WHAT is the Difference between the expression Earthing and Grounding

[romex jockey]

We don't need to add the term earthing...we just need to use the term grounding only for conductors that connect directly to a grounding electrode. All of the other conductors in the NEC that use the word grounding are really bonding conductors as they do not connect directly to a grounding electrode.

Then perhaps i should rethink this....

Iirc, from the wayback machine, wasn't it 'All grounding is bonding, but not all bonding is grounding' ...do i have that right Don?

If so, why can't it be expressed in our terminology in such a way that this is evident?

~RJ~

 

[peter d]

Personally, I think the key is better education on what these conductors and earth connections actually do, and don't do. Changing the terms won't mean much if people are still believing falsehoods about grounding and bonding.

 

[haitham]

IF I may ask, what are the requirements for TN-C-S and TN-S in your country with grounding electrodes?

here at Egypt ,code depends on IEC and BS requirements and relating to earthing system it is the same requirements of BS 7430

 

[don_resqcapt19]

Then perhaps i should rethink this....

Iirc, from the wayback machine, wasn't it 'All grounding is bonding, but not all bonding is grounding' ...do i have that right Don?

If so, why can't it be expressed in our terminology in such a way that this is evident?

~RJ~

I like that.

I tried to get Equipment Grounding Conductor changed to Equipment Bonding Conductor in the 1995 code cycle...a majority of CMP 5 agreed but that majority was one vote short of the 2/3s majority that is required to accept a change.

 

[don_resqcapt19]

Personally, I think the key is better education on what these conductors and earth connections actually do, and don't do. Changing the terms won't mean much if people are still believing falsehoods about grounding and bonding.

The Canadian Electrical Code changed from Equipment Grounding Conductor to Equipment Bonding Conductor a number of years ago and some of their instructors have told me that the change has made it much easier to teach these concepts.

 

[mbrooke]

here at Egypt ,code depends on IEC and BS requirements and relating to earthing system it is the same requirements of BS 7430

Sounds good. But what type of earthing system is normal? TT, TN-C-S or TN-S?

 

[Tony S]

Egypt comes under International Electrotechnical Commission. All member countries of the commission have clearly defined terms of reference for earthing and bonding.

This may help

http://www.legrand.com/files/fck/File/pdf/Guide-International.pdf

 

[mbrooke]

Awesome doc, thanks


In terms of what the OP mentioned, doesn't the UK (or other IEC countries) use grounding electrodes to help with an open neutral in some cases?

 

[romex jockey]

I like that.

well i believe i got it from you quite some time ago Don....

I tried to get Equipment Grounding Conductor changed to Equipment Bonding Conductor in the 1995 code cycle...a majority of CMP 5 agreed but that majority was one vote short of the 2/3s majority that is required to accept a change.

A shame , methinks it would have gained clarity for so many art 250 misconceptions.....~RJ~

 

[romex jockey]

Sounds good. But what type of earthing system is normal? TT, TN-C-S or TN-S?

Well we can look up who does what , along with the pro's/con's

But then some systems don't have a neutral at all , which when we draw out a M.E.N. system , looks like we're using the entire structure, if not neighborhood as a 'return' conductor

~RJ~

 

[mbrooke]

Well we can look up who does what , along with the pro's/con's

But then some systems don't have a neutral at all , which when we draw out a M.E.N. system , looks like we're using the entire structure, if not neighborhood as a 'return' conductor

~RJ~

Id be skeptical of wikipedia... however each does have its pros and cons.


TN-C-S, and TN-C is often nothing more than a MEN system in many cases just because of so many parallel paths. With water, phone, metal footings it all becomes one noodle.

 

[mbrooke]

Well we can look up who does what , along with the pro's/con's

But then some systems don't have a neutral at all , which when we draw out a M.E.N. system , looks like we're using the entire structure, if not neighborhood as a 'return' conductor

~RJ~

Although departing from the NEC this is rather interesting, though Id argue partially incorrect:

 

[romex jockey]

Id be skeptical of wikipedia... however each does have its pros and cons.

10-4 Mr MBrooke, the 'self correcting' feature is...well.....somewhat less than efficient...

TN-C-S, and TN-C is often nothing more than a MEN system in many cases just because of so many parallel paths. With water, phone, metal footings it all becomes one noodle.

Oh Gawd yes, One can hear Kirchoff's ghost chucklin' along rather frequently...

~RJ~

 

[mbrooke]

10-4 Mr MBrooke, the 'self correcting' feature is...well.....somewhat less than efficient...

I know right? :lol:

For example, they say no risk of broken neutral in IT and TT, but a high one in TN-S. Assuming they mean risk of touch potential that is completely untrue. In TN-S the neutral from the point of origin to the load is just as isolated from earth/grounding system as TT and IT.

TN-C-S and Tn-C is where the danger is legit.

Oh Gawd yes, One can hear Kirchoff's ghost chucklin' along rather frequently...

~RJ~

In many such system grounding and bonding masks an open noodle, often effectively. In fact, it is often a primary driver. One of the reasons behind the heavy bonding of pools is if the POCO MGN opened it protects the people in the pool from the massive voltage gradients that would arise. And the mild ones that arise from TN-C/MEN in the first place.

 

[haitham]

Sounds good. But what type of earthing system is normal? TT, TN-C-S or TN-S?

it is a combined of TT and TNC-S,
TT system is used for big areas specially domestic areas ,although some places may be high level of living using TNC-S and they using electrodes vertical rods ,also as strips in the building foundation or others shapes ,1:5 ohm earth resistance is sound good here some places cant get it so they working in improve soil resistivity by coke coal or other chemical materials .. most of formulas refers to BS ,
TN-c is common in factories although in the same factory using combined of TNC-S and TT for some parts ..
bonding is required here but they just say for making NO VOLTAGE DIFFERENCE BETWEEN CHASSIS MAY TOUCHED AT THE SAME TIME
IT isn't recommended here

 

[mbrooke]

it is a combined of TT and TNC-S,
TT system is used for big areas specially domestic areas ,although some places may be high level of living using TNC-S and they using electrodes vertical rods ,also as strips in the building foundation or others shapes ,1:5 ohm earth resistance is sound good here some places cant get it so they working in improve soil resistivity by coke coal or other chemical materials .. most of formulas refers to BS ,

Is this low impedance to guard against open neutral? Or other reasons?

TN-c is common in factories although in the same factory using combined of TNC-S and TT for some parts ..
bonding is required here but they just say for making NO VOLTAGE DIFFERENCE BETWEEN CHASSIS MAY TOUCHED AT THE SAME TIME
IT isn't recommended here

Sounds good.

 

[haitham]

Is this low impedance to guard against open neutral? Or other reasons?


.

contrary to NEC ,here they using the earth as a ground fault current path ,so the low impedance to pass enough current to trip the OCD ,, here OCD or RCD is allowed for TT and TNC-S ,
and essentially to limit the touching voltage on the equipment during GF.

Lightning system is apart away and have its own system,electrodes...

 

[mbrooke]

contrary to NEC ,here they using the earth as a ground fault current path ,so the low impedance to pass enough current to trip the OCD ,and essentially to limit the touching voltage on the equipment during GF.

Lightning system is apart away and have its own system,electrodes...

But for TT you are required to have an RCD, correct?

 

[haitham]

But for TT you are required to have an RCD, correct?

yea it is allowed to use both RCD or OCD ,for OCD the using this equation the impedance of fault path = source voltage /n*In
where In is the rated current of OCD ,and n is multiple depend on the class of OCD , but yes it is recommended to use RCD if low res path can't be achieved

 

[haitham]

During an open utility neutral the RCD will not trip, no matter how sensitive. All current flowing in and out of the appliance will go through the RCD, into the panel, and then through the PEs.

.

why RCD ill not trip
for TNC-S when N opened the current will path from Line to PE to the electrode backing to the source through mass of Earth there will be difference between the current in Line and N so RCD have to trip ?