Are grounding tabs on 3-prong to 2-prong adapters doing anything at all?

[Tester101]

3-prong to 2-prong plug adapters have a "grounding" ring, that is meant to have the receptacle cover plate screw go through it. But is this thing really doing anything, other than maybe holding the adapter in place? Even if we assume the cover plate screw hole is part of the yoke assembly, and the yoke is in contact with a metal box. If the metal box is not grounded, where the **** does fault current go? Even if we make this assumption, if the receptacle is not a self grounding type (which it's not since it's 2 prong) is it possible to have adequate grounding through the yoke anyway?

 

[LEO2854]

3-prong to 2-prong plug adapters have a "grounding" ring, that is meant to have the receptacle cover plate screw go through it. But is this thing really doing anything, other than maybe holding the adapter in place? Even if we assume the cover plate screw hole is part of the yoke assembly, and the yoke is in contact with a metal box. If the metal box is not grounded, where the hell does fault current go? Even if we make this assumption, if the receptacle is not a self grounding type (which it's not since it's 2 prong) is it possible to have adequate grounding through the yoke anyway?

In most cases there is no ground there,so it's just a feel good thing,In my opinion those things should not be sold.

 

[augie47]

In almost all, if not all, situations, they are worthless as a grounding means due to the points you mention.

 

[GoldDigger]

In almost all, if not all, situations, they are worthless as a grounding means due to the points you mention.

The one place they would work to provide an effective EGC would be a building wired in conduit but using two-wire receptacles because the three-wire was not invented yet.

Sent from my XT1080 using Tapatalk

 

[junkhound]

Use then all the time in the lab to isolate O-scope from ground to avoid ground loop test noise. Obviously, use ones with no tab.

 

[gar]

131213-0808 EST

Wiring done in BX would likely provide a path. The home I grew up in, built in 1928, had BX, and originally built with a 50 A 120-0-120 supply. This home was built by an executive of the Michigan Central Railroad and they lost it in the crash of 29.

It had a built in refrigerator with a separate compressor in the basement. My parents acquired it in 32. My dad ran a circular saw on 220 as it was nominally called then. The water heater was originally electric, but that was way too expensive at $ 0.025 / kWh. All thru the depression electricity was at this price level, I believe into 50s, and possibly somewhat into the 60s.

The coal, hand fired, steam furnace had a water heating section. At some point the primary source of water heating was changed to a manually lit gas burner. Around 37 the furnace was replaced with an oil fired unit. Ignition by a high voltage, possibly 10,000 V, spark. The high pressure oil burner was a constant problem. Later converted to natural gas when the natural gas price dropped resulting from pipeline supply. Then ignition was by a pilot light. The natural gas burner was very reliable.

In the 30s fuel oil was about $ 0.06 to 0.07 per gallon (250 gallons about $17.50), and gasoline about $ 0.11 per gallon. By 1958 gasoline was about $ 0.28 per gallon.

Not much to do about the adapters, but interesting history.

The adapters are great for isolating a scope from the EGC. I haven't had the need lately, but useful when needed. Three prong plugs began to appear on scopes and other test equipment in the early to mid 1950s.

.

 

[ggunn]

I used one of those things once to ground an outdoor "stage" for a band I was running sound for many moons ago. The "stage" had only a single outlet, and it had no EGC, just the two prongs, and everything (PA amp, guitar amp, bass amp, etc.) had to branch out from it. I inserted a ground lift between the outlet and the power strip I was using as a distro, drove a tire iron into the ground by the outlet, and connected a wire from the ring to the iron. The mics were a bit shocky before I did that, but not afterwards.

Of course, knowing what I know now I wouldn't even unload the trailer for a gig like that.

 

[jaylectricity]

I'm amazed at how often the metal boxes are grounded when I see a home with two-prong plugs. Most of the time the EGC is wrapped around the end of the cable jacket and squeezed under the metal clamps of the box.

There must have been a time when they decided grounding circuits was a good idea, but appliances weren't yet being sold with three-prong plugs.

If you can verify ground, a properly installed adapter is much better than ripping off the third prong.

 

[infinity]

For older homes with AC cable the adapter will work just fine to provide a ground path.

 

[kwired]

In most cases there is no ground there,so it's just a feel good thing,In my opinion those things should not be sold.

Great, now we have to cut off the EGC pins on all our "grounding type" cords

I'm amazed at how often the metal boxes are grounded when I see a home with two-prong plugs. Most of the time the EGC is wrapped around the end of the cable jacket and squeezed under the metal clamps of the box.

There must have been a time when they decided grounding circuits was a good idea, but appliances weren't yet being sold with three-prong plugs.

If you can verify ground, a properly installed adapter is much better than ripping off the third prong.

Things must be different where you are. If we have two prong receptacles here and it is original wiring from before equipment grounding was required, there is no ground at that box if supplied by NM cable or K&T wiring. I've even seen old AC cable used a few times that was tapped from a K&T circuit and the sheath was not bonded to any EGC.

For older homes with AC cable the adapter will work just fine to provide a ground path.

But also consider old AC cable may have high enough resistance in the spiral sheath that it is not all that effective of an EGC, which is why AC cable for many years now has had the bonding strip that is under the sheath.

 

[jaylectricity]

Great, now we have to cut off the EGC pins on all our "grounding type" cords

Things must be different where you are. If we have two prong receptacles here and it is original wiring from before equipment grounding was required, there is no ground at that box if supplied by NM cable or K&T wiring. I've even seen old AC cable used a few times that was tapped from a K&T circuit and the sheath was not bonded to any EGC.

We have all that too, which is why it surprises me how often I run into grounded metal boxes with two-prong receptacles.

We also have a few towns with NM with no ground.

 

[ritelec]

131213-0808 EST

Wiring done in BX would likely provide a path. The home I grew up in, built in 1928, had BX, and originally built with a 50 A 120-0-120 supply. This home was built by an executive of the Michigan Central Railroad and they lost it in the crash of 29.

It had a built in refrigerator with a separate compressor in the basement. My parents acquired it in 32. My dad ran a circular saw on 220 as it was nominally called then. The water heater was originally electric, but that was way too expensive at $ 0.025 / kWh. All thru the depression electricity was at this price level, I believe into 50s, and possibly somewhat into the 60s.

The coal, hand fired, steam furnace had a water heating section. At some point the primary source of water heating was changed to a manually lit gas burner. Around 37 the furnace was replaced with an oil fired unit. Ignition by a high voltage, possibly 10,000 V, spark. The high pressure oil burner was a constant problem. Later converted to natural gas when the natural gas price dropped resulting from pipeline supply. Then ignition was by a pilot light. The natural gas burner was very reliable.

In the 30s fuel oil was about $ 0.06 to 0.07 per gallon (250 gallons about $17.50), and gasoline about $ 0.11 per gallon. By 1958 gasoline was about $ 0.28 per gallon.

Not much to do about the adapters, but interesting history.

The adapters are great for isolating a scope from the EGC. I haven't had the need lately, but useful when needed. Three prong plugs began to appear on scopes and other test equipment in the early to mid 1950s.

.

That was great..thanks gar