Grounding Two Wire Outlet, Part 1

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Old 04-17-15, 12:07 PM
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Grounding Two Wire Outlet, Part 1

My house was built in 1956 and has two prong, two wire outlets throughout.

About 2 decades ago, I was having problems with my old desktop computer (remember Windows 3.1) crashing due to powerline transients. So, I pounded about 7 feet of an 8 foot chunk of rebar into the ground, drilled a hole in the outer wall, ran a length of #12 wire from a new grounded outlet to the rebar and clamped it down tightly. The problem went away and 20 years later the setup is exactly the same.

Recently, though, while having a conversation with someone, they said this isolated ground wasn't safe, and I can't figure out why. Would it make any difference if I used an isolated ground receptable (orange dot)? I don't see it... the box that the receptacle is in isn't grounded to anything anyway. I'd appreciate some feedback.

TIA
 
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Old 04-17-15, 12:16 PM
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The ground rod you drove has nothing to do with the third prong on a receptacle. It will not trip the breaker. It was a waste of time and material and also not code compliant.
 
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Old 04-17-15, 12:24 PM
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Grounding Two Wire Outlet, Part 2

My house was built in 1956 and has two prong, two wire outlets throughout.

About 10 years ago, I had the bathrooms remodeled and while doing so, installed a new 200 amp breaker box in the garage, then pulled three strands of 12/2 with ground so that each bathroom has its own breaker for outlets, while lights are on a shared circuit. Done right and to code by a licensed electrician.

While I was having the new breaker box installed and the bathroom lines pulled, I also had the electrician pull and additional four 12/2 with ground lines over top my kitchen ceiling with about 25 feet coiled so that whenever I finally do get around to doing something about remodeling the kitchen the power is there by adding breakers into the box and hooking them up.

Now, this means that the remainder of the outlets in my bedrooms, den, and living room are still 2 prong ungrounded outlets. I thought about installing GFCI outlets but there are two problems. It's very difficult to determine, for any given circuit which is the 'head' outlet, and second, my house was built with these odd, undersized electrical boxes which means the GFCI won't fit unless I replace the box.

Finally getting to the question... thank you for bearing with me. In order to get these outlets grounded, I've been toying with the idea of using a wire tape to pull a single #12 wire from the outlet into the attic. My question is this: Can I use the ground wire in the electrical wiring in the bathrooms (splice in at the junction box) to get to the ground bar in the breaker box or do I need to run a separate wire?

As I envision it, with 3 or 4 ungrounded outlets in each room, I'd tie them together in a junction box, then, run the ground wire to the bathroom wiring. I'd be surprised if this wasn't a code violation but in addition to that, is there any safety issue that arises?

TIA
 
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Old 04-17-15, 12:29 PM
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I'm quite aware it won't trip the breaker. It was not a waste of time as the power supply in the old computer required a grounded outlet in order to deal with transient voltages and once I made the installation, I had no more issues.

I don't understand your comment, "The ground rod you drove has nothing to do with the third prong on a receptacle". If I were running 12/2 w/ground from the outlet, the ground prong would be grounded in the breaker box at the ground bar. As it is, the ground prong is connected to the rebar. Perhaps you can illuminate? Thank you.
 
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Old 04-17-15, 01:06 PM
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The ground prong is bonded to the neutral in the service panel. This bond is what allows the breaker to trip. The resistance of the earth is too high to trip a breaker. A receptacle can be grounded without a ground rod.
 
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Old 04-17-15, 06:06 PM
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The ungrounded receptacles in the bedrooms, etc. can be grounded temporarily by running a separate bare ground wire from each down to the panel where the respective breaker is located. This wire may follow the route of the circuit conductors back tot he panel exactly, approximately, or vaguely. Should this ground wire first reach a fat ground wire running from the main panel to a ground rod or to the main water pipe close to where the latter exits the house undeground, it may end and be clamped on there.

I would run one such separate ground wire for each branch circuit needing grounding and daisy chain it or tap off of it to the various receptacles on that branch circuit and needing grounding.

The way you first had it, you had the body of the computer grounded to the earth outside using the ground rod you added. To be correct, each additional ground rod you add needs to be bonded to the house electrical ground using a #6 copper wire. This fat wire is run outdoors as much as possible, and tied to the fat copper wire coming from an already existing ground rod or be run into the panel with the first whole house switch or breaker to be attached to the ground/neutral bus bar inside that panel.

The body of the computer grounded only to the earth outside will provide some protection and stabilization of the computer given transients including static shocks from a person walking across the carpet and touching the computer. This is limited; grounding to the house electrical system is better.

A proper 3 prong receptacle grounded system will provide considerable although not perfect protection from electrocution if a malfunction inside the computer or appliance should cause the outer body to become energized. Note that the electrocution protection here is accomplished by this grounding path being of low enough resistance to draw enough unwanted current to quickly trip the breaker thus de-energizing the outer body of the computer, etc.

A ground fault circuit interrupter will provide near perfect protection from electrocution with or without grounding although it will provide little or no protection of the computer from transients.
 

Last edited by AllanJ; 04-17-15 at 06:29 PM.
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Old 04-18-15, 01:27 AM
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The correct way to handle this (other then rewiring) would be to add a whole house surge suppressor. The model I used on my 1955 house was the $110 Square-D HEPD80.

PS: Home Depot website has the HEPD80 on sale until the 19th for only $66. That's almost half off.
 
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