History of NEC

[ramsy]

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.

"Assured" Bonding strarts with 250.92(B).
Mike Holt wrote about it here

Bonding bushing flowchart attached

 

[480sparky]

You don't because conduits do not carry current normally with load to indicate sub- par connection methods.

And your 'prefect' ground conductors DO normally carry current?

 

[Dennis Alwon]

And your 'prefect' ground conductors DO normally carry current?

Exactly what I was thinking... A piece of emt has less impedence then a copper conductor sized for the circuit. That being said we always ran a grounding conductor also known as an equipment grounding conductor.

 

[mbrooke]

And your 'prefect' ground conductors DO normally carry current?

They do when they are colored or identifed other than green, bare or green with a yellow stripe.

 

[480sparky]

They do when they are colored or identifed other than green, bare or green with a yellow stripe.

Then they ain't exactly EGCs, are they?

 

[mbrooke]

Then they ain't exactly EGCs, are they?

Only by definition. Otherwise the prove the overwhelming conductance of wires, splices and termination.

 

[ActionDave]

Only by definition. Otherwise the prove the overwhelming conductance of wires, splices and termination.

And they also prove the overwhelming number of connection failures.

 

[480sparky]

I've seen far more ungrounded and grounded conductor failures than I have metal raceway as grounding conductor failures.

 

[kwired]

You don't because conduits do not carry current normally with load to indicate sub- par connection methods.

neither does the wire type EGC.

When it is called upon to do it's job it is either going to work or it is not, no early warnings.

 

[kwired]

I've seen far more ungrounded and grounded conductor failures than I have metal raceway as grounding conductor failures.

Outside of a poor install, same here.

Run into many 60's thru 80's installs of EMT that wasn't properly supported, or just poor routing selection also contributes, especially in attics and over time you get broken fittings (particiularly die cast fittings) from people that have been working in that attic.

 

[mbrooke]

neither does the wire type EGC.

When it is called upon to do it's job it is either going to work or it is not, no early warnings.

Right, however a wire EGC differs in no way from a wire carrying load current.

 

[mbrooke]

And they also prove the overwhelming number of connection failures.

Which out of the billions of splices and connections in existence, only a small minority fail.


Unless you're saying this is common:

 

[ActionDave]

Which out of the billions of splices and connections in existence, only a small minority fail.

And out of the billions of conduit connections only a small minority fail.

 

[kwired]

Right, however a wire EGC differs in no way from a wire carrying load current.

For instances that need a 8 AWG EGC or larger, I think are typically made up pretty well, and maybe are somewhat bullet proof.

Raceways or even non metallic wiring methods containing 14 or 12 AWG EGC's, I think you run into higher chance of a bad connection. Unlike the ungrounded conductors, it will never be known majority of the time. But with a metallic wiring method you also have a certain amount of redundancy even if someone forgets to tighten a set screw or compression nut on occasion.

 

[480sparky]

We're saying a grounding conductor, for the purpose, functions the same as using a metal raceway for the purpose of providing an ECG. Both are accepted by the NEC. Both function as designed... if installed correctly. Do sloppy work, and either can fail. Have a wire slip out of a wire nut when you shove it in the box? Installer error. Forget to tighten a set-screw on a connector? Installer error.

In terms of ability, the metal raceway far exceeds the capacity of any wire it can contain for fault clearing.

 

[mbrooke]

And out of the billions of conduit connections only a small minority fail.

We don't know that because they do not carry current, or is there something similar like Fe current carrying conductors to test that concept.

 

[mbrooke]

For instances that need a 8 AWG EGC or larger, I think are typically made up pretty well, and maybe are somewhat bullet proof.

Raceways or even non metallic wiring methods containing 14 or 12 AWG EGC's, I think you run into higher chance of a bad connection. Unlike the ungrounded conductors, it will never be known majority of the time. But with a metallic wiring method you also have a certain amount of redundancy even if someone forgets to tighten a set screw or compression nut on occasion.

Of course, but if a particular conductor, splice, or termination is of poor design or formulation you find out about it on current carrying via joule heating. Copper, wire nuts, wagos, lever nuts, screw terminals ect have all evolved around carrying current continuously.

 

[kwired]

We don't know that because they do not carry current, or is there something similar like Fe current carrying conductors to test that concept.

Fe carries current fine, not as good as same cross section area of copper, but a raceway will almost always have more current carrying ability than the minimum required EGC that would be pulled through it. The problem is going to be quality of connections for both the raceway and the copper conductor. Installers can make a mistake with either.

 

[mbrooke]

We're saying a grounding conductor, for the purpose, functions the same as using a metal raceway for the purpose of providing an ECG. Both are accepted by the NEC. Both function as designed... if installed correctly. Do sloppy work, and either can fail. Have a wire slip out of a wire nut when you shove it in the box? Installer error. Forget to tighten a set-screw on a connector? Installer error.

In terms of ability, the metal raceway far exceeds the capacity of any wire it can contain for fault clearing.

Sure. But how do we know correctly installed conduit has the same impedance over time vs when new? How do we know the steal doesn't oxide?

 

[mbrooke]

Fe carries current fine, not as good as same cross section area of copper, but a raceway will almost always have more current carrying ability than the minimum required EGC that would be pulled through it. The problem is going to be quality of connections for both the raceway and the copper conductor. Installers can make a mistake with either.

Of course. Fe carries current just fine as well as 4000 series aluminum. However, would you wire a home with 4000 series aluminum?

Just making a comparison, don't mean to come across as a hard head answering your questions/statments with questions