250.32 (A), doubt.

[INGMRS]

Hello,

I have a doubt related to the scope of the section 250.34 (A).


I have attached as illustration a design of 4 different electrical services ( i mean 4 different houses feeded by one unique service), as it should be, and here is the question;


¿is required to install a rod in each house, and bond it to the grounding cable that has been bonded to the neutral cable in the hot gutter?


Because normally in this type of installation, in my country, people place the ground wire from the "hot gutter" after bonding it to the neutral, to the grounding bar in the house panel, and that is all.

Of course in the service side, the grounding array is made by 3 or 4 rounds of 10 ft approx. of length
I appreciate your clarification for this doubt,


Thanks in advance,

Note: I apologise for my poor english, i hope the question be clear.

 

[don_resqcapt19]

Is there an overcurrent protective device at the location of the meters?

 

[INGMRS]

Is there an overcurrent protective device at the location of the meters?

Hi,

How are you, thanks for answer,

In the hot gutter is the bonding of the neutral cable with the grounding electrode of the system, each feeder has its own main breaker after the meter. To this breaker arrive a neutral cable that is coming from the hot gutter, directly to a bar, then from this bar two cables goes to the load, to two bars independent from each other, one for neutral, and the other one for grounding.

In the drawing Is only represented the grounding cables and the grounding rods.

Muy doubt is... if it Is necessary a second rod in each building.

Regards,

 

[don_resqcapt19]

Hi,
...
Muy doubt is... if it Is necessary a second rod in each building.

Regards,

Yes, a grounding electrode system is required at each building. The grounding electrode conductor will be connected to the feeder equipment grounding conductor at the disconnects in each building.
The language in 250.32(A) requires a grounding electrode at every building or structure that is supplied by a feeder. The fact that you have one at the meter/disconnect does not change anything. Grounding electrodes are required at both locations.

 

[INGMRS]

Yes, a grounding electrode system is required at each building. The grounding electrode conductor will be connected to the feeder equipment grounding conductor at the disconnects in each building.
The language in 250.32(A) requires a grounding electrode at every building or structure that is supplied by a feeder. The fact that you have one at the meter/disconnect does not change anything. Grounding electrodes are required at both locations.

Hello don_resqcapt19,


Thanks for your reply,


This is quite interesting, because during several trainings, the instructors say that this second "rod" is not necessary, they say that if you lay down the GEC from the meter to the grounding bar in the panelboard inside the building (house or structure), everything is bonded, so is not necessary at all.


But, as i understood you, all the houses in USA have a second rod or grounding electrode in the load side, just near to the panelboard, right?


By other way, could it be a parallel route for a lightning?


Again, thanks for your answer,


Regards,

 

[rambojoe]

How many conductors in the overhead (suspended) cables? 2 hot and one bare? this also dictates what/where to bond and what not to bond.

 

[Adamjamma]

By your response to Don, I am assuming that you are using a PEN conductor system, such as in UK or Europe, to create the single phase system in the home? If so, you are correct..no ground rod usually needed for the home as the ground and neutral are connected back to the transformer. But, you still must bond to the other utilities... gas, cable, telephone, water, etc... unless the other utilities enter using a non conductive piping, in the case of gas or water...

but, your system would not be subject then to the NEC, as I understand.

 

[don_resqcapt19]

By your response to Don, I am assuming that you are using a PEN conductor system, such as in UK or Europe, to create the single phase system in the home? If so, you are correct..no ground rod usually needed for the home as the ground and neutral are connected back to the transformer. But, you still must bond to the other utilities... gas, cable, telephone, water, etc... unless the other utilities enter using a non conductive piping, in the case of gas or water...

but, your system would not be subject then to the NEC, as I understand.

We typically don't create a single phase system for swelling units. Most are fed from the secondary of a transformer that supplies 120/240 three wire to the dwelling unit. The neutral is connected to earth at the secondary of the transformer by the utility, and connected again to the earth by the electrician at the building service disconnect. Once you are on the load side of the service disconnect, no additional connections are permitted between the neutral and earth.

The application in this thread has feeder conductors running to the buildings from the service disconnect. Those circuits would have two ungrounded conductors, a neutral (grounded) conductor and an equipment grounding conductor. A grounding electrode system is required at the building and the grounding electrode conductor if required to connect the feeder equipment grounding conductor at the building disconnect.

 

[don_resqcapt19]

How many conductors in the overhead (suspended) cables? 2 hot and one bare? this also dictates what/where to bond and what not to bond.

Unless it is an existing installation, installed prior to the 2008 code, you don't have a choice as to the number of conductors run to the buildings. The code requires the ungrounded conductors, the grounded conductor, and an equipment grounding conductor.

 

[INGMRS]

By your response to Don, I am assuming that you are using a PEN conductor system, such as in UK or Europe, to create the single phase system in the home? If so, you are correct..no ground rod usually needed for the home as the ground and neutral are connected back to the transformer. But, you still must bond to the other utilities... gas, cable, telephone, water, etc... unless the other utilities enter using a non conductive piping, in the case of gas or water...

but, your system would not be subject then to the NEC, as I understand.

Hello adamjamma


The NEC (the latest version in Spanish) is currently the official electrical standard for the country, and we usually have 4 cables, 2 hot wires, neutral and ground wire, (could be done with quadruplex if it's by air, or series 8000, THHN inside), the ground cable is connected to the neutral in the main switch, that is, after the meter, or inside the "hot gutter", if there are several feeders for a single service.


We do not use gas, and our entire water system is made with PVC pipes. therefore, the grounding system is for receptacles and special outlets, such as a thermic shower, cloth dryer or electric heater (i mean for houses)


Due to our climate, we do not need heating or air conditioning.


Regards,

 

[INGMRS]

We typically don't create a single phase system for swelling units. Most are fed from the secondary of a transformer that supplies 120/240 three wire to the dwelling unit. The neutral is connected to earth at the secondary of the transformer by the utility, and connected again to the earth by the electrician at the building service disconnect. Once you are on the load side of the service disconnect, no additional connections are permitted between the neutral and earth.

The application in this thread has feeder conductors running to the buildings from the service disconnect. Those circuits would have two ungrounded conductors, a neutral (grounded) conductor and an equipment grounding conductor. A grounding electrode system is required at the building and the grounding electrode conductor if required to connect the feeder equipment grounding conductor at the building disconnect.

Don,


This apply also for houses? the section says "Buildings and Structures"


I mean, if is only one house, but the service breaker and the meter are in the limit of the property, is it required?


One question else, in a tipical home in USA, do you connect a "grounding rod" in the load side?


Thanks,

 

[Adamjamma]

Ok, I looked it up and you are using the NESC, which is put out by the IEEE... changes every five years and is currently in eight edition...

I normally am in Jamaica, which is considering the NEC or the NESC, so has a few of us studying both in regards to the last Jamaican code book and the British and Canadian codes. Which is one reason I am currently in the UK studying the BS7671.

your electricity system.. is it USA based like Jamaica’s, running from Transformers to meters to disconnects then to residence? With the meter and main disconnect requiring a ground rod? Then neutral, live and ground from disconnect to breaker panel?
Or is it a live and PEN conductor from the transformer, to the meter, and then live, neutral and ground to the panel, like many European countries? I know that one reason the proposed caricom electrical code never got off the ground was the multitude of systems in the Caribbean.

 

[INGMRS]

Ok, I looked it up and you are using the NESC, which is put out by the IEEE... changes every five years and is currently in eight edition...

I normally am in Jamaica, which is considering the NEC or the NESC, so has a few of us studying both in regards to the last Jamaican code book and the British and Canadian codes. Which is one reason I am currently in the UK studying the BS7671.

your electricity system.. is it USA based like Jamaica’s, running from Transformers to meters to disconnects then to residence? With the meter and main disconnect requiring a ground rod? Then neutral, live and ground from disconnect to breaker panel?
Or is it a live and PEN conductor from the transformer, to the meter, and then live, neutral and ground to the panel, like many European countries? I know that one reason the proposed caricom electrical code never got off the ground was the multitude of systems in the Caribbean.

Hi,

We are currently using the NEC 2014 from USA (Spanish versión), and yes we bond the neutral from the secundary of the transformer with the grounding electrode in the main disconnect service, and then four conductors (L1,L2,N,GEC) goes to the main panel of the residencial, just like is in the drawing.

Regards,

 

[don_resqcapt19]

Don,
This apply also for houses? the section says "Buildings and Structures"

A house is a building. A structure is most everything else, other than equipment.

I mean, if is only one house, but the service breaker and the meter are in the limit of the property, is it required?

If the service disconnect is not located at the building or structure, you are required to run 4 conductors to the building or structure and provide a grounding electrode that is connected to the feeder equipment grounding conductor.

One question else, in a tipical home in USA, do you connect a "grounding rod" in the load side?
Thanks,

In general a grounding electrode is never connected to the neutral or grounded conductor on the load side of the service disconnect. In a typical US dwelling unit, the utility runs two ungrounded conductors and the grounded conductor to the building. The electrician connects those conductors to the service equipment (disconnect and OCPD). He will also install grounding electrodes and connect them to the neutral at the service equipment. Having the service equipment remote from the house, is not typical.

 

[Adamjamma]

Don, it is in the caribbean, though... Meters are usually located at the property line and then the disconnect is located a lot of times on the property side but there as well, with a lock on it that the firemen can cut if they need to disconnect the services. Sometimes you are allowed to mount the disconnect on your building but it is almost always an exterior mount. Then you run inside to a main panel.

All this is due to hurricane and earth quakes...

Some of the countries in the caribbean are under NESC which at one time I believe was the International Electrical Codes compared to the NEC... Because I still have a copy of the IEC on my shelf in Jamaica from the Eighties.
Others have adopted the Caricom Unified Electrical Code, others are using the Canadian Electrical Code, and others are on the NEC... or are using old Dutch, English, French or Spanish electrical codes that are Pre-Harmonization.

Thus we have things like wire colors that are Black- White Green *NEC Based
Red - Black -Green/yellow UK Based
Blue- Brown- Green/yellow Europe Based

and an electrician licensed on most of the islands with a caricom passport can work on the other islands but is expected to know automatically the code changes etc on those islands along with how to wire for appliances from 220 countries.

 

[INGMRS]

Don, it is in the caribbean, though... Meters are usually located at the property line and then the disconnect is located a lot of times on the property side but there as well, with a lock on it that the firemen can cut if they need to disconnect the services. Sometimes you are allowed to mount the disconnect on your building but it is almost always an exterior mount. Then you run inside to a main panel.

All this is due to hurricane and earth quakes...

Some of the countries in the caribbean are under NESC which at one time I believe was the International Electrical Codes compared to the NEC... Because I still have a copy of the IEC on my shelf in Jamaica from the Eighties.
Others have adopted the Caricom Unified Electrical Code, others are using the Canadian Electrical Code, and others are on the NEC... or are using old Dutch, English, French or Spanish electrical codes that are Pre-Harmonization.

Thus we have things like wire colors that are Black- White Green *NEC Based
Red - Black -Green/yellow UK Based
Blue- Brown- Green/yellow Europe Based

and an electrician licensed on most of the islands with a caricom passport can work on the other islands but is expected to know automatically the code changes etc on those islands along with how to wire for appliances from 220 countries.

Hi,

All that you say Is not about our country, first, se are located in Central America, the meter and the main disconnect service, both, are in the limit of the property due to the accesibility of the utility company to read the consume kwh of the client, however in some areas this measurament is remote.
All relative to the instalation, specification and design is according to the NEC from USA, and the IEEE standards, mainly because our system works with a 60Hz Frecuency, San Jose capital of Costa Rica, was the third city lighted in the world, so we have standards for Power system pretty defined.
And i never have seen people from Jamaica or other island coutry working as electrician here.
My doubt with the 250.32(A), was related the definition of separated buildings and its approch, but it has been clarify by don now.

Thanks for your interest and the info of the diferent codes in the caribbean.

Regards,

 

[INGMRS]

A house is a building. A structure is most everything else, other than equipment.


If the service disconnect is not located at the building or structure, you are required to run 4 conductors to the building or structure and provide a grounding electrode that is connected to the feeder equipment grounding conductor.


In general a grounding electrode is never connected to the neutral or grounded conductor on the load side of the service disconnect. In a typical US dwelling unit, the utility runs two ungrounded conductors and the grounded conductor to the building. The electrician connects those conductors to the service equipment (disconnect and OCPD). He will also install grounding electrodes and connect them to the neutral at the service equipment. Having the service equipment remote from the house, is not typical.

Don,

Definitely we are agreed that the ground bar, and the neutral bar should not be connected at the load side. We dont want current flowing by the grounding wire.

Thanks a lot for your clarification, now i have a technical doubt regarding the need of this second rod, of course the main reason would be the lightning strike at the load side.

Thanks and Regards

 

[don_resqcapt19]

...
Some of the countries in the caribbean are under NESC ...

The NESC is the National Electrical Safety Code and is the "utility" code. It addresses utility power transmission and distribution. It does not address the wiring of buildings. It stops at the "service point", the point where the building conductors connect to the utility conductors.

 

[jumper]

Don,

Definitely we are agreed that the ground bar, and the neutral bar should not be connected at the load side. We dont want current flowing by the grounding wire.

Thanks a lot for your clarification, now i have a technical doubt regarding the need of this second rod, of course the main reason would be the lightning strike at the load side.

Thanks and Regards

Are you asking about the need to install 2 rods instead of just one at each house?

If ground rods are your only electrodes being used for the GES, then the NEC requires that a second one called a supplemental electrode be installed unless you can prove a resistance of 25 ohms or less.

NEC section 250.53 covers this.

Usually we just add the second rod because it is easier than testing.

 

[JPinVA]

Hello don_resqcapt19,

But, as i understood you, all the houses in USA have a second rod or grounding electrode in the load side, just near to the panelboard, right?

Yes. The primary purpose of the grounding electrode (ground rod) and connections is to dissipate over voltages from lightning, and static electricity, etc. For lightning overvoltages, a short path is best because impedance factors become a dominant issue with lightning. You want those to bleed to ground in as short a run as a possible (i.e., at the structure grounding electrode).

You are also correct that once you establish the second ground, you've established a parallel path via the ground. I believe our NEC is written the way it is because the danger at the structure (due to overvoltages from lightning) is considered more dangerous than the parallel path created by the two ground points. We accept the relatively small problem with the parallel ground path to solve the bigger problem of lightning.