History of NEC

[kwired]

Let's face the truth, folks:

There is NO WAY to GUARANTEE ANY GROUNDING METHOD WILL BE PERFECT FOR THE NEXT 200 YEARS.

or for 2 days.

 

[480sparky]

How about 30 or 40 years?

I don’t have it but what does NFPA 70B say about grounding maintenance?

30 or 40 seconds..... no guarantees.

 

[mbrooke]

Screwdriver and 3 pound hammer

On all those fittings?

 

[electrofelon]

IMO, the quality of the ground fault loop is thee most essential part of any electrical system.

I disagree. This complete obsession with bonding as being the quintessential critical aspect of an electrical system and the greatest advancement in electrical safety since the fuse drives me crazy. It's all anyone cares about anymore and this causes other things that are just as, if not more important, to be overlooked. Sure it certainly adds safety to an electrical system, but the whole thing has become like a bus full of nuns, each with a kitten, will die a horrible death if an OCPD doesn't open in 36.7 milliseconds. Christ, everyone chill out. Even if we have a fault happen, and even if it doesn't clear, and even if no one notices it, and even if someone touches it, and even if they complete a path to ground and actually get a shock.....it is very unlikely anything will happen besides "ow". Probably more emphasis on a proper wire nut connection would have prevented that fault in the first place.....in the 20 years I've been doing this, NEVER had an electrical inspector check one of my wire nut connections.....

P.S. just want to clarify, I am not saying a wire egc is better but it doesn't matter. Personally I think the conduit system is better.

 

[electrofelon]

Correct, copper can oxide. However, I see a splice or screw termination as a cold weld whereby the electrical to electrical (R1+R2+R3+R4) contact surface area is protected from oxidation or corrosion. Conduit on the other hand is subject to expansion and contraction whereby its movement within fittings repeatedly breaks any original metal to metal compression such that two long term oxidized surfaces can make contact.

IMHO, conduit expansion and contraction, along with the use of expansion joints is under emphasized.


IMO, the quality of the ground fault loop is thee most essential part of any electrical system.

Mbrooke, you know love ya man....but....you seem to be falling into the same trap as what you (and many of us) despise about the NEC: the lack of requirements that are based on science and statistics. Where are the statistics or evidence of the inadequacy of a raceway EGC??? So many people think the wire EGC is so much better, but I have never ever seen any evidence of that anywhere, ever.

 

[Natfuelbilll]

I don’t have it but what does NFPA 70B say about grounding maintenance?

 

[mbrooke]

Mbrooke, you know love ya man....but....you seem to be falling into the same trap as what you (and many of us) despise about the NEC: the lack of requirements that are based on science and statistics. Where are the statistics or evidence of the inadequacy of a raceway EGC??? So many people think the wire EGC is so much better, but I have never ever seen any evidence of that anywhere, ever.

Thanks for the love, I need it sometimes

The thing is that its often masked due to structural steel and other parallel pathways when a fitting is loose.

But I do get where you are coming from- testing might actually show conduit as not changing R with age.

 

[Natfuelbilll]

Thanks for the love, I need it sometimes

The thing is that its often masked due to structural steel and other parallel pathways when a fitting is loose.

But I do get where you are coming from- testing might actually show conduit as not changing R with age.

Perhaps that the NEC is the minimum required for safety. While it doesn’t provide time factor for how long of a life this safe installation will exist.

 

[kwired]

Thanks for the love, I need it sometimes

The thing is that its often masked due to structural steel and other parallel pathways when a fitting is loose.

But I do get where you are coming from- testing might actually show conduit as not changing R with age.

And in some cases an EGC isn't exactly needed even though NEC still requires it. Grain storage bins interconnected with conveyors, walkways, etc. That I have been around all my career are one of those places. We run EGC's (or use metal raceways as EGC's) anyway but there is pretty much indefinite fault return path in those applications.

 

[electrofelon]

And in some cases an EGC isn't exactly needed even though NEC still requires it. Grain storage bins interconnected with conveyors, walkways, etc. That I have been around all my career are one of those places. We run EGC's (or use metal raceways as EGC's) anyway but there is pretty much indefinite fault return path in those applications.

Yeah I have actually found it is HARD to find a piece of metal in a building that isn't solidly grounded. It probably isn't a 250.118 compliant egc, but still provides a low impedance back to the source

 

[ActionDave]

Yeah I have actually found it is HARD to find a piece of metal in a building that isn't solidly grounded. It probably isn't a 250.118 compliant egc, but still provides a low impedance back to the source

And if it's a piece of conduit that is isolated and has a faulted wire in it having a green wire in there does nothing to clear the fault.

 

[Natfuelbilll]

And if it's a piece of conduit that is isolated and has a faulted wire in it having a green wire in there does nothing to clear the fault.

Faults don’t normally occur mid-run. Faults normally occur at the load end of a circuit - at the piece of equipment where it is best to have a wire type EGC.

 

[ActionDave]

Faults don’t normally occur mid-run. Faults normally occur at the load end of a circuit - at the piece of equipment where it is best to have a wire type EGC.

I've got a metal conduit coming out of a metal panel strapped to metal framing with metal straps going to a piece of metal equipment which equals an near infinite number of parallel paths for fault current.

The Cult of the Green Wire has such an oppressive grip on the electrical I doubt we will ever be free from it now but it was not the case not very long ago. Buildings from the 1960s on through the early 2000s have no green wires in the metal conduit and they are getting along just fine.

 

[Natfuelbilll]

I've got a metal conduit coming out of a metal panel strapped to metal framing with metal straps going to a piece of metal equipment which equals an near infinite number of parallel paths for fault current.

The Cult of the Green Wire has such an oppressive grip on the electrical I doubt we will ever be free from it now but it was not the case not very long ago. Buildings from the 1960s on through the early 2000s have no green wires in the metal conduit and they are getting along just fine.

I hope it’s not my hand to hand touch in series with one of your infinite paths.

 

[Natfuelbilll]

Isn’t there that work “intentional” in the EGC definition?

 

[ActionDave]

I hope it’s not my hand to hand touch in series with one of your infinite paths.

It's there every time your hand touches a live piece of service equipment or transformer

 

[Natfuelbilll]

At a plant where electrical distribution system was installed ~ 1980. They did not run wire equipment grounding conductors with feeders from the 4160V/480V transformers to 480V MCCs. When was EGC brought into Code?

What is a wonderful online source to peek around NEC history?

Well, this discussion went around and round.

The OP is really asking for the 250.118 list of EGC from late ‘70s NEC.

 

[mbrooke]

I disagree. This complete obsession with bonding as being the quintessential critical aspect of an electrical system and the greatest advancement in electrical safety since the fuse drives me crazy. It's all anyone cares about anymore and this causes other things that are just as, if not more important, to be overlooked. Sure it certainly adds safety to an electrical system, but the whole thing has become like a bus full of nuns, each with a kitten, will die a horrible death if an OCPD doesn't open in 36.7 milliseconds. Christ, everyone chill out. Even if we have a fault happen, and even if it doesn't clear, and even if no one notices it, and even if someone touches it, and even if they complete a path to ground and actually get a shock.....it is very unlikely anything will happen besides "ow". Probably more emphasis on a proper wire nut connection would have prevented that fault in the first place.....in the 20 years I've been doing this, NEVER had an electrical inspector check one of my wire nut connections.....

P.S. just want to clarify, I am not saying a wire egc is better but it doesn't matter. Personally I think the conduit system is better.

Well... if I may...

The fuse is part of a total protection scheme. The fault loop would be the second, yet equal part of the scheme. Neither will work without the other.

When a fault occurs on a final branch circuit, an EGC does not remove the touch voltage- usually being half the nominal line to neutral voltage.

You are correct under variety of conditions this voltage will not harm or end up being below the "let go" value.

The CMPs thought the same thing for decades.

Unfortunately moist hands, concrete, large grounded objects, objects where the hand curves around them ie handles or tools, ect have proved otherwise fatal.

Work done shows that 1000 ohms in "dry" locations is not unreasonable and 300-600 ohms is not unreasonable in "wet" locations.

Also shown that 150 volts beyond 0.5 second and 75 volts beyond 1 second are enough to trigger ventricular fibrillation.

With this in mind, effective ground fault current paths are proving essential.

What is very difficult I think for the industry to acknowledge is that the code making panels failed to define 250.4 A 5- they were wrong about grounding and bonding from a theoretical and a human physiological perspective. AFCIs, GFCIs, SPGFCI, voltage limits, sub divison of circuits ect all being a litigatory reaction to this. However, as time moves on, these devices are still not capable of solving the ever escalating limitations of article 250.

Even if we have a fault happen, and even if it doesn't clear,

The thing is this only increases the odds of electrocution. Healthy adults may simply walk away each time, and that is often what happens with energized light poles, railing, ect... until a child makes contact and a fatality results or a person just happens to be grounded.

 

[kwired]

Faults don’t normally occur mid-run. Faults normally occur at the load end of a circuit - at the piece of equipment where it is best to have a wire type EGC.

They possibly do when physical abuse of the raceway occurs.

You can run raceways where you think they are out of the way, run RMC instead of EMT, etc. but people operating forklifts, front end loaders, or other similar machinery still find a way to hit something occasionally.

 

[Natfuelbilll]

Only way I know how is via a loop impedance tester:

232 amps / 20 amps = 11.6x the handle rating is enough to trip the breaker in under 0.8 seconds.

However, this assume that there are no parallel paths in relation to the conduit itself.


In my world view, the wire type EGC is the only acceptable fault current path unless demonstrated otherwise.

Until chapter 9 can list the impedances for each conduit size, and that research is done to verify stable restive values with age I personally (in my humble world view) can not acknowledged metal raceways as a reliable fault current path.