Bonding before main disconnect

[LarryFine]

As you can see, our POCO-supplied meter bases have extra neutral terminals, too, but we can't use them.

 

[Doc13067]

Mostly, yes. Electrodes may connect to the service neutral wherever convenient, including the main panel, and they all need not be connected to it in the same place.

You're lucky; we're not allowed to land ours in the meter, which is a shame, as it's the ideal location to land the GEC to driven rods.

Sorry to be redundant Larry, but just to recap while I have your intellect available, my existing ground rod has a GEC that runs to a meter can. I have a newly run GEC from the water pipe. Based on what you’re saying I should join the water pipe portion of the GEC to the meter socket so the grounding electrode system can be made to include the rod and the pipe. Then only 3 wires (two hots one neutral) leave the meter socket and go in to the panel. In that panel there will be no GEC since it terminates in the meter but in the panel the neutral will be bonded to the enclosure, essentially causing the service grounded conductor to do the job of bonding the main panel enclosure to the grounding electrode system. From there all EGCs will also gain fault clearing ability through being bonded to the neutral plus lighting prevention through the EGCs being bonded to the GEC via the service neutral which comes from the meter. Thanks as always.

 

[Doc13067]

As you can see, our POCO-supplied meter bases have extra neutral terminals, too, but we can't use them.

View attachment 2571400

Very clean work! And that’s kinda silly because why does the EGC have to be accessible but the service conductors can be sealed? And what electrician can’t access a sealed meter anyway

 

[LarryFine]

Based on what you’re saying I should join the water pipe portion of the GEC to the meter socket so the grounding electrode system can be made to include the rod and the pipe.

No, I'm saying you can land the rod GEC in the meter, since you're allowed to, and you can land the water-pipe GEC in the panel if it's more convenient. They do not need to terminate in the same place.

The grounded conductor and any metallic enclosures or raceways are seen collectively as the neutral.

 

[LarryFine]

Very clean work!

Thanx!

 

[Doc13067]

No, I'm saying you can land the rod GEC in the meter, since you're allowed to, and you can land the water-pipe GEC in the panel if it's more convenient. They do not need to terminate in the same place.

The grounded conductor and any metallic enclosures or raceways are seen collectively as the neutral.

Ah, ok so the neutral almost becomes a sort of bonding jumper that joins the water pipe section to the ground rod section of the grounding electrode system.

 

[LarryFine]

Ah, ok so the neutral almost becomes a sort of bonding jumper that joins the water pipe section to the ground rod section of the grounding electrode system.

You could say that since, while not its purpose, it becomes part of the pathway between electrodes.

 

[Doc13067]

You could say that since, while not its purpose, it becomes part of the pathway between electrodes.

Makes total sense. Thank you sir as always. This is in my own home. I’m experimenting with one of the new Leviton panels. Normally I’m a Siemens guy but I try to keep an open mind so after seeing these in the depot for years I want to see what they’re like so I’m using myself as a guinea pig here.

 

[Strathead]

Grounding and bonding is hard to understand. The terminology is often misused, too. First I noticed you used the term GEC system. There is no “ system”. There are grounding electrode/s and all of them must be bonded to the grounded conductor at or before to first means of disconnect by one or more grounding electrode conductors at one or more locations, period. Now clear that from your mind. The main bonding jumper bonds the neutral to the grounding system. NOT the grounding electrode system, the grounding system. The grounding system consists of all non current carrying metal parts and all grounding electrodes. In many residences all non current carrying metal parts are bonded by going to the same bus bar as neutrals. Then the only system bonding jumper is to the service enclosure. In other cases the neutral and ground are separate and then main bonding jumpers are supplied between the can the neutral and the ground. Hope this helps clear up some confusion.

 

[Doc13067]

Grounding and bonding is hard to understand. The terminology is often misused, too. First I noticed you used the term GEC system. There is no “ system”. There are grounding electrode/s and all of them must be bonded to the grounded conductor at or before to first means of disconnect by one or more grounding electrode conductors at one or more locations, period. Now clear that from your mind. The main bonding jumper bonds the neutral to the grounding system. NOT the grounding electrode system, the grounding system. The grounding system consists of all non current carrying metal parts and all grounding electrodes. In many residences all non current carrying metal parts are bonded by going to the same bus bar as neutrals. Then the only system bonding jumper is to the service enclosure. In other cases the neutral and ground are separate and then main bonding jumpers are supplied between the can the neutral and the ground. Hope this helps clear up some confusion.

Thanks for trying to help. The term grounding electrode system is used extensively in the NEC to refer to the places the GEC is terminated and in my case I’m using it to refer to my specific residential case which many times incorporates a water pipe within 5’ of entering, both sides of the water meter, a bonding bridge for low voltage systems to connect to the GEC, and two rods. This is all I’m referring to when I’m talking about the grounding electrode system so I would disagree that it is not a system and just various electrodes. But assuming I know all of this, my confusion came from specifically what happens when the grounded conductor is bonded to the GEC at the meter socket or service drop.

 

[CoolWill]

There is parallel neutral current running all over service equipment connected together by metal conduits and nipples and the code allows it. Because it is allowed and even specifically required by requiring each disco to have an MBJ, it is not considered objectionable.

 

[Doc13067]

There is parallel neutral current running all over service equipment connected together by metal conduits and nipples and the code allows it. Because it is allowed and even specifically required by requiring each disco to have an MBJ, it is not considered objectionable.

Really? I’m going to put my meter on the enclosure and see how much current is on it and reread the objectionable current part of the code. I would think that because current takes the easiest path back to the source that it would stay on the conductors. And as far as the current on the service enclosures not being objectionable, how is the GEC allowed to have current on it? I’m having a hard time seeing how this is different from bonding a sub panel.

 

[CoolWill]

Really? I’m going to put my meter on the enclosure and see how much current is on it and reread the objectionable current part of the code. I would think that because current takes the easiest path back to the source that it would stay on the conductors. And as far as the current on the service enclosures not being objectionable, how is the GEC allowed to have current on it? I’m having a hard time seeing how this is different from bonding a sub panel.

Current doesn't take the easiest path, it takes all paths. There will be current on the GEC because the service neutral is connected to the earth at the transformer, and at your neighbor's service and every other service everywhere. There is current running everywhere due to the multi-grounded neutral system we use.

 

[LarryFine]

I would think that because current takes the easiest path back to the source that it would stay on the conductors.

Actually, current takes all parallel pathways, divided inversely proportionate to pathway impedances. Yes, the neutral conductor should carry most of it, but parallel pathways are unavoidable.

Where there is a common metallic water pipe system, like in most older cities, the water electrode can carry current so well that an open neutral can sometimes avoid detection for years.

And as far as the current on the service enclosures not being objectionable, how is the GEC allowed to have current on it? I’m having a hard time seeing how this is different from bonding a sub panel.

Because the neutral effectively defines the zero-volts-to-earth point of the service, the metallic parts are considered part of the neutral, and are subject to carry some of the current.

It's more important that there be as little voltage between the neutral and local earth (and grounded conductive surfaces) as practicable, than that there be little current flowing along it.

That also points out why it's so important to have sure contact and bonding between metallic parts of the service, so they behave like a conductor, especially during certain types of fault.

 

[Strathead]

Thanks for trying to help. The term grounding electrode system is used extensively in the NEC to refer to the places the GEC is terminated and in my case I’m using it to refer to my specific residential case which many times incorporates a water pipe within 5’ of entering, both sides of the water meter, a bonding bridge for low voltage systems to connect to the GEC, and two rods. This is all I’m referring to when I’m talking about the grounding electrode system so I would disagree that it is not a system and just various electrodes. But assuming I know all of this, my confusion came from specifically what happens when the grounded conductor is bonded to the GEC at the meter socket or service drop.

Your confusion is what I was trying to address by getting you not to think of it as the GE system. ALL grounding electrodes are bonded to the neutral ANYWHERE at or before the first means of disconnect. The neutral and the ground are always bonded together at the first means of disconnect. The first is the grounding electrode "system," and the second is the neutral to ground bonding. The first potentially carries fault current in a high resistance path from earth (hence the #4 maximum wire size) or low resistance path via water pipe, building steel etc. The second potentially carries low resistance current from non current carrying metal parts, hence the larger bonding wire. Grounding is 100% the hardest part of the code in my experience. Why do you think 90% of engineers just provide a typical grounding diagram and oversize all the grounds?

 

[electrofelon]

Your confusion is what I was trying to address by getting you not to think of it as the GE system. ALL grounding electrodes are bonded to the neutral ANYWHERE at or before the first means of disconnect.

Strat I'm going to push back a little. The NEC uses the exact phrase "grounding electrode system". Most of the wording is aimed at the philosophy of their being a single grounding electrode conductor, and then bonding jumpers interconnecting the electrodes. (Note I am not saying that I believe you can only have one GEC).

 

[Doc13067]

Your confusion is what I was trying to address by getting you not to think of it as the GE system. ALL grounding electrodes are bonded to the neutral ANYWHERE at or before the first means of disconnect. The neutral and the ground are always bonded together at the first means of disconnect. The first is the grounding electrode "system," and the second is the neutral to ground bonding. The first potentially carries fault current in a high resistance path from earth (hence the #4 maximum wire size) or low resistance path via water pipe, building steel etc. The second potentially carries low resistance current from non current carrying metal parts, hence the larger bonding wire. Grounding is 100% the hardest part of the code in my experience. Why do you think 90% of engineers just provide a typical grounding diagram and oversize all the grounds?

Indeed when I want to study I almost always go to article 250 so I’m with you there. I really appreciate the insight. It’s so easy to get tripped up. I still get confused on how to size the ground going to a sub panel lol. Is it an EGC or a GEC? I have to look up old conversations here every time I’m putting in a sub panel that’s fed with conduit and individual conductors of my choosing.

 

[Doc13067]

Actually, current takes all parallel pathways, divided inversely proportionate to pathway impedances. Yes, the neutral conductor should carry most of it, but parallel pathways are unavoidable.

Where there is a common metallic water pipe system, like in most older cities, the water electrode can carry current so well that an open neutral can sometimes avoid detection for years.


Because the neutral effectively defines the zero-volts-to-earth point of the service, the metallic parts are considered part of the neutral, and are subject to carry some of the current.

It's more important that there be as little voltage between the neutral and local earth (and grounded conductive surfaces) as practicable, than that there be little current flowing along it.

That also points out why it's so important to have sure contact and bonding between metallic parts of the service, so they behave like a conductor, especially during certain types of fault.

Interesting. Thanks as always Larry. I have absolutely seen the ground carry neutral current when the neutral bug has been loose for years and only when the ground was taken off the pipe would we get sparking and a bunch of dim lights! Haven’t seen it in a while but I always look for it.

 

[Strathead]

Indeed when I want to study I almost always go to article 250 so I’m with you there. I really appreciate the insight. It’s so easy to get tripped up. I still get confused on how to size the ground going to a sub panel lol. Is it an EGC or a GEC? I have to look up old conversations here every time I’m putting in a sub panel that’s fed with conduit and individual conductors of my choosing.

It is an EGC. Here is a thing that might help you to figure out which table to size by. First and easiest, if there is overcurrent protection before or at the point of the ground wire termination, then it is always 250-122 which is based on the amperage of the OCPD. Otherwise, you must use either 250.66 or 250.102. There is sense in this since how can you size to amperage when there isn't an OCPD.

 

[Doc13067]

It is an EGC. Here is a thing that might help you to figure out which table to size by. First and easiest, if there is overcurrent protection before or at the point of the ground wire termination, then it is always 250-122 which is based on the amperage of the OCPD. Otherwise, you must use either 250.66 or 250.102. There is sense in this since how can you size to amperage when there isn't an OCPD.

Awesome thank you! That makes perfect sense! Of course it must be based on conductor size because there is not yet an OCPD! If it’s after a breaker then you’ve got a definitive limit on the circuit you are grounding So you can base your ground size on that. Thanks a million for giving me something I will remember that by.