pulling grounding conductors

[crossman]

If you guys will get the utility companies to run a grounding wire along with their conductors

I now realize what you are saying. When you said "their conductors" I visualized the POCO secondary service drop to the point of attachment. Didn't realize you were talking about the primary side. I hope you understand and can sympathize with my misunderstanding.:wink:

 

[peter d]

-the stray current due to poor utility neutrals causing current to flow through water mains and such is also another reason that the utility should have a grounding conductor, taking the current off all these unwanted things and putting it directly back to source

It's true that the MGN system is a source of stray current, but I don't see it changing from here to the next million years.

 

[nakulak]

no sweat dude, hearing all these tales of plumbers getting zapped and current flowing down fences due to return utility current really bugs me. An electrician could even get hit on a correctly installed meter housing, and all this for no other reason than bad design which has yet to be corrected.

 

[iwire]

Your right Bob. I spend the extra money and do the extra work just so I can say I'm better than some one else. Has nothing to do with your saftey, mine or the next guy's!

Just like the CMP you have no evidence at all that properly installed metal raceways do not provide an adequate ground fault path.

I am sorry your upset but you are not looking at the issue objectively.

Do you run redundant EGCs with other wiring methods?

If not, why not?

 

[iwire]

belt and suspenders can't hurt.

No it can not 'hurt' it can waste money, but my real question is do you go the belt and suspenders route with other wiring methods just in case your don't make a nice termination?

 

[nakulak]

I am sorry your upset but you are not looking at the issue objectively.

lets look at it objectively.

lets say you are running 3/4 emt, and comparing it with running an extra #10 egc.

a) well, the emt is like running a #6 egc, right ?, so that's, what, almost twice the ampacity ?

b) so improperly connected emt is the issue ? as bob stated, every wiring method is capable of being installed improperly. I think the issue here is the perception that emt is often poorly installed. But as the "pictures of the week" often show, there is virtually no facet of the trade that isn't susceptible to poor workmanship, causing any number of failures, including bad bonds and grounds. Is the idea here that emt is particularly susceptible to poor installation ? If that is the case then maybe this is a valid issue, but I think this is the only issue, and I don't see the evidence. If someone will present the evidence I will gladly change my tune, but I see a lot of good pipe work out there, so I am not of the opinion that all the emt in the world is falling out of ceilings and/or electrocuting guys everywhere, ( cause I haven't seen that.)

 

[JohnJ0906]

and was confident that I hadn't left a screw loose.

George, I think I speak for all of us when I say, we are glad you don't have a screw loose.....


Are you sure?

 

[Dennis Alwon]

I really don't think one can say pulling 2 grounds in a pvc is the same as pulling a ground in emt. Yes, they are 2 ground paths but their connections are not depenedent on each other. Two EGC will be spliced together and if the connection is loose it is likely that both conductors may be loose.

I am not advocating that an egc is necessary or required by the NEC but many of us here go beyond the NEC as we want more than minimum protection. In a company with many workers I can see that pulling an egc would take away the error factor to some degree, however I don't see those that don't pull an egc as being slack EC's.

I find this to be one of those issues that electricians do just so they can say they are better then those that don't.

I think this is an unfair statement,unnecessary and a bit insulting to many of us. I don't do much pipe work but I never had said that an ec was not good because of a lack of an EGC in metal conduit.

IBM use to require us to use 12/3 AC cable (way back when) and remove the insulation on the red wire. It was there choice to have a redundant ground. If a company bids the ground in the emt and wins the contract then I say "why not".

 

[iwire]

I really don't think one can say pulling 2 grounds in a pvc is the same as pulling a ground in emt.

I can and will. :grin:

The EMT is an EGC of much less impedance of any wire EGC you will pull inside it.

If you believe for safety reasons metal conduits need redundant grounding then you must also believe all methods need redundant grounding.

A single bad EGC splice in a typical NM wired home can leave many outlets entirely ungrounded....not poorly grounded like a loss EMT fitting but entirely ungrounded.

Maybe I am alone here but I have found many more bad splices then I have found pulled apart EMT fittings. And as Peter D pointed out, many times the one really poorly made splice in a box is in fact the EGC as it often has the most conductors and has also been added to over time.

Merry Christmas everyone, have a great new year. Run as many EGCs as makes you happy.

My main point here has been to make people consider things deeper usual and make them ask themselves why.

 

[iwire]

I think this is an unfair statement,unnecessary and a bit insulting to many of us.

If you run an EGC with EMT voluntarily there has to be a reason why you do so.

If you do not have any evidence that it makes the job 'better' then the only reason can be for the self satisfaction of it.....and there is really nothing wrong with that......if the money your spending is coming out of your own pocket....IMO it becomes much more questionable when spending the bosses money.

 

[chris kennedy]

I'm starting to think these threads (EGC in EMT) should go join "Ground up or down"

I don't see any benefit.

Hoppy Holidays All:smile:

 

[iwire]

I'm starting to think these threads (EGC in EMT) should go join "Ground up or down"

I don't see any benefit.

Hoppy Holidays All:smile:

I see a benefit, the benefit is that people are learning what the NEC does and does not require.

I often see links in these threads that show without a doubt that properly installed metal conduit systems have less impedance the any wire EGC you would install inside them.

An example where I intentionally left out an EGC to save money.

I had to run a 480 volt, 1,200 amp feeder about 400' through a steel frame building.

I ran three 3" EMTs using steel set screw fittings each tightened with a socket and ratchet, every 10' the EMTs sat on a Unistrut rack with each uni-strut clip also securely fasted, with each rack secured to the steel building structure every 10'.

That group of conduits impedance would most definitely be below the impedance of the EGC that would have been required. Do I have the least bit of worry that it is not 'grounded enough' nope, no thought of that at all.

Besides about 1,300' less 3/0 CU the EMT size was reduced and the labor for pulling and terminating was reduced. (It was design build)

I also used the building steel as a grounding electrode jumper to save a 400' run of 3/0 copper to water pipe from the service.

Knowing the code is power, when we choose to use that power is up to each one of us and the prints.

 

[don_resqcapt19]

Bob,
Doing a quick run with the GEMI software (from the steel tube institute) it shows that with a 12,000 amp fault and 600 kcmil circuit conductors a 3" EMT is a suitable EGC for about 325' and a 3/0 copper is for about 50'.
Don

 

[iwire]

Bob,
Doing a quick run with the GEMI software (from the steel tube institute) it shows that with a 12,000 amp fault and 600 kcmil circuit conductors a 3" EMT is a suitable EGC for about 325' and a 3/0 copper is for about 50'.
Don

Don while that is interesting for comparison sake, what is the criteria for deciding what is enough?

How fast does the OCPD have to open in order to decide a particular EGC is enough?


BTW....you did nail the size, it was 3 sets of 600 CU.

 

[chris kennedy]

Bob,
Doing a quick run with the GEMI software (from the steel tube institute) it shows that with a 12,000 amp fault and 600 kcmil circuit conductors a 3" EMT is a suitable EGC for about 325' and a 3/0 copper is for about 50'.
Don

I don't get this Don, 3/0 Cu. EGC is only suitable for 50'? What about a PVC install?

Also wouldn't a fault occur at the level of the available fault current for a 1/2 cycle or more depending on the breaker settings?

 

[don_resqcapt19]

Chris,

I don't get this Don, 3/0 Cu. EGC is only suitable for 50'? What about a PVC install?

The same would apply to the PVC run with a copper EGC. Remember that 250.122 is the minimum size EGC that is permitted by the code. 250.4 may require a larger EGC.

Also wouldn't a fault occur at the level of the available fault current for a 1/2 cycle or more depending on the breaker settings?

I based it on 12,000 amps because Bob said he had a 1,200 amp circuit. That is a reasonable number for an instantaneous trip current level on a 1,200 amp breaker. Even if I take the fault current down to 6000 amps, I get less than 100' for the 3/0 copper.
You can get the software and other information on the GEMI program here.
Don

 

[iwire]

250.122 is the minimum size EGC that is permitted by the code.

I agree.

250.4 may require a larger EGC.

I disagree that the wording is there for that.

They would have to spell out some sort of number that must be obtained.

 

[chris kennedy]

I based it on 12,000 amps

I'm sorry, I read it quickly and thought you based it on 1200A. Makes sense now.

 

[don_resqcapt19]

Bob,

They would have to spell out some sort of number that must be obtained.

Yes it is a subjective rule, but there are lots of them in the code. Are you saying that they are all unenforceable?
Don

 

[iwire]

Bob,

Yes it is a subjective rule, but there are lots of them in the code. Are you saying that they are all unenforceable?
Don

All I am saying is that an 'effective ground fault path' has been left in the eye of the beholder.

If I follow 250.118 / 250.122 it is my opinion I can say I have created an effective ground fault path.