Precise dating of the construction would help since the Code on grounded receptacles was changing in the 1959-1965 period. Aluminum was not typical for flex conduits in that period. A magnet is an easy and certain test. Identification of the specific conduit type would be helpful. Do the receptacles test to be grounded?

Official data lists it as built in 1960, that's probably as precise as I can get. Thanks for the tip on the magnet test - will try, it can certainly be steel. How can I tell the conduit type? I have an outlet tester with an "advanced" ground testing feature, which I assume does nothing more than an impedance test. Some outlets test as grounded, some not, and some are inconclusive - can test good/bad periodically. I guess I can try an ohmmeter but it is bad ground everywhere as far as I'm concerned. There are no set-screw or clamp type of connectors at junction boxes, only the screw-in type which goes inside the conduit.

This post was edited by Valdemar on Mon, Mar 24, 14 at 20:05

It might read that it is grounded but that doesn't mean it is "properly grounded". The only armoured cable I know of that was/is rated to be used as the EGC is AC cable with the integrated bond wire. The old BX cable that was common in older homes from the 20s to the 50s is not rated as a EGC even if it tests out as grounded.

I experience no illusions about the quality of grounding in this home. All I'm trying to establish if it is plausible the 3-prong outlets were there since the original construction in 1960.

The 1959 NEC Article 334 shows Types AC, ACV, ACL with integral bonding strip of either aluminum or copper. Such a strip, if present, hopefully will be visible at the ends and will be folded back over the outside of the armor at the end. But not all installers do it that way.
Type MC is newer than 1960.
The 1959 NEC required grounding receptacles if installed "at the sink location" in the kitchen-- no further definition offered. Also in basements and outdoor locations.
I have no knowledge of CA codes, past or present.

Here is a link that might be useful: Installation

This post was edited by bus_driver on Tue, Mar 25, 14 at 7:51

"I experience no illusions about the quality of grounding in this home. All I'm trying to establish if it is plausible the 3-prong outlets were there since the original construction in 1960."

LOL, you may be under the illusion that computer forums (fora, if you prefer) are characterized by on-point answers. Alas, it has never been thus.

Continuing in the off-point vein, two prong outlets are much less cumbersome than they used to be cuz the majority of the stuff that we get from China*Mart and even Harbor Freight are replete with two prong plugs anyway. They are 'double insulated', you know.. Sez so right on the package.

You might be better off with two prong outlets, which if I consult my childhood memories were prevalent in the early 60's, and would be grandfathered in probably w/o question.

OK, late childhood memories.

"You might be better off with two prong outlets"

I cannot agree more with this statement but unfortunately there is also a trend to use grounding plugs on modern equipment.

Will it be an appropriate solution to replace 3-prong outlets with GFCIs in this case? One issue is that the label "GFCI protected no equipment ground" doesn't apply here, "GFCI protected bad equipment ground" would be more correct, but I suspect such a label would not comply with the NEC :)

You can replace the existing devices with GFCI receptacles all day long, with the label "no equipment ground", and be code compliant. No need to mention the possibility of false ground readings on the label. It makes no diference if it is a bad ground or no ground it is still not considered an equipment ground. It will just confuse matters in the future.

"It makes no diference if it is a bad ground or no ground"

Yes and no, if there is a fault in one of the devices or inside the raceway but there is no path to ground then all metal appliances with grounding plugs on that branch will become hot. If the fault voltage is coming from a device connected to a GFCI-protected outlet the risk of someone getting injured is probably minimal, but not so when a short happens inside the raceway from a non-GFCI protected conductor, or a non-GFCI protected outlet. I suppose this also applies in the case when there is a proper EGC is installed, one difference however is that metallic flex conduit is inherently bad EGC so the probability of breakers not tripping on a fault is much higher.

"The 1959 NEC Article 334 shows Types AC, ACV, ACL with integral bonding strip of either aluminum or copper."

I cannot see any sort of bonding strip. The conduit looks like the 1/2" flex conduit you can get from HD. I'm pretty sure the wires were pulled into the conduit, after it was installed, as there are different wire color variations here and there inside it. My understanding AC already has wires inside from the factory. Sounds like all 3-prong outlets are bootleg?

"if there is a fault in one of the devices or inside the raceway but there is no path to ground then all metal appliances with grounding plugs on that branch will become hot."

Not exactly. The quoted statement assumes that the metallic conduit will perfectly conduct between receptacles on that circuit and will not conduct at all back to the panel from which that circuit originates. Illogical.
The newcomers here reveal a lack of knowledge of GFCI and use of GFCI to provide substantial protection against ground fault hazards to people on circuits that do not have equipment grounding conductors. The proposal to use only receptacles accepting only two prong plugs is not a code requirement and in fact invites the creation of potential hazards.Frustration in having no place to use 3- prong plugs invites destroying the third prong which then renders that device ungrounded even if subsequently plugged into a properly grounded receptacle.
The person posting originally is now arguing with good advice.
If it was mine, I would add GFCI protection for each circuit, label the other receptacles as GFCI protected-ungrounded -- which is fully compliant with all codes with which I am familiar.
Flame away at me.

"Not exactly. The quoted statement assumes that the metallic conduit will perfectly conduct between receptacles on that circuit and will not conduct at all back to the panel from which that circuit originates. Illogical"

Is it? The high fault current will flow to the panel, any high-impedance transitions will heat-up instantly, spark, the metal will melt and oxidize preventing further conductivity. Will the circuit breaker open when this happens? Who knows. Conductivity between receptacles doesn't have to be perfect to be lethal on the other hand.

I'm not arguing against GFCIs and agree they would provide the best protection. The key is to have all outlets GFCI-protected. I was just trying to point to additional dangers of metallic conduit in the absence of proper EGC, and make a point there is a difference between no ground and bad ground.

This post was edited by Valdemar on Tue, Mar 25, 14 at 16:30

Residentially nowadays you won't have flex for bonding the devices together but there will be a bare ground redundant to the neutral white wire doing double duty as a bond and as a backup current drain. Just for yucks, the pic attached is of a ground that someone added to a glass-fused 2-wire bathroom I demo'd. It's ugly, sloppy, un-passable. It's probably functional, but not when family is involved!

In fixing this lameness I eventually bit the bullet and bought a new modern entry panel and a lot of Romex, and have become very adept at fixing drywall holes. Sometimes a problem is an opportunity.

Sometimes a solution is inexpensive, but that hasn't happened to me yet...

This post was edited by cold_weather_is_evil on Tue, Mar 25, 14 at 16:36

I'm missing something. If the circuit is protected by a GFCI the metal case, grounded or not, is not going to remain energized or melt or oxidize, at least not form anything fed from the protected side of the circuit. The GFCI is going to open at 6ma.

"I'm missing something. If the circuit is protected by a GFCI the metal case, grounded or not, is not going to remain energized or melt or oxidize, at least not form anything fed from the protected side of the circuit. The GFCI is going to open at 6ma."

Yes, but if the fault happens on the unprotected side then bad things can happen. The chances of this happening are pretty slim though, but a sloppy splicing somewhere in the attic in a box buried under insulation is not unheard of, I'm sure.

Cold_weather_is_evil said:

"Residentially nowadays you won't have flex for bonding the devices together but there will be a bare ground redundant to the neutral white wire doing double duty as a bond and as a backup current drain."

The bare equipment ground is NOT redundant to the neutral. They both play a completely different role in the electrical system. This is why they are not bonded together at any point past the first disconnecting means. The bare equipment ground is NOT a "current drain" either. It is intended to ensure all metallic components that are likely to become energized remain at the same potential and to provide a path for fault current to allow to allow the breaker to trip.

"The conduit looks like the 1/2" flex conduit you can get from HD"

It sounds like you have flexible metallic tubing (FMT), or Greenfield as a lot of us call it. It does not sound like you have armored cable or AC or MC cable.
FMT is covered by Article 360 and for grounding purposes we are referred to Article 250.118(7) which tells us that FMT is permitted to be used as a grounding conductor when terminated with listed fittings, the circuit conductors are protected by OCP devices of 20 amps or less, and the total length of the ground fault current path does not exceed 6 feet.

This has been in the code for as long as I can remember.

This post was edited by joefixit2 on Wed, Mar 26, 14 at 9:27

Cold_weather_is_evil posted:

"Just for yucks, the pic attached is of a ground that someone added to a glass-fused 2-wire bathroom I demo'd. It's ugly, sloppy, un-passable. It's probably functional, but not when family is involved! "

They must have used the same contractor the PO of my house used, only difference was that mine attached it to the sink drain. I guess I was just lucky it wasn't needed after I replaced my sanitary stack with ABS.

As far as the original post was concerned I can't say if it was code since I am not an electrician and I'm in an entirely different jurisdiction but around here it was reasonably common, my 1964 range was built to be hardwired into the wall and grounded via the cladding.