Unique solution to an expensive situation.

[brian john]

YA, I do. If a tire shop puts a cheap patch on a tire instead of replacing it, you save money now, but if it blows out on the freeway and you total the car how is that savings ? Cheap is cheap, it is not savings.
"Penny wise and pound foolish".
This is a store, what type of equipment is now at risk, due to a questionable ground? Seeing that the solution in the OP is written in the past tense, it is a mute point. The job is done, to a code minimum. So I guess it must be safe.:roll:

I cannot speak for this building but in MOST commercial establishments.


Posted by me earlier

if there are metal ducts, piping and metal studs, concrete with rebar, metal trusses and/or a drop ceiling, testing the EMT will do little to prove the EMT is sufficient.

EMT is NEC compliant and in use in 1000's of 1000's commercial and industrial establishemnts, by your standard I assume you always use #10 AWG copper on 20 amp circuits? #8 on 30 amp circuits? You pipe all your residential projects? NEMA 3R for all panels and FSS's indoors? Dedicated circuits for every 20 amp receptacle to minimize possible over loadings? Suspenders with your belt? And the list of extra precautions could be as thick as the NEC.

 

[acrwc10]

I cannot speak for this building but in MOST commercial establishments.


Posted by me earlier


EMT is NEC compliant and in use in 1000's of 1000's commercial and industrial establishemnts, by your standard I assume you always use #10 AWG copper on 20 amp circuits? #8 on 30 amp circuits? You pipe all your residential projects? NEMA 3R for all panels and FSS's indoors? Dedicated circuits for every 20 amp receptacle to minimize possible over loadings? Suspenders with your belt? And the list of extra precautions could be as thick as the NEC.

Nope, I only use suspenders on my toolbelt.:grin:

I have seen to many emt runs that, over time, come apart and leave NO ground path. I know "1000 & 1000's" of commercial buildings use emt for the ground path, and there are thousands of circuit runs that have no ground path due to this. Like I said Penny wise and pound foolish. If you are the building owner the additional cost of the ground wire ( instead of using emt as the ground ) is not that much, especially if you have thousands of dollars of product at steak. The cost amortized over a few years or the life of the equipment is pennies not dollars. Why would you see your self as a hero after delivering an inferior product ?

 

[One-eyed Jack]

LOL,LOL,LMAO. This horse was dead when you started beating it. It is no more or less dead and some of you are bone tired from the effort. The OP is proud of it and it is code compliant.

 

[iwire]

Nope, I only use suspenders on my toolbelt.:grin:

I have seen to many emt runs that, over time, come apart and leave NO ground path. I know "1000 & 1000's" of commercial buildings use emt for the ground path, and there are thousands of circuit runs that have no ground path due to this. Like I said Penny wise and pound foolish. If you are the building owner the additional cost of the ground wire ( instead of using emt as the ground ) is not that much, especially if you have thousands of dollars of product at steak. The cost amortized over a few years or the life of the equipment is pennies not dollars. Why would you see your self as a hero after delivering an inferior product ?

The BS is running very deep today.

 

[roger]

The BS is running very deep today.

Ain't it though?

Roger

 

[Jim W in Tampa]

This all comes down to trusting emt. Min. code is just that. Would you trust a long run of emt that you personally did not install ? Not sure i would unless i could check every screw. We all have seen pipes that came apart. What do they do for a ground if a ground wire was not ran ? It's called taking a chance and maybe one that kills someone. Choice was his. After someone gets hurt or killed they will not thank your for saving the money.

 

[Volta]

This all comes down to trusting emt. Min. code is just that. Would you trust a long run of emt that you personally did not install ? Not sure i would unless i could check every screw.

You would have to if you had employees.
If you have a job, someone has to trust you, too.

We all have seen pipes that came apart. What do they do for a ground if a ground wire was not ran ? It's called taking a chance and maybe one that kills someone. Choice was his. After someone gets hurt or killed they will not thank your for saving the money.

This world is full of unofficial cost/risk analysis that we do constantly.

 

[Jim W in Tampa]

You would have to if you had employees.
If you have a job, someone has to trust you, too.

This world is full of unofficial cost/risk analysis that we do constantly.

All true but we do not need to take extra risks. There is a high chance his install is ok but still a small one that it is not. Now the liability is all his. Trust is not something i have in a job i did not do or even know who did the work. Have had helpers on jobs that flat out lie about things. Only the OP seen the job so hopefully he is right. I am the first to admit that i sometimes miss a srew when running emt.

 

[Volta]

All true but we do not need to take extra risks. There is a high chance his install is ok but still a small one that it is not. Now the liability is all his. Trust is not something i have in a job i did not do or even know who did the work. Have had helpers on jobs that flat out lie about things. Only the OP seen the job so hopefully he is right. I am the first to admit that i sometimes miss a srew when running emt.

Well I'll hurry to be the second! I almost always run a wire type EGC in my metal raceway for similar reasons. Not because a small piece of copper is better than a large surface area of steel, 'cause the wire tends to have a higher resistivity, but because the two paths are statistically more likely to have less impedeance than one.

And that just seems better.

 

[SAC]

With that high a resistance, the original plan is dead in the water.

Last I checked, "less than one ohm" included zero ohms - can't get much lower than that. I don't think that there is enough information in the "less than one ohm" statement (is it .01 ohm or .99 ohm?) to draw a reasonable conclusion about the suitability of this particular EMT run for EGC use.

 

[brian john]

Last I checked, "less than one ohm" included zero ohms - can't get much lower than that. I don't think that there is enough information in the "less than one ohm" statement (is it .01 ohm or .99 ohm?) to draw a reasonable conclusion about the suitability of this particular EMT run for EGC use.

Unless I am missing something, the OP tested the copper EGC to the EMT assuming he tested properly with the copper EGC isolated one ohm or less than one ohm is unacceptable.

 

[SAC]

Unless I am missing something, the OP tested the copper EGC to the EMT assuming he tested properly with the copper EGC isolated one ohm or less than one ohm is unacceptable.

The statement that I quoted seemed to be expressing concern that "less than one ohm" was "too high" to be used as an EGC. Since the test was not adequately described by the OP, almost any conclusion can be drawn about what the test actually was. However, the intent of the test was described as being to determine if the EMT was continuous for use as the EGC. In order to do this, one would disconnect the EGC wire at the load end, leaving it connected at the panel. At the load end, measure the resistance between the EGC wire and the EMT. If the resistance is sufficiently low, then one can conclude that the EMT is continuous from the load end to the panel (where the EGC and EMT are bonded) and can be used as the EGC once the EGC wire is repurposed for the neutral. However, "less than one ohm" could be as high as .99 ohm, which really isn't low enough for a good fault current path - though .01 ohm is plenty low enough.

 

[hillbilly1]

I seem to remember at one time code required emt fittings be listed for grounding purposes, to allow it to be used as the equipment ground. They may have removed that requirement? Back then I could not find that listing on the box, so that may be why the majority of emt installs I've seen in the past 20 years or so, have a seperate equipment ground pulled. The only time I've seen emt used as equipment ground is old installations >30 years old.

 

[Smart $]

The statement that I quoted seemed to be expressing concern that "less than one ohm" was "too high" to be used as an EGC. Since the test was not adequately described by the OP, almost any conclusion can be drawn about what the test actually was. However, the intent of the test was described as being to determine if the EMT was continuous for use as the EGC. In order to do this, one would disconnect the EGC wire at the load end, leaving it connected at the panel. At the load end, measure the resistance between the EGC wire and the EMT. If the resistance is sufficiently low, then one can conclude that the EMT is continuous from the load end to the panel (where the EGC and EMT are bonded) and can be used as the EGC once the EGC wire is repurposed for the neutral. However, "less than one ohm" could be as high as .99 ohm, which really isn't low enough for a good fault current path - though .01 ohm is plenty low enough.

Highlighted in red is a stretch. As mentioned before, you have to [megger?] test the wire for isolation from the emt by unlanding both ends. This test has to be donw to assure the wire was not bonded somewhere along the way.

As for the one ohm (or less), that is not an assurance either. If the EMT run used conductive supports to a steel structural members, there are multiple paths to the MBJ/SBJ. So a conductive break in the EMT may still test as low ohmage to ground.

 

[kwired]

Highlighted in red is a stretch. As mentioned before, you have to [megger?] test the wire for isolation from the emt by unlanding both ends. This test has to be donw to assure the wire was not bonded somewhere along the way.

As for the one ohm (or less), that is not an assurance either. If the EMT run used conductive supports to a steel structural members, there are multiple paths to the MBJ/SBJ. So a conductive break in the EMT may still test as low ohmage to ground.

If there is a lot of steel structure around with conductive supports attached to it and multiple steel raceways, possibly other metal piping systems - then you have a lower resistance fault return path through all of this than you have from a green conductor pulled in a raceway, whether you like it or not that is the way it is. NEC does not recognize these other things as an equipment grounding conductor, but if they are all bonded together intentionally or not they are grounded.

In a place where there is a lot of steel around I have absolutely no problem with knowing something is grounded. I have been around grain elevators a lot and seen equipment people connect the ground cable for their welder to the nearest convenient point and run the electrode cable a hundred plus feet up the leg to weld something up there and had no problem making the welder work - everything is bonded together very well.

 

[kwired]

.

..This world is full of unofficial cost/risk analysis that we do constantly.

All true but we do not need to take extra risks....quote]


We take a risk everytime we energize something, plug something in, drill or cut something, use tools or equipment, sometimes when turning something off it is a higher risk than leaving it on.

I feel safer doing most of my work than I do driving with all the other idiots that are on the road.

 

[Smart $]

If there is a lot of steel structure around with conductive supports attached to it and multiple steel raceways, possibly other metal piping systems - then you have a lower resistance fault return path through all of this than you have from a green conductor pulled in a raceway, whether you like it or not that is the way it is. NEC does not recognize these other things as an equipment grounding conductor, but if they are all bonded together intentionally or not they are grounded.

In a place where there is a lot of steel around I have absolutely no problem with knowing something is grounded. I have been around grain elevators a lot and seen equipment people connect the ground cable for their welder to the nearest convenient point and run the electrode cable a hundred plus feet up the leg to weld something up there and had no problem making the welder work - everything is bonded together very well.

Your post almost seems contradictory to the point I tried to make. I agree these additional paths provide a lower resistance grounding. That in itself is great.

But as you said, the NEC does not recognize these extra paths as an equipment grounding conductor. Therefore, simply testing with an ohmeter will not verify the continuity of the EMT run.

The run, short of physically testing the mechanical integrity at each joint, would have to be at least visually confirmed for continuity... and I'm not saying one has to inspect every single inch, but at least to a degree of reasonable certainty for the issue at hand.

 

[Jim W in Tampa]

Here is what could happen in a situation like this. The panel has many runs of emt and it is possable one of them runs is making connection to build steel. That now gives you a path to ground so you get 0 ohms. Now the problem, remodeling for some reason removes that run of emt. Now your run that you thought was grounded just lost its ground.
An ohm meter will not prove you have the ground you think you have. It can prove you do not have connection

 

[brian john]

The statement that I quoted seemed to be expressing concern that "less than one ohm" was "too high" to be used as an EGC. Since the test was not adequately described by the OP, almost any conclusion can be drawn about what the test actually was. However, the intent of the test was described as being to determine if the EMT was continuous for use as the EGC. In order to do this, one would disconnect the EGC wire at the load end, leaving it connected at the panel. At the load end, measure the resistance between the EGC wire and the EMT. If the resistance is sufficiently low, then one can conclude that the EMT is continuous from the load end to the panel (where the EGC and EMT are bonded) and can be used as the EGC once the EGC wire is repurposed for the neutral. However, "less than one ohm" could be as high as .99 ohm, which really isn't low enough for a good fault current path - though .01 ohm is plenty low enough.

If the GEC was grounded on one end the reading should be "0" anything else assumes an ELECTRICIAN with a MEGGER should have a fair idea about what he is doing. Maybe the OP could post exactly what and how he tested this as this has gone around and around.

Personally I like my first ideaTransformer and small panel.

 

[iwire]

Personally I like my first idea Transformer and small panel.

Gee you like your idea, what a shocker. :grin: (I always like my ideas the best as well )

The question would be 'can that idea be sold to the customer'? Seeing as I actually have daily experience with retail stores I can tell you with confidence that they only desire the bare minimum that meets code and I for one have no problem providing the customer with as little or as much as they are willing to pay for.

Then of course there is the practical aspect, the OP said this was an 'island' on the stores sales floor. I bet there is no space at all in this island to add a transformer. The 'walls' of the island will be about 36" AFF and all them will be shelving or cabinets stuffed with stuff.