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Another Electrical Question: Old Metal Wall Boxes Login/Join 
Get my pies
outta the oven!

Picture of PASig
posted
My house was built in 1951 and has mostly two prong outlets which I had begun to start to prep for replacing. I’ve traced a lot of the wiring back to the panel, it all mostly appears to be very early Romex 14/2 and 12/2 with a black or silver sheath and if there’s a ground wire, it’s a smaller gauge. All the wall boxes are metal, and I suspect they attached the ground wire to the box in the rear if they used it at all.

I went around my dining room where there are four receptacles, of the 4 there one appears to have been added some time in the 1980s or 1990s with a 3 prong outlet. When I take the plates off the other three and use my voltage tester, the type that has the two little probes and the light, and touch the hot slot with one probe and the box or any metal part of the outlet itself with the other, it glows bright.

However going around my living room, where there are 8 outlets, the same happens for 2 but the other 6, the tester glows very weakly.

Why is that? Is there not good ground continuity there?

Wherever there appears to not be a ground or not a good ground I plan on putting a GFCI.

Are the grounds there in those boxes but just not very securely?


 
Posts: 29951 | Location: Pennsylvania | Registered: November 12, 2007Reply With QuoteReport This Post
Get my pies
outta the oven!

Picture of PASig
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No one yet has any insight on this???

I just read something interesting in an electrical forum, the person was explaining that in the early days when they started to go with a ground wire that a lot of the electricians of that era did not trust this bare copper wire and that’s the reason why they either didn’t use it or wrapped it around something outside the box, it wasn’t that they didn’t know what to do with it, it was more that they didn’t trust having a bare conductor in the box and considered it a hazard.

Which also leads to this interesting question: Why is it that North America uses a bare ground while the rest of the world strictly prohibits it? If you look at Europe the ground is insulated with a green and yellow striped jacket, never, ever bare copper.


 
Posts: 29951 | Location: Pennsylvania | Registered: November 12, 2007Reply With QuoteReport This Post
Run Silent
Run Deep

Picture of Patriot
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Do you have a proper multi tester? Can you get one?

Bright or dim doesn’t rally tell you the whole story.

Hot to ground should get you 120v with a proper tester.

You can also check continuity from a known ground rod to each box frame. A beep would tell you it’s grounded back to the main rod ground.


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Posts: 6520 | Location: South East, Pa | Registered: July 04, 2002Reply With QuoteReport This Post
Ammoholic
Picture of Skins2881
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quote:
No one yet has any insight on this?


There is no way to answer your question over the internet. It would involve an electrician on site opening multiple outlets or all of them (including switches).

It sounds like your house was wired using rag wire or the very first iterations of Romex style wiring. These featured a cloth wrapped outer jacket with individual conductors wrapped in paper. The next generation of wire featured a hard plastic outer jacket with paper only on the ground. Both of these early versions came with a 16awg ground instead of one that matches the size of the conductors.

During the era your house was build they could have also used some ungrounded wiring as well. I've seen houses build with mixed wire types many times. As you stated there is no consistency with the period. The grounds could be cut off, screwed to the inside of the box, screwed to the clamp where the wire enters the box, or just tucked in the back of the box.

The only way to ensure things are properly grounded you would need a professional. If you insist on doing it yourself at least buy a decent tester. The light up kind won't tell you voltage and definitely not continuity. If you test hot to neutral and get 122v, but test hot to ground and only get 109v (made up numbers) then you do not have a ground even though your light up tester illuminated.

Here's my favorite general purpose tester. It's on a huge sale currently. I use it 99% of the time only pulling out the more expensive true RMS meter for very small voltages, testing capacitors, or very accurate resistance readings. If an outlet is grounded you will get nearly the same voltage hot to ground as hot to neutral, if one has higher voltage than the other then you don't have a proper ground. Sometimes you will get a higher voltage on ground due to load on the circuit and poor connections of neutrals, if it's slightly higher hot to ground than hot to neutral no big deal if it's more than 2-3v then you need to start checking for lose neutrals because it's an arc/fire hazard.

After testing your hot connections, next test neutral to ground. If you have continuity and the voltage was the same on the above testing, you are most likely properly grounded. Next step would be to remove the outlet/switch and make sure they aren't 'cheating' the ground by tapping off the neutral wire to fool a tester into thinking the outlet was grounded.



Jesse

Sic Semper Tyrannis
 
Posts: 19419 | Location: Loudoun County, Virginia | Registered: December 27, 2014Reply With QuoteReport This Post
Excitable Boy
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Do yourself a favor and buy an inexpensive receptacle tester like this.
https://www.homedepot.com/p/Po...ALw_wcB&gclsrc=aw.ds
I balked at the idea of buying one for years because I had a voltmeter and knew how to use it. Now, I have one and it's a great time saver. You'll just have to put a 2 prong adapter on it (I bet you have one or two of those) to check your old plugs.



China is Asshoe
 
Posts: 2263 | Location: Michigan | Registered: March 09, 2006Reply With QuoteReport This Post
Ammoholic
Picture of Skins2881
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^^^ The tester listed above will not tell you if your outlets are grounded. I would not trust that at all. You need a voltage and continuity tester. Those testers are great for initial assessment, but you would be left trying to guess if one light is brighter than the other and never really know if you had a proper ground. It will however tell you if a ground is not present at all definitively.



Jesse

Sic Semper Tyrannis
 
Posts: 19419 | Location: Loudoun County, Virginia | Registered: December 27, 2014Reply With QuoteReport This Post
Get my pies
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Picture of PASig
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I do have a regular voltage meter as well, I will use that to check the actual voltage.


 
Posts: 29951 | Location: Pennsylvania | Registered: November 12, 2007Reply With QuoteReport This Post
Get my pies
outta the oven!

Picture of PASig
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quote:
Originally posted by Skins2881:


It sounds like your house was wired using rag wire or the very first iterations of Romex style wiring. These featured a cloth wrapped outer jacket with individual conductors wrapped in paper. The next generation of wire featured a hard plastic outer jacket with paper only on the ground. Both of these early versions came with a 16awg ground instead of one that matches the size of the conductors.




It is early Romex I think

Looks like a silvery or black woven outer jacket and the stuff I’ve removed here and there or looked in the panel bus bars show it’s got what looks like plastic insulation on it, white and black wires and the neutral bar has a whole bunch of thinner gauge bare ground wires.

The only fabric/rubber insulation wiring is the dryer run which I’m replacing soon with modern 10/3 wiring as that old stuff definitely doesn’t have a ground and it’s in a BX type flexible conduit. My electrician friend told me it may also be asbestos in the fabric outer jacket and told me it would probably be a good idea to replace.


 
Posts: 29951 | Location: Pennsylvania | Registered: November 12, 2007Reply With QuoteReport This Post
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