Ufer ground

[MRKN]

Not what I said. IF the footer for the skid qualifies as a GE, you have to use it. It may not. For instance it may use wire mesh instead of rebar as the steel reinforcement. If there is no qualifying CEE, you should just pound in two ground rods and use them as your GES.

What I said is you do not have to bond the GES of the new skid to the GES of the existing structure, although the EGC of the feeder or branch circuit going from the existing structure to the new skid will effectively bond the two GES together.

Here's a thought for you. Would you consider adjacent pipe supports (each with two footings w/ rebar-based CCEs) independent of each other when considering their EGS? They would only be connected by the pipes resting on them (which you can argue can be painted/coated). Is it a matter of physical proximity (10' apart, 20', etc.)? What defines separate EGS?

 

[MRKN]

only if it is in the footing.

You quoted:

"Metallic components shall be encased by at least 50 mm
(2 in.) of concrete and shall be located horizontally within that
portion of a concrete foundation or footing that is in direct
contact with the earth or within vertical foundations or structural
components or members that are in direct contact with
the earth."

I can still very easily see how an inspector can look at a 20" slab of concrete with rebar in it and say it qualifies under a "concrete foundation in direct contact with the earth". Am I missing some civil/structural jargon that precludes a slab from being a foundation?

 

[ActionDave]

I can still very easily see how an inspector can look at a 20" slab of concrete with rebar in it and say it qualifies under a "concrete foundation in direct contact with the earth". Am I missing some civil/structural jargon that precludes a slab from being a foundation?

The NEC does not contain a definition of footing or foundation, but they are common terms in building trades. A footing is underground below frost line and a slab is not. If an inspector wants to get pushy building codes could be referenced.

 

[MRKN]

Thank you

 

[kwired]

If it's already poured and the AHJ didn't hold them up from pouring you're good to go under 250.50 "that are present". Welp, guess it's no longer present now.

They changed wording in about 2008 or 2011 because the way it was worded before that is exactly what was happening. "are present" is what got changed from "if available" or something close to that wording. Before the change - concrete was poured before EC was ever on site and it "wasn't available" and seldom was ever used as an electrode.

Now that it says "that are present", just because it got covered up before you got there doesn't make it "not present". They did throw in an exception for existing construction though, you don't need to tear up a footing just to gain access to the rebar when putting new service into existing construction. New construction you need to plan accordingly though.

The steel that is encased in the concrete would be the rebar mentioned in the code.

250.50 says all the GE at a structure have to be bonded together. however you are dealing with a separate structure here. The new skid CEE is not associated with the existing structure.

I agree sounds like this generator pad possibly is a separate structure and if so it needs it's own grounding electrode system. Question then is whether there is a qualifying CEE or not, and that sounds like it may depend if there truly is a footing or just a slab. If no qualifying CEE then pound in two rods and move on.

A lot of "if's" go along with this for no more then what we know.

You quoted:

"Metallic components shall be encased by at least 50 mm
(2 in.) of concrete and shall be located horizontally within that
portion of a concrete foundation or footing that is in direct
contact with the earth or within vertical foundations or structural
components or members that are in direct contact with
the earth."

I can still very easily see how an inspector can look at a 20" slab of concrete with rebar in it and say it qualifies under a "concrete foundation in direct contact with the earth". Am I missing some civil/structural jargon that precludes a slab from being a foundation?

There is a fairly recent thread where this is under debate. (is a slab a footing, can a slab with thicker perimeter be considered a footing) There is mixed opinions on it, and NEC isn't really all that clear either for some situations.

 

[MRKN]

"Now that it says "that are present", just because it got covered up before you got there doesn't make it "not present". They did throw in an exception for existing construction though, you don't need to tear up a footing just to gain access to the rebar when putting new service into existing construction. New construction you need to plan accordingly though."

I still tend to interpret this to mean they have a right to not let you pour the concrete, but if you have already poured, as you say they can't make you tear it up.

I don't really understand the risk of not bonding a rebar CEE to the GES, can anyone give me one example of why this would be of benefit?

 

[kwired]

"Now that it says "that are present", just because it got covered up before you got there doesn't make it "not present". They did throw in an exception for existing construction though, you don't need to tear up a footing just to gain access to the rebar when putting new service into existing construction. New construction you need to plan accordingly though."

I still tend to interpret this to mean they have a right to not let you pour the concrete, but if you have already poured, as you say they can't make you tear it up.

I don't really understand the risk of not bonding a rebar CEE to the GES, can anyone give me one example of why this would be of benefit?

They changed wording because they found out that CEE's weren't being used all that much.

CEE's have much more contact surface with soil and therefore usually much lower resistance to earth then a typical ground rod driven into same soil. In fact if you have a CEE you don't even need to drive any rods per NEC. Rods are just the simplest thing to use if there is no other electrode present or with water pipe electrodes they do require a supplemental electrode. If you have a CEE, or qualifying building steel electrode, then that is the supplemental electrode to the water pipe - no rods required.

They can and have made people tear up concrete to gain access to reinforcing steel on new construction. The exception is for existing construction. Brand new building with a qualifying CEE - NEC says you must make it a part of your GES.

First sentence of 250.50:

All grounding electrodes as described in 250.52(A)(1) through (A)(7) that are present at each building or structure served shall be bonded together to form the grounding electrode system.

(A)(3) is concrete encased electrodes. It no longer says where accessible (or something close to that), this new wording (new about 10 years ago) means if it is there it will be used.

the exception says:

Concrete-encased electrodes of existing buildings or structures shall not be required to be part of the grounding electrode system where the steel reinforcing bars or rods are not accessible for use without disturbing the concrete

Only applies to existing buildings.

 

[MRKN]

Fair enough, is there a set of notes from the committee that validates what you're saying? It would be nice to have on hand in case someone does ask concrete to be torn up. It seems to me without an understanding of the history it is unreasonable to expect every electrical engineer to interpret the gray area of the code this way and plan accordingly for hold points during the foundation work. And it doesn't do the relationship between the owner and inspector any good if the inspector chooses to force costly foundation rework in this type of example..

 

[kwired]

Fair enough, is there a set of notes from the committee that validates what you're saying? It would be nice to have on hand in case someone does ask concrete to be torn up. It seems to me without an understanding of the history it is unreasonable to expect every electrical engineer to interpret the gray area of the code this way and plan accordingly for hold points during the foundation work. And it doesn't do the relationship between the owner and inspector any good if the inspector chooses to force costly foundation rework in this type of example..

Find the ROPS from when the change was made - I'd bet at least some of what I said is in there. My comments are from recollection of what went on for discussions back when that change went into effect.

Concrete was being ordered to be torn up back then. Now the majority of the concrete contractors are on board with this rule and if the EC doesn't approach them about it, they often are trying to contact the EC to coordinate with them. Might not be same in other places, but our inspectors were notified by their department heads of the change back then and no matter where you went within the jurisdiction (which is statewide) it was being enforced pretty consistently. Our State AHJ has been pretty good at addressing new code changes in the past as a group and all the inspectors are usually on the same page when it comes to knowledge of changes in code.

Add: and especially true for changes to items in chapters 1-4, which apply to things they see all the time. A change in chapters 5-7 could be something they don't see all that often and might have a better chance of being missed.

 

[MRKN]

250.50 seems at odds with 250.52(A)(3) wherein it states "If multiple CCEs are present a building or structure, it shall be permissible to bond only one into the GES". I presume this statement overrides the require of 250.50 that all grounding electrodes in a GES are bonded together?

 

[ActionDave]

250.50 seems at odds with 250.52(A)(3) wherein it states "If multiple CCEs are present a building or structure, it shall be permissible to bond only one into the GES". I presume this statement overrides the require of 250.50 that all grounding electrodes in a GES are bonded together?

That's the way I read it

 

[infinity]

250.50 seems at odds with 250.52(A)(3) wherein it states "If multiple CCEs are present a building or structure, it shall be permissible to bond only one into the GES". I presume this statement overrides the require of 250.50 that all grounding electrodes in a GES are bonded together?

If the rebar is less than 1/2" you don't need a CEE, 1/2" or larger and 20' or longer rebar you need only one CEE. So if the structure has an existing CEE and you put on an addition with 20' of 1/2" rebar in the footing you are not required to connect it.

 

[MRKN]

Thanks Rob and Dave.

Digging around it looks like the verbiage changed from "If available" to "when present" in 2005 code cycle. The ROP from 2004:
https://www.nfpa.org/Assets/files/AboutTheCodes/70/70-A2004-ROP-Part1.pdf

Looks like 5-115 Log #1559 NEC-P05 is the only proposal where this was suggested, but it came back negative with 3 negative votes and an "explanation of negative". So I'm at a loss for support of this change.

 

[MBLES]

The inspector did require the CEE but accepted the ground ring as acceptable. He mentioned that the rebar qualified as CEE and needed to be instaled.

 

[kwired]

The inspector did require the CEE but accepted the ground ring as acceptable. He mentioned that the rebar qualified as CEE and needed to be instaled.

If rebar meets or exceeds minimum of 1/2 diameter and 20 feet length, and is not coated with insulating material is used then it must be used as an electrode. NEC does not require adding qualifying rebar if the structural design doesn't use a qualifying material for reinforcement. Adding 20 feet of 4 copper is also optional - and a way to make a CEE if you don't already have one by structural design.

 

[MRKN]

Yes but what if the footing does not contain any structural metal that is likely to be energized?

 

[infinity]

Yes but what if the footing does not contain any structural metal that is likely to be energized?

How would it be "likely" to become energized? If there is no qualifying rebar then you simply are not required to use a CEE. If there is a qualifying amount of rebar then you must use a CEE. You can use the rebar or lay in 20' of bare #4 and make your own.

 

[MRKN]

I should have said "structural metal which is likely to be energized", I'm referring to 250.104(C) - (that's off the top of my head and I believe it's the correct reference). My point is that without any conduit or electrical equipment whatsoever involved with the structure it is not likely to be energized. What I am trying to get at is when does the NEC even apply. If I install a concrete footing out in the middle of nowhere with 20' of rebar in it, and a pipe support T on top of it, it would be a code violation of the NEC if I didn't connect the rebar to the anchor bolts to the structural steel?

 

[ActionDave]

...... What I am trying to get at is when does the NEC even apply. If I install a concrete footing out in the middle of nowhere with 20' of rebar in it, and a pipe support T on top of it, it would be a code violation of the NEC if I didn't connect the rebar to the anchor bolts to the structural steel?

My personal experience, while annecdotal, is there needs to be electricity on site or nearby before anyone even asks about wires let alone code compliance.

 

[kwired]

Yes but what if the footing does not contain any structural metal that is likely to be energized?

I should have said "structural metal which is likely to be energized", I'm referring to 250.104(C) - (that's off the top of my head and I believe it's the correct reference). My point is that without any conduit or electrical equipment whatsoever involved with the structure it is not likely to be energized. What I am trying to get at is when does the NEC even apply. If I install a concrete footing out in the middle of nowhere with 20' of rebar in it, and a pipe support T on top of it, it would be a code violation of the NEC if I didn't connect the rebar to the anchor bolts to the structural steel?

250.104 is not about CEE's, and subpart (C) is about structural steel that isn't also a qualifying grounding electrode.

250.52(A)(2) describes what structural metal is a qualifying grounding electrode. Such metal that is also a qualifying electrode must be connected to the grounding electrode system whether likely to become energized or not.

Isolated steel beam in a wood framed building is one example of something that is structural steel that may or may not need to be bonded to.