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Thread: Adding Ground Wire to Outlets in 2- Wire House

  1. #1
    Join Date
    Apr 2017

    Default Adding Ground Wire to Outlets in 2- Wire House

    I've been remodeling my bathroom and having those walls exposed I decided it would be a good idea to replace the two prong outlets with three prong and then add a new ground wire to those outlet locations. I went on different websites and found this to be okay as long as the new ground wires were connected to the same panel as the original circuit and landed on the neutral bar in the panel that is set up to 2-wire service... there is no ground bar and I was told this is okay to use the neutral if this is the panel servicing the house. I did this work already and checked the outlets with at tester which indicates the new ground working. I also have run my skill saw on the outlets just to see that they work without tripping the breakers. Later I was speaking to someone at Home Depot and was told the new ground wires should take the same route through the house as the old wiring supplying the outlet. The reason given was something like the ground and the neutral 'read' off each other when they are proximal to one another - a nuance of electrical work I as a novice am not up to speed on. So my question is, is this routing of my new ground wires separate from the old wiring supplying the outlets a significant issue? Is it an issue that poses a risk of burning down my structure or failing to ground a faulty piece of equipment? Or is it something that causes specific trouble in specific situations?


  2. #2
    Join Date
    Feb 2012
    Kent, WA


    You won't burn down your house, but he's right the pathway for the equipment grounding conductor (ground wire in a circuit) should follow the same path as the other wires. Taking the same path reduces the impedance (AC resistance) in that wire. Impedance is important because when something shorts out you can have hundreds of amps flowing in that ground wire, and increased impedance will reduce the current flow which means the circuit breaker will take longer to trip. The circuit breaker is designed to trip very quickly when these high currents (typically, over 70 to 100 amps) are flowing on a normal house circuit.

    Another thing you are supposed to do is go through the same holes in metal boxes as the power wires. If the ground comes in through one hole and the hot in another, ferrous metal can get hot. If you house is old enough to not have ground wires, it probably has metal boxes too. So if you can route that ground wire through the same cable clamp as the power cable coming into that circuit, then that is best.

    When you realize the requirements, it becomes apparent that it would generally be just as easy to route a new romex cable to those outlets instead of just a ground wire. This also has the benefits of new insulation (it breaks down over many years) and a higher temperature rating than what was available prior to 1986.

    Finally, for many things, a ground wire doesn't do much. Only if a power cord has the 3rd grounding prong does it make a difference. With so many plastic appliances now days, many things are not grounded for safety because they can't shock you. It is always good to bond metal boxes, as the outlet screw could shock you if a hot wire in that box came loose or an outlet side screw was touching the box. It is permitted now days to use GFCIs to provide shock protection where no ground is available if you still have some outlets that you can't retrofit a ground to. These GFCI's should have a "No Equipment Ground" sticker and will show as ungrounded if a tester is used. But a GFCI doesn't need the ground wire to work and will still provide shock safety. It won't dissipate static (computers and radio antenna equipment has this issue) or surges though -- you need the ground wire to do that.
    Kent, WA

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