Grounding Outlet In Older House

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  #1  
Old 03-25-07, 09:17 AM
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Smile Grounding Outlet In Older House

I just found this site and there is a lot of very useful information here.

I've been searching and reading post dealing with my question for the past couple hours and I think I found some of the answers. However, when comes to electrical issues I've learned to listen to professionals and less to DIY'er.

I sure could use some help from you pros here to help me decide how best to solve my grounding issue: Here goes...

Because I live in an older Rental house (built 1960) that only has 2-prong receptacle outlets, I have in the past couple years driven 2 copper grounding rods (7') to connect to a couple of 3 prong receptacle that I installed for my 2 computers (different rooms).

Also, there is a 3rd grounding rod that is on the other side of my house where the electrical power comes in. This grounding rod has a ground wire that runs from the rod to the electrical meter and then down to into the breaker box right below the meter.

Since I now have three(3) grounding rods around my house one electrician has suggested that they should be connected by a heavy conductor ( 1/2 in. pipe) that goes around the perimeter of the house to reduce possible damaged due to a lightning strike.

Building codes require that there is only 1 electrical ground for the building. Having the 3 ground rods tied together might qualify as a single ground but you would have to use a very heavy conductor like a 1/2 in. pipe.

If I' understanding, a better option would be to get an electrician to run a grounded power line from the electrical breaker box for my 2 computers and remove the extra ground rods.

What is wrong (other than I might not meet code) about having the 2 outlets connected to their own grounding rod since I don't have a ground wire running into my house? Is this creating a dangerous situation, or can I feel safe about this configuration?

I live in a rental house that was origninally consutructed as military housing and it has a very shallow attic so I don't think it will be easy to run new wiring even if the landlord allowed.

As you can see, I sure could use you help.

Thank you.
 
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  #2  
Old 03-25-07, 09:44 AM
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Your extra ground rods are useless for the purpose you installed them for. In fact, as they exist they dangerous of they are anything. I suggest that you remove them ASAP.

The only solution that will work for you is to have an electrician properly ground the existing junction boxes, or replace the cable so that the entire circuit is grounded, or install new receptacles for your computer.

As this is a rental, you can do nothing yourself.
 
  #3  
Old 03-25-07, 10:49 AM
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Thank you for your comments Bob...

I don't understand all you said so I'm hoping you might elaborate a bit more for my benefit.

When you say "install new receptacles for your computer", what's wrong with the 3-prong receptacles I have now? What kind of receptacle would I put in if not the 3-prong... or is the issue just with the ground rod/cable I've used?

Can you explain a bit more why this is dangerous...please don't misunderstand me, I'm not arguing your point...I'm trying understand.

Thank you.
 
  #4  
Old 03-25-07, 11:05 AM
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In my opinion...A isolated ground rod is useless for equipment grounding.

It must be bonded (securely attached electrically) to the grounded service conductor.

The ground rods must be a minimum of 5/8" diameter x 8' long and fully driven into the earth.

There is no limit to the number of ground rods that a electrical service can have....actually (IMO) the more the better.

If all that exist are ground rods for the grounding electrodes....this means no water pipe used as the grounding electrode, no foundation steel used as the grounding electrode...only ground rods on the system to provide earth grounding....then...in my opinion...it is allowed to use a #6 copper conductor as bonding jumpers to bond all of the ground rods together and connect (bond) them to the service (power company) ground to make them part of the grounding electrode system.

In my opinion...If the (#6) bonding jumper is not exposed to damage, it can run exposed (attached) along the outside of the house, under the house or buried underground.

Also...IMO... Two (listed) clamps on each ground rod must be used to attach the #6 copper to the rod....either that or use one continuous piece....two wires can't be put under the same clamp...
Find the ( 2005) National Electrical Code and read 250.53, 250.58, 250.64, 250.66, 250.68, 250.104.

Again...In my opinion...After the ground rods are effectively bonded together and to the service ground, a equipment grounding conductor can be run from isolated receptacles and bonded (with listed connector) to the ground rods or bonding jumpers (between the rods) at the closest point.
Read 250.130(C).
Remember....The equipment grounding conductors and bonding conductors have to be free from exposure to damage after installed.

From your post, it sounds (to me) like all your system needs is bonding of all of the ground rods together and back to the service ground..using minimum #6 copper.
The equipment ground wires (the ones from the receptacles to the ground rods or bonding jumpers) need to be #12 copper (or larger) for a 20 amp circuit, #14 copper (or larger) for a 15 amp circuit, and #10 or larger for a 30-60 amp circuit.


This information is for reference only and I will not be held responsible for it's accuracy and or suitability for a specific problem.
Use it at your own risk.
I am not suggesting that you do this work yourself.
Since you are renting, you should discuss this with the property owner before making any changes to the residence.
Electricity can and will kill.
You be the judge as to your ability to do the work safely and legally.
I will not be held responsible for any loss or injury because of the use or mis-use of this freely given advice and information.
That's my sermon (and disclaimer) for today.
steve
 
  #5  
Old 03-25-07, 11:14 AM
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steve...

Thanks for you very informative comments. This is very interesting and helpful.
 
  #6  
Old 03-25-07, 11:18 AM
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This problem is common all over the world, if you get one fault, the current goes to ground, just as you want. But! the internal resistance in the soil causes different voltage betwen each grounding, and the grounding has no mission. One huge wire konecting the grounding together may give you a more secure grounding, but will normaly not matter.

As far as you not touchses some real ground as piping etc and the equipment with fault who shold be grounded the grounding has a almoast no value.

An internal connection chassis to chassis PC screen, printer may be smart.

dsk
 
  #7  
Old 03-25-07, 11:37 AM
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Install new receptacles. Brand new circuits run from the panel to new receptacles.

In the event of an equipment failure, you want the fault current to travel along the ground wire and then back to the source. In a normal and proper setup this happens at the point where the ground and neutral are connected. This is usually at the main circuit breaker panel in the house. although it could be at the main disconnect near the meter.

In your little setup, you have no path for any fault current, other than through the soil... In other words, you have no fault path for fault current.

In your setup, you have installed these grounds mainly for a ground reference point, not for safety. However, because the ground is at a different potential than the real ground on your system, it supplies a different reference. Under the right circumstance, this could put a significant current on the ground wire, one that would no be there if the ground were at the same potential as the neutral.
 
  #8  
Old 03-25-07, 12:25 PM
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Smile

Ok, I think this is beginning to make sense.

I have an electrician coming next week to look over my situation and your comments will help me better understand what's required and why.

Thanks very much racraft and hillbilly ace for your help.
 
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