Adding Ground to Old Wiring

Reply

  #1  
Old 06-19-05, 01:43 AM
ljg
Visiting Guest
Posts: n/a
Adding Ground to Old Wiring

Part of my house has old wiring in that it is 12-2, no ground wire in the Romex cable. I want to get the outlets in those rooms equiped with grouned receptacles. The 12-2 wiring is in very good condition and was well done when installed probably 50 years ago. Can I just thread in a no. 12 green or bare wire into those outlet boxes and run them to a common that I connect to a ground terminal in the intake box? I know that it will do what I want it to do but is that permissible? The wiring book that I have seems to imply that you can do that but doesn't come right out and say it. I don't like to wire in receptacles that have the grounding connection but have no ground wire attached.
I screwed up the title in my initial post, sorry.
ljg
 
Sponsored Links
  #2  
Old 06-19-05, 06:12 AM
Member
Join Date: Jan 2004
Location: Oregon
Posts: 1,219
Received 0 Votes on 0 Posts
There are ways that you can do this which would be legal and meet code. However there are details that I am not going to bother confirming right now because I am going to try to convince you not to do this. Please note that an added ground does not have a low an impedance as a built in ground unless the added ground exactly follows the original cable. This may or may not make a safety difference.

Running a ground wire properly is essentially as much work are running an entire new cable. You have this small long thing that you have to fish into walls, anchor and protect when exposed, cut holes in your drywall and then patch them, etc. New romex is somewhat thicker and stiffer, but when you factor in all the work that you will be doing, putting in new romex is only a small percentage increase in work.

In addition, you may find yourself having difficulty at the junction boxes, figuring out how to safely bring the new wire in. But new romex just goes right into the cable clamp.

Even if your 50 year romex is in fine shape, the insulation does age, and old romex is rated for 60C, the new stuff for 90C. This makes a difference if you insulate the walls where the cable runs.

Finally, even if the wire is in perfect shape, it is almost certainly the case that you use more power now. You are probably better off dividing the various circuits so that more total power is available.

-Jon
 
  #3  
Old 06-19-05, 06:29 AM
ElectricalMan's Avatar
Member
Join Date: Feb 2005
Location: Harrisonburg
Posts: 744
Received 0 Votes on 0 Posts
ljg,

I have to concur with Winnie on this one. By the time you made the attempt to pull a grounding wire from each box and try to either bring them to a grounded source such as the waterpipe or the panel itself under the NEC guidelines....you would probably be better off just pulling new romax.

Now I can go into more detail and all the possible methods of grounding an ungrounded plug but we have to look at the reasons you want to do this first.

1.) Is it for safety......if so just replace the first recep. in the circuit with a GFCI Recep. and you are about as safe as you can get basically.

2.) Are you doing it for computers?...if that is the case you would save more time just running a dedicated feed to a new recept. in the location you wish to have a computer...heck nothing better than a dedicated ground to a computer....ahh..the debate will go on if that is needed now days with the new computers and so on...

Anyway.....we can go into more detail on this if you wish but you have to break down the OVERALL reason you want this as it is ALOT of work trying to make something OLD work than making something OLD NEW....and NEW is always better.
 
  #4  
Old 06-20-05, 10:54 PM
ljg
Visiting Guest
Posts: n/a
Responding to the new wire pitch

Thanks to Winnie and ElectricalMan for your thoughts regarding new wiring to my outlets. I know that "new is better" is sometimes good advice but in this case I don't think it will improve the functionality or safety of my circuits over what I am thinking of doing. The 12-2 cable has the label General Cable on it and is rated for 600 volts. It is in excellent condition. I think I can get to the outlets I want to change from the basement without too much trouble. So I can just install GFI outlets for safety. I still like to have my outlets grounded because I do occasionally plug in a tool or piece of electronic equipment that should have the ground connection. I accept the statement about changing the impedance but I am not sure that has much relavence to what I want to achieve. I guess i have to be convinced that what I am proposing is in some way very much against code or there is a safety issue involved. One of you mentioned that putting in new cable would give a better distribution of load. The loads are already very well distributed. I have a 200 amp breaker panel. We NEVER pop a breaker due to overloading a circuit. All circiuts are 20 amp. I don't claim to know everything but have had some experience with wiring.
 
  #5  
Old 06-21-05, 04:21 AM
Member
Join Date: Jan 2004
Location: Oregon
Posts: 1,219
Received 0 Votes on 0 Posts
If you elect to run a new equipment grounding wire, rather than a new cable, you need to follow NEC code. The relevant portion is 250.130(C) which specifies where you may connect a new ground wire, but you should read the entire section on grounding. Go to the library and _read_ this section carefully, because you have to get it right. You can connect the equipment grounding conductor to the following: properly installed and bonded to your electrical system grounding electrodes, the grounding electrode conductors, or to grounding terminals in your panel.

Be aware that you cannot simply do the following: connect the equipment ground wire to a new ground rod. connect the equipment ground wire to a random metal pipe. connect the equipment ground rod to any available water pipe. Some of these things will work but not meet code, and some of these things are actually more dangerous than not having an equipment ground at all. You are limited to the specific points listed in the code.

I repeat: read the relevant section of code. Improper grounding is an easy way to reduce the safety of your electrical system.

In most cases, properly running a new equipment grounding conductor means running a wire from the receptacle back to the panel.

The basis of my main argument for running a new romex cable is that the effort involved in running this equipment grounding conductor is essentially the same as running the new romex. In fact, since the list of allowed connection points does not include other equipment grounding conductors, a most restrictive read of the code would say that you need to run a separate wire for _each_ receptacle, which would be _more_ work than running a new romex unless it was only one or two receptacles.

-Jon
 
  #6  
Old 06-21-05, 11:28 PM
ljg
Visiting Guest
Posts: n/a
More on adding ground wires

OK, so if, say, two or three of the outlets are on the same circuit and if wired with 12-3, they would have only one ground wire back to the breaker box. However, if I now add a ground wire to the 12-2 wiring, I have to run a separate wire from each outlet back to the breaker box (which is where I was planning to go but not with a separate run from each outlet)?? I don't see any "makes sense" reason for that but if that is what the code says I suppose I have no choice. Would this be the case even if the three outlets in one room are currently on the same circuit?

Now if I do rewire the outlets with 12-3, what do I do with the 12-2 going into each outlet box? Do I just cut off the presently used conductors, put a wire nut over the end of each and leave them there? What if there isn't room in that small box for that and new cable coming in as well? Or do I have to pull the old cable out of the receptacle box, follow it back to a junction box somewhere and disconnect it there, or can I just cut it off and terminate it at some convenient place in a new junction box?

Thanks for your answers, ljg
 
  #7  
Old 06-22-05, 05:09 AM
Member
Join Date: Jan 2004
Location: Oregon
Posts: 1,219
Received 0 Votes on 0 Posts
I repeat: you have to go and read the relevant code sections yourself. You are asking questions for which my personal answer has been, and continues to be 'Doing this correctly requires more effort than simply replacing the circuit, so I'm not going to even bother trying to figure out exactly how to do this correctly.'

As I said, 'A most restrictive read of the code....'. It doesn't make sense to me that you should not be able to 'daisy-chain', but the reality is either that the writers of the NEC do not want you to daisy chain, or that they assume that 'shall be permitted to be connected' implicitly includes daisy-chaining. The only reasonably way that you can determine what is safe enough for installation in your own home is to go and read the code yourself, and then go and call your local electrical inspector and ask them what they will want to see when you are pulling your permit.

What you do about installing a new circuit depends upon how the current romex is clamped to the boxes. You don't want to leave the old romex sitting in your current boxes, even with the conductors cut right to the clamp. Fishing to the old boxes will depend upon how the boxes clamp the new cable. You must clamp the cable somehow, but some boxes have clamps _inside_, and others _outside_. After you disconnect the cable old cable from the box, you can simply abandon it in the walls as long as it is totally disconnected from your electrical system. I personally like to use a wire-nut on the end of an abandoned cable, shorting all of the wires together, so that if by mistake it was not disconnected from the supply, it will trip the breaker.

Another suggested route is to simply leave the current wiring in place, use GFCIs to provide protection with no ground wire, and then simply run brand new circuits to those locations where you actually need an equipment ground. This eliminates trying to figure out how to clamp new wires to old boxes, gives you a good ground where you need it, and provides safety wher eyou don't need the ground.

Oh, when romex is described, it is '12-2 with ground', not '12-3'. Modern 12-3 contains _4_ conductors, 3 insulated conductors for power and a bare equipment ground conductor.

-Jon
 
Reply

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


Thread Tools
Search this Thread
 
Ask a Question
Question Title:
Description:
Your question will be posted in: