Ground Rod Installation

[Dennis Alwon]

Without reinforcement steel rods embedded in the concrete,it can not be bonded.

That is not entirely true. As stated a concrete patio around a pool must be bonded whether there is steel or not. It is an equipotential bond and is required by 680.26-- specifically 680.26(B)(2)(b)

 

[T.M.Haja Sahib]

That is not entirely true. As stated a concrete patio around a pool must be bonded whether there is steel or not. It is an equipotential bond and is required by 680.26-- specifically 680.26(B)(2)(b)

I am afraid your wordings are not clear,See

http://www.erico.com/public/library/fep/LT1242.pdf and the following

''680.26(B)(1) & (B)(2):

(B) Bonded Parts. The parts specified in 680.26(B)(1) through (B)(7) shall be bonded together using solid copper conductors, insulated, covered, or bare, not smaller than 8 AWG or with rigid metal conduit of brass or other identified corrosion-resistant metal. Connections to bonded parts shall be made in accordance with 250.8. An 8 AWG or larger solid copper bonding conductor provided to reduce voltage gradients in the pool area shall not be required to be extended or attached to any remote panelboards, service equipment, or electrodes.

(1) Conductive Pool Shells. Bonding to conductive pool shells shall be provided as specified in 680.26(B)(1)(a) or 680.26(B)(1)(b). Poured concrete, pneumatically applied or sprayed concrete and concrete block with painted or plastered coatings shall all be considered conductive materials due to water permeability and porosity. Vinyl liners and fiberglass composite shells shall be considered to be non-conductive materials.

a. Structural Reinforcing Steel. Unencapsulated structural reinforcing steel shall be bonded together by steel tie wires or the equivalent. Where structural reinforcing steel is encapsulated in a non conductive compound, a copper conductor grid shall be installed in accordance with 680.26(B)(1)(b).




b. Copper Conductor Grid. A copper conductor grid shall be provided and shall comply with (b)(1) through (b)(4).
(1) Be constructed of minimum 8 AWG bare solid copper conductors bonded to each other at all points of crossing.
(2) Conform to the contour of the pool and the pool deck.
(3) Be arranged in a 12 inch by 12 inch network of conductors in a uniformly spaced perpendicular grid pattern with a tolerance of 4 inches.
(4) Be secured within or under the pool no more than 6 inches from the outer contour of the pool shell.

(2) Perimeter Surfaces. The perimeter surface shall extend for 3 feet horizontally beyond the inside walls of the pool and shall include unpaved surfaces as well as poured concrete and other types of paving. Bonding to perimeter surfaces shall be provided as specified in 680.26(B)(2)(a) or (2)(b), and shall be attached to the pool reinforcing steel or copper conductor grid at a minimum of four (4) points uniformly spaced around the perimeter of the pool. For non-conductive pool shells, bonding at four points shall not be required.

(a) Structural Reinforcing Steel. Structural reinforcing steel shall be bonded In accordance with 680.26 (B)(1)(a).

(b) Alternate Means. Where structural reinforcing steel is not available or is encapsulated in a non conductive compound, copper conductor(s) shall be utilized where the following requirements are met:
(1) At least one minimum 8 AWG bare solid copper conductor shall be provided.
(2) The conductor(s) shall follow the contour of the perimeter surface.
(3) Only listed splices shall be permitted.
(4) The required conductor shall be 18 to 24 inches from the inside walls of the pool.

(5) The required conductor shall be secured within or under the perimeter surface 4 inches to 6 inches below the sub grade.''

Simply wrapping a grounded conductor around the perimeter of the plain concrete surface will not make it an equipotential plane against indirect contact with live wires and it is not the intent of the code also.

 

[Dennis Alwon]

Read the last section- (b)- where there is no structural steel bonding is still required. Your statement was that you needed steel to bond. Different situation yes but it is not always the case. Also a concrete encased electrode does not need steel to create a GEC-

 

[T.M.Haja Sahib]

Read the last section- (b)- where there is no structural steel bonding is still required.

Consider this.The plain concrete surface is 'bonded' along its perimeter per the last section- (b).Suppose there is an indirect contact with live wire.There is no way that the touch voltage will be within safe limits simply because there is 'perimeter bonding'.If such be the case there would be no need for extensive substation earthing with concrete floor.Then why is it provided?Just to reduce the voltage gradient along the surface inside the perimeter in case an earth fault occurs outside it or vice versa.

 

[Dennis Alwon]

Suppose there is an indirect contact with live wire.There is no way that the touch voltage will be within safe limits simply because there is 'perimeter bonding'.

Are you saying that it would be different if there were structural steel in the concrete? Maybe I am confused by what was being said in the first place. My comment was to correct the comment you made earlier about structural steel being necessary for bonding. I fail to see the difference with rebar in the concrete except that there would probably be less resistance in the slab.

 

[T.M.Haja Sahib]

Are you saying that it would be different if there were structural steel in the concrete? Maybe I am confused by what was being said in the first place. My comment was to correct the comment you made earlier about structural steel being necessary for bonding. I fail to see the difference with rebar in the concrete except that there would probably be less resistance in the slab.

Yes.I am saying that it would be different if there were structural steel in the concrete.The intent of the code to provide grounded conductor around the perimeter of the plain concrete cement surface is to make it an equipotential plane for earth faults outside its perimeter and not for earth faults inside its perimeter for which structural steel embedded in it is necessary for unsafe touch voltages.

 

[kwired]

Bonding surfaces around pools is not for protection from incidental contact with a live conductor, it is for equalizing the potential between conductive objects within reach of the users of the pool. The chance of contact with a live conductor is not that great if the NEC has been followed as there will not be much chance of a live conductor existing in the area to make contact. There are rules for minimum distances for different types of equipment from the pool, if the equipment is not directly serving the pool it typically must be kept away, if it is directly serving the pool it must have any non current carrying conductive parts bonded to the equipotential grid in some way and typically will require GFCI protection also.

Stray currents in the earth, most of which started their path at a grounding electrode, will seek a path back to their source via other grounding electrodes, are the biggest reason for all the equipotential grounding at pools. If we did not use the grounded service conductor to carry neutral current, but only as an equipment grounding conductor to help clear ground faults, this problem would not really be as much of a problem. The fact that the power company uses a grounded conductor to carry current means even if you have no neutral load in your facility, you still have POCO neutral voltage drop imposed on anything grounded, and bonded to the electric service grounding electrode system.

 

[George Stolz]

The intent of the code to provide grounded conductor around the perimeter of the plain concrete cement surface is to make it an equipotential plane for earth faults outside its perimeter...

That's not correct. Watch this video:
Mike Holt's Stray Voltage Video

 

[T.M.Haja Sahib]

That's not correct. Watch this video:
Mike Holt's Stray Voltage Video

Are you saying that providing a grounded conductor around the perimeter of the plain concrete will not make it an equipotential plane per the definition of an equipotential plane in NEC.Then for what purpose is it provided? I think you will never find an explicit answer in NEC.Do you?

 

[T.M.Haja Sahib]

Bonding surfaces around pools is not for protection from incidental contact with a live conductor, it is for equalizing the potential between conductive objects within reach of the users of the pool. The chance of contact with a live conductor is not that great if the NEC has been followed as there will not be much chance of a live conductor existing in the area to make contact. There are rules for minimum distances for different types of equipment from the pool, if the equipment is not directly serving the pool it typically must be kept away, if it is directly serving the pool it must have any non current carrying conductive parts bonded to the equipotential grid in some way and typically will require GFCI protection also.

Stray currents in the earth, most of which started their path at a grounding electrode, will seek a path back to their source via other grounding electrodes, are the biggest reason for all the equipotential grounding at pools. If we did not use the grounded service conductor to carry neutral current, but only as an equipment grounding conductor to help clear ground faults, this problem would not really be as much of a problem. The fact that the power company uses a grounded conductor to carry current means even if you have no neutral load in your facility, you still have POCO neutral voltage drop imposed on anything grounded, and bonded to the electric service grounding electrode system.

Here we are discussing about the two conditions from post no 76.Since the plain concrete floor can not provide protection against indirect contact for unsafe touch voltages,as it can not be made an equipotential plane for this condition,only condition no.2 in post no.76 should be satisfied for absence of above touch voltages.

 

[George Stolz]

Are you saying that providing a grounded conductor around the perimeter of the plain concrete will not make it an equipotential plane per the definition of an equipotential plane in NEC.

No. You said

The intent of the code to provide grounded conductor around the perimeter of the plain concrete cement surface is to make it an equipotential plane for earth faults outside its perimeter...

I don't know what an "earth fault" is, but I know that the intent of the equipotential bonding requirements around pools in Article 680 is to safely and uniformly energize the pool and surrounding structures to one voltage.

I have no idea how you're pulling grounding into this, and I have no idea what this concept has in common with your idea about a grounding electrode system (which is a totally different animal) eliminating the shock risk of an open neutral. These concepts have almost nothing in common.

 

[T.M.Haja Sahib]

No. You said

I don't know what an "earth fault" is, but I know that the intent of the equipotential bonding requirements around pools in Article 680 is to safely and uniformly energize the pool and surrounding structures to one voltage.

What I see is this:
When a live conductor comes in contact with ground,we have an earth fault and if this happens outside the plain concrete surface, the perimeter of which is bonded with grounded conductor,the plain concrete surface becomes an equipotential plane.

But if the same earth fault takes place inside the perimeter,there is no way that unsafe touch voltages do not arise,simply because the perimeter of the plain concrete is bonded with a grounded conductor.An equipotential plane near that earth fault is necessary for protection against unsafe touch voltages.In other words,the metal on which earth fault happens should have a low contact resistance with concrete i.e 'low earth resistance' for touch voltages to be in safe limit.

 

[George Stolz]

I see a series of words tied together devoid of any meaning at all. Care to try again? :?

 

[T.M.Haja Sahib]

I see a series of words tied together devoid of any meaning at all. Care to try again? :?

Yes.Suppose there exists a plain concrete surface,the perimeter of which is provided with a grounded conductor.A metal post partly buried is standing in its middle.A live 120V conductor contacts with it and a leakage current is flowing through the metal post.Is the touch voltage on the metal post is unsafe or not?

 

[George Stolz]

Since the post supplied was connected to an equipment grounding conductor as required by the NEC, then yes, it's perfectly safe. The breaker tripped five cycles into the fault.

Otherwise, no, I would not expect a single conductor equipotential bonding conductor embedded in the concrete to effectively raise the potential around the post throughout the concrete pad to 120V. There would be a noticeable gradient around the post to someone barefoot and wet.

 

[T.M.Haja Sahib]

Since the post supplied was connected to an equipment grounding conductor as required by the NEC, then yes, it's perfectly safe. The breaker tripped five cycles into the fault.

You are wrong.The condition that brings electrocution not only depends on the duration but also on the magnitude of the current flowing through the heart of the victim.

QUOTE=George Stolz;1340903]
Otherwise, no, I would not expect a single conductor equipotential bonding conductor embedded in the concrete to effectively raise the potential around the post throughout the concrete pad to 120V. There would be a noticeable gradient around the post to someone barefoot and wet.[/QUOTE]

Then what is the purpose of below (post no.83) ?

Read the last section- (b)- where there is no structural steel, bonding is still required.

 

[George Stolz]

That's bad luck to be touching the pole during the five cycles of fault.

The purpose would be clear if you watch the video I linked to earlier.

 

[SG-1]

Please see

http://en.wikipedia.org/wiki/Single-wire_earth_return

What does a SEWR system have to do with this discussion ? SEWR systems operate in the medium to high voltage range. This discussion is concerning 120 V loads which cannot operate through an earth return.

The most dangerous aspect to a residence losing the grounded conductor is that electronic devices will smoke & the house can burn to the ground as 240 volts divides unevenly across the 120 volt loads that are now in series with each other across a 240 volt source.

 

[T.M.Haja Sahib]

The purpose would be clear if you watch the video I linked to earlier.

I want your own interpretation in brief my dear friend for Mikeholt may not be available for further discussion.

 

[T.M.Haja Sahib]

What does a SEWR system have to do with this discussion ? SEWR systems operate in the medium to high voltage range. This discussion is concerning 120 V loads which cannot operate through an earth return.

Earth is a good conductor. The trouble is that we cannot make a good low impedance connection with it.

You made a general comment in post no.71