to your satellite ground proves to be better than the path to your house main ground, its gonna go there. Equalizing the two via a common bond ensures that won't likely happen. You get ground loops when the path of least resistance ends up being across your signal wires and the result is you end up hearing the 60hz noise produced by electricity. Audio hum in that situation can easily be the least of your problems.

So vegassatellite, is bonding of both ground rods important for illuminating ground loops, lightning surges, or electrical shorts in the home?

 

[vegassatellite]

That is a definite yes. Any difference in grounding potential between two isolated ground rods can at a minimum cause a 60hz audio hum and at worse kill someone.

 

[Mike_H]

The purpose of grounding the dish is to provide a low impedance ground path to any sort of electrical charge that is placed at the dish. Lightning, static, a downed power line.

The purpose of bonding the ground to the whole house ground system is to ensure a common ground potential exists through-out the satellite equipment. Having a difference in ground potential can lead to an induced current that as was mentioned, could just cause a hum, or generate sufficient current to injury someone.