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Unread 07-01-2003, 02:31 PM   #1
Sonnie Layne
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Electrical question

Just finished a whole house interior refinish. We're going to next change out the receptacles, switches and cover plates. This house is an ungrounded system, but it has metal conduit throughout.

Legal to ground to the metal boxes so we can replace the two prong receptacles with grounded receptacles?
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Unread 07-01-2003, 08:50 PM   #2
JC
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You can ground it to the boxes, it is probably the only thing you can do.."old work" in the codes allows for alot of makeshift kinda work like that.

The house is grounded...the conduit is probably the ground.

To change over to a three hole receptacle simply black to black...white to white and ground to the medal box.

Just to put your mind to ease over this remember that probably 80 percent of the houses in this country are wired the old way where at the main panel all the ground wires and all the nuetral(white) wires are actually attached to the same nuetral bus bar (aluminum terminal)...meaning they go to the exact same place anyways!!

With your newer electric panels and the new codes there is supposed to be an extra SEPARATE bus bar for the ground and the nuetral..many times this requires having to purchase the additional bus bar and installing it onto the panel your self...Nuetral bus bar is the one that has insulation behind it so it doun't actually touch the medal panel enclosure and the "ground" bus bar is attached directly to the bare medal of the panel.....as a result all white now goto the "nuetral" bus bar and all ground goto the "ground" bus bar.

However even today alot of contractors and even some electrictians beleive it or not still skip the step of having to buy and install the extra bus bar and wire everything to the same place...still works just fine and unless you know the code noone notices.

The whole idea of even having an extra ground wire anyways is becuase it is felt that the nuetral is doing double duty and the extra ground takes some of the load off of it.

So you see it really does'nt make any differance as long as the panel currently now has both the ground and the nuetral tied to the exact same bus bar anyways(most likely). I mean that unless you rewire the whole house and change over the panel your really not doing anything by having that three prong receptacle rather then the old two prong weather you wire it to the box or not..I would still hook the ground to it anyways if for no other reason then for redundancy.


Does that help any?

Last edited by JC; 07-01-2003 at 08:58 PM.
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Unread 07-01-2003, 10:47 PM   #3
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Be careful with that, Sonnie. While JC is correct that allowances are frequently made for remodeling, the issue of grounding is not usually subject to much discretion. I would check with the code compliance people before I installed a grounded outlet in place of a two-pronged one, even if the particular box was metal and had its wiring in EMT.

I think you'll find that, although it was once accepted practice, metal conduit systems are not usually accepted as a grounding path, you still need to pull a ground wire along with the service wires. Maybe they'll let you use the conduit in your case, but I'd sure ask first.

Now, you can still change out the two-pronged outlet with a new two-pronged outlet in an un-grounded circuit. But when you install a grounded outlet, you best be sure you have an actual, approved grounding path for that third hole, lest you be hanging your ass out there big-time.


And I have to take issue with JC about the rationale for the grounding wire. It's not there to assume any part of the system's load. While the common wire and the grounding wire are indeed connected to the same point, electrically and physically, at either the service entry (old way) or at the meter loop (new way), the grounding wire is never expected to carry any load and is there only for safety.

The new method of running a separate grounding wire all the way to the meter loop does make little sense to some of us, but it is now required (I just pulled 200 feet of #6 wire along with a service entry this very morning that would not have been required just a few years ago). It is alleged that it makes a difference to some of the electronics prevalent in many common appliances now, which, I'm told, is why a separate common and grounding wire are required in runs to ovens and stoves and clothes dryers and such now, too. Don't know if it's really useful, but I know it's required if you are to meet code. Also helps keep the copper industry healthy and happy, I'm sure.

Your turn, JC.
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Unread 07-02-2003, 05:46 AM   #4
Rob Z
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CX, Sonnie, JC

I meet with my electrician today on a job, so I'll run this past him.

I always thought that the metallic sheathing of BX carried the ground, and, when BX is connected to steel boxes...the ground of the receptacle was mechanically attached to the box. Will this work the same way with conduit, or not?
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Unread 07-02-2003, 12:33 PM   #5
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Hey guys....

I'm going to weigh in here even though I am not currently practicing...

First; the neutral in any circuit can be a load carrying conductor. It definitely is not the same as the ground which is not designed or expected to carry a load (as CX mentioned). This is why ground wires are usually one or two sizes smaller than the load carrying conductors. They are a "safety valve" only.

Second; conduit is not acceptable as a ground path because of the way it bonds to itself (piece to piece). You might get by with it...but I wouldn't.

Third; there is one acceptable way (and legal) to change out those receptacles. Replace them with GFCI receptacles wired for ungrounded circuits. They're legal, safe, and proven in this application. Also, not too expensive.



Oh,...if you have an uninterrupted run of conduit, you could always pull a ground wire (long, hard process).
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Unread 07-02-2003, 03:45 PM   #6
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Cx,Hobbit are of course correct but I suspect your customer might not be ready to install a new bigger service wire and new 200amp panel and run all new circuits though her old plaster walls..all I am saying is that by changing out the two with the three..is not going to hurt anything..yea it won't serve any purpose either though other then make the place look newer and allow her to not have to rip the ground prongs off of her appliances...which I suspect is all she really wants at this point anyways since your at the painting stage..she probably all ready knows she could use all new electrical service at some point soon anyways.
If your worried just don't even hook up the ground wire from the new plug..it will be the exact same thing as she had before...I don't see the harm in that. If she wants it done correctly she should get an electrician and be prepared to spend some money.

If you do decide to touch it be careful with those old dry rotted wires and recover them with electrical tape.

>>GFCI receptacles wired for ungrounded circuits<<

I am not familiar with those Hobbit..how do those work?
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Unread 07-02-2003, 06:03 PM   #7
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Yes, Z, it probably does work most of the time. I know it was once the accepted practice. Even before all Romex was made "with ground", there were grounded circuits using EMT and metal boxes, usually in commercial installations, but also residential in some places. My understanding of the method's fall from favor (and code) was that the connections could get loose, corroded, etc. and lose continuity. After that you had to pull a ground wire along with the conductors. Maybe your electrician can enlighten us more. Is he an old guy? This change ain't recent, as in, you weren't doing construction at the time.

JC, you gotta stop thinking like that about changing out them duplex outlets without actually installing an approved ground first. I'm serious. The worst thing you can do is just put a three pronged outlet into a circuit that doesn't provide a ground for that third hole. Having that type outlet in the wall suggests to the user that it is grounded when it is not, and if somebody gets theirownselfs a major electrical "experience" whilst using such they are real likely to come looking for a body part of the person who installed it. That part is generally referred to as the ass. Don't do that.

Hobbit say sooth about it being legal and proper to install a GFI outlet in such a situation. How do they work? Not worth a damn, in my limited experience, but they will prevent harmful shocks. They also prevent the use of a lot of stuff you wanna plug in'em, but they may have improved in recent years as have regular GFI outlets. I don't know.

And I don't think any of us were suggesting the rewiring of the service entry to provide the separate grounding wire from there to the meter loop. Ain't necessary. Ain't required.

Hobbit's suggestion of pulling a ground wire might not be at all out of the question if the situation is right. If the conduit runs are identifiable from box to box and to the service entry, it might be a very good improvement. Easiest way would be to pull new wires (hot, common, ground - or a piece of Romex) through the conduit using the existing two-wire as a pull tape. Stick your air compressor hose in one end and see where dust comes out to find where the runs go. If you're doin' one of them little bitty, waaaaay expensive old places in "North Dallas", it can't be very far from any one thing to any other, eh?

Unfortunately, a lot of those old conduit runs weren't actually continuous.

Oh, yeah, then there's the change to the national code this very year about outlets in sleeping areas. Maybe Z's 'lectrician can enlighten us on how that works on remodel. I haven't had to deal with that yet, but the little free-standing art studio I just wired could be considered a sleeping area, so I had to put two of the new AFCI (?) circuits in there with two-each, fortysome dollar breakers in the service entry. And you can't have not nothin' except bedroom wall outlets on those circuits - no outlets in other kinds of room, no lighting circuits, etc. Big pain in the popo. But I'm sure it's for our own good.

Anyway, easiest and least expensive legal thing you can do is replace the outlets with new two-prong outlets; second cheapest is to install GFI outlets, if you're allowed to do that in sleeping areas under the new code. Like I said before, I'd call the local code compliance guys before I committed to anything.

My opinion; worth price charged.
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Unread 07-02-2003, 06:16 PM   #8
Scooter
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Remuddling

I usually find a good ground somewhere in the friggin home. Be it a panel, a ground stake, or the water main. One good way is to pound in a ground stake and braid it to a water main. The ground comes off the stake.

Armed with a ground, run a No. 12 wire in the crawspace to a central location, hopefully in a box. Ground the box. I try to snake a ground up to the attic alongside a chimney or hearing duct and to a central box up in the attic.

I then run separate green ground wires (No. 12 again) to whatever boxes I want to ground.

The only other method is to rip out the wiring and start from scratch with new flex or romex. That is out of the question.
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Unread 07-02-2003, 06:35 PM   #9
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I tend to agree that most building authorities will not grandfather grounding. They'll make you run new bond wires if there's nothing else in place. Same for GFCIs. You just gotta do it.
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Unread 07-02-2003, 06:38 PM   #10
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The service wire will be needed cuase it is silly to install new wiring in the home without switching to breakers (assuming of course the present is fuses since it is only a two prong kinda home now) then most likely the old fuse panel is only 100amp or something small...so no sense in getting a new panel unsless you goto 200amp or better..and thus for that ampere you will then most likely need the fatter service wire...at least that is the way it always seemed to work when I use to re-wiring old homes.

I see your point about getting zapped Cx..but how would they get zapped if the ground was not hooked up...it would be the exact same as now....well then again if they were to run a circular saw out in the rain they may get shocked worse I suppose...not sure...can you get zapped for not having a extra ground? I mean if the box was not grounded via the nuetral wire already in the first place the outlet would not even work at all.

Also as far as the GFI goes I don't see how it could work without having a proper ground....Unless they invented a new type I don't know about the ones I always dealt with would could not operate correctly without proper grounding..yea they work but they won't trip right...Don't they work by sensing an interuption in the grounding loop? No loop...no sensing right? Maybe I am missing something?

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Unread 07-02-2003, 08:06 PM   #11
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Well, I had a short class with Todd today...He did confirm that the NEC allows conduit to do the grounding, just as with BX (I have been paying attention on jobs, afterall!). I printed out this thread for him to read.

As it has been noted, the ground wire carries no current. The BUS bar is not installed seperately except in the case of where a sub panel has been installed off of the main panel. There were more corrections, but I didn't take any notes.
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Unread 07-02-2003, 08:12 PM   #12
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Devices with a three pronged plug are usually wired so that the ground prong/wire is wired to the chassis of the piece. The purpose of the ground is to hold that sucker's potential down at earth level so that peeps don't get zapped. Nothing more. The ground prong/wire has nothing to do with the current carrying wires.

Remember that wire is a resistor, although a very low value one. It will drop voltage under load. The longer the run, the higher the current, the crappier the connections between the outlet and the panel all cause the voltage drop to increase. So that means that if the white wire at the panel is zero volts with respect to earth, the other end of the wire at the outlet can be higher.

The ground wire, since it is never supposed to carry current, will remain at earth potential. No current, no voltage drop.
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Unread 07-02-2003, 08:28 PM   #13
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>>As it has been noted, the ground wire carries no current. The BUS bar is not installed seperately except in the case of where a sub panel has been installed off of the main panel. There were more corrections, but I didn't take any notes.
<<

Really Rob?

The way I learned that was from an inspector who made me change my panels that way to get passed years ago..however now that I think about it was a triplex and did have a main panel and three sub panels in each apartment as required(quick access for tenents). I just assumed it was code for ALL panels..but your saying that the main is differant then?...then again the same guy inspected the main also and I believe it was separated also???? you sure about that Rob? I must have separated 12 panels like that since and not just sub-panels either!
Ask your friend how serious that is...but hey then again they did get inspected though ??....

Last edited by JC; 07-02-2003 at 08:34 PM.
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Unread 07-02-2003, 11:38 PM   #14
Sonnie Layne
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Contacted University Park inspector today. He said he'd have no problem with the concept of grounding to the box with EMT conduit, but asked that I check for impedance. Otherwise, they still allow a 3 prong installed in a two wire box IF there's a sticker placed on the faceplate that states it's not a grounded receptacle. Problem with that is, I haven't seen the stickers in a while.

Anyway, this is a CA 1920 duplex, and I'm working on the upper 2 floors, so even tho' I've got some cable pulling gear, I ain't doin' that. This is the rental portion, quite nice at nearly 3000 sf, but the budget's getting tight, and I'd rather go back with 2 holers and spend the money on other things that need to be done. I may even move in, but I'd have to repaint before I moved in .

Thanks guys for the info, I was even able to understand all of it. Remember when computers were just being put into use and you needed isolated grounds?
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Unread 07-03-2003, 09:27 AM   #15
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I'm going to add a couple of things...then back out of here.

First. The NEC is advisory in nature. It has no "teeth," no enforcement arm. Local regulatory agencies provide the enforcement and are not obligated to enforce the national code. Some local agencies have less stringent requirements, some have more stringent. If your local code guy says its okay with him...so be it.

Second. Just because the existing metal boxes have EMT fastened to them, that is no guarantee that the run of conduit is continuous to the panel. Hence the need to check for continuity from the box back to the panel.

Third. The NEC does not allow the use of a three wire grounded outlet in an ungrounded circuit even if it is labeled (IIRC). The appliance (whatever it may be) that is plugged into this outlet can not read the label. But your local guy might allow it....see number one above.

Fourth, and last. Even if the conduit is continuous to the panel, and the panel is properly bonded, I would still install the GFCI outlets. Why run the risk? They're inexpensive and easily installed in each box. AND if the conduit run is not continuous (or shows a high impedance path)...I would definitely use the GFCI receptacles.

My opinion..nuff said..FWIW.
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