Service Entrance Grounding

[BlaineXD]

I am reviewing some specs and came across this section. I was wondering what you all thought of creating a loop with the grounds and connecting the ends back together, like the state is suggesting. It is not a configuration that I am familiar with. I am new to the field, but I know that a grounding system can and-- in an industrial setting-- generally does have some amount of current on it. By creating this loop, would you be degrading and making a less efficient system? I mean, because the path of least resistance is a loop? Also, what implications would this have for cathodic protection and the degradation of components (lugs, cables, and such) over time?
Thanks for any insights and opinions.
--Nate

 

[ActionDave]

Grounding or earthing, as in a connection to the earth gets far more attention than it deserves. It gets spoken about in hushed, reverential terms, and people come up with all kinds of schemes to appease the spirits of the electron. In reality it's about the least important part of a buildings electrical system. More important is good equipment grounding practices, that's what keeps things safe.

 

[infinity]

Although I can see it I cannot read the text in your graphic. Not sure why a loop would matter but maybe I'm not understanding the setup. Also in industrial or any other setting an EGC should not carry any current under normal conditions.

 

[al hildenbrand]

I believe the OP is asking after Service Entrance Grounding, rather than Equipment Grounding Conductors.

BlaineXD, I believe you are starting to think about the actual circuit diagram of a real world Premises Wiring (System) (see Art. 100 Definition). The actual circuit diagram, from source (the Power Company transformer secondary), through the Service to the Utilization Equipment with the various connections to Earth, gets to be a set of parallel current paths, especially for the Grounded Service Conductor with its connections to Earth through the Grounding Electrode System.

Try sketching it out. Remember that current takes ALL available paths. The current return paths to the transformer secondary windings are many-fold.

 

[BlaineXD]

Hi all, thanks for the comments. Sorry for the terrible image (I guess that's what you get for not previewing the post before sending it out The text reads as follows in reference to the service entrance grounding (where the drop meets the state's equipment, like Al said):

(A) Install 3 ground rods in the vicinity of the service entrance. The ground rods must be at leas 6 feet apart.
(B) Install grounding cable as sized on the plans. Grounding cable shall be one continuous cable. It shall start on the neutral bar in the service panel, go completely through the ground bar, then through the neutral bond, and then equipment ground bond, then out through the conduit to the first ground rod, then the 2nd ground rod, and then the 3rd rod before returning back through the conduit to the service panel neutral bar.

I took your advice and sketched it out myself (see attached). Sketching it out hasn't really helped my thought process, though. It still seems, at the very least, and unusual requirement, and at worst, something that has created an unnecessary loop that undermines the purpose of the ground; creating a path of least resistance back to the terminal lugs.

I might just be overthink the whole thing... Any more opinions would be great!
Thanks,
--Nate View attachment Model.pdf

 

[ActionDave]

I took your advice and sketched it out myself (see attached). Sketching it out hasn't really helped my thought process, though. It still seems, at the very least, and unusual requirement,

It looks like a silly requirement to me. For instance, how does it make one bit of difference if the wire to the ground rods is one continuous piece instead of one jumper from the first ground rod to the second. It doesn't, it's a stupid piece of copper tying one ground rod to the next, the ground rods have no idea if the wire is spliced or not either, they are stupid too. There is also no reason to bring the grounding electrode conductor back to the neutral buss, there is no reason not to either other than it's a wast of material and effort.

and at worst, something that has created an unnecessary loop that undermines the purpose of the ground; creating a path of least resistance back to the terminal lugs.

Any connection to the earth has no purpose in creating any path of least resistance or clearing a fault, that is what good equipment grounding practices are for.

I might just be overthink the whole thing... Any more opinions would be great!
Thanks,
--Nate View attachment 19789

Unless you are working on a telecom or similar site, or maybe a fancy server room or similar then earthing connections are not a big deal.

 

[kwired]

Unless you are working on a telecom or similar site, or maybe a fancy server room or similar then earthing connections are not a big deal.

And even in those applications it may be useless to go above and beyond code minimum requirements, but to designers of these sites it is like having Sports Illustrated swimsuit edition pictures posted all around the facility would be to many others:happyyes:

 

[al hildenbrand]

I took your advice and sketched it out myself (see attached). Sketching it out hasn't really helped my thought process, though.

Ah. Interesting text associated with the photo.

I was able to see, in the photo, that the panel was single phase, and I assumed 240 / 120 V.

Three ground rods ! ! Are there no other Grounding Electrodes present at this Structure? I had assumed that there was, at the very least, something like water pipe and / or a concrete encased electrode. I apologize for the assumption, if such is not the case.

Given three ground rods as your only grounding electrode, a missing part of the circuit diagram is the Grounded Service Conductor between the neutral in the circuit breaker panel (shown in the photo) and the Power Company transformer neutral terminal. The Power Company transformer neutral will also have a wire type conductor leading to an local ground rod (or ground "ball"), and this same wire-type conductor will be solidly connected to any Power Company primary neutral (from the high side of the transformer). The primary neutral may only be the lightning protection conductor run with a purely delta circuit.

If there is a potable water service provided in metallic piping by a municipal water utility, and there are neighbors, who share electrical supply from the same transformer, there will be multiple "loops" formed by the low impedance water piping from Grounding Electrode Conductor (GEC) connection to GEC connection in all the premises that have a Grounded Service Conductor connection to the single Power Company transformer neutral terminal.

The current path through Earth, from premises grounding electrodes to the Power Company transformer Earth connection also are additional "loops".

The circuit diagram, including the source (transformer secondary, and, maybe even the primary transmission circuit) becomes any number of loops.

 

[infinity]

Hi all, thanks for the comments. Sorry for the terrible image (I guess that's what you get for not previewing the post before sending it out The text reads as follows in reference to the service entrance grounding (where the drop meets the state's equipment, like Al said):

(A) Install 3 ground rods in the vicinity of the service entrance. The ground rods must be at leas 6 feet apart.
(B) Install grounding cable as sized on the plans. Grounding cable shall be one continuous cable. It shall start on the neutral bar in the service panel, go completely through the ground bar, then through the neutral bond, and then equipment ground bond, then out through the conduit to the first ground rod, then the 2nd ground rod, and then the 3rd rod before returning back through the conduit to the service panel neutral bar.

I took your advice and sketched it out myself (see attached). Sketching it out hasn't really helped my thought process, though. It still seems, at the very least, and unusual requirement, and at worst, something that has created an unnecessary loop that undermines the purpose of the ground; creating a path of least resistance back to the terminal lugs.

I might just be overthink the whole thing... Any more opinions would be great!
Thanks,
--Nate View attachment 19789

In looking at the attachment there is basically a waste of material. The GEC goes from the rods to the neutral, the MBJ bonds the neutral to the EGC bar. Nothing else is required. The loop and extra jumpers are just a waste of money.

 

[al hildenbrand]

The loop and extra jumpers are just a waste of money.

Yup.

I my opinion, residential services in towns and cities, by far the most common of services, are replete with "loops."

It is the cognitive disonnance at the core of America's distribution system.

 

[electrofelon]

(A) Install 3 ground rods in the vicinity of the service entrance. The ground rods must be at leas 6 feet apart.
(B) Install grounding cable as sized on the plans. Grounding cable shall be one continuous cable. It shall start on the neutral bar in the service panel, go completely through the ground bar, then through the neutral bond, and then equipment ground bond, then out through the conduit to the first ground rod, then the 2nd ground rod, and then the 3rd rod before returning back through the conduit to the service panel neutral bar.

Looping through the rods and coming back to the panel is a very common practice here in upstate NY. You will find most grounding done that way. I am not sure how it originated, but I would guess it was a utility requirement. One of the utilities here, NYSEG, shows such an arrangement in a sketch in their spec book with the words "typical installation" or something like that which to me doesnt make it a requirement rather a suggestion. I havent been installing GEC with the loop for years and have never gotten any pushback from anyone. I cant speak for your neck of the woods.

 

[kwired]

The earthing of the grid being done in so many places is what gives the overall system a low impedance to earth.

By adding another electrode at each service just adds to those thousands of electrodes already in place, should that one electrode become compromised it doesn't really have much impact on the overall system voltage to ground.

Too much emphasis is put on grounding when it comes to safety concerns the most emphasis should be put on bonding.

Even if you don't install an electrode at all on your utility supplied service - the grounding network of the entire grid still leaves you with very stable voltage to ground. Grounding electrode does help with bleeding off surges, but at same time is not a lightning protection system.

 

[electrofelon]

The earthing of the grid being done in so many places is what gives the overall system a low impedance to earth.

By adding another electrode at each service just adds to those thousands of electrodes already in place, should that one electrode become compromised it doesn't really have much impact on the overall system voltage to ground.

Too much emphasis is put on grounding when it comes to safety concerns the most emphasis should be put on bonding.

Even if you don't install an electrode at all on your utility supplied service - the grounding network of the entire grid still leaves you with very stable voltage to ground. Grounding electrode does help with bleeding off surges, but at same time is not a lightning protection system.

I just think it is worth noting that there are extensive areas that do not have a MGN distribution system thus the secondary is isolated from the primary. I know some think MGN is the way it always is and might find this odd. In upstate NY here, we have lots of 4800 delta, so the secondary neutral is isolated from the primary supply. Utility does add a GE at the pole, but sometimes that GEC has been stolen, leaving the GEC at the served structure the only earth connection. Note I am not claiming that in these cases the house GE is very important as there will still very likely be an earth reference or two on the system, such as by the well casing, etc. Even if there were absolutely no earth reference , IMO still very unlikely to be a safety issue.

 

[kwired]

I just think it is worth noting that there are extensive areas that do not have a MGN distribution system thus the secondary is isolated from the primary. I know some think MGN is the way it always is and might find this odd. In upstate NY here, we have lots of 4800 delta, so the secondary neutral is isolated from the primary supply. Utility does add a GE at the pole, but sometimes that GEC has been stolen, leaving the GEC at the served structure the only earth connection. Note I am not claiming that in these cases the house GE is very important as there will still very likely be an earth reference or two on the system, such as by the well casing, etc. Even if there were absolutely no earth reference , IMO still very unlikely to be a safety issue.

What does that GE at the pole tie to? If a shield wire that runs all throughout the system, you still have a pretty large grounding network, and even better then a MGN because it isn't normally current carrying so no voltage drop issues to cause rise in voltage on the grounded conductor.

Distribution around here is all MGN, transmission lines don't ordinarily have a neutral but still have shield wire that is tied to an electrode at nearly every structure.

 

[electrofelon]

What does that GE at the pole tie to? If a shield wire that runs all throughout the system, you still have a pretty large grounding network, and even better then a MGN because it isn't normally current carrying so no voltage drop issues to cause rise in voltage on the grounded conductor.

Distribution around here is all MGN, transmission lines don't ordinarily have a neutral but still have shield wire that is tied to an electrode at nearly every structure.

I am not sure what the configuration of the larger distrubution and transmission lines are, but they typically have a shield wire. Typical rural distibution however is just two wires, two delta phases, no shield wire. Secondary neutral and arrestors just tie to rod at base of pole, thats it.

 

[kwired]

I am not sure what the configuration of the larger distrubution and transmission lines are, but they typically have a shield wire. Typical rural distibution however is just two wires, two delta phases, no shield wire. Secondary neutral and arrestors just tie to rod at base of pole, thats it.

You probably can't answer but is also likely that distribution system is not grounded? They may have some sort of ground fault detection system to warn them of troubles, but at same time only one fault in the system - the system would remain in operation as long as there isn't a second fault on another line.

 

[electrofelon]

You probably can't answer but is also likely that distribution system is not grounded? They may have some sort of ground fault detection system to warn them of troubles, but at same time only one fault in the system - the system would remain in operation as long as there isn't a second fault on another line.

I think historically this system was 4800 delta (ungrounded), although most road have only two of the phases. I know some of these lines are now fed off newer wye systems. When that is the case, I am not certain if they are isolated or not. For example if a 4800 line was fed off a grounded wye system via autos, it would of course retain the earth reference from the wye system. That is just conjecture, I am not sure if they do that or not. I know of one case where they use an isolation transformer off a 7.2/13.62 wye to feed an old 4800 line. The same thing happens with my road, fed off a 7.62/13.2 wye and I know where that bank is but I havent looked close enough to try to figure out if its an auto or an isolation.

 

[Jamesco]

It looks like a silly requirement to me. For instance, how does it make one bit of difference if the wire to the ground rods is one continuous piece instead of one jumper from the first ground rod to the second. It doesn't, it's a stupid piece of copper tying one ground rod to the next, the ground rods have no idea if the wire is spliced or not either, they are stupid too. There is also no reason to bring the grounding electrode conductor back to the neutral buss, there is no reason not to either other than it's a wast of material and effort.


Any connection to the earth has no purpose in creating any path of least resistance or clearing a fault, that is what good equipment grounding practices are for.


Unless you are working on a telecom or similar site, or maybe a fancy server room or similar then earthing connections are not a big deal.

>>>>>>>

It looks like a silly requirement to me.

Maybe to you but not the Licensed EE that wrote the spec. The EE wants it done that way.

For instance, how does it make one bit of difference if the wire to the ground rods is one continuous piece instead of one jumper from the first ground rod to the second.

The EE wants the GEC continuous unbroken. Maybe he has a thing with unnecessary added connections in the EGC. Maybe his thinking is long term well past the time of the date of the installation. Maybe he is looking out 5, 10, 20, or ?? years down the road. The top of the ground rods and ground rod ground clamps will be buried below earth 4" to 6". Maybe the EE worries about corrosion at unnecessary connections. If the GEC is continuous it's not a problem. In the end it really doesn't matter. That's the way the EE wants it done.

As for why the EE wants a continuous closed loop GEC maybe it is for simple redundancy. Agan, that what the EE wants.

 

[jim dungar]

As for why the EE wants a continuous closed loop GEC maybe it is for simple redundancy. Agan, that what the EE wants.

Maybe it is because the EE does not understand grounding and is simply repeating what 'granddad did'. Just because an EE asks for it does not make it automatically a good or bad design.

 

[ActionDave]

As for why the EE wants a continuous closed loop GEC maybe it is for simple redundancy. Agan, that what the EE wants.

When it comes to The Ground there a lot of people who come up with a lot of things that don't make sense.