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building grounding

H

Hyrax4978

Registered User
Joined
Nov 28, 2016
Messages
205
Location
Hartford, CT
We have a building going up (concrete foundations right now) and the electrical engineer just said that technically per code the building doesn't need to be grounded. we were directed to ground the building steel and the plumbing piping to the electrical system. but not the foundation rebar and no ground rods.

We were surprised that grounding the rebar system was not required and even more so that grounding rods where not required.

Can anyone confirm this is kosher?

Thanks,

Brian
 
@ = @

Yes **Hydrax4978**, ...the building does need an
approved method of grounding.......There are choices
of which elements that be can used as the grounding
system.

Which Electrical Code is applicable in your application ?

Also, please have "that engineer" cite the applicable
Code sections to you in writing, that do not require an
approved method of grounding......Then come back
on here and let us know what is submitted to you.

@ = @
 
The electrical system needs to be grounded:

250.50 Grounding Electrode System. 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.

Unless the electrons in Connecticut are a different color than here in California, that code section should be correct.
 
I believe the electrical engineer is correct based on an understanding of electronics.

Grounding wires are needed to provide a safe path for excess electrons to get to the ground thus protecting the inhabitants and the structure. Elements of the building that do not create or transfer electrons do not need to be grounded. Thus since concrete and its reinforcement do not provide a source of electrons they do not need to be grounded.

Part of the confusion is because sometimes the rebar in the foundation is used as the building ground. This is known as a Ufer ground. But this is not needed if another path to ground is provided. When a non-conducting membrane is installed between the concrete foundation and the ground a ufer ground would not work since it would result in a floating ground.

Sometimes the rebar is bonded together if corrosion is a concern but that is not a safety concern.

I do not encourage the use of a buildings steel frame as part of the grounding system both because of the potential corrosion that could result from the grounding current and because I do not have confidence that the normal bolted connections provide a low resistance path. There is also the concern that in some cases the bonding of the grounding wires to the buildings structural frame could create problems.
 
@ ~ @ ~ @

Using the building steel is one approved method of
grounding [ RE: Article 250.52(A)(2), `08 NEC ].

@ ~ @ ~ @
 
Mark K said:
....................
I do not encourage the use of a buildings steel frame as part of the grounding system both because of the potential corrosion that could result from the grounding current and because I do not have confidence that the normal bolted connections provide a low resistance path. There is also the concern that in some cases the bonding of the grounding wires to the buildings structural frame could create problems.
Click to expand...

Grounding current? Do you mean fault current? The grounding electrode system should only see current during a fault.
 
steveray is from CT, hopefully he will shine some light on this topic.

Apparently CT is enforcing the 2017 NEC (see below).

Hyrax may want to further clarify correct use of terms to set this topic on the correct path of discussion.

"we were directed to ground the building steel and the plumbing piping to the electrical system" this as written could be construed as a bonding requirement, not part of the grounding electrode system.

The 2017 NEC changed 250.52(A)(2) to "Metal In-Ground Support Structure" from "Metal Frame of the Building" to qualify for it to meet specific conditions to be considered a grounding electrode. The metal support structure must be in direct contact with the earth vertically for 10 ft. or more (with or without concrete encasement).
Alternatively the hold-down bolts securing the structural steel column connected to the rebar in the foundation (concrete-encased electrode) will serve as the grounding electrode.

CT codes.JPG
 
So if i understand this correct that by connecting the building steel and water service piping to the neutral bus, those are methods of grounding the system. and if ICE is correct, because we have rebar, and that is one method listed we need to tie that to the neutral as well. So then since it is a new building, and grounding rods do not currently exist, do they need to be added and also tied to the neutral bus.

Thanks,

Brian
 
You don't need rods....You do need one grounding electrode whatever that might be....As ICE said where any of the "approved " electrodes are available, they have to bonded together as part of the grounding electrode system..Like ICE said by 250.50.....The only time you "need" rods is when you use the water pipe as the GE it requires a supplemental electrode, which is typically rods...
 
Just because you have one or more elements that may be a part of the grounding system you do not have to automatically ground them as long as you provide the necessary grounding using a option listed in the code.

The fact that the buildings metal frame or reinforcing in the foundation may be used as part of the grounding system doesn't mean that it is always considered a grounding electrode. You have to p0rovide grounding but you can do it in several different ways.

Is it possible that the electrical engineer knows what he is talking about? This option has not seemed to be considered by the inspectors responding.

Not all possible currents in the ground wiring will be from what is normally considered as a fault.
 
Mark K said:
Just because you have one or more elements that may be a part of the grounding system you do not have to automatically ground them as long as you provide the necessary grounding using a option listed in the code.

The fact that the buildings metal frame or reinforcing in the foundation may be used as part of the grounding system doesn't mean that it is always considered a grounding electrode. You have to p0rovide grounding but you can do it in several different ways.

Is it possible that the electrical engineer knows what he is talking about? This option has not seemed to be considered by the inspectors responding.

Not all possible currents in the ground wiring will be from what is normally considered as a fault.
Click to expand...


ICE answered this. And it seems to be written in plain enough language that even an engineer should understand it:

250.50 Grounding Electrode System. 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. Where none of these electrodes exist, one or more of the grounding electrodes specified in 250.52(A)(4) through (A)(8) shall be installed and used.

"All that are present" means all of them. If you have more than one, you must bond them together.
 
250.52 (A) is about "Electrodes Permitted for Grounding". Just because an option is permitted does not make it a grounding electrode. If it is not a grounding electrode it is not present as an grounding electrode and thus does not need to be bonded.

The problem that the electrical engineer has is that he knows what is the intent of the code and what makes electrical sense. He then interprets the code in this context.
 
Pretty sure the intent of the code is that IF you make one of these things available, you WILL bond it to the others.

There's not a lot to interpret in 250.50 - that's as plain as code language gets. "If you have this you must do that", is pretty elementary.

But since I know you struggle listening to anything a lowly inspector has to say, here's a snippet from the 2014 NEC Handbook Commentary on 250.50:

"The Code does not specify that metal water pipe, structural metal frame, or concrete-encased-type electrodes have to be installed, only that where they have been installed as part of the building construction they are to be used as components of the grounding electrode system."

So it would appear that the folks at the NFPA don't see it your way...
 
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