adding test procedures to the NEC code

[gnuuser]

well Ive joined the NEC forum and sent a post about adding a testing procedure section to the code book
heres the post.

I know that testing procedures are taught in apprenticeship but Ive found it to be severely lacking in clarity and tends to be an issue with many apprentices not being taught properly.
I would like to see a section in the codes that covers proper testing procedures and standard practices as well as proper documentation of results.
there should be no question on what procedures to follow and how to carry them out

we'll see if it flies or goes over like a lead balloon

 

[Engineer54]

You need to mention the correct sequence in which these tests should be conducted and what tests you'd like to see incorporated??

So, ...how are you getting on with the new Earth Loop Impedance meter you recently purchased?? What was the on-line English manual link like that gave you?? Was it more Chinglish than English?? lol!!

 

[gnuuser]

love it it works great
our local inspector is happy that ive got one
and i'll probably be getting a lot of calls from him
got the manual in english and have located a company that will do the calibration if
and i saved the testing sequence you fellas have posted before as a reference for them

 

[gnuuser]

You need to mention the correct sequence in which these tests should be conducted and what tests you'd like to see incorporated??

well submitted the proposal to the nfpa site for code change so we'll see how it goes

 

[Engineer54]

love it it works great
our local inspector is happy that ive got one
and i'll probably be getting a lot of calls from him
got the manual in english and have located a company that will do the calibration if
and i saved the testing sequence you fellas have posted before as a reference for them

Any chance of posting that English link for the manual gnuuser, i'd be interested to see it??

 

[gnuuser]

here is the site they refered to for download of the english manual
pdf file
http://storeinfinity.com/dy4100-digital-earth-ground-resistance-tester-meter.html

 

[Engineer54]

here is the site they refered to for download of the english manual
pdf file
DY4100 Digital Earth Ground Resistance Tester

Sorry gnuuser, but that tester isn't an Earth Loop Impedance meter, it's a straight foward 3 point earth/ground resistance meter!! Check out the forum sponsor website at the top of the page to see various ELI meters and their function. (test-meter.co.uk)

 

[gnuuser]

Sorry gnuuser, but that tester isn't an Earth Loop Impedance meter, it's a straight foward 3 point earth/ground resistance meter!! Check out the forum sponsor website at the top of the page to see various ELI meters and their function. (test-meter.co.uk)

ok will check it out later
have to go see my father
went to hospital last night

 

[Richard Burns]

ok will check it out later
have to go see my father
went to hospital last night

I hope all is well.

 

[gnuuser]

yes hes doing ok , a bit sore though
had a cellulitis infection and infected bursa under the knee cap
they drained it and have him on a strong anti-biotic




ill probably get this meter as it will probably suit the need better for loop testing.
http://www.test-meter.co.uk/martindale-ez2500-e-ze-test/

but the ground resistance meter will still come in handy for new installation (more tests and happier inspectors)

 

[Engineer54]

yes hes doing ok , a bit sore though
had a cellulitis infection and infected bursa under the knee cap
they drained it and have him on a strong anti-biotic




ill probably get this meter as it will probably suit the need better for loop testing.
Martindale EZ2500 E-Ze Test Non-Trip Loop Tester, EZ-2500 16th Edition Tester

but the ground resistance meter will still come in handy for new installation (more tests and happier inspectors)

Very handy, as TT earthing is almost the norm in many areas of the States!! Not just for new installations either, also use to test existing earth electrodes at various times of the year (Spring / Summer/ Winter) to check for stability of the electrode.


Not sure that particular ELI meter will be suitable for you in the States. Try looking for a budget meter that is suitable for your 120/240v system and supplied with test leads (rather than just a receptacle plug top) that's available in the States. Possibly from the same Chinese manufacturer as the earth tester you recently purchased (not all Chinese products are cheap tat (crap), some are well made bits of kit). Oh and forget about the no-trip function, this is for 30mA GFCI's not your 5/6mA GFCI breakers!! lol!!

Glad to hear the old boy's on the mend!! lol!!

 

[Gardner]

Very handy, as TT earthing is almost the norm in many areas of the States!! Not just for new installations either, also use to test existing earth electrodes at various times of the year (Spring / Summer/ Winter) to check for stability of the electrode.


Not sure that particular ELI meter will be suitable for you in the States. Try looking for a budget meter that is suitable for your 120/240v system and supplied with test leads (rather than just a receptacle plug top) that's available in the States. Possibly from the same Chinese manufacturer as the earth tester you recently purchased (not all Chinese products are cheap tat (crap), some are well made bits of kit). Oh and forget about the no-trip function, this is for 30mA GFCI's not your 5/6mA GFCI breakers!! lol!!

Glad to hear the old boy's on the mend!! lol!!

You mean the United states? TT earth is absolutely forbidden in the United States. In fact it has never been used, most electricians haven't even heard of it.

 

[Engineer54]

You mean the United states? TT earth is absolutely forbidden in the United States. In fact it has never been used, most electricians haven't even heard of it.

Really, Perhaps you can explain to us why this earthing method is described in in NFPA 70 (NEC) and even gives a maximum Ra value of 25 ohms for a single earth rod, or a second rod must be provided.
So either you don't know or unfamiliar with the term ''TT'' system, (which i suspect is the case here), or you haven't a clue what you're talking about.... because earth (ground) rods are probably the most prominent means of providing and earth (ground) point, especially for domestic installations in USA. Now tell me that again that TT earthing (grounding) systems is absolutely forbidden, and has never been used??

Perhaps i'd better explain that i've worked on several large overseas projects over the years where your NEC has been the Specifications electrical standard, so i'm more than well versed in it's content, as well as the electrical red, green, buff etc books !!

 

[Gardner]

Really, Perhaps you can explain to us why this earthing method is described in in NFPA 70 (NEC) and even gives a maximum Ra value of 25 ohms for a single earth rod, or a second rod must be provided.
So either you don't know or unfamiliar with the term ''TT'' system, (which i suspect is the case here), or you haven't a clue what you're talking about.... because earth (ground) rods are probably the most prominent means of providing and earth (ground) point, especially for domestic installations in USA. Now tell me that again that TT earthing (grounding) systems is absolutely forbidden, and has never been used??

Perhaps i'd better explain that i've worked on several large overseas projects over the years where your NEC has been the Specifications electrical standard, so i'm more than well versed in it's content, as well as the electrical red, green, buff etc books !!

That has absolutely nothing to do with clearing a fault. Tell me, since you are so versed, using ohms law: how does 25 ohms generate enough fault current to trip a non RCD breaker, which accounts for 99.99% of American breakers?

And if you are so well versed in the NEC, you would know more than well that a bonding jumper is required at every American service where a neutral is present.

To tell me who lives in the US, spent decades applying the NEC, and working with power systems first hand that TT earthing is routine in the USA is beyond arrogant.

If you are wiring power system as TT overseas using NFPA 70 you are going to get someone killed if you have no already. Perhaps that is why I hear so much stories of people being electrocuted overseas. Your line thinking is beyond mortifying.

 

[davesparks]

I was under the impression that most installations in the USA were TNCS with an additional earth electrode connected to the MET (or American equivalent of MET)

 

[Gardner]

I was under the impression that most installations in the USA were TNCS with an additional earth electrode connected to the MET (or American equivalent of MET)

All installations in America are TN-C-S. TT has never been used and is absolutely forbidden. The extra rods are more for lightning protection and higher voltage contact, but nothing to do with fault clearing.

 

[Rockingit]

[......goes off to get the popcorn..]

 

[Ultrafault]

Really, Perhaps you can explain to us why this earthing method is described in in NFPA 70 (NEC) and even gives a maximum Ra value of 25 ohms for a single earth rod, or a second rod must be provided.
So either you don't know or unfamiliar with the term ''TT'' system, (which i suspect is the case here), or you haven't a clue what you're talking about.... because earth (ground) rods are probably the most prominent means of providing and earth (ground) point, especially for domestic installations in USA. Now tell me that again that TT earthing (grounding) systems is absolutely forbidden, and has never been used??

Perhaps i'd better explain that i've worked on several large overseas projects over the years where your NEC has been the Specifications electrical standard, so i'm more than well versed in it's content, as well as the electrical red, green, buff etc books !!

Dear Sir,

When I read your post I was motivated to create an account.

I am a Master electrician licensed in Missouri. Gardner is absolutely correct. I am afraid when you fully research your mistake you will find it hard to sleep. The situation you have described creating would be extremely dangerous. All electrical systems in the United States must have the X0 terminal (neutral) bonded to all metal associated with the electrical system and in fact all structural metal in a building. Without this provision there is no way for a breaker to clear a fault. Your groud rod will hower provide voltage gradients to electrocute people.

 

[Engineer54]

Well for a kick off, on the overseas projects i'm involved in, ground fields are the norm with Ra values always being sub 0.5 ohm's. TNC-S is never used, all LV distribution is always TN-S....

Now i've worked with or known a good few American Engineers and what you call Master Electricians over the years and from what they have told me, is it's the common practice to connect an earth electrode to the MET of every installation. None have mentioned anything about using TNC-S, so i'm now suspecting that N-E links at the service heads are the means of ensuring a low Ze via the TT earth electrodes connection at the MET??

So if i have somehow misunderstood what i've been told in the past, then i apologize....

By the way, how do you test that the Ze at the origin of every properties supply meets the requirements to trip final circuit breakers in the required time?? As far as i remember, your breakers had pretty high time/current curves that were in the region of 15 to 20X the rating of the breaker.

Surely you don't use TNC-S earthing systems on say factory installations where dedicated on site MV-LV distribution transformers are present, ...or do you??

 

[Gardner]

Well for a kick off, on the overseas projects i'm involved in, ground fields are the norm with Ra values always being sub 0.5 ohm's. TNC-S is never used, all LV distribution is always TN-S....

Now i've worked with or known a good few American Engineers and what you call Master Electricians over the years and from what they have told me, is it's the common practice to connect an earth electrode to the MET of every installation. None have mentioned anything about using TNC-S, so i'm now suspecting that N-E links at the service heads are the means of ensuring a low Ze via the TT earth electrodes connection at the MET??

So if i have somehow misunderstood what i've been told in the past, then i apologize....

By the way, how do you test that the Ze at the origin of every properties supply meets the requirements to trip final circuit breakers in the required time?? As far as i remember, your breakers had pretty high time/current curves that were in the region of 15 to 20X the rating of the breaker.

Surely you don't use TNC-S earthing systems on say factory installations where dedicated on site MV-LV distribution transformers are present, ...or do you??

A ground rod is required at every service entrance if no UFER (concerte rebar) is present. Even if the supply is TN-S, a ground rod is still driven. Only 1, and if over 25ohms 2 and thats it. Low ground rod Zs are not a requirment in the NEC. Perhaps a job spec but its not considered an issue even if 2 ground rods are 10,000ohms. as long as the grounding system has 2 then everything is all set.


What clears a fault in the NEC is a required link from the neutral to the grounding system (bonding jumper) at the supply transformer or service. The ground rod is not considered in earth fault loop impedance, even though required by code. Once an appropriate bonding jumper is in place, it is this that provides a low earth fault loop impedance to trip a breaker. All installations are like this in the NEC. TT earthing is never allowed. IT is in some cases but limited.



Here is on video on the subject:

https://www.youtube.com/watch?v=qNZC782SzAQ

Short version

https://www.youtube.com/watch?v=xn4az8EuNO0