ECN Forum Forums General Topics of the Trade Non-US Electrical Systems & Trades Do we need grounding?

Here in Norway it is strictly forbidden to put up a grounded outlet without proper grounding, but if I remember right; the US NEC will not forbid to put up a grounded outlet without a ground wire if you have a GFCI.

Any body who know anything about this, or at least has any ideas?

Correct, as a replacement:

406.4(D)(2)(c) permits a non-grounding receptacle to be replaced by a grounding type if fed thru a GFCI and clearly marked (after installation) "GFCI Protected" and "No Equipment Ground"

I always point out that you should verify there is no ground actually present before going this route. There was a period in the post WWII years where they were using an NM cable with a ground but still using non grounded receptacles (NEMA 1-15). In that case the box will be grounded but no provisions for a grounded plug cap. In that case you could use the existing ground for a NEMA 5-15 grounded receptacle. The only question is whether you should trust the "self grounding" type or pigtail a ground in from the box, I prefer the latter.
The other issue is the ground in that old Romex is a reduced size but a 16ga wire should still be sufficient to clear a fault on a 15a breaker.

“Grounding” of US household electrical systems has changed quite a bit over the years, as have the common wiring methods. Pre-1960 wiring, depending on the wiring materials, often had a “ground path,” though there was no real intent to provide one.
Growing up, I was actually present when the “electrical greats” debated various topics. I am sometimes amused when I see some creative soul today echo earlier ideas, thinking they came up with them.
What is “grounding?” What is “grounding” supposed to accomplish? Why do we “ground” things? In my life I’ve seen major changes in theory as our understanding has improved. I’ve watched these ideas reflected in code requirements. Many of the stranger parts of our codes when it comes to grounding reflect some of these earlier beliefs.

Another puzzling aspect to our code is the recognition of two very similar wiring methods: Armored Cable and Metallic-clad Cable (AC and MC). A related method is “Flexible Metallic Conduit,: or “flex” (BX). Is the spiral metal sheath of these methods a reliable grounding path? The answer, in code, is “yes” for AC, “maybe” for flex, and “no” for MC. We can attribute the different methods to competing manufacturers.
Does the metal make an effective ground path? Testing done on lightweight metal conduit (EMT) showed that even an extremely poor assembly of components would still carry a surprising amount of fault current. I guarantee that no electrician is capable of actually measuring the effectiveness of a ground path in the field.

In new work, today’s most common household wiring methods are either AC or non-metallic cable (NMC or “(Romex). Both of these require the use of a ground wire. When we add to, repair, or modify an older system that lacks a ground wire, we’re pretty much prevented from trying to add a ground. Earlier use of nearby plumbing is today defeated by the common use of plastic plumbing pipe. An old house without a ground wire will never have a ground wire. There’s no place for that third prong to go.

So how are we supposed to use modern appliances with three-prong plugs? Before we answer that, let’s ask “Why do we ground appliances?” The common answer “safety” falls flat when you realize it requires less than 1/10 amp to kill someone, and your smallest breaker / fuse is 15 amps. You’ll be well fried well before that overload ever trips.

As a compromise — a nod to reality — our rules allow such older circuits to be protected only by GFCI’s, and overlook the lack of a ground wire. The GFCI will operate in the event of a very small amount of electricity “getting lost.” This accommodation is allowed only for existing, older circuits. New circuits (complete circuits originating at the panel) must have that ground wire.

A final note:
My house was built in 1957, before three-prong plugs existed. It was wired using a two-wire, cloth wrapped cable (Romex). Yet, every receptacle had ordinary 3-prong receptacles. Not a single GFCI to be found.
Clearly, someone had dealt with the necessity of being able to plug in 3-prong plugs by simply changing the receptacles. The code change allowing the use of GFCI’s was in recognition of this need.
The “compromise” was of limited use, as the device boxes used will be completely filled by a GFCI device, leaving no room for the necessary wires.

I have completely rewired the house.

It must have depended on where you lived. My 1953 house had 2 prong NEMA 1-15 receptacles but there was a ground present. The Romex with the 16ga bare wire in it. I was just a kid who was learning about electricity when I pigtailed NEMA 5-15s everywhere and later when I got my first bug eye tester, they were all good.
Later in life IBM gave us ECOS testers that did test the grounding integrity under load and verified <1 ohm ground impedance. It also wanted something greater than 0 ohms to catch bootleg grounds.
The purpose of the ground is to create a very low voltage delta between the case of your appliance and the surrounding "earth" reference. That is only as good as the integrity of the grounding electrode and the grounding path in the branch circuit. It is also why NFPA finally decided in 1996 that we should not be using the neutral to ground things. There will be voltage drop in that neutral that shows up as a voltage rise at the appliance.

The major difference between AC and MC cable is the little bonding strip in the bundle that shunts out the wraps in the armor and prevents it from becoming a choke. That choke effect is also what limits FMC as a ground path to fairly short runs. I would still use a green wire ground tho, no matter how short the run is.
The relatively new "MC Lite" has a much larger bonding conductor inside and is OK for grounding and you are not required to connect that bonding conductor in the box.
I completely agree retrofitting just about anything but the normal 5-15 in a box can be challenging if they were sized to the normal "2x the largest conductor" deduction for the device. I am sure it has been proposed but I think the oversize devices should get a different fill specification. I ran into this trying to put USB receptacles in. One work around that doesn't look horrible is to use a surface raceway box over the regular box as a box extender.
When I was working for the state one of my inspections was to test the integrity of WWII era EMT installed in a building they wanted to use as a hospital. They wanted to be sure that old EMT was sufficient for the redundant ground path. I was surprised but every one I tested with my Ecos had less than 1 ohm of impedance. I was glad I wasn't the one snaking in the new green wire tho.

One other thing the NEC allows [ 250.130(C) ]is running a independent ground wire, such as a #10 AWG green, back to the grounding electrode system. This can be a good option when the ampacity of the branch circuit is sufficient for the load and you just need a grounding type receptacle, such as a old 3 wire NM 10/3 cable for a dryer can be converted to a 4-wire NEMA 14-30.

Grounding receptacles existed but were neither required nor readily available back then.

Lots of voodoo around grounding. When dealing with receptacles and utilization equipment, the most important aspect is not that the metal is connected to the earth. The important thing is that it is connected to the service neutral so that an OCPD will open if a fault occurs. Being connected to earth is just a side effect because neutral is connected to earth.

Sometimes grounding is more harmful than good. Consider a generator insulated from the earth. It will just have a receptacle on it that has a ground terminal bonded to neutral. Suppose you plug in a metal power tool. If the tool is ungrounded, there is no chance for the user to get shocked unless you get in the circuit between the line conductors. But if the tool is grounded, you basically put one of the line conductors in your hand.

If the generator is ungrouded, what is the fault path to earth?