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Adding Ground Wire to OLD Circuit

How do I add a ground wire to an old circuit?  I'm in the process of buying an 85 year old house and want to add GFCI's in it, but there are only 2 wires in the box.


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Posted 2012-11-12T16:34:34+0000  by bruceshoots bruceshoots

Hi bruceshoots,


Thanks for your question and welcome to the community!


I get this question a lot working in the electrical department at my Home Depot store here in Atlanta as well as here on the forums. 


Almost every older home such as yours  has this issue regarding polarized (2 wire), and not grounded (3 wire) wiring systems. The only surefire to ground a circuit is to do its entirety, that is, running a ground wire from the main panel to the receptacles. This also means re-wiring the circuit by updating the existing wires to a grounded Romex wire.

12-2NM-WG 100' Romex


With that said, a grounded circuit only effectively works if the main breaker panel's main ground wire leads to the outside and is attached to a ground rod driven into the ground.  It can be a difficult project to tackle alone depending on where the main circuit panel is located indoors, and if you have access to running new wires to the GFCI's. 


You may or may not have a ground rod in place outside. They are typically located near the meter socket or disconnect where the power runs into the home. If you don't have this, you will need to purchase one, alongside a bar copper wire, to run to the panel itself. 


 Before we continue anymore on this project, I'll need you to check if you:


  • have a circuit breaker panel or a fuse panel
  • if there is any ground wires you see in the panel
  • if there is a ground rod/wire outside going inside the house

Let us know, and then we can go further from here. This is honestly one of those projects where a licensed electrician would have the know-how, code knowledge, and materials to get your wiring updated. It may cost you up front, but it can guarantee you a safe and up-to-code wiring system for a very long time.


Please update us on your situation,


Posted 2012-11-12T19:12:39+0000  by Joseph_HD_ATL

Hey bruceshoots.


I also have an 85 year old home without any ground wires showing.


If your home uses conduit to enclose the wiring from box to box, you may find that the conduit itself is acting as a system ground.  My home had two prong outlets throughout, so until I changed them to 3 prong outlets only the system internals were provided any ground protection.  Once I wired in the new outlets I had ground continuity on that ground prong, and thus to whatever I plugged into those outlets.  Your mileage may vary, as even a metal conduit system needs to be carefully grounded in order to work properly.  To check for system ground use a volt meter to probe the hot lead and touch the other lead to the metal box.  If you get house voltage then your system is grounded.  Also check to see that there is a ground wire running from your panel to a water pipe, and that the water meter has a ground strap jumper going from one side to the other.  If you have conduit and it is not grounded, then pulling a ground wire through the conduit would not be so difficult.


I mention this because while some form of NM type cable that Joe describes did exist when your house was built, it was rare.

Knob and Tube systems were also in use then.  These would not provide any ground, or an easy way to provide for one.


Your main question seems to really pertain to adding GFCI's to your home.  As an interesting twist, a GFCI outlet will provide shock protection even if it is not grounded!  These outlets work by sensing the current flow differential between the hot and neutral sides of the outlet.  Any even minor difference between them means that something, (or someone), is carrying current and completing the circuit.  At this point the GFCI will trip.  You can install a GFCI outlet in a non-grounded system IF you use the stickers that come with the GFCI which state that this is a non-grounded outlet.  Please call your local building department and talk to an electrical inspector about doing this, as there may be local codes that prevent using a non-grounded GFCI.  But as I have said, it is safer to have a non-grounded GFCI than not to have one at all.


Is this what you were looking for?  Let us know what kind of house wiring you have, and if you still need to rewire.  Pictures would help greatly.






Posted 2012-11-16T21:06:22+0000  by Chris_HD_CHI
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