Ungrounded outlets, sort of . . .

[Bain]

I checked out a pre-1960s house today, and noticed there were very few ground wires on the terminal bar. But when I began checking outlets, many newer ones designed for three-prong plugs were showing positive for grounds. My first thought was that there must be bootleg grounds, but when I removed a few cover-plates, there were no wires at all on the grounding screws.

Interestingly, when I began removing the screws that secure the outlets to the junction boxes, the tester flickered and registered open grounds. I assume this means someone grounded (or bonded) the j-boxes to the pipes or something else, and that's why the tester was fooled.

I was in the crawlspace before I checked out the interior of the house, but don't remember seeing any dangling wires that might have been used for grounds.

IF the junction boxes were grounded, DOES that constitute a LEGITIMATE ground? Or might there have been something else going on that I missed or that I'm not hip to?

The photos are a little out of focus, but you can see the wireless grounding screws at the upper rights of the outlets.

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[Brandon Whitmore]

If you had old BX cable, that would provide the ground to the metal J box. The receptacle yoke would then ground the receptacles.

[Bain]

If you had old BX cable, that would provide the ground to the metal J box. The receptacle yoke would then ground the receptacles.

No armored cable. Just your garden-variety cloth-jacketed wiring.

[Jim Katen]

I remember hearing about a pre-1960s grounding method that was local to some particular area back east. I don't remember where. It consisted of running a thin bare wire, similar to stone wire, from one metal box to the next along the surface of the studs.

As I recall, it was one of those peculiar regional things. Anyone else remember that?

- Jim Katen, Oregon

[Bill Kibbel]

I remember hearing about a pre-1960s grounding method that was local to some particular area back east. I don't remember where. It consisted of running a thin bare wire, similar to stone wire, from one metal box to the next along the surface of the studs.

As I recall, it was one of those peculiar regional things. Anyone else remember that?

Levittown, PA, built in the early through mid '50s. Each house had to be built in one day and 40 houses were completed every day.

[kurt]

All other considerations being satisfactory, that'd work, wouldn't it?

[Tom Raymond]

Sure it would, but today it would violate that pesky 'all conductors of a circuit must run together' rule.

Sorry Jim, I haven't memorized the NEC yet.

[Douglas Hansen]

Prior to the use of plastic or bakelite boxes, it was pretty common to see metal boxes grounded by some other means than the wiring method. Since at least 1923, the NEC required all metal boxes to be grounded, then gave exemptions for those which had some requisite distances from other grounded objects. The net effect of the rule - at least around here - was to find that the boxes in bathrooms, kitchens, laundry rooms, and some exterior locations would be "grounded."

Woody and I like to refer to this method as "nail to nail" grounding, since it typically involved whatever wire was handy being looped around the box mounting nails, then eventually being wrapped or clamped to a water pipe. It does seem likely there would be regional variations on this theme. It did still take place in the 1950's with rag-wrap romex.

It raises interesting questions for code compliance. Whenever we replace a receptacle in a location where a grounding means exists, we are supposed to use a grounding type receptacle and utilize that grounding means. Ordinary receptacles don't quite qualify, since the mounting screws are not intended as a grounding means unless they are "self grounding" receptacles with one screw captive in a metal washer secured to the yoke. The other side we could question is whether that grounding means is really effective. It isn't going to be the low-impedance path or the method that would be used today, though it is better than nothing.

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[mgbinspect]

Prior to the use of plastic or bakelite boxes, it was pretty common to see metal boxes grounded by some other means than the wiring method. Since at least 1923, the NEC required all metal boxes to be grounded, then gave exemptions for those which had some requisite distances from other grounded objects. The net effect of the rule - at least around here - was to find that the boxes in bathrooms, kitchens, laundry rooms, and some exterior locations would be "grounded."

Woody and I like to refer to this method as "nail to nail" grounding, since it typically involved whatever wire was handy being looped around the box mounting nails, then eventually being wrapped or clamped to a water pipe. It does seem likely there would be regional variations on this theme. It did still take place in the 1950's with rag-wrap romex.

It raises interesting questions for code compliance. Whenever we replace a receptacle in a location where a grounding means exists, we are supposed to use a grounding type receptacle and utilize that grounding means. Ordinary receptacles don't quite qualify, since the mounting screws are not intended as a grounding means unless they are "self grounding" receptacles with one screw captive in a metal washer secured to the yoke. The other side we could question is whether that grounding means is really effective. It isn't going to be the low-impedance path or the method that would be used today, though it is better than nothing.

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I know this is getting away from outlets a bit Douglas, but while we're talking about grounding, I called a friend (electrician) that worked for a large manufacturing plant, a year or so back, about a sub-panel I ran across in an OLD garage that had no ground whatsoever - not even back to the main panel - nothing (the box was bonded though). He suspected that, while it was a pretty lousy and unreliable ground, that the masonry wall that the box was surface mounted to actually might provide one. He wasn't citing code, but rather recalling his schooling. Is that possible? (I still called for a formal ground, but I was VERY careful while inspecting that panel.)

[Tom Raymond]

Michael, I think you answered your own question. What was the box bonded to? That became the ground path, but probably not a very good one.

My in-laws have a detached garage with a 2 wire overhead supply (I assume because nearly all of the house is 2 wire circuits) to a fused disconnect. The garage circuits are all 3 wire, and the disco is grounded to a piece of rebar (yes, steel rebar) driven into the ground. While they had their travel trailer plugged into the garage to prep for a trip the furnace control board and the tank monitor board got fried because of the poor ground.

As far as the masonry becoming the ground path, it might have when it was wet. Ever place an old metal bodied power tool on damp concrete or masonry? If conditions are right you get quite a jolt. Don't ask me how I know.

[mgbinspect]

Michael, I think you answered your own question. What was the box bonded to? That became the ground path, but probably not a very good one.

My in-laws have a detached garage with a 2 wire overhead supply (I assume because nearly all of the house is 2 wire circuits) to a fused disconnect. The garage circuits are all 3 wire, and the disco is grounded to a piece of rebar (yes, steel rebar) driven into the ground. While they had their travel trailer plugged into the garage to prep for a trip the furnace control board and the tank monitor board got fried because of the poor ground.

As far as the masonry becoming the ground path, it might have when it was wet. Ever place an old metal bodied power tool on damp concrete or masonry? If conditions are right you get quite a jolt. Don't ask me how I know.

Well, saying it was bonded, may be an inaccurate statement. If memory serves (and it's been a few years back), it was two wire to the sub-panel (no ground wire that I recall) and no ground wire to a rod. Just a bus screwed to the back of the box that had the neutrals in it (and any circuit grounds, if there were any). (It may even be that it wasn't a sub-panel but was a separate service.) That's why I called him. Whatever the exact setup was, I had never seen a setup quite like it and really concluded that the entire system had no ground at all, unless as the friend proposed, the masonry provided one. So, therein, is my real question: Can masonry possibly constitute a ground? Would a qualified electrician (possibly old school) ever do this truly believing it was right?

[Bain]

That makes perfect sense, Douglas. Thanks. Regarding the effectiveness of the grounds, I opted to leave that up to someone else. I seldom refer out to others, but did on this house RE the grounds that I didn't understand.

[mgbinspect]

(Sorry for the thread drift, Sir Bain)

[Bain]

(Sorry for the thread drift, Sir Bain)

Never, EVER, do it again.

I'm joking, of course.

We don't always get to see or hear what happens after we leave a house. It would be interesting to know how an electrician diagnoses this particular situation, and if he/she has the expertise to suspect and then confirm what Douglas explained, and finally whether the set-up is given a thumbs-up or whether the call is that modifications are necessary.

[Jim Port]

With the older NM cables the grounding conductor was back-wrapped around the sheath where it enters the box and was secured by the cable clamp. This would ground the box, although probably not as effective as a grounding screw.

[Douglas Hansen]

Michael - I think the "old school" electrician is demonstrating that grounding and bonding remain the most misunderstood of subjects, even among veteran electricians.

As Tom said, the masonry wall could become a good enough conductor to help give you a jolt, though that has nothing to do with creating a fault return path. Earth is never an equipment grounding conductor. It can't be relied upon to carry enough current to trip a breaker, but it can carry enough current to kill you.

One possible way that an industrial electrician could be confused upon this point is that a concrete or masonry surface is considered a "grounded" surface for purposes of required clearances opposite live parts of electrical equipment (110.26 in the NEC). In that sense "grounded" is not synonymous with "effective fault return path." I see it as one more unfortunate example that the NEC's poor choice of words has led to. We say "ground" when we mean earth, and we say "ground" when we mean bond.

Jim - my experience with this is that pre-1960's romex didn't have equipment grounding conductors. When romex started to show up with an equipment grounding conductor, electricians weren't always sure what to do with it. Here in California, the 1962 NEC requirement for grounding-type receptacles sometimes wasn't enforced until 5 or 6 years later, but the romex from the supply house had a grounding conductor by 1962. Since the old "nail to nail" method had been to put the grounds on the outside of the box, that is what electricians did with it. I know of some jurisdictions that even required it to be that way, though eventually the NEC made it crystal clear that the grounds get made up inside the box. There was a short period of time there - about 6 years - when those equipment grounds were also a smaller gauge - 16AWG on 12AWG cable, and 18AWG on 14AWG cable.

Douglas Hansen

[randynavarro]

In many 50's era homes in the Seattle area, it's common to find a three-wire circuit to the metal j-box and a two-slot receptacle installed. The cable is typically 12 or 14 gage conductors with a small, maybe 16 or 18 gage grounding conductor where the grounding conductor bonds/grounds the metal box only.

Is it acceptable to upgrade with a three-slot grounding type receptacle and just jumper off the metal box to the grounding terminal on the receptacle?

[Terence McCann]

Earth is never an equipment grounding conductor.

Douglas Hansen

Can you expand on that a bit Douglas? I seem to be slow on the updraft.

(Sorry John, more thread drift)

[Matt Fellman]

In many 50's era homes in the Seattle area, it's common to find a three-wire circuit to the metal j-box and a two-slot receptacle installed. The cable is typically 12 or 14 gage conductors with a small, maybe 16 or 18 gage grounding conductor where the grounding conductor bonds/grounds the metal box only.

Is it acceptable to upgrade with a three-slot grounding type receptacle and just jumper off the metal box to the grounding terminal on the receptacle?

I see the same thing here down the I5 in Portland... I've always told people it's fine to convert to 3-prong and jump to the metallic box. I believe there's an illustration of this in the "Codecheck" electrical book.

I use an old fashioned two-prong "wiggie" from the hot slot to the middle plate screw.... and also check for ground wires at the panel. It's usually in late 50s or early 60s houses.

[Jim Port]

I see the same thing here down the I5 in Portland... I've always told people it's fine to convert to 3-prong and jump to the metallic box. I believe there's an illustration of this in the "Codecheck" electrical book.

I use an old fashioned two-prong "wiggie" from the hot slot to the middle plate screw.... and also check for ground wires at the panel. It's usually in late 50s or early 60s houses.

It is not always fine to ground to the metallic box. The wiring method would need to be listed as an acceptable grounding method. Not all metallic cables were able to be used as they lacked the bonding strip. Without the strip the sheath can be a high resistance ground path. I have seen older cables glowing red from a short and would not trip the breaker due to this poor conductivity.

[hausdok]

Hi,

I'm pretty certain that you're mistaken about the outer sheath being a high-resistance ground path; however, so far I don't think they've been talking about armor clad or metal clad cabling - they've been referring to various early methods to add equipment grounding to NM cable when it first came out.

I don't think that the aluminum bonding wire inside armor (AC/BX) cable is meant to be a ground path; the outer sheath is the accepted ground path - the bond wire is only there to prevent the metal tape that makes up the outer sheath from becoming a transformer coil when/if the tape becomes separated or unravels. That little aluminum wire is not supposed to be brought into the panel at all.

Metal clad (MC) looks similar to AC but it lacks the aluminum bond wire; instead it has an insulated equipment grounding conductor and both the outer sheath and the EG conductor provide the ground path.

I wish I could remember how my father wired our house when I was 7. He bought a house in 1958 that didn't have electricity and then he wired it himself according to how he'd been taught by a local electrician that did the electrical work on the houses my father built for others. He went through the house, cut out a slew of receptacle holes and then pushed wires through the walls and had me reach my arm inside, grab the loose end when it got near the receptacles and pull it through until it was the length of my foot outside of the wall and then I bent it over the rim of the hole to keep it there. After he got all the wiring in place, he came through with a bunch of metal boxes and metal rings designed to grip plaster and lath and installed the boxes and receptacles.

It's been more than half a century, but I know for certain that house is wired with a whole bunch of that silver-colored rag-wrapped Romex and I'm certain that every circuit has an equipment-grounding conductor. I remember watching him ground the EGC to the back of each metal box and then he attached a short pigtail from the screw in the back of the box to the receptacle. What I can't remember is if he ran a separate EGC alongside every piece of Romex when he pulled them or if the EGC was already in the wire.

I know the folks that bought that house; maybe I should track down their phone number and give the guy a call. After nearly 40 years of ownership I'll bet he knows exactly how the old man wired that place.

ONE TEAM - ONE FIGHT!!!

Mike