ungrounded outlets


  #1  
Old 12-29-03, 01:30 PM
amritsari
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Unhappy ungrounded outlets

We bought a house in 2002. Everything was fine till last month when I connected my new computer with a TV receiver card to the cable TV cable. I noticed small sparks between the cable and the computer case and a slight "tingling" feeling in my hands. I started investigating and discovered that my electrical outlet is ungrounded while my cable TV cable is grounded. There is a 70V difference between cable TV ground and electrical ground. This explains the sparks and shock that I received. The question is - what are my options ? Can I ground the electrical outlets in my house - I counted 11 ungrounded outlets. Apparently the original house (1946) is ungrounded while the newer addition is grounded ? I haven't done any electical work on my own and neither do I have the tools. Our house has a crawl space with copper plumbing.
Alternately, how can I get recommendations for decent electrical contractors in the san gabriel valley area in southern california ?
 
  #2  
Old 12-29-03, 02:11 PM
J
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You describe a 70-volt difference between the cable TV ground and electrical ground. How did you measure this? I thought you said you had no electric ground.

If you are really getting a shock, it is likely that someone in the past has installed illegal outlet grounding. You should have a qualified person check each outlet for improper grounding.
 
  #3  
Old 12-29-03, 02:43 PM
amritsari
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more details

I used a multimeter to measure the difference between the cable shield and the computer case. The computer has a 3 prong connection but since the ground isn't going anywhere, the case floats to some value determined by the internal circuitry of the computer (my guess). Later I borrowed a ground tester thingie from my neighbour and tested the outlets. It showed there was no ground connection in the old part (~1950) of the house and a ground did exist in the newer part of the house. In fact there are a couple of GFCI's in the new part as well.
 
  #4  
Old 12-29-03, 03:00 PM
R
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There are several issues here.

If you thought you had a ground, but in fact do not, then someone incorrectly installed three prong outlets. You should not ihave three prong outlets that are not grounded unless the outlets are on a GFCI protected circuit. They may be protected by a GFCI outlet or a GFCI breaker, but one (or both) must be present. Additionally, the outlet should be marked "NO EQUIPMENT GROUND".

You should immediately investigate exactly how these outlets are wired. Is the ground just unconnected, or is the ground connected to something? Connecting the ground to anything with one exception (see below) is wrong.

Now to answer your question.

To ground these outlets you have two options. Install a ground wire that goes from the outlet all the way back to the circuit breaker panel or fuse box and connects to the same place as the other grounds and neutral wires. This ground must be the same size as the outlet wire, usually 14 gauge or 12 gauge.

Or you can replace the cable that feeds the outlet with a new cable containing a ground.

The other option (as I mentioned) is to install a downstream GFCI outlet or breaker so that the outlets are protected from ground faults.

Unless you take one of the above actions, you should remove the three prong outlets and replace with two prong outlets.

Under no circumstances should the ground wire be connected to the neutral wire or to a nearby water pipe or other "ground" source. This is dangerous and could present a life threatening situation.
 
  #5  
Old 12-29-03, 04:21 PM
J
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The 70 volts you measured is meaningless since the case is floating. Chances are that the coax itself will provide the ground reference for the computer's electronics. I'm not sure if you are saying that once you connect the coax that you can still get shocked by the computer case. Are you saying that?
 
  #6  
Old 12-29-03, 04:44 PM
amritsari
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yet more details

I get a shock if I hold the cable in one hand and the computer case with the other. If I bring the cable near the case and gently slide it across the case I notice tiny sparks between the two. Ofcourse once I connect the cable there is no more shock/sparks/voltage difference. The 70 V is measured with the cable disconnected from the computer.
I also traced the cable and observed that it is grounded to an external electric panel - the cable TV cable comes from the cable company to a cable distribution box located next to the electric panel (one of two electric panels located on the outside of the house. This one has the electric meter in it). The cable shield is then grounded to the electric panel. A cable then goes off to each bedroom, in one of which the computer is located.
 
  #7  
Old 12-29-03, 04:46 PM
amritsari
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Its clear to me from racraft's mail that I'll atleast have to open up the outlets and check if the ground is hooked to a wire or not. The previous owners may have installed 3 prong outlets just to be able to plug in 3 prong appliances (e.g. the washer dryer are plugged into ungrounded outlets as well !).
 
  #8  
Old 12-29-03, 04:51 PM
amritsari
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Thanks for your advice racraft. My neighbour, who is a general contractor, was suggesting that I get somebody to thread a wire through the floor and connect it to the plumbing under the house. Clearly you think this is unwise. Can you please elaborate ? As I see it, this could pose a danger if there is a short to ground and someone is holding onto some plumbing at the same time (e.g. tap, shower etc). But then the plumbing is really grounded and should provide the least resistance path compared to the person holding it ??
 
  #9  
Old 12-29-03, 05:00 PM
J
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Under no circumstances should you ground this to a plumbing pipe under the house. This is a significant hazard, as you guessed. And be sure never, ever to use that contractor to do any work at your house. He has shown a tendency to cut corners and compromise safety.
 
  #10  
Old 12-29-03, 05:12 PM
R
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As John has stated, and you have figured out, you should not ground your outlets to the plumbing.

To comment on what John is saying regarding the contractor...

I am not familiar with code history or with former practices, but I think that the practice of simply grabbing a ground from a convenient water pipe was common years ago.

My house was buils in tha late 40s. When I moved in, the elctric range was still original. It was grounded to a nearby water pipe. Further, several outlets had been grounded to nearby water pipes. I have since fixed these problems, but I still here people tell me that a contractor made the connection, or that it's okay to do so. Adding to the mess, the big box stores sell clamps for just this purpose.

Fact is, regardless of who did it or when it was done, it is not safe to do so. Any and all such incorrect ground connections should be fixed ASAP.
 
  #11  
Old 12-29-03, 08:13 PM
amritsari
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I opened an outlet and it turns out there are only two wires connected to the 3 prong outlet. But another intriguing feature was a nut sticking out of the 3 prong outlet and touching the junction box and there seems to be a bare wire connected to the junction box and disappearing into a hole. I'm guessing this might be some kind of grounding. Is it something that is/was done ? The nut touching the junction box seems highly iffy.
 
  #12  
Old 12-29-03, 08:22 PM
J
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Is the box metal? Is the house wired with metal conduit?

I can't quite picture this "nut".

I suggest you spend $8 at Home Depot on an outlet tester, the kind with two amber lights and one red one.
 
  #13  
Old 01-02-04, 03:21 PM
amritsari
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please help

ok, I had two electricians come to the house and both gave estimates of $2500-$3000 to do the following:
run new ground wires to 12 outlets.
replace a 4-fuse panel with a breaker panel

one of them would even install 2 bathroom vents for me in the quoted price !

Anyway, some important questions came up that I would like help on:
1 One suggested that since he is going to pull ground wire to the outlets and since my old wires are "cloth" insulated (which are more susceptible to burning ??), he might as well pull a 3 wire "romex" (??) to give me new wires for all the 12 outlets. Is this necessary ? I don't know the vintage of the cloth wires.

2 The same guy said a permit might be necessary since we are rewiring in which case he would have to put outlets every 12 feet. But then I objected that we are only rewiring part of the house and he said that excuse might work but I wasn't convinced. Question - when is a permit necessary ?

3 The same guy said that I should replace the fuse panel with breakers on an outside breaker panel that has space instead of putting in a new panel inside the house (the fuse panel is inside the house).

4 None of them said they would patch any holes they would make in the walls to pull the wires. What kind of language should I use in the contract to insure that they do minimal damage ?

5 What kind of wire(s) should be used for this project ?

6 Both of them pointed out that I don't have an 8 foot ground rod (against code), and the second one also pointed out that the present ground connection of the main panel to the plumbing does not seem to be correct because the house has been repiped and the portion of the plumbing to which the ground connection is made doesn't have water in it (and is also NOT copper, another giveaway). Ofcourse somebody would have to go under the house to investigate this. So he basically convinced me that my house has NO ground protection ! Is there any way to test this ?
 
 

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