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Grounding Your Ungrounded Electrical Receptacles

February 21, 2007

I have an older home with 2 prong receptacles and I need to ground them. How do I do this?

This is a common question I see all of the time on Yahoo! answers. I am often frustrated by the answers given by all of the self-proclaimed experts. I recommend not using Yahoo! answers for your electrical questions and consulting with a local electrician, your local building codes department or ask your question on this blog.  

So, let’s clear up a couple of things. You are not permitted to run a ground wire to the closest metallic water line, metallic pipe, gas line or drive a separate ground rod. These are the answers that I often see and this is very dangerous.

Let’s start with the water line. Let’s say you had a metallic water line break and a plumber repaired it with the new pex piping. If you have a fault, the electricity has no place to go. The pex pipe is not metallic, therefore your entire water system would become live. I’m sure you can imagine how dangerous this is. 

Your water meter will also have rubber or neoprene bushings on each side of the connection. These bushings break the continuity of your water line so, connecting a ground wire to any point on your metallic water line will do nothing. The original electrician that wired your house was supposed to run a ground wire to the street side of the water meter first and then install a jumper across the water meter. However, this was not done is older homes.

You are never permitted to run a ground wire to a metallic pipe or gas line. Yes, the gas line is required to be bonded, but you can’t ground to it. Never connect any wire, cable or conductor to your gas line.

To properly ground your receptacles, you need to run a ground wire to the equipment grounding terminal bar within the electrical service box on the outside of your house or in your breaker box. You are also permitted to run a ground wire to any accessible point on the grounding electrode conductor. The grounding electrode conductor in a house is the wire that attaches to either an 8′ ground rod, within 5′ of the water meter or to a concrete encased electrode (ufer ground).

If you have a home with the 2 prong receptacles, chances are that you have the old knob and tube wiring. I recommend replacing this and run a new 2 conductor cable with a ground back to your breaker box. The problem with the old knob and tube wiring is it has cloth insulation which breaks down, then becomes very brittle and ineffective.

To learn more about grounding requirements, get a copy of the current edition of the National Electrical Code® and read article 250. To verify the grounding requirements for ungrounded receptacles read section 250.130(C).

If you just need a 3 prong receptacle, you are permitted to install a GFCI receptacle in place of the 2 prong receptacle [NEC section 406.3(D)(3)]. These GFCI receptacles need to be marked as having “no equipment ground”. However, just installing a GFCI receptacle does not ground the receptacle.

If you have questions or need further clarification please submit your questions in the comment section of this post. 

 

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Comments

3 Responses to “Grounding Your Ungrounded Electrical Receptacles”

  1. Hotmail1 on March 28th, 2009 3:36 pm

    So I cannot put a three prong outlet in place of the two prong,and run a ground to a nearby heating duct? I am only doing this to keep a recently purchased UPS quiet when it detects a “building wiring fault”.
    thanks!

  2. Howard Buchin on January 4th, 2012 2:39 pm

    Hi Master Electrician,

    My apartment is electrically deficient to say the least. I.e. the fridge is plugged into a three prong socket that shows a reverse hot-ground, which I understand is really a broken neutral wire or electricity power coming from other wires besides the black (only).

    This three prong plug is connected to a circuit which runs other appliances, computers televisions etc etc.

    What do you think of this circumstance?

    Thanks for your input.

    Howard
    Ps. My battery back up (APC) flashed a site unsafe message and immediately switched to battery power when I plugged it in to this same outlet.

  3. Ernie Serna on May 22nd, 2012 7:22 am

    I am trying to install a watt stopper senor switch where the wall switch is located but as I understand it, it will not work without a ground connection,there is no ground wire coming into the box. I tried to connect the ground to the metal box itself but it still won’t work.

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