Grounding..Yes,Grounding.

[rpearson]

Ive heard and read of 50 ways to skin this cat,I just had to bring this to Tek-Tips.

I was sent on a job to troubleshoot some problems that were known to be with the OSP copper cable plant protectors for a companies back-bone 100 pr. feed.Upon inspection I noticed that one end of one protector was grounded to the structural steel,and one end was grounded to a red fire system water pipe(Tell me this is wrong).My practice has always been to run a minimum #6 back to a ground rod or electrical MDP ground,and in a last ditch, ground to bare steel structure.Comments,Guidence,Tips?Thanks.

Oh...and the problem with the copper was that they terminated the protectors backwards.

Thanks again.

 

[Servamatic]

You are correct...water pipes are to be bonded to the grounding system, but they are NOT to be used as a primary grounding source.
The methods you described using are the correct methods.
Although under the new 607-A standard #6 may not be adequate depending upon length of the conductor.

Is the OSP cable metallic covered? If so both ends of the shield must be bonded to ground as well, unless they fall under the exceptions in the NEC for Interbuilding Protection.


Richard S. Anderson, RCDD

http://www.servamatic.net

 

[rpearson]

Thanks.The shields were not bonded either.

 

[grimmer]

Ground both ends of the shield?

Doesn't that render the shield ineffective?

 

[mikeydidit]

You would bond the shield at the termination points. You would install a bonding clamp to the sheath of both ends of the cable and then attach a grounding wire to it. Between the protectors and the bonding of the sheath, you have a grounded and bonded installation.


Mikey

 

[daronwilson]

Grounding the shield at both ends does not make it ineffective in any way. What DOES make it ineffective (and makes the shield an antenna) is not grounding it at either end. Grounding at one end is often required in instrument and audio wiring due to nasty ground loops and ground hum that can be produced.

Often the entrance cable shield is isolated from the building ground with a large capacitor, and depending on the installation between buildings this may be an issue as well. Two different buildings, two different electrical services, could cause you to experience a different ground potential at each end of the cable. Bonding both ends of that to ground (in theory) should cause that ground to be at the same potential. However, if there is a difference, the current will be flowing on the shield of your cable in an effort to make the ground potential the same. Obviously, having current flowing on your ground/shield is not a desirable feature.

I honestly think grounding is more of an art than a science, depending on what you are working with. But as always the first priority is safety, so grounding should comply with NEC and applicable standards. If that causes you noise problems, you may have to do some interesting things to make the electronics happy. We've experienced challanging issues with fire alarm systems between buildings, as they are extremely picky about ground faults, and sometimes a few tests and trials have to be done to find the best solution.

Good Luck!

It is only my opinion, based on my experience and education...I am always willing to learn, educate me!
Daron J. Wilson, RCDD
daron.wilson@lhmorris.com

 

[EdPorts]

Yes... definetely ground the sheath at both ends to achieve the correct results.

Here's an important thing to remember:

With your ground wire, the larger guage the better. Remember that we're talking about huge amounts of electricity, so we want to give it an adequete path. Secondly, never make 90 degree bends with your ground wire, make gentle curves -- and try to make it as short as possible. If you're ending up with a ground wire run of 20 feet or more, you may want to consider finding a better, closer source. Testing will illustrate that a long grounding run, or tight bends in the wire along with a poor grounding choice will give you no support whatsoever in the event of high amounts of voltage coming over your line.

Starting in 2003, we have completely elminated grounding to pipes, etc. Independent tests show that it's not very consistant in providing an adequete ground. We use sachs clamps, which work very well -- they clamp to the power meter (which by NEC standards has to be grounded) and penetrate through the paint. If not that, a good old ground rod will do.

Remember to always ground both sides of your cable, be it OSP grade copper, some fiber has strength members -- you may want to check out if it needs to be grounded, coaxial cable is also a big grounding issue. RG-6, 59, and 11 can all be grounded via ground blocks which look like a barrel with a grounding clamp on them. 1/2" and above can all be grounded via amplifiers, taps, directional couplers, or if you haven't got any of those in your line... they also make ground blocks for hardline.

Big thing here is that you'll see guys ground something, but you know that any source of voltage isn't going to jump to ground because of how it's ran, it's going to torch everything in its path. We've all seen it before...

 

[JBeav]

I believe a metallic water pipe could be used as a primary electrode IF it is in contact with earth for at least ten feet and if the connection to it is made within five of where the water main enters the building.

The metal frame of a building is often considered the best grounding electrode system. Sometimes the frame is not used as the primary electrode but it bonded to a water pipe or other primary electrode system.

As always, confirm what the local code requires.

Jeff

 

[Servamatic]

Water pipes have not been used as primary ground source in many localities since about the 1990 code if I remember correct. Many water companies would cut the metal pipes and insert a length of plastic pipe to insulate them from the grounding system. The current flow to ground through the water pipe in many cases was causing early failure of metal water pipes. It’s not very often if at all anymore you find new metal water pipes being used underground up to about 5’ of building entrance.
You still bond the water pipes as it is a metal apparatus inside the building.
You need to remember the difference between grounding and bonding...grounding is the one point a buildings electrical system is actually connected to earth in some fashion. Bonding is the deliberate joining of all metallic components in the building to the grounding system.
The NEC describes it better, but since I don't have my code book handy at the moment....
The NEC does REQUIRE the metallic shield of the cable be bonded at both ends, unless certain exception criteria are met. i.e. 140' of cable length or less.



Richard S. Anderson, RCDD

http://www.servamatic.net

 

[Jtodd]

To look further, Hubbell has a great PowerPoint for grounding and bonding. It's in their Hub-Club forum (yeah another forum to sign up for!) It goes into everything.

http://www.hubbell-premise.com

Justin T. Clausen
Physical Layer Implementation
California State University, Monterey Bay

 

[Sphoneman]

Always do a DC & AC voltage test with your meter on your grounds or bonds!!!!!!!!

The old school was ground is ground the world around- not so as we found out years later.

A differential in grounds can get you or someone else killed.

Find out the state & local codes in reference to grounds where you are working. They may be more stringent than the NEC (ie Working down in Maryland years ago ( I think around 1984 ) they went to single source point in buildings. How you can tell that is in the Electrical Gear Room/area you will find a copper plate with holes drilled into it. Then you will see different ground connections on it- Electrical,Building Steel,Water etc.Always feel free to add yours to it- by adding your own lug- never undo one that is there.

Steve
tele-dataservices.com

 

[EdPorts]

Justin Justin Justin...

How are you my friend. How's Josh doing? How about Carl? I've talked to Don a few times.

Nick, your pole setting pal.

 

[Jtodd]

Nick!

How's it going? What are you up too these days?

Justin T. Clausen
Physical Layer Implementation
California State University, Monterey Bay

 

[EdPorts]

Aye, not too much.

Going to school as usual, as well as working for Charter Communications part time in installation and repair. It's piecework, so quite fun.

Looking to transfer again in the fall of 2004 to Chico State, majoring in Construction Management.

I tried to turn carl onto this forum a while back, but he isn't too into the computer side of things as we all know.

Give me the rundown on what the latest is over there. I think I'll have to come up and visit soon enough.

Nick