In my early 1950s house, I decided to upgrade the bathroom outlet fixture to a GFCI, 20-amp circuit.
When removing the old, metal outlet box, I found that the ground wire to the outlet was connected to a screw in the back of the box. The separate bare wire coming down from the attic, was "connected" to the box by a couple of turns around one of the nails holding the box to the stud!
This surely wouldn't meet any code in the USA today (I don't think), but it was obviously not a modification.
So either it met code at construction-time, or it was not properly inspected during construction.
One thing the electrical codes have always required is an "approved" connection whether soldered, clamped, twisted (via a wire nut) or screw. Wrapping a wire around a steel nail, which could rust, would never have made it. The intent, of course, is to have a reliable connection from the box to ground.
A lot of the older metal boxes did not have threaded holes for ground screws. So, using a nail was all that was possible, unril they came out with the clamps that snap over the edge if the box. If the nail is tight, it's likely a good ground, but not allowed by code. In the past, if I've had to work on old wiring and boxes without ground screw holes, I opted to use a screw in place of a nail, and put a washer under the screw head. Then wrap the wire under that washer. Again, it's not allowed by code, but it works.
I dont know what was allowed by code in the old days, but there are probably millions of boxes grounded just on a nail. Remember, the old wiring did not use grounds, so it's not always easy to upgrade without ripping out walls and stuff.
The correct way would be to drill a hole in the box, thread it, and insert a ground screw.
When was the requirement for the boxes to be grounded actually introduced? I'm just curious - my data point, house built in 1947 or 48 did not have any grounded boxes other than those provided by connection to BX (house was a mix of exposed BX and concealed "rag" wiring.) Clearly if an "early 1950s" house had grounds, it was somewhere in that time frame that it was introduced.
which is not hard; Klein makes a tap tool with a screwdriver handle for just this purpose. Have used it quite a few times for just this application. (trying to use a standard tap with T-handle is difficult due to the depth of the boxes, but you don't need a whole lot of torque to thread the steel of a typical electrical box.)
I would, however, splice the ground wires on the cables entering the box together, along with a long bare pigtail of the proper gauge, with a wire nut. The pigtail then loops under the box's ground screw and then is connected to the ground terminal of the device installed in the box. If both of the ground wires coming from the cables are long enough, you could loop one under the box's ground screw, the other under the device's terminal, then splice with wire nut. This way all connections are good and proper, and you don't have to mess with BS like trying to shove two short wires under a single screw without a Sta-Kon.
Aside: Why don't spec grade "back wire" devices allow two ground wires to be inserted under a single screw like the hots and neutrals?
Your "1950s" date sounds right, Nate. I don't have copies of the National Electrical Code that go back that far, but that's when I remember 3-prong outlets appearing. It took a while to change practice however. I had a house that was built in 1958 that was wired with knob and tube - no ground wires in that.
The problem with old wiring is that there is often no bare wires. The wiring is armoured cable (BX), or metal conduit. The conduit is normally a good ground, but only the BX with the bare metal insert in the cable is a decent ground. Aside from ripping the whole house apart, one can only use what exists as a ground.
I fully agree, actually all devices *could* have more than one ground screw to make wiring easier. At least two screws, since probably hanf the outlets and switches feed at least 2 cables. (the source wire and the wire that goes to the next fixture).
When I wire a box, I normally make one cable longer, than take the bare and wrap it to the box screw near the entry point (box clamp). Then the end of that bare wire goes to the outlet or device. If there are two or more wires, that means more wirenuts. Which of course fills the box faster and makes wiring harder.
My parents house that I was raised in, was built in 1951. It had NO grounded outlets anywhere. The wiring was BX in the walls, and metal EMT conduit in the basement. In the early 60's an electrician added some circuits and put in grounded outlets on the new additional outlets, and more when when a garage was built. When I was in my late teens, I replaced the outlets in the basement by the workbench with grounded ones, because I got sick of using ground adaptors on every power tool. My father would not touch electrical stuff, so he asked me to also change the one by the washer and dryer, and the ones by the kitchen counter. Eventually I changed more of them in the house.
This says that it was *after* 1951 that grounded outlets became code.
I use two metal soup cans and over 20 miles of string between them. I hear my data one byte at a time, write it down, and wait for the next byte. When I get all the bytes, I have to punch them into punch cards and put the card into a punch card reader. After half a day, I get a printed black and white photo of someone. This high technology is real amazing. I hear someday they will run that string across the ocean. I'm not sure why, but I bet it's so we can listen to fish talk to each other.
My guess is that if you replace the receptacle while the circuit is live you break the ground downstream. The same is true of the neutral. You can have a "hot" neutral or ground downstream. A hot neutral is not likely to be a problem (except for the person changing the receptacle). A hot ground, even for a short time, can be fatal.
For multiwire (Edison) circuits you are not allowed to connect the neutral through the receptacle. It has to be spliced separately, and a single neutral wire connects to the receptacle. If replace the receptacle hot, and break the neutral, one downstream leg-to-neutral can wind up at 240V and the other 0V.
This one did, but was only used to connect the outlet ground lug to the outlet box.
The thought of dissimilar metals seems like a sure miss to me (for a dependable connection). And the fact that a nail used to hold the outlet box to the stud is never going to be dependably tight--the box gets pushed and pulled every time something is plugged in or unplugged. Especially when the studs are soft redwood.
When I wired up my garage, I put 2x4s spanning between studs, and screwed the boxes to those. None of those boxes are wiggly at all!
It works long enough to get paid for the job, anyway.
In this case, the separate, bare ground was wrapped around the nail used to mount the box to the stud. This couldn't have been done post-construction, as there is no evidence of the sheetrock having been disturbed, and the nail is otherwise innaccessible.
And have a direct connection from ground to the recepticle, as opposed to chaining the ground thru the box (says this untrained homeowner).
Copper to steel still sounds like a questionable technique to me, even tho I know it is still the most common (only?) way of grounding steel boxes. The slightest bit of moisture.... And if you live near the ocean?
So why then aren't all plugs required to be 3-prong? Unless you have a 3-prong plug, it doesn't really matter whether you have a grounded outlet or not. My
1957 rental came with wierd triple outlet with obviously no ground. They are polorized, though.
plug, it doesn't really matter whether you have a grounded outlet or not. My
1957 rental came with wierd triple outlet with obviously no ground. They are polorized, though.
A lot of equipment does not really have anything to ground.
The house I grew up in had 3 wire Romex with the 16ga ground but 2 pin (NEMA 1-15) receptacles. The boxes were grounded but no 3 prong receptacles. It was built in 1953. The story was at that time any GI bill house needed a grounded wiring method. This was DC so they actually had a GI bill inspection., That may not have happened out if flyover land.
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