# Mechanical ground



## user4818 (Jan 15, 2009)

Ummm...ok. :blink:

Whatever you are referring to must be NYC code because it's certainly not the NEC.


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## Mrs. Rewire (Jul 17, 2011)

Powerfull said:


> I am thrilled to know that we r no longer allowed to rely on a mechanical ground anymore. I never saw that method as being safe. I always argued with my cowokers and teachers in the past about it not being a safe practice and apparently someone agree's with me because we aren't allowed to use BX cable or MC without a equipment ground. Everything now has to have a equipment ground and I'm rubbing it in everyones face lol


Your a fool


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## Xjourneybenderx (May 31, 2011)

Powerfull said:


> I am thrilled to know that we r no longer allowed to rely on a mechanical ground anymore. I never saw that method as being safe. I always argued with my cowokers and teachers in the past about it not being a safe practice and apparently someone agree's with me because we aren't allowed to use BX cable or MC without a equipment ground. Everything now has to have a equipment ground and I'm rubbing it in everyones face lol


Emt you do not need a ground. I always pull grounding conductor no matter what I think it's an unsafe practice. One set screw loose and pipe separates no more ground.


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## Powerfull (Jul 11, 2011)

Well I was looking for the article to support it and I haven't found it yet. It just might b a jurisdiction thing, who knows. I can't b sure as of yet. All I know is that's what I was told from my boss on Friday


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## user4818 (Jan 15, 2009)

Powerfull said:


> Well I was looking for the article to support it and I haven't found it yet. It just might b a jurisdiction thing, who knows. I can't b sure as of yet. All I know is that's what I was told from my boss on Friday


See post #2.


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## macmikeman (Jan 23, 2007)

The New York City electrical code.... oui vey!


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## user4818 (Jan 15, 2009)

macmikeman said:


> The New York City electrical code.... oui vey!


I'd like to see how it compares to the NEC. Some things I have heard over the years about the NYC code, though all hearsay so probably not accurate - No NM cable allowed in NYC (so all SF dwellings on Staten Island and elsewhere have to be in MC/BX cable?), fire alarm 120 volt power has to be in RMC, minimum 3/4", #10 wire.


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## Magnettica (Jan 23, 2007)

Peter D said:


> I'd like to see how it compares to the NEC. Some things I have heard over the years about the NYC code, though all hearsay so probably not accurate - No NM cable allowed in NYC (so all SF dwellings on Staten Island and elsewhere have to be in MC/BX cable?), fire alarm 120 volt power has to be in RMC, minimum 3/4", #10 wire.


You'd be hard pressed to find any romex sold in an of the five boroughs (from I am told). NYC is douchy like Chicago is with EMT.


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## Powerfull (Jul 11, 2011)

And why is that Mr. Rewire??


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## Powerfull (Jul 11, 2011)

Mrs. Rewire said:


> Your a fool


And why is that Sir??


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## gold (Feb 15, 2008)

Magnettica said:


> You'd be hard pressed to find any romex sold in an of the five boroughs (from I am told). NYC is douchy like Chicago is with EMT.


Isn't that how BX got its name? Bronx wire? Something about all the rats eating through the wire so they had to invent a special wire for the area. I don't know if thats true or not just something I was told.


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## MDShunk (Jan 7, 2007)

gold said:


> Isn't that how BX got its name? Bronx wire? Something about all the rats eating through the wire so they had to invent a special wire for the area. I don't know if thats true or not just something I was told.


I found a very old magazine article that called it -Type B, eXperimental.


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## gold (Feb 15, 2008)

MDShunk said:


> I found a very old magazine article that called it -Type B, eXperimental.


I kinda thought there was some BS to that story. Ironically tho I heard it from the guy teaching the class at Eaton.


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## 76nemo (Aug 13, 2008)

Peter D said:


> See post #2.


 
His boss is a fool? I am on the boss' bridge, I am dead set on a seperate EC. I also expect you won't make mockery out of this Peter. Tradition and statisics don't really mean squat to me with Murphy's Law.


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## Magnettica (Jan 23, 2007)

BX = Bronx Cable Company

When the cable was packaged it was stamped with a "BX Cable Company" stamp.


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## Shockdoc (Mar 4, 2010)

Them NYC rats are known to eat thru EMT ........I'd run a ground too.


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## Wirenuting (Sep 12, 2010)

Shockdoc said:


> Them NYC rats are known to eat thru EMT ........I'd run a ground too.


No Rats


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## user4818 (Jan 15, 2009)

76nemo said:


> His boss is a fool? I am on the boss' bridge, I am dead set on a seperate EC. I also expect you won't make mockery out of this Peter. Tradition and statisics don't really mean squat to me with Murphy's Law.


What are you talking about? :blink:


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## BBQ (Nov 16, 2010)

Peter D said:


> What are you talking about? :blink:


:drink::drink:


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## BBQ (Nov 16, 2010)

76nemo said:


> His boss is a fool? I am on the boss' bridge, I am dead set on a seperate EC. I also expect you won't make mockery out of this Peter. Tradition and statisics don't really mean squat to me with Murphy's Law.


In other words don't confuse me with facts my mind is already made up. :laughing:


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## Mike in Canada (Jun 27, 2010)

Mrs. Rewire said:


> Your a fool


Does that count when the spelling is wrong?


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## Mike in Canada (Jun 27, 2010)

Xjourneybenderx said:


> Emt you do not need a ground. I always pull grounding conductor no matter what I think it's an unsafe practice. One set screw loose and pipe separates no more ground.


 In the Canadian rules EMT needs a separate bonding when run in concrete.

I use a separate bond all of the time, pretty much.


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## electric_avenue (Aug 7, 2010)

Mike in Canada said:


> Does that count when the spelling is wrong?


Ask your stepson #1 because from what I understand he cannot spell either.


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## 76nemo (Aug 13, 2008)

Peter D said:


> What are you talking about? :blink:


Okay, here's where you and BBQ can throw me a few fists, I'll take it. I don't give a flying hoot about a jacket or a raceways ability to carry fault current. Quite very frankly, I am very well suprised the NEC is so quaint on subject.


Yeah Bob, had a few cold ones, but you can quit with that jab.

I'm allowed to disagree.


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## user4818 (Jan 15, 2009)

76nemo said:


> Okay, here's where you and BBQ can throw me a few fists, I'll take it. I don't give a flying hoot about a jacket or a raceways ability to carry fault current. Quite very frankly, I am very well suprised the NEC is so quaint on subject.


For starters, I never called the man a fool. That was "Mrs. Rewire."


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## RIVETER (Sep 26, 2009)

76nemo said:


> Okay, here's where you and BBQ can throw me a few fists, I'll take it. I don't give a flying hoot about a jacket or a raceways ability to carry fault current. Quite very frankly, I am very well suprised the NEC is so quaint on subject.
> 
> 
> Yeah Bob, had a few cold ones, but you can quit with that jab.
> ...


It has been proven that a properly installed mechanical raceway will carry the vast majority of the fault current if the phase conductor contacts it, even with an egc installed.


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## electricmanscott (Feb 11, 2010)

RIVETER said:


> It has been proven that a properly installed mechanical raceway will carry the vast majority of the fault current if the phase conductor contacts it, even with an egc installed.


You can't fool Murphy! :thumbsup:


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## macmikeman (Jan 23, 2007)

RIVETER said:


> It has been proven that a properly installed mechanical raceway will carry the vast majority of the fault current if the phase conductor contacts it, even with an egc installed.


Riveter is not making this up, its true.


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## Big John (May 23, 2010)

macmikeman said:


> RIVETER said:
> 
> 
> > It has been proven that a properly installed mechanical raceway will carry the vast majority of the fault current if the phase conductor contacts it, even with an egc installed.
> ...


 It may be true, but I think most people object to using EMT as the sole equipment ground because you often see couplings broken apart, in which case the conduit most decidedly _won't _carry the fault current.

-John


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## brian john (Mar 11, 2007)

Xjourneybenderx said:


> Emt you do not need a ground. I always pull grounding conductor no matter what I think it's an unsafe practice. One set screw loose and pipe separates no more ground.


One set screw loose on a mechanical connector no ground. Proper work practices can always be messed up by a slacker. Be a professional.


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## macmikeman (Jan 23, 2007)

Big John said:


> It may be true, but I think most people object to using EMT as the sole equipment ground because you often see couplings broken apart, in which case the conduit most decidedly _won't _carry the fault current.
> 
> -John


The thing is Riveter said a properly installed conduit system. Now, we may possibly have different opinions on what that constitutes, but in my experience when I see seperated emt runs, they are usually strung out on batwings and little attention paid to running them to code. Or runs in places where physical damage was likely in the first place, like parking garage runs mounted to the underside of the beams, or better yet , mounted to struts mounted to the underside of beams, just waiting for a driver of a high truck to clip. Or somebody cannot be bothered to tighten up set screws or compression fittings. If it keeps you happy, I have stuck a green or green taped conductor into every emt I have strung for the last 20 years at least if not 25.


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## brian john (Mar 11, 2007)

In most commercial buildings, there are thousand of fault paths. Metal duct work, water pipe, studs, structural steel, rebar and countless other paths. In test I believe the EMT carried 80% of the fault current over the Copper branch circuit EGC.

Having said that we almost always pull a copper ECG (mostly due to site work requirements data centers/hospitals). But like many things lack of understand (ignorance) plays into unnecessary fears and concerns.

I’d bet in the typically commercial building a branch circuit in PVC without a ground with a dead short to ground at the load would not affect the trip time of the OCP.

Lastly having investigated major faults, I have found welded EMT, all-thread hardware, kindorf welded to the all-thread and evidence of arcs and faults all over between the source and fault.


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## user4818 (Jan 15, 2009)

brian john said:


> I’d bet in the typically commercial building a branch circuit in PVC without a ground with a dead short to ground at the load would not affect the trip time of the OCP.


You're assuming the return path is over the metallic systems and framing of the building itself, right?


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## RIVETER (Sep 26, 2009)

brian john said:


> In most commercial buildings, there are thousand of fault paths. Metal duct work, water pipe, studs, structural steel, rebar and countless other paths. In test I believe the EMT carried 80% of the fault current over the Copper branch circuit EGC.
> 
> Having said that we almost always pull a copper ECG )mostly due to site work (data centers/hospitals). But like many things lack of understand (ignorance) plays into unnecessary fears and concerns.
> 
> ...


The hope is that you are right. A lot of damage or injury may possibly be avoided if the OCD just trips a few cycles sooner. Who knows,for sure. If shoddy workmanship is the norm and a person should always place an egc conductor inside the raceway then the engineers at the NEC should make it mandatory do so. But what about the situation where an egc is there and the conduit is broken...will the fault current experience an inductive choke at the point of interruption of the conduit. That could delay the interruption of the OCD.


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## brian john (Mar 11, 2007)

Peter D said:


> You're assuming the return path is over the metallic systems and framing of the building itself, right?


Yep. Also assumes these features are in the building, in lieu of a wood framed structure.

When screen shake was a problem (older CRT monitors) I was amazed at the range of the current paths evident by locating the source of the neutral ground short, knowing the origination of the BC and all the CRTs in varying locations with the shakes due to all the current paths.


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## user4818 (Jan 15, 2009)

brian john said:


> Yep. Also assumes these features are in the building, in lieu of a wood framed structure.


I don't doubt the fault would clear, but do you really think it would happen as quickly as with an EGC in close proximity as required by the code?


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## brian john (Mar 11, 2007)

RIVETER said:


> The hope is that you are right. A lot of damage or injury may possibly be avoided if the OCD just trips a few cycles sooner. Who knows,for sure. If shoddy workmanship is the norm and a person should always place an egc conductor inside the raceway then the engineers at the NEC should make it mandatory do so. But what about the situation where an egc is there and the conduit is broken...will the fault current experience an inductive choke at the point of interruption of the conduit. That could delay the interruption of the OCD.


All I know is there are 1000’s of paths available in a typical commercial establishment. I always say if the slacker leaves the EMT connector loose, he may leave the copper EGC connector loose. We cannot account for slackers.

Or as my grandmother use to say, if, if, if; if a frog had wings he would not bump he tushie on the ground.


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## RIVETER (Sep 26, 2009)

Peter D said:


> I don't doubt the fault would clear, but do you really think it would happen as quickly as with an EGC in close proximity as required by the code?


I would say no. Why would the building people do their work any tighter than we do. There would possibly be a high resistance/impedance at the final connection where it could find the best path to the source. Just a thought.


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## Big John (May 23, 2010)

macmikeman said:


> The thing is Riveter said a properly installed conduit system....


We installed a run of 1" rigid conduit on a wall the other day, mounted with 1/4" drop-in anchors and straps every 7 feet. A crane set up about a week later, somehow snagged it with the load and ripped it clear off the building. 

There's no end to the ways people will break things, no matter how good a job we do putting it in. To me, pulling grounds are cheap insurance against that.

-John


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## macmikeman (Jan 23, 2007)

Big John said:


> We installed a run of 1" rigid conduit on a wall the other day, mounted with 1/4" drop-in anchors and straps every 7 feet. A crane set up about a week later, somehow snagged it with the load and ripped it clear off the building.
> 
> There's no end to the ways people will break things, no matter how good a job we do putting it in. To me, pulling grounds are cheap insurance against that.
> 
> -John


So the equipment ground conductor came thru the crane ripping the whole thing clear off the building all fine then? How did the egc insure the conduit run from the crane ripping it off the building? 

I run ground wires, I just was affirming what Riveter said, studies by the steel conduit companies have proven it to be a better fault clearing path than a copper egc installed inside the run.


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## RIVETER (Sep 26, 2009)

Mike in Canada said:


> In the Canadian rules EMT needs a separate bonding when run in concrete.
> 
> I use a separate bond all of the time, pretty much.


I can see the importance of that. After the conduit has rusted away, at points, the concrete becomes the raceway and you need the separate egc.


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## macmikeman (Jan 23, 2007)

We used to always paint a coat of lap seal on emt going in ground floor slabs to prevent any rusting. I havent used emt on grade slabs for a pretty long time now, why when pvc is cheaper and better to use for it. Up on the tenth floor in the slab, plain emt in the slabs stands up pretty well as long as the plumbers do their jobs well....


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## brian john (Mar 11, 2007)

RIVETER said:


> I can see the importance of that of that. After the conduit has rusted away, at points, the concrete becomes the raceway and you need the separate egc.



Yet the NEC has pushed concrete as the BEST electrode, for it’s conductivity.


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## RIVETER (Sep 26, 2009)

brian john said:


> Yet the NEC has pushed concrete as the BEST electrode, for it’s conductivity.


Electrode...yes. EGC...not, but I see what you are saying; It could help some.


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## brian john (Mar 11, 2007)

RIVETER said:


> Electrode...yes. EGC...not.


Better than a 5/8” copper clad 10’ rod, and then there is the rebar?


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## BBQ (Nov 16, 2010)

Big John said:


> It may be true, but I think most people object to using EMT as the sole equipment ground because you often see couplings broken apart, in which case the conduit most decidedly _won't _carry the fault current.
> 
> -John


One wire nut made up poorly and the wire EGC is no good ..........


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## RIVETER (Sep 26, 2009)

brian john said:


> Better than a 5/8” copper clad 10’ rod, and then there is the rebar?


Are we not talking about two different animals? An electrode is for aberrant voltage protection. The EGC is solely for short circuit protection.


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## Big John (May 23, 2010)

macmikeman said:


> So the equipment ground conductor came thru the crane ripping the whole thing clear off the building all fine then...?


 All the conductors had damaged insulation, but stayed intact, yes.

-John


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## kwired (Dec 20, 2009)

RIVETER said:


> ...will the fault current experience an inductive choke at the point of interruption of the conduit. That could delay the interruption of the OCD.


Interruption of conduit = open circuit = no current flow through that point which means there is no inductive choke at this point either.


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## RIVETER (Sep 26, 2009)

Big John said:


> All the conductors had damaged insulation, but stayed intact, yes.
> 
> -John


Where would it stop? If I installed a great conduit system and used the conduit as the egc and someone tore it down and did not fix it promptly, would it be my fault if something bad happened? Let's say that I am a very good electrician and run an extra egc in that very well installed conduit system just to make sure that in case someone breaks the conduit system they still have protection. Would it then be my fault if the conduit system was interrupted and the egc was, as well...and I did not run a second egc?


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## macmikeman (Jan 23, 2007)

Big John said:


> All the conductors had damaged insulation, but stayed intact, yes.
> 
> -John


This is a pretty clear code violation. You installed emt and a grounding conductor in a location subject to physical damage........ from a bad crane operator..:laughing: Schedule 80 rigid and a grounding conductor would have been a much better choice...:whistling2: Hope you learned from your mistake..




Just kidding around , but I still don't know why we're retorting, I did mention I always use ground wires didn't I ? I only reported Riverters having a real fact in his post. The emt carries more fault current than the properly sized copper ground wire inside.


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## Big John (May 23, 2010)

macmikeman said:


> ...Schedule 80 rigid and a grounding conductor would have been a much better choice...:whistling2:


 It _was _schedule 80 rigid. I was sure that conduit would be there for 50 years, and it barely lasted 5 days.:wallbash:


> ...I still don't know why we're retorting, I did mention I always use ground wires didn't I...


 I was just trying to explain my thinking behind why I do it, that's all. Not trying to argue. Why do you pull one in?


RIVETER said:


> Where would it stop...?


 For me it stops after the I pull that ground wire. Like I said, it's just cheap insurance.

-John


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## brian john (Mar 11, 2007)

RIVETER said:


> Are we not talking about two different animals? An electrode is for aberrant voltage protection. The EGC is solely for short circuit protection.


I am talking conductivity.


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## brian john (Mar 11, 2007)

kwired said:


> Interruption of conduit = open circuit = no current flow through that point which means there is no inductive choke at this point either.


But if it has limited conductivity it could be a spot for possible fire ignition.


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## macmikeman (Jan 23, 2007)

I always pull an egc cause after all these years, one thing I have learned is........ Never trust crane operators..........


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## BBQ (Nov 16, 2010)

I usually pull an EGC, I won't say always because sometimes I don't. Yet I still sleep well.


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## gold (Feb 15, 2008)

The problem I have with relying on conduit as an egc is if its damaged in such a way that separates a fitting from a box a ground fault against the box or conduit could put one at a higher potential then the other. When someone comes along to make a repair or push them back together they grab the box with one hand and the pipe with the other and bam. I'm not so much concerned with an electrician doing it .... hypothetical; fork lift driver backs into an outlet surface mounted in a 1900 box with emt. Pipe separates from the box and theres a short against the box that occurs after the separation. Driver jumps down and attempts to put the two back together so no one notices ... LAMPED. Obvious that is just one very hypothetical situation but it seems to me (perhaps wrongly so) that damage that can result in injury is more likely without an EGC conductor because the ground path is more likely to survive if the conduit system is damaged. Damage that interrupts the ground path can also be caused by corrosion, improper alterations, or simply compromised by loose fittings and time. 

Has there ever been a study done on the cast aluminum fittings and there ability to conduct as they age? What about electrolysis between the two different metals from transient voltages I know its a stretch but is it possible even remotely?

Just my opinion I'm not closed minded on this at all.


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## CraigV (May 12, 2011)

brian john said:


> I am talking conductivity.


 
Dry, cured concrete in _good_ condition is a poor conductor at >120 ohms per meter. A footing buried in damp soil is a better conductor, and of course the presence of rebar increases conductivity greatly. Ironically, concrete's resistance is lower if the concrete is in poor condition, but the rebar's resistance greatly increases as it corrodes.


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## brian john (Mar 11, 2007)

CraigV said:


> Dry, cured concrete in _good_ condition is a poor conductor at >120 ohms per meter. A footing buried in damp soil is a better conductor, and of course the presence of rebar increases conductivity greatly. Ironically, concrete's resistance is lower if the concrete is in poor condition, but the rebar's resistance greatly increases as it corrodes.


 
But it is a complete system, most buildings I have worked in have footers and a slab in contact with the Earth.


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## CraigV (May 12, 2011)

brian john said:


> But it is a complete system, most buildings I have worked in have footers and a slab in contact with the Earth.


Two different animals. For footing GES's, concrete is good. But the discussion was about corroded pipe within poured concrete buildings. Riveter stated "_After the conduit has rusted away, at points, the concrete becomes the raceway and you need the separate egc_". 

You then stated that NEC considers concrete to be the ideal conductor. But that's in the context of a grounding electrode system., In the context of discussion, which was rusted branch or feeder circuit conduit, concrete would not be remotely acceptable.


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## brian john (Mar 11, 2007)

CraigV said:


> Two different animals. For footing GES's, concrete is good. But the discussion was about corroded pipe within poured concrete buildings. Riveter stated "_After the conduit has rusted away, at points, the concrete becomes the raceway and you need the separate egc_".
> 
> You then stated that NEC considers concrete to be the ideal conductor. But that's in the context of a grounding electrode system., In the context of discussion, which was rusted branch or feeder circuit conduit, concrete would not be remotely acceptable.


 
My point was conductivity.


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## CraigV (May 12, 2011)

brian john said:


> My point was conductivity.


Riveter's point was that a rusted-away conduit in concrete provides a very poor conductivity path if it's relying on concrete to jump the rusted parts. I agree. Unlike a Ufer GES, you don't know how far away the rebar may be, or its condition. There's also no direct connection to the rebar. I would never assume a rusted-out conduit was still making a decent grounding connection.


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## brian john (Mar 11, 2007)

CraigV said:


> Riveter's point was that a rusted-away conduit in concrete provides a very poor conductivity path if it's relying on concrete to jump the rusted parts. I agree. Unlike a Ufer GES, you don't know how far away the rebar may be, or its condition. There's also no direct connection to the rebar. I would never assume a rusted-out conduit was still making a decent grounding connection.


 
I would not bet, because I hate to loose money, but I would THINK a conduit in the deck would be a very good ground with all the connections to rebar, other conduits and the like.

But I could be wrong.


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## Wirenuting (Sep 12, 2010)

brian john said:


> I would not bet, because I hate to loose money, but I would THINK a conduit in the deck would be a very good ground with all the connections to rebar, other conduits and the like.
> 
> But I could be wrong.


I think of it as a wet location & TW don't last long there. 
I'll drop rigid in the hole. 

I'll pull an EGC in old work if it looks bad or if it's in a location subject to damage.


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## CraigV (May 12, 2011)

brian john said:


> I would not bet, because I hate to loose money, but I would THINK a conduit in the deck would be a very good ground with all the connections to rebar, other conduits and the like.
> 
> But I could be wrong.


I'd be very interested to see actual resistance readings in buildings that has been around a while. Fresh (uncured) concrete has good conductivity but as it cures over the course of a year or more, its resistance increases steadily, even if it remains damp.


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## brian john (Mar 11, 2007)

I base this on several jobs we did years ago the customer wanted 100% isolated equipment in telco rooms. The EC isolated everything, yet when we ran resistance test the installation failed the test. 

No matter how careful the EC was there was something grounded, anchors for cable tray, all-thread touching the drop ceiling, coax for the switch and on and on.


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## tkb (Jan 21, 2009)

Wirenuting said:


> I think of it as a wet location & TW don't last long there.
> I'll drop rigid in the hole.
> 
> I'll pull an EGC in old work if it looks bad or if it's in a location subject to damage.


TW is rated for dry or wet locations. :no:

I would not hesitate to use EMT as an EGC or AC cable.
They are both good ground paths that are recognized by the NEC.

If there was a problem with them the code making panels would make changes to eliminate them.


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## brian john (Mar 11, 2007)

Can you buy TW, these days?


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## tkb (Jan 21, 2009)

brian john said:


> Can you buy TW, these days?


I haven't seen it for many years.
I remember it coming in boxes, like romex.


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## Xjourneybenderx (May 31, 2011)

I once did a service call at a restaurant. In the kitchen there is a huge metal counter. This is where the chefs set there food down so the waitress can pick up the food and take it to the customers. Well the owner called me and told me that he had been shocked from touching a receptacle over the counter. So first thing I did was hold my wiggy up to the metal cover plate of the receptacle. I got no beep nothing was wrong so I take my wiggy and hold it to the counter. I get beeps and flashes saying that the counter is hot. On the counter top was a brand new soda machine . So I unplugged it and the counter wasn't hot anymore . The receptacle was not grounded and the soda cord was pinched so it heated up the counter top. 
My point is that a loose ground can always happen. I think it is always important to pull a grounding conductor threw conduit because now you have doubled your chance of not loosing the Grc and without the Grc accidents are more likely to happen! But then again the grounding part of a receptacle can always break and no more Grc.


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## brian john (Mar 11, 2007)

tkb said:


> I haven't seen it for many years.
> I remember it coming in boxes, like romex.


And the boxes broke open then you had a mess. Remember THW?


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## brian john (Mar 11, 2007)

Xjourneybenderx said:


> I
> My point is that a loose ground can always happen. I think it is always important to pull a grounding conductor threw conduit because now you have doubled your chance of not loosing the Grc and without the Grc accidents are more likely to happen! But then again the grounding part of a receptacle can always break and no more Grc.



For every up I can give you a down, for every right a left. Point is if two is good we should install3 EGCs.

Be professional, do quality work and you cannot be responsible for someone else’s stupidity, laziness or lack of understanding the trade..


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## RIVETER (Sep 26, 2009)

kwired said:


> Interruption of conduit = open circuit = no current flow through that point which means there is no inductive choke at this point either.


I can't say your are wrong...totally, but here is the deal. If you have an intentional path for fault current, let's say it is the egc, and you have an auxiliary path for fault current and it is the conduit, you have a parallel path for the fault current to get back to the source...right? If one or the other is impaired at some point, and it may not be totally open, do you not think that the OCD will be compromised?


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## Xjourneybenderx (May 31, 2011)

When making up an iso transformer do you bond land the iso to the cage with the other grounding conductor or do you land it directly to the xo?


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## RIVETER (Sep 26, 2009)

Xjourneybenderx said:


> When making up an iso transformer do you bond land the iso to the cage with the other grounding conductor or do you land it directly to the xo?


It is important to know what you are trying to do in the first place. Bonding is totally different as far as connection to ground, or making the metallic components of an electrical system to be at the same potential.


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## brian john (Mar 11, 2007)

Xjourneybenderx said:


> When making up an iso transformer do you bond land the iso to the cage with the other grounding conductor or do you land it directly to the xo?


In the whole scheme of things it does not make a difference. I prefer everything on the XO with a single bond jumper to the can. Minimizes circulating current in the transformer. While this circulating current does no harm it complicates trouble shooting ground issues. Though these days many transformers have a factory bond.


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## Wirenuting (Sep 12, 2010)

brian john said:


> And the boxes broke open then you had a mess. Remember THW?


TW, I ment thinwall...

And the THW & TW I pulled from old concrete encased thinwall was soaked and rotten. 
It was all under a hospital kitchen built in 1960. It has that slimy green goo dripping from the terminations.


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## RIVETER (Sep 26, 2009)

brian john said:


> In the whole scheme of things it does not make a difference. I prefer everything on the XO with a single bond jumper to the can. Minimizes circulating current in the transformer. While this circulating current does no harm it complicates trouble shooting ground issues. Though these days many transformers have a factory bond.


I have never heard of circulating current. What is that?


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## brian john (Mar 11, 2007)

RIVETER said:


> I have never heard of circulating current. What is that?


Ground curent, taking more than one path.


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## RIVETER (Sep 26, 2009)

brian john said:


> Ground curent, taking more than one path.


Okay, here we go. Why would any current want to go to ground? Ground is not a normal way of getting to where it wants to go.


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## user4818 (Jan 15, 2009)

brian john said:


> Can you buy TW, these days?


The only modern TW I've ever seen is #8 green solid. They call it "pool bonding wire" which is silly because it makes a lot more sense for it to be bare. I don't know who would ever buy it, but they sell it. Maybe B4T buys it because he's into that weird stuff. :laughing:


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## Mike in Canada (Jun 27, 2010)

Peter D said:


> The only modern TW I've ever seen is #8 green solid. They call it "pool bonding wire" which is silly because it makes a lot more sense for it to be bare. I don't know who would ever buy it, but they sell it. Maybe B4T buys it because he's into that weird stuff. :laughing:


 Up here in Canada, if you're using bare copper it has to be #6 or larger. Smaller sizes have to be protected from mechanical damage, so they coat it for pulling through a conduit.

So that 2HP pool pump has a #6 bare copper bond to it - cheaper and easier than running conduit just for that purpose.


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## CraigV (May 12, 2011)

brian john said:


> I base this on several jobs we did years ago the customer wanted 100% isolated equipment in telco rooms. The EC isolated everything, yet when we ran resistance test the installation failed the test.
> 
> No matter how careful the EC was there was something grounded, anchors for cable tray, all-thread touching the drop ceiling, coax for the switch and on and on.


 
That's interesting, how old was the building and do you recall any of the readings?


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## brian john (Mar 11, 2007)

RIVETER said:


> Okay, here we go. Why would any current want to go to ground? Ground is not a normal way of getting to where it wants to go.


 
Not EARTH, the metallic enclosure and the multiple (if they exist) copper bonding conductors.


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## brian john (Mar 11, 2007)

CraigV said:


> That's interesting, how old was the building and do you recall any of the readings?


 
Cannot remember the readings, this was in several buildings one was 35 years old, the rest were 5-10 years old.


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## 1capybara (Feb 27, 2009)

BBQ said:


> One wire nut made up poorly and the wire EGC is no good ..........


the Brits got a solution to this: all EGCs are home runs in new construction. do we really wanna do this? well, no, not unless we're working on a British spec job. and they call EGCs circuit protective conductor [CPC].


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## bobelectric (Feb 24, 2007)

brian john said:


> One set screw loose on a mechanical connector no ground. Proper work practices can always be messed up by a slacker. Be a professional.


 I doubt that a loose set screw would result in a coupling having no metallic contact. But I'm not a recognized testing lab.


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