Single Point Ground
- Thread starter bennie
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hurk27
Senior Member
- Location
- Portage, Indiana NEC: 2008
Re: Single Point Ground
This would depend on how one would look at it.
single point connection at the service or single point connection at the electrode. The NEC describes the connection at the service as being a single point when all the EGC's connect at that point. but as you have said this does give multiple points of connection to earth. the question is which point being single would provide the most safety? I think this should be analyzed.
In my studies of lightning when I was in Florida we found that the more rod's spaced properly that you have in the ground the better protection you will have. also the lower the resistance will be to earth. so having a single point ground at the electrode seems to defeat the purpose of installing more GE's into the earth as it is known that the greater the separation of the GC'S the better the effect of the bond to earth.
And if you only have one point of connection there is a chance that you wont even meet the 25 ohm requirement of the NEC.
Now a quick look at multi-point connection at the service.
If we make connections to the service at more that one point we stand a chance of inducing voltage gradients across the multiple points and also we are giving lightning paths into our homes when we should be directing it out of the home. fault currents will even magnify the problem by putting the voltages on grounded metal that could be high enough to cause a shock.
So to sum it up I think that having a single point connection at the service would be the best choice and provide the safest installations.
This would depend on how one would look at it.
single point connection at the service or single point connection at the electrode. The NEC describes the connection at the service as being a single point when all the EGC's connect at that point. but as you have said this does give multiple points of connection to earth. the question is which point being single would provide the most safety? I think this should be analyzed.
In my studies of lightning when I was in Florida we found that the more rod's spaced properly that you have in the ground the better protection you will have. also the lower the resistance will be to earth. so having a single point ground at the electrode seems to defeat the purpose of installing more GE's into the earth as it is known that the greater the separation of the GC'S the better the effect of the bond to earth.
And if you only have one point of connection there is a chance that you wont even meet the 25 ohm requirement of the NEC.
Now a quick look at multi-point connection at the service.
If we make connections to the service at more that one point we stand a chance of inducing voltage gradients across the multiple points and also we are giving lightning paths into our homes when we should be directing it out of the home. fault currents will even magnify the problem by putting the voltages on grounded metal that could be high enough to cause a shock.
So to sum it up I think that having a single point connection at the service would be the best choice and provide the safest installations.
Re: Single Point Ground
Wayne: All the equipment ground conductors will connect to the service neutral/ground by default, there's no where else to connect them.
Add a second panel and the equipment ground conductors, from the panel, will land at the ground bus in that panel. Now there's two places where the wires are grounded.
Wayne: All the equipment ground conductors will connect to the service neutral/ground by default, there's no where else to connect them.
Add a second panel and the equipment ground conductors, from the panel, will land at the ground bus in that panel. Now there's two places where the wires are grounded.
Re: Single Point Ground
Bennie, there is two definitions for single point ground.
1. SPG For Power Supplies: Where one current-carrying member of a separately derived power source is connected to a ground reference at only one point, it is single point grounded. In contrast to this, grounded conductors having more than connection to a ground reference along their length are classified as multigrounded systems.
Two examples of single point grounded power supplies are:
a. A -48 volt dc power plant power source supplying an isolated ground plane digital switching loads is grounded by a single connection from the insulated ?48 volt return buss in the power plant to the main grounding bus (MGB) within the ground window serving the system.
b. The ac power service to a building or a step-down/isolation transformer is grounded by a single connection from its neutral to the building grounding electrode system.
Single-Point Ground For Equipment Frames: A method used to ground a set of equipment frames for a given electronic entity that can have only one grounding connection from a given set of frames to a planned ground reference. Because this set of frames does not have multi-connections (either planned or incidental) to other ground planes, it is classified as an isolated ground plane.
It is almost impossible to construct a true single point ground system. To construct a SPG from a AC electrical distribution system would require establishing a "Ground Window" at the service entrance, and completely isolating all equipment and raceways from concrete, building steel, metallic objects, etc (called the integrated ground plane) downstream from the ground window. Only place I have seen it done is in telephone offices on digital switching and transmission equipment. If you succeed in a true SPG it is impossible for outside currents (common mode) and fault currents such as lightning to flow in the isolated ground plane. If compromised at one point, all effort is lost, and damage is likely to occur.
So Bennie I know where you are heading. It is not feasible or practical for most to construct SPG to eliminate common mode currents. The other side of the coin is to construct a multiground (many connections to building earth electrode system) reference for the equipment frames to minimize voltages developed in the common mode and SPG the power source.
Bennie, there is two definitions for single point ground.
1. SPG For Power Supplies: Where one current-carrying member of a separately derived power source is connected to a ground reference at only one point, it is single point grounded. In contrast to this, grounded conductors having more than connection to a ground reference along their length are classified as multigrounded systems.
Two examples of single point grounded power supplies are:
a. A -48 volt dc power plant power source supplying an isolated ground plane digital switching loads is grounded by a single connection from the insulated ?48 volt return buss in the power plant to the main grounding bus (MGB) within the ground window serving the system.
b. The ac power service to a building or a step-down/isolation transformer is grounded by a single connection from its neutral to the building grounding electrode system.
Single-Point Ground For Equipment Frames: A method used to ground a set of equipment frames for a given electronic entity that can have only one grounding connection from a given set of frames to a planned ground reference. Because this set of frames does not have multi-connections (either planned or incidental) to other ground planes, it is classified as an isolated ground plane.
It is almost impossible to construct a true single point ground system. To construct a SPG from a AC electrical distribution system would require establishing a "Ground Window" at the service entrance, and completely isolating all equipment and raceways from concrete, building steel, metallic objects, etc (called the integrated ground plane) downstream from the ground window. Only place I have seen it done is in telephone offices on digital switching and transmission equipment. If you succeed in a true SPG it is impossible for outside currents (common mode) and fault currents such as lightning to flow in the isolated ground plane. If compromised at one point, all effort is lost, and damage is likely to occur.
So Bennie I know where you are heading. It is not feasible or practical for most to construct SPG to eliminate common mode currents. The other side of the coin is to construct a multiground (many connections to building earth electrode system) reference for the equipment frames to minimize voltages developed in the common mode and SPG the power source.
Re: Single Point Ground
Excellent composition Dereck. Where I am hoping to go with this topic is to call attention to ground conductor routing and connection points must be planned and not indiscriminately done.
I know there is many contacts with earth by the electrical equipment. These have varying degrees of impedance. They are not planned, they happen.
The planned earth connection should only be at one place and connected at the service. Any other earth contact that produces unwanted current flow can be isolated if necessary.
A planned earth connection, other than the one at the service, is a code violation.
Excellent composition Dereck. Where I am hoping to go with this topic is to call attention to ground conductor routing and connection points must be planned and not indiscriminately done.
I know there is many contacts with earth by the electrical equipment. These have varying degrees of impedance. They are not planned, they happen.
The planned earth connection should only be at one place and connected at the service. Any other earth contact that produces unwanted current flow can be isolated if necessary.
A planned earth connection, other than the one at the service, is a code violation.
charlie
Senior Member
- Location
- Indianapolis
Re: Single Point Ground
Bennie, I assume you feel like the Code prohibits the addition of supplimental grounding electrodes at various points in the electrical system and connected to the grounding conductor of a branch circuit or feeder? It is my guess that you are just spoiling for a fight! LOL Nah, you wouldn't do that . . . would you/
Bennie, I assume you feel like the Code prohibits the addition of supplimental grounding electrodes at various points in the electrical system and connected to the grounding conductor of a branch circuit or feeder? It is my guess that you are just spoiling for a fight! LOL Nah, you wouldn't do that . . . would you/
Re: Single Point Ground
No Charlie. Supplemental electrodes are permitted for connecting to the earth as long as they are properly bonded to the other electrodes making up the ground plane. When not bonded,(shorted), they constitute multi-ground points.
It involves focusing the current by utilizing an inductor and impedance, as the highway.
No Charlie. Supplemental electrodes are permitted for connecting to the earth as long as they are properly bonded to the other electrodes making up the ground plane. When not bonded,(shorted), they constitute multi-ground points.
It involves focusing the current by utilizing an inductor and impedance, as the highway.
Re: Single Point Ground
Charlie: You are definitely the one who should agree the ground electrode at the service is only a single point for the premises. It is the end of the utility distribution MGN.
The service ground is a multi-ground system. The premises ground is a single point system.
Lektrik work is fun
Charlie: You are definitely the one who should agree the ground electrode at the service is only a single point for the premises. It is the end of the utility distribution MGN.
The service ground is a multi-ground system. The premises ground is a single point system.
Lektrik work is fun
charlie
Senior Member
- Location
- Indianapolis
Re: Single Point Ground
Bennie, I sort of agree with you. You do have a MGN up to the service equipment and you establish a single point ground at the service equipment. However, it is permitted to have supplemental electrodes past that point if they are connected to either the grounding electrode system or a grounding conductor of a branch circuit or a feeder.
250.54 Supplementary Grounding Electrodes. Supplementary grounding electrodes shall be permitted to be connected to the equipment grounding conductors specified in 250.118 and shall not be required to comply with the electrode bonding requirements of 250.50 or 250.53(C) or the resistance requirements of 250.56, but the earth shall not be used as the sole equipment grounding conductor.
Bennie, I sort of agree with you. You do have a MGN up to the service equipment and you establish a single point ground at the service equipment. However, it is permitted to have supplemental electrodes past that point if they are connected to either the grounding electrode system or a grounding conductor of a branch circuit or a feeder.
250.54 Supplementary Grounding Electrodes. Supplementary grounding electrodes shall be permitted to be connected to the equipment grounding conductors specified in 250.118 and shall not be required to comply with the electrode bonding requirements of 250.50 or 250.53(C) or the resistance requirements of 250.56, but the earth shall not be used as the sole equipment grounding conductor.
charlie
Senior Member
- Location
- Indianapolis
Re: Single Point Ground
Bennie, lectrik work is the best fun around. The most fun is all the fussin' without gitten mad at anyone. I can tell you that you are all wet and you tell me the same and we still are just havin' fun.
Bennie, lectrik work is the best fun around. The most fun is all the fussin' without gitten mad at anyone. I can tell you that you are all wet and you tell me the same and we still are just havin' fun.
hurk27
Senior Member
- Location
- Portage, Indiana NEC: 2008
Re: Single Point Ground
But Charlie being wet and standing on concreit with a power wire in your hand dont feel to good LOL
But Charlie being wet and standing on concreit with a power wire in your hand dont feel to good
LOL
charlie
Senior Member
- Location
- Indianapolis
Re: Single Point Ground
At least, in this case it doesn't contradicts itself. All this is saying is that you must establish the grounding electrode system for the service. Then, you may install additional grounding electrodes that are not part of the grounding electrode system and that are attached to the grounding conductor. The grounding conductors are still required to get back to the grounding electrode system. This may be done with parking lot lighting columns and any other location you desire (this sound like another thread, doesn't it?).
Sorry Bennie, I don't agree with you. You know the NEC never contradicts itself. LOL
At least, in this case it doesn't contradicts itself. All this is saying is that you must establish the grounding electrode system for the service. Then, you may install additional grounding electrodes that are not part of the grounding electrode system and that are attached to the grounding conductor. The grounding conductors are still required to get back to the grounding electrode system. This may be done with parking lot lighting columns and any other location you desire (this sound like another thread, doesn't it?).
deangrabowski
New member
Re: Single Point Ground
I am not an expert first of all. But, it would seem to me that the best type of grounding would be a single point. It seems that with multiple grounds you would have the potential for stray currents, maybe ground loops or something. From what I understand, it would seem that stray ground currents would be undesirable in a home due to that "noise" that could be created in your electrical system. This noise wouldn't affect your toaster, but couldn't it have an effect on radio/TV recievers and other sensitive electronics?
I am not an expert first of all. But, it would seem to me that the best type of grounding would be a single point. It seems that with multiple grounds you would have the potential for stray currents, maybe ground loops or something. From what I understand, it would seem that stray ground currents would be undesirable in a home due to that "noise" that could be created in your electrical system. This noise wouldn't affect your toaster, but couldn't it have an effect on radio/TV recievers and other sensitive electronics?
Re: Single Point Ground
Dean: I like your style. It is true that both the neutral and equipment ground can be regrounded in certain situations according to the NEC.
Notice that the situations will keep the EMF outdoors not in the dwelling.
A sub-panel in a separate building can be regrounded, a sub-panel in the same building can not.
Lighting in a parking lot can be re-grounded, but not inside the dwelling.
Dean: I like your style. It is true that both the neutral and equipment ground can be regrounded in certain situations according to the NEC.
Notice that the situations will keep the EMF outdoors not in the dwelling.
A sub-panel in a separate building can be regrounded, a sub-panel in the same building can not.
Lighting in a parking lot can be re-grounded, but not inside the dwelling.
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