Bonding of Concrete without rebar in classified areas

[kenaslan]

I hope this is the correct forum for this topic.

We have a vessel being installed on a concrete foundation in a refinery. Class 1 Div 2. The foundation will be 60" thick, and in direct contact with the earth, however with no rebar.

We all can agree that all rebar (Grounding Electrode) needs to be bonded. However the foundation in question has no rebar.

It seems that 250.50 implies that all foundations need to be bonded to the Grounding Electrode System and if no electrode exists then one must be added.

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 grounding electrodes exist, one or more of the grounding electrodes specified in 250.52(A)(4) through (A)(8) shall be installed and used.

Section 250.50 introduces the important concept of a grounding electrode system, in which all electrodes that are present at a build-
ing or structure are bonded together, as illustrated in Exhibit 250.22. Rather than total reliance on a single grounding electrode to perform its function over the life of the electrical installation, the NEC requires the formation of a system of electrodes where multiple grounding electrodes are at the building being served. Metal structural members, metal water pipe, and concrete footings or foundations are found in many buildings and structures and are required to be integrated into the grounding electrode system if they qualify under the conditions specified in 250.52(A).

However the Structural engineer does not want to add rebar or a copper electrode to this foundation.

So my question is, must this foundation be bonded to the Grounding Electrode System?

 

[jumper]

If there is no rebar and EE has a valid reason for not using a wire type CEE, then it is not required. You will just have to establish a GES using alternative methods.

This would be any standard type of structure.

However, you mentioned refinery so I am not sure what else would apply.

 

[gadfly56]

If there is no rebar and EE has a valid reason for not using a wire type CEE, then it is not required. You will just have to establish a GES using alternative methods.

This would be any standard type of structure.

However, you mentioned refinery so I am not sure what else would apply.

There may be some API standards involve. I'm not familiar with them, just know of them.

 

[kenaslan]

Don't know what a type CEE wire is as it is not listed in the code book.
You misunderstand. Yes there is a Grounding Electrode System, the question is must this foundation be connected to the GES for equipotential bonding?

 

[jumper]

Wire type CEE is 20' of #4 bare copper wire embedded in concrete.

250.52(A)(3).

 

[jumper]

Yes there is a Grounding Electrode System, the question is must this foundation be connected to the GES for equipotential bonding?

Normally no, but you are in a classified area-different rules may apply.

 

[kwired]

I hope this is the correct forum for this topic.

We have a vessel being installed on a concrete foundation in a refinery. Class 1 Div 2. The foundation will be 60" thick, and in direct contact with the earth, however with no rebar.

We all can agree that all rebar (Grounding Electrode) needs to be bonded. However the foundation in question has no rebar.

It seems that 250.50 implies that all foundations need to be bonded to the Grounding Electrode System and if no electrode exists then one must be added.

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 grounding electrodes exist, one or more of the grounding electrodes specified in 250.52(A)(4) through (A)(8) shall be installed and used.

Section 250.50 introduces the important concept of a grounding electrode system, in which all electrodes that are present at a build-
ing or structure are bonded together, as illustrated in Exhibit 250.22. Rather than total reliance on a single grounding electrode to perform its function over the life of the electrical installation, the NEC requires the formation of a system of electrodes where multiple grounding electrodes are at the building being served. Metal structural members, metal water pipe, and concrete footings or foundations are found in many buildings and structures and are required to be integrated into the grounding electrode system if they qualify under the conditions specified in 250.52(A).

However the Structural engineer does not want to add rebar or a copper electrode to this foundation.

So my question is, must this foundation be bonded to the Grounding Electrode System?

No rebar present it is not a grounding electrode for the intent of art 250 part III.

Don't know what a type CEE wire is as it is not listed in the code book.
You misunderstand. Yes there is a Grounding Electrode System, the question is must this foundation be connected to the GES for equipotential bonding?

For NEC - no, not sure about other codes that may apply.

 

[kenaslan]

A Concrete Encased Electrode is not a wire type. THHN THWN XHHW are wire types, Rebar is a CEE and it is not a wire

 

[jumper]

A Concrete Encased Electrode is not a wire type. THHN THWN XHHW are wire types, Rebar is a CEE and it is not a wire

Wanna bet a donut that I can have a wire type CEE?

Did you read the section Iposted?

 

[kenaslan]

We will then agree to disagree, as a retired IBEW Master Electrician I can tell you that is not a wire type, Also all the PEs here also agree that is not a wire type.

However I digress, I believe that the foundation in question must be bonded with the addition of a bare copper wire. API 2003. The reason is the tank is bonded, and concrete is a conductor all be it a poor one. therefor a person standing on the concrete may have a static charge because of the high resistivity of concrete. By adding a bonding cable to the grid, you effectively lower the resistivity of the concrete and more quickly dissipate any static charge the person my have on his clothing. Then when he touches the tank no spark, no boom.

 

[kwired]

A Concrete Encased Electrode is not a wire type. THHN THWN XHHW are wire types, Rebar is a CEE and it is not a wire

A CEE is concrete with a conductor embedded in it. To be a NEC compliant CEE said conductor must be 1/2 or larger steel or #4 AWG copper. Both need to be at least 20 feet in length to be considered a CEE, and I believe encased in at least 2 inches of concrete.

If structural design doesn't require rebar or doesn't use qualifying reinforcement material and you still want to have a CEE - you can lay #4 copper in the concrete.

 

[jumper]

A CEE is concrete with a conductor embedded in it. To be a NEC compliant CEE said conductor must be 1/2 or larger steel or #4 AWG copper. Both need to be at least 20 feet in length to be considered a CEE, and I believe encased in at least 2 inches of concrete.

If structural design doesn't require rebar or doesn't use qualifying reinforcement material and you still want to have a CEE - you can lay #4 copper in the concrete.

Well he does not believe me, hopefully he may listen to you.

I give up.

 

[texie]

We will then agree to disagree, as a retired IBEW Master Electrician I can tell you that is not a wire type, Also all the PEs here also agree that is not a wire type.

However I digress, I believe that the foundation in question must be bonded with the addition of a bare copper wire. API 2003. The reason is the tank is bonded, and concrete is a conductor all be it a poor one. therefor a person standing on the concrete may have a static charge because of the high resistivity of concrete. By adding a bonding cable to the grid, you effectively lower the resistivity of the concrete and more quickly dissipate any static charge the person my have on his clothing. Then when he touches the tank no spark, no boom.

As others have already mentioned, a CEE is not limited to rebar. See 250.52(A)(3)(2).
As to the question of weather the slab/foundation requires any bonding/GES in this application, I think the NEC is silent on this. Maybe some other standards are applicable though.

 

[kwired]

We will then agree to disagree, as a retired IBEW Master Electrician I can tell you that is not a wire type, Also all the PEs here also agree that is not a wire type.

However I digress, I believe that the foundation in question must be bonded with the addition of a bare copper wire. API 2003. The reason is the tank is bonded, and concrete is a conductor all be it a poor one. therefor a person standing on the concrete may have a static charge because of the high resistivity of concrete. By adding a bonding cable to the grid, you effectively lower the resistivity of the concrete and more quickly dissipate any static charge the person my have on his clothing. Then when he touches the tank no spark, no boom.

Resistance of the concrete in contact with earth is low but not so low it is a reliable conductor to intentionally carry current on it. Is great for static reduction, but bring in a person with clean, high resistive footwear and put a static charge on him, he can still be discharged when he touches the tank, or the concrete

Putting a conductor inside concrete and placing it in the ground increases the contact area to the ground which gives you a lower resistance connection to ground then just laying the same conductor directly in the dirt. Soil conditions will vary the results but this statement is generally true over a large variety of soil conditions.

 

[USMC1302]

Kenaslan, seems there is a misunderstanding due to wording. I would also offer that your definition of wire types THHN, etc I would call insulation types. I believe what was meant is that a CEE can be established using wire, a "wire type" CEE. Least that's what it means to me...

 

[kenaslan]

I am not saying stick the conductor in the ground. It must be connected to the ground grid/ring, hence a low impedance path

 

[tom baker]

We will then agree to disagree, as a retired IBEW Master Electrician I can tell you that is not a wire type, Also all the PEs here also agree that is not a wire type.

The original study and code proposal by Herb Ufer was for 20 ft of bare 4 AWG copper, as it was commonly available on new construction sites/

A wire type CEE is most certainly recognized and allowed by the NEC. The NEC allows either reinforcing steel or a minimum bare 4 AWG copper

 

[ActionDave]

I am not saying stick the conductor in the ground. It must be connected to the ground grid/ring, hence a low impedance path

If you are talking about an equi potential grid, similar to what is done around an in ground swimming pool or power station then that is a far different animal than a CCE and neither has anything to do with creating a low impedance path.

 

[ActionDave]

I hope this is the correct forum for this topic.

We have a vessel being installed on a concrete foundation in a refinery. Class 1 Div 2. The foundation will be 60" thick, and in direct contact with the earth, however with no rebar.

We all can agree that all rebar (Grounding Electrode) needs to be bonded. However the foundation in question has no rebar.

It seems that 250.50 implies that all foundations need to be bonded to the Grounding Electrode System and if no electrode exists then one must be added.

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 grounding electrodes exist, one or more of the grounding electrodes specified in 250.52(A)(4) through (A)(8) shall be installed and used.

Section 250.50 introduces the important concept of a grounding electrode system, in which all electrodes that are present at a build-
ing or structure are bonded together, as illustrated in Exhibit 250.22. Rather than total reliance on a single grounding electrode to perform its function over the life of the electrical installation, the NEC requires the formation of a system of electrodes where multiple grounding electrodes are at the building being served. Metal structural members, metal water pipe, and concrete footings or foundations are found in many buildings and structures and are required to be integrated into the grounding electrode system if they qualify under the conditions specified in 250.52(A).

However the Structural engineer does not want to add rebar or a copper electrode to this foundation.

So my question is, must this foundation be bonded to the Grounding Electrode System?

The NEC has nothing to say about structural engineering. If the structural engineer doesn't want steel in the concrete you are not going to find a code reference making him add it.

There is no NEC requirement to bond rebar that doesn't exist, just like there is no NEC requirement to add building steel to a wood structure.

Either way, if you want rebar you are going to have to justify it on something other than art. 250.

 

[steve66]

Not sure what the codes says, but personally I would want the concrete bonded. Maybe the tank anchor bolts already effectively bond the concrete and tank?

If not, why would the structural engineer care if 20' of copper wire was added to a concrete foundation?