Well casing as Grounding Electrode

[electricmanscott]

I don't wire many houses with wells so I am a little fuzzy on something. To keep it simple would you consider a metal well casing to fall into the category of rod, pipe, or plate electrode thereby requiring a resistance of 25 ohms or less?

 

[jwelectric]

Re: Well casing as Grounding Electrode

Originally posted by electricmanscott:
I don't wire many houses with wells so I am a little fuzzy on something. To keep it simple would you consider a metal well casing to fall into the category of rod, pipe, or plate electrode thereby requiring a resistance of 25 ohms or less?

2005 250.52 Grounding Electrodes.
(A) Electrodes Permitted for Grounding.
(1) Metal Underground Water Pipe. A metal underground water pipe in direct contact with the earth for 3.0 m (10 ft) or more (including any metal well casing effectively bonded to the pipe)

It may very well need to comply with 250.53 (D)(2) but I don?t think it needs to comply with 250.56. If the electrode installed to comply with 250.53 (D)(2) is a rod, pipe or plate it will need to comply with 250.56.

 

[George Stolz]

Re: Well casing as Grounding Electrode

Scott, the key in my mind is: Is the well present at the structure, or is it 30' away from the structure?

In general, IMO, 250.122(M) (off the top of my head, that might not be quite right) leads me to believe that while you could use the well casing as an electrode if you were to run clear out to it, the NEC considers the copper pipe entering the structure from the well to be the electrode. The casing would need to be bonded to the BC EGC.

If you were to try to use it as an electrode, I'd say it is part of 250.52(A)(1). The parenthetic "(including any metal well casing effectively bonded to the pipe)" states that, while the CMP recognizes that the primary function of the well casing is not acting as a "water pipe", they intentionally ignore that fact. When bonded to the pipe carrying the water, the metal well casing is by NEC standards part of that water pipe.

With that, your metal well casing would require a supplemental electrode per 250.54. or .56, whichever it is.

Too lazy to open the book this morning.

 

[jwelectric]

Re: Well casing as Grounding Electrode

George let?s take a look at the section you are trying to refer to. As we can see one is talking about the equipment grounding conductor for the pump and the other is talking about the grounding electrode.

250.112 (M) Metal Well Casings. Where a submersible pump is used in a metal well casing, the well casing shall be bonded to the pump circuit equipment grounding conductor.

250.52 Grounding Electrodes.
(A) Electrodes Permitted for Grounding.
(1) Metal Underground Water Pipe. A metal underground water pipe in direct contact with the earth for 3.0 m (10 ft) or more (including any metal well casing effectively bonded to the pipe)

Now let?s look at the question being asked.

Originally posted by electricmanscott:
I don't wire many houses with wells so I am a little fuzzy on something. To keep it simple would you consider a metal well casing to fall into the category of rod, pipe, or plate electrode thereby requiring a resistance of 25 ohms or less?

Scott is asking about using the well casing as part of the electrode as outlined in 250.52 (A)(1) and weather or not that this would require a 25 ohms of resistance.
To answer his question we would first need to know if the well casing is part of the electrode system. 250.52 (A)(1) states that if there is 10? or more of metal water pipe in direct contact with the earth and the well casing is bonded to this pipe either through the pipe its self or other effective means then it is part of the electrode system.

As to the 25 ohms, the casing would not need to meet this requirement but the requirements of 250.53 (D)(2) will require the rod, pipe or plate that would be used to supplement the pipe and casing would need to adhere to 250.56.

250.112 states that even if the casing is used as the electrode system and a submersible pump is installed the equipment grounding conductor is to be bonded to the casing also but in no way relieves the use of the casing as part of the electrode system.

Now quit being lazy and look this stuff up so you can get the section numbers right as well as the section quotes.
All in all you did alright in my book.

 

[electricmanscott]

Re: Well casing as Grounding Electrode

The water pipe from the well to the house is plastic. The well motor circuit is bonded to the well casing. There is 130' of #4 bare copper running in a trench out to the steel well casing. The well casing is the sole grounding electrode. In my view this is not a rod, pipe, or plate electrode, it is a well casing which is specifically mentioned as a grounding electrode, but not mentioned when requirements for supplemental electrodes are listed. I do not believe it needs a supplemental rod which would of course be less than 25 ohms thereby requiring another rod. I'd say that the 130' wire in the ground coupled with the well casing is more than adequate and that two rods will offer absolutely nothing.

 

[jwelectric]

Re: Well casing as Grounding Electrode

I will agree with you that 130 foot of #4 buried in the ground is more of a ground than two rods could ever be.
Unfortunately it does not meet the requirements of a grounding electrode outlined in 250.52
.

250.52 (A)(1) Metal Underground Water Pipe. A metal underground water pipe in direct contact with the earth for 3.0 m (10 ft) or more (including any metal well casing effectively bonded to the pipe)

Here we are told that the well casing is required to be effectively bonded to the pipe which you say is a plastic pipe and does not meet the requirements of 250.52 (A)(1)

The #4 that is buried might have been alright for 250.52 (4) Ground Ring if it had been size #2.

As it is I would say get out the hammer and a couple of rods and a notepad. The hammer to drive the rods and the notepad to take a note to self that this installation does not work.

 

[electricmanscott]

Re: Well casing as Grounding Electrode

On this note to self should I include 250.52 (A) (7) ?
"Other local metal underground systems or structures such as piping systems, underground tanks, and underground metal well casings that are not effectively bonded to a metal water pipe"

 

[jwelectric]

Re: Well casing as Grounding Electrode

yep that is a good idea indeed

 

[George Stolz]

Re: Well casing as Grounding Electrode

Originally posted by jwelectric:
I will agree with you that 130 foot of #4 buried in the ground is more of a ground than two rods could ever be.
Unfortunately it does not meet the requirements of a grounding electrode outlined in 250.52
...

Here we are told that the well casing is required to be effectively bonded to the pipe which you say is a plastic pipe and does not meet the requirements of 250.52 (A)(1)

Step back for a second here. The casing doesn't qualify as a water pipe, true. Why doesn't it qualify as a pipe, under 250.52(A)(5)(a)?

But the NEC doesn't require him to, IMO.

Drive two ground rods at the service: 250.50. If none of the electrodes are present (as seems to be the case), then an electrode specified in 250.52(A)(4) - (7) needs to be installed. The electrode 130' is not present at the structure, IMO. I could easily see an AHJ having a similar view.

Is lightning really going to go on that road trip?

 

[electricmanscott]

Re: Well casing as Grounding Electrode

George what are you saying? Should I not use this as an electrode? Are two rods better than 130' of buried #4 and the well casing. I don't think so.

 

[George Stolz]

Re: Well casing as Grounding Electrode

Scott, I'm not saying you shouldn't use it, I'm just saying that you shouldn't be required to, and it might not relieve you of driving a couple rods at the service.

You're going above and beyond, there's nothing wrong with that--I think you probably usually do.

I'm only making my opinion clear, so it can be debated and discussed, and maybe the discussion would be good.

[ September 02, 2005, 08:10 AM: Message edited by: georgestolz ]

 

[jwelectric]

Re: Well casing as Grounding Electrode

Scott, help me out just a little. Are you using the well casing to fulfill 250.52 (A)(5)(a) Electrodes of pipe or conduit shall not be smaller than metric designator 21 (trade size ?)

I don?t think that the well casing can be used to fulfill the requirements of a pipe electrode due to the fact that it is outlined in 250.52 (A)(1) Metal Underground Water Pipe. A metal underground water pipe in direct contact with the earth for 3.0 m (10 ft) or more (including any metal well casing effectively bonded to the pipe)

The well casing can be part of the water pipe electrode if it is bonded to the pipe in some way. I don?t believe that it could be used for 250.52 (A)(5)(a)

In my opinion the 130? of #4 is as good if not better than two or three 8 ft. rods.

 

[electricmanscott]

Re: Well casing as Grounding Electrode

The well casing is the grounding electrode for the house. It is permitted to be used in 250.52 A 7.

 

[jwelectric]

Re: Well casing as Grounding Electrode

(7) Other Local Metal Underground Systems or Structures. Other local metal underground systems or structures such as piping systems, underground tanks, and underground metal well casings that are not effectively bonded to a metal water pipe.

This is new to the 2005 cycle. The Analysis shows the well casing being used as the electrode. It also states that the casing is not subject to the requirements of 250.53 (D)(2)

Based on this change in the 2005 cycle I must retract my earlier statements based on 250.52 (A)(1)

Scott I do believe that you are in compliance with the 2005 cycle

 

[George Stolz]

Re: Well casing as Grounding Electrode

Originally posted by jwelectric:
Based on this change in the 2005 cycle I must retract my earlier statements based on 250.52 (A)(1)

Okay--but let's back up. Let's ignore (A)(7) for a second; let's go back to '02 for this next quote, I have a purpose.

I don?t think that the well casing can be used to fulfill the requirements of a pipe electrode due to the fact that it is outlined in 250.52 (A)(1)

Mike, this statement is erroneous. Just because something is mentioned in (A)(1), and doesn't qualify for this one type of grounding electrode due to the PVC plumbing, doesn't mean it's not an electrode by the standards of other electrodes.

Without 2005's (A)(7) in place, it would still qualify as a "pipe" that is greater than 3/4" in diameter.

In my opinion the 130? of #4 is as good if not better than two or three 8 ft. rods.

True or not, that statement is baseless in the eyes of the NEC.

The fact remains: there is no electrode present at the structure, so one of the electrodes listed in (A)(4) - (A)(7) is required to be installed.

NEC-2002 250.4(A)(1) Electrical System Grounding. Electrical systems that are grounded shall be connected to earth in a manner that will limit the voltage imposed by lightning, line surges, or unintentional contact with higher-voltage lines and that will stabilize the voltage to earth during normal operation.

There is no electrode present at the structure to dissipate lightning (silly as that function may be, IMO). That casing with the 130' of #4 would do a stellar job of the other functions: line surges, unintentional contact. It's an excellent supplementary electrode. But it's just too far away to be considered a required grounding electrode for the structure, IMO.

It's just not "present."

Edit: Accidentally bolded everything.
Edit again: moved some words, added "IMO's"

[ September 02, 2005, 08:45 PM: Message edited by: georgestolz ]

 

[electricmanscott]

Re: Well casing as Grounding Electrode

George here is the flaw I see in your argument. I don't see anything that says the electrode has to be "at the structure" per se. By that I mean within a certain specified distance. I do see that it says if certain types of electrodes are present at the structure they must be bonded together. I have none of the items listed so I have to make my own electrode or I can use the items in 250.52(A)(7). Nowhere is there a maximum distance from the structure given. I really have a hard time buying two piddly eight foot rods closer to the service is any better than 130' of #4 buried 6 feet in the ground not even taking into account the well casing. I am no expert however. For what it's worth the inspector was happy with it.

 

[jwelectric]

Re: Well casing as Grounding Electrode

George the well casing is described in 250.52 (A)(1) of the 2002 cycle and the requirement that it is to be bonded to the water pipe puts the well casing here and here only.

By moving the well casing to 250.52 (A)(7) in the 2005 as well as having the casing in 250.52(A)(1) shows that it is no longer locked to (A)(1).

It has never been the intent of the code that the well casing be part of 250.52 (A)(5)(a) or it would have been mentioned there as it was in 250.52 (A)(1).

I don?t think that a code panelist would want to require me, you or anyone else to drive a rod or pipe through the water line in order to gain 25 ohms or less. To include the well casing as part of 250.52 (A)(5)(a) would require it to adhere to 250.56 which could cause some poor Joe to cut the water supply line trying to fulfill the requirements of 250.56. Do you see what I mean? Can you understand where I am coming from? Can you tell me where I am at now?

 

[jwelectric]

Re: Well casing as Grounding Electrode

Originally posted by electricmanscott:
rods closer to the service is any better than 130' of #4 buried 6 feet in the ground not even taking into account the well casing. I am no expert however.

 

[George Stolz]

Re: Well casing as Grounding Electrode

Originally posted by jwelectric:
George the well casing is described in 250.52 (A)(1) of the 2002 cycle and the requirement that it is to be bonded to the water pipe puts the well casing here and here only.

By moving the well casing to 250.52 (A)(7) in the 2005 as well as having the casing in 250.52(A)(1) shows that it is no longer locked to (A)(1).

No--look at it this way: Let's say we had a bunch of #2 CU and wanted to make electrodes for a house, for fun, or whatever.

So, we look in the code and find that according to 250.52 (A)(4), we can make a ground ring out of it. So does that mean that #2 CU can not be used to create a concrete encased electrode too?

You're saying since an "object" is specifically mentioned one section, if must be specifically mentioned by name in every section for a section to apply to it?

I'm going to start calling ground rods "henry's", and stop driving them. Henry's aren't specifically referenced by the NEC.

 

[George Stolz]

Re: Well casing as Grounding Electrode

Originally posted by electricmanscott:
George here is the flaw I see in your argument.

...That I am out of my depth?

By that I mean within a certain specified distance.

You're right. That is entirely within the realm of AHJ's interpretation. What is "present at the structure"?

Your AHJ accepted it, so you're right. If he declined it, I'd be right. What changed? The NEC didn't.

I really have a hard time buying two piddly eight foot rods closer to the service is any better than 130' of #4 buried 6 feet in the ground not even taking into account the well casing.

Like I said, "What #4?" It's too small to consider an electrode on it's own.

I am no expert however.

That's why I'm around.