NEC 250 Equipment Grounding quandary--how do I prove contractor is not correct?

[Snowjob]

The contractor has installed a system I am inspecting using Method 1 for an Equipment Ground.
I don't belive this is a sound practice even though all components are metal because over the time bolts loosen and rust. Also the ground used is not a low impedance ground.

I believe Method 2 is correct but I can't find the specific line in Section 250 that proves me correct.

Can anyone help?

 

[George Stolz]

What is the grounding electrode?

If it's a Concrete Encased Electrode (CEE) then it is fine.

My question in looking at the diagram is, are these components actually all built on the same rack?

 

[Snowjob]

Yes they are.

Yes they are.

All of these panels are on the same rack and all of them have 120/240 VAC in them

 

[SG-1]

Continuous

Continuous

I have to make a few assumptions...

The 2 ground rods exist because of 250.56. One rod does not meet the 25 ohms to ground requirement or it could not be measured, so the second rod was added.

The real question here is the manner in which the rods are bonded together.

260.64(C) States the GEC shall be installed in one continous length without a splice or joint. Method 1 has many joints & therefore does not qualify as continous.

 

[Smart $]

...

I believe Method 2 is correct but I can't find the specific line in Section 250 that proves me correct.

Can anyone help?

Assuming SDM stands for service disconnecting means, and everything to its left is non-service equipment, the section you are looking for is 250.24(A)(1)...

250.24 Grounding Service-Supplied Alternating-Current Systems.

(A) System Grounding Connections. A premises wiring
system supplied by a grounded ac service shall have a
grounding electrode conductor connected to the grounded
service conductor, at each service, in accordance with
250.24(A)(1) through (A)(5).

(1) General. The grounding electrode conductor connection
shall be made at any accessible point from the load end
of the service drop or service lateral to and including the
terminal or bus to which the grounded service conductor is
connected at the service disconnecting means.

 

[augie47]

I'm afraid I have more questions than answers.
The thread is entitied equipment grounding, but I assume we are discussing groujnding electrode connections.
If so, Method 1 is out, due to 250.24 that Smart$$ posted. The GEC has to connect to the grounded conductor at some point, not to a support;.
How is the connection made in the SDM ?
You show a #2 which would be oversized for a ground rod or CEE but is fine.
The #6 would be fine for either rod.
Does the #6 run contnuoulsly from the SDM to the rod ?

Bottom line to me, #2 is more compliant than #1, but still may not meet Code

 

[Snowjob]

The conductor sizes weren't the real question, and i'm sorry for confusing you people.

My biggest worry concerns equipment grounding.

Method 1 presents a unreliable impedance path to the counterpoise whereas method 2 is a more reliable. impedance path

Over time the cabinets and panels (all with 120/240 AC) will rust and their bolts will loosen and rust as the frame shakes. By tying a continuous 6 AWG conductor to all cabinets and terminating it at the Service Disconnect ground, a more reliable equipment ground is obtained.

 

[Snowjob]

Assuming SDM stands for service disconnecting means, and everything to its left is non-service equipment, the section you are looking for is 250.24(A)(1)...

​

Thats what I was looking for...

 

[George Stolz]

Why are there two connections to the same electrode from the same rack?

Sorry, I missed that method 1 wasn't returning to the service disconnect.

 

[electricmanscott]

I have to make a few assumptions...

The 2 ground rods exist because of 250.56. One rod does not meet the 25 ohms to ground requirement or it could not be measured, so the second rod was added.

The real question here is the manner in which the rods are bonded together.

260.64(C) States the GEC shall be installed in one continous length without a splice or joint. Method 1 has many joints & therefore does not qualify as continous.

You do not have to have one continuous conductor from point a to rod 1 to rod 2. The GEC goes to the first rod. After that you have a bonding jumper from the first rod to the second rod.

 

[Snowjob]

My fault, there are 6 ground rods. The ground rods were kind of symbolic. I'm assuming a standard counterpoise at 1 ohms

 

[hurk27]

I think there is a big misunderstanding as to what ground rods actually do, I wouldn't miss any sleep over this installation other then some court judge pointing out that diagram #1 is in violation of the code (as pointed out) but there have been many test even for lightning strikes at Camp Blanding, Fl. that prove a little ground rod does almost nothing at a service.

Do a search on here about ground rods and you will find many threads that will show how little ground rods do anything to make a service safer.

 

[Snowjob]

Contractor at resort installing communications system provided equipment ground by (a) using two pressure clamps on frame support legs with #4 AWG running to EES and (b) relying on metal to metal contact of cabinets, frame members, bolts, nuts and other connecting hardware to provide equipment ground. This is potentially a high impedance path

Contract called for #6 AWG (see arrows) equipment grounding wire running from cabinet to cabinet to frame to Service Disconnect Ground tie to EES per drawing above.

What code clause can I cite him on. He isn't cooperating. I am sure the previous clause cited is the correct one, but I want to have it all spelled out clearly. is there anything else out there?

 

[hurk27]

110.3 if those diagrams are part of the manufactured instructions.

but if those are engineered submitted plans then that would fall under local or state law if it applies.

It appears that those plans call for extensive re-bar connections in the concrete below the cabinets and in the vertical column in the middle, but its kind of too small to read on here.

 

[al hildenbrand]

Snowjob,

With all due respect, it's kind of hard to understand you.

You are asking for National Electrical Code (NEC) citations to support your position. That's clear. But your responses to our questions aren't clarifying the installation you are inquiring about.

The National Electrical Code (NEC) has a collection of defined terms, primarily located in Article 100 in alphabetical order. Look at the "G" set of terms for "grounding xxx". Also look at the "B" set of terms including "bonded" and "bonding xxx".


Your terms:

1. EES
2. SDM
3. Equipment grounding wire
4. Counterpoise
5. unreliable impedance path

Your terms don't translate well to the terms defined in the NEC. This alone may well be part of the difficulty with "the contractor".

Your diagram seems to show a CEE, i.e., Concrete Encased Electrode (see 2008 NEC 250.52(A)(3)) as the primary Grounding Electrode (see 2008 NEC Article 100 Definitions).

The six ground rods will do little, if anything, to improve the Earth connection (see Article 100 Definition "Ground") beyond what the CEE has already established.

 

[Joe Villani]

Equipment Grounding quandry

Equipment Grounding quandry

Snowjob,

Are all the raceways metallic and comply with 250.118?. If so, the equipment grounding would be accomplished.

If the raceways are non metallic and/or don't comply with 250.118 then,

Take a look at 250.136(A) and 250.134 (A) and (B)

See if that helps

Joe Villani

 

[SG-1]

You would like the contractor to run the GEC through each enclosure & bond it to each enclosure ?

 

[Snowjob]

You would like the contractor to run the GEC through each enclosure & bond it to each enclosure ?

Yes.
Thats my only concern.
(Sorry to everyone for the confusion.I'm not concerned about the counterpoise and rebar and all that but I am a one fingered typer and it takes me hours to write simple posts! Its sheer pain.)

I dont think you get good equipment grounding through the frame, bolts and enclosures by bonding the frame through #4 AWG to the earth electrode system with the two pressure clamps.

Everything will rust, loosen and flex through the years. Also this is a high impedance path.

By installing the 6AWG GCE as the drawing shows and connecting it to the Service Disconnect Means ground, I feel a good equipmnet ground is established.

Anyway I got all my answers, and i won my case this afternoon. Thanks everyone

BTW for future readers of this, EES = earth electrode system, SDM = service disconnect means

 

[al hildenbrand]

You would like the contractor to run the GEC through each enclosure & bond it to each enclosure ?

Yes.
Thats my only concern.

Bonding.

I don't think you get good equipment grounding through the frame, bolts and enclosures by bonding the frame through #4 AWG to the earth electrode system with the two pressure clamps.

Everything will rust, loosen and flex through the years. Also this is a high impedance path.

You made this very clear. This is the fourth time you make this claim, including your opening post (OP). Your claim has no basis in the NEC that is really supportable. Several responses to this thread are heading in that direction. Adhering to your claim smacks of "Do it MY way! I'm not listening."

By installing the 6AWG GCE as the drawing shows . . .

"GCE" - a new term of yours.

I got all my answers, and i won my case this afternoon.

. . . ? . . . I suspect "the contractor" is giving in to stop talking with you, and just be quit with the job.

BTW for future readers of this, EES = earth electrode system, SDM = service disconnect means

As an engineer you must be working inside a large set of private standards. You seem entitled to the right to not use the NEC as anything other than a foil for your own agenda.

 

[George Stolz]

This thread is closed.