Raceway as the grounding conductor

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Strathead said:
Read the statement and my response. My point was that an ohmmeter, does not take in to account the current carrying capacity of a conductor. So, using a multimeter to prove that an EMT conduit run is properly assembled and will act as a proper ground path is not effective. Every coupling and connector could be loose, and you could still be capable of reading virtually zero ohms.
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Agree:thumbsup::thumbsup:
Ohm meter reading may very well be a false reading.
 
OK. So, speaking in the context of this thread coming from the Opening Post. . . taking DC resistance readings from a neutral in a Jbox back through the Main Bonding Jumper and back out on the EGC to that same Jbox, and making note of that Ohmic value along with conduit run length, diameter and wire gage. . . is offered as an exercise for one person to do, with a single mulitimeter used for all measurements gathered, when learning about real world installations.

The value is in the differences between the resistance readings. There is no value, practically, in leaping all the way to absolute complex impedance values. . .

Let's start with a few simple real world observations in a DC model and talk about the findings. . .

Remember, the OP is leaning towards the local tradition, in his experience, of an added wire type EGC in parallel with the EMT raceway EGC, rather than "assuming" there is an actual EGC in the EMT.

I offer the simple idea of personal DC resistance measurements of real world assemblies to expand one's personal knowing of truth. . .

It has absolutely nothing to do with "proving an effective ground path" or with the possible errors of multimeter use.
 
Most everybody around here always uses an equipment ground. I never bothered to ask as I do the same thing. Always seemed better to have a two paths back, since sometimes in remodels you are pulling wires through existing conduits and aren't going to take the time to inspect all of it.

About the broken/damaged conduits, I was working in a car wash pump room the other day and noticed that the RIGID conduits running down through the floor were extremely corroded and a couple were completely separated. Bad place to not have a path back to ground. On the other hand, I can only suggest they have me replace these conduits. Will they until there is a problem, doubtful. It costs money.

Just my opinion.
 
2017 NEC now requires a wire type EGC for raceways on roofs
WA has required a wire type EGC in EMT installed in wet locations
The CMPs for raceways has always opposed wire type EGC as they maintain the product is safe if installed correctly.
 
We had a local amendment where I lived in OR that required wire EGC in conduit. Rationale was that it is a seismically active area, and they wanted to improve the chances of the ground stating intact if a wall shifted / conduit parted during an earthquake. Always seemed reasonable to me.




SceneryDriver
 
mivey said:
I don't have a problem with the install for the most part but EMT just does not hold up well over time. IMO, too flimsy to be used as an EGC except in an area with very limited access to the general public/employee.

I would and do use rigid for an EGC.
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Rigid gets damaged by heavy equipment at times too.

dkidd said:
Huh? :happysad: "Conductivity of the conduit under load"? The EMT does not conduct under load.
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It does when carrying a ground fault, which is when we want it to have a low impedance.

iwire said:
So basically you are saying by pulling an EGC you don't have to repair damaged conduits.

Like Roger I am of the belief that if you think the EMT is going to be damaged it is either not the right product or not being installed properly.
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+1
 
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