Importance of NEC 250.64 (E)

[Aaro]

I have been given the responsibility of looking at the work of a contractor on behalf of my organization. We had a contractor install a 480/277V service to part of a large building. I noticed that the electrical contractor ran the grounding electrode conductor (GEC) from the service inside of the commercial building through EMT and to the ground rods. I also noticed that the EMT is bonded at the service end but not at the ground rod end. I called out a code violation and sited 250.64 (E) to my boss who passed it on to the project manager in our organization that handles dealing with the contractor. The comment that came back to me was that it was bonded at one end and that was good enough. I get the impression that the contractor convinced our projects guy that it was good enough. I know that 250.64 (E) is very clear. What I would like to know is what trouble could we see from this code violation. Does anyone have any information on this?

One thing that I am not sure that I fully understand is how the incorrect bonding would effect various needs.

1. Static discharge
I am not an engineer. So, I don't know how static discharge would be effected by faulty bonding. Maybe it could make a great capacitor. Ha!

2. Lightning
I know that lightning is static discharge on a much higher level. I know that Mike Holt had mentioned that there is a frequency to lightning even though it is not AC.

3. Fault current
As far as fault current, I am not sure that is even an important issue. The ground rods make a terrible path for current back to the transformer--as far as I can tell. Does it matter?

As far as loads in the building, There is a large AHU run on 480V 3-phase. There is a transformer to step down to 208/120V for lighting and office space. Also there is IT equipment including desk top PCs. It is likely that we may add more loads in the future.

Thank you for any information that you could provide. It would be helpful to show them what kind of damage that could be caused if in fact it is a problem. I assume that the NEC is written by experienced people who have good reasons.

 

[BillyMac59]

What are your qualifications to be inspecting a contractor's work? Was the contractor's work inspected by the local AHJ? Have you discussed your concerns with the local AHJ?

 

[infinity]

Bonding to the GEC is required at both ends for ferrous raceways.

 

[Aaro]

What are your qualifications to be inspecting a contractor's work? Was the contractor's work inspected by the local AHJ? Have you discussed your concerns with the local AHJ?

I was an electrical contractor for 25 years. I have a state electrical contractors license. I am working in the electrical maintenance department of the educational institution that I am employed at now. So, I was asked to do some walk throughs from time to time to document and report on the progress of the work for my organization. I have no authority over the contractors.

 

[Aaro]

Bonding to the GEC is required at both ends for ferrous raceways.

Yes. I am aware of that. My question is not about how it should have been done. I am interested in knowing if there is some motivational information that I might be able to pass on to cause someone to wake up. It could be information on how this causes damage to equipment, something about lightning starting fires, or some other bit of information that makes them realize that the "choke effect" is undesirable or even dangerous.

 

[jim dungar]

The NEC is not based on science it is based on a hundred years of actual installations.
It says what it says.
There are very very few situations where code requirements can be modified based on an engineer's opinion, grounding and bonding is not one of these.

 

[takelly]

Bonding at both ends is necessary to create a parallel current path between the raceway and the conductor. The impedance of the circuit is approximately double if the grounding electrode conductor in a metal raceway is not bonded at both ends. It could create a choke coil during a lightning strike. The grounding electrode conductor has been reported to burn off near where it exits the metal raceway if not bonded

 

[TwistLock]

What about linking to videos and articles about the choke effect (that specifically reference GEC in ferrous conduit) with sources like M.H. videos, Ecmag, Ecmweb etc. and let those reinforce your point ?

 

[takelly]

I got this information several years ago from an article that was written by Phil Simmons. I do not have the article or book that it come from. Mr. Phil Simmons Is well respected by the electrical industry and is known for his expertise in grounding and bonding.

 

[Aaro]

The NEC is not based on science it is based on a hundred years of actual installations.
It says what it says.
There are very very few situations where code requirements can be modified based on an engineer's opinion, grounding and bonding is not one of these.

Not based on science?

I agree that it should not be modified. I believe these panels are made up of very well trained people who have given and can continue to give us a safe standard for doing electrical. My problem is that some people don't see the importance of following that standard the way that you and I do. They think that if it works then that is good enough.

Sometimes showing someone a video or picture of what could happen wakes them up before something or someone blows up.

 

[Aaro]

Bonding at both ends is necessary to create a parallel current path between the raceway and the conductor. The impedance of the circuit is approximately double if the grounding electrode conductor in a metal raceway is not bonded at both ends. It could create a choke coil during a lightning strike. The grounding electrode conductor has been reported to burn off near where it exits the metal raceway if not bonded

"The grounding electrode conductor has been reported to burn off."

Now that gives me something to research. Thank you.

 

[Aaro]

What about linking to videos and articles about the choke effect (that specifically reference GEC in ferrous conduit) with sources like M.H. videos, Ecmag, Ecmweb etc. and let those reinforce your point ?

That is what I have in mind. I have had trouble knowing where to find videos that show what happens when you violate 250.64 (E).

​

 

[Aaro]

I got this information several years ago from an article that was written by Phil Simmons. I do not have the article or book that it come from. Mr. Phil Simmons Is well respected by the electrical industry and is known for his expertise in grounding and bonding.

Thank you. I will do a search on that information.

 

[TwistLock]

That is what I have in mind. I have had trouble knowing where to find videos that show what happens when you violate 250.64 (E).

EcMag Article

I would swear I saw a M.H. video on it once but perhaps it was someone else (?)

As long as you have documented & made concerned parties aware then you’ve done your due diligence and it’s on them - unless there’s anything identifying you as a ‘supervisor’.
If you feel the need to follow up, by forwarding any links, you could CC 'any' department head in the same email as well (if it won’t ruffle any feathers) to change it from a disagreement to those siding with the contractor now having skin in the game.

My go-to when talking to clients about the importance of any violations being corrected or a subs 'faux pas' is to say that the insurance company will first deny any claim as standard practice, then after you lawyer up they look for any code violations next to blame & weasel out.

 

[gene6]

Sounds like the OP is the owners rep and a good one, I have worked on many projects with an owners rep that was far more scrupulous than our local inspection agency. When our foreman complained to our boss about the guy and asks if we had to listen to the rep the boss man asked the foreman if he wanted to get paid, You see our contract said everything had to comply with 'all applicable codes', and all the pages and pages of fine print in the plans, not just pass inspection.
The HVAC guys had it the worst they actually had payments get held up and had to redo hangers.

 

[Aaro]

Sounds like the OP is the owners rep and a good one, I have worked on many projects with an owners rep that was far more scrupulous than our local inspection agency. When our foreman complained to our boss about the guy and asks if we had to listen to the rep the boss man asked the foreman if he wanted to get paid, You see our contract said everything had to comply with 'all applicable codes', and all the pages and pages of fine print in the plans, not just pass inspection.
The HVAC guys had it the worst they actually had payments get held up and had to redo hangers.

When I was a contractor out on jobs, we would have inspectors that would just sign off on the job. As a contractor, part of me loved it. But, I knew that was not the way that it was supposed to be for the owner. But, I do appreciate all of the inspectors from my younger years that taught me some good lessons.

 

[tom baker]

If you don’t bond at both ends it creates an impedance choke and reduces the current in a lightning strike by 97%. Source: IEEE green book on grounding. The best installation practice is to install the GEC in Sch 80 PVC conduit.

 

[electrofelon]

Not based on science?

. Most of the grounding electrode and grounding electrode conductor requirements are not based on science, they are based on tradition. The GEC is the least important conductor yet it has the most stringent requirements.

I believe these panels are made up of very well trained people.

Have you seen the kind of stuff the CMP's put on the code lately??? The NEC has become a complete joke.

 

[electrofelon]

Bonding at both ends is necessary to create a parallel current path between the raceway and the conductor. The impedance of the circuit is approximately double if the grounding electrode conductor in a metal raceway is not bonded at both ends. It could create a choke coil during a lightning strike. The grounding electrode conductor has been reported to burn off near where it exits the metal raceway if not bonded

If you really think bonding at both ends of a GEC raceway will cause a lightning strike to pass to ground and cause less damage, I have a really nice bridge in Brooklyn I will sell you.

 

[tom baker]

If you really think bonding at both ends of a GEC raceway will cause a lightning strike to pass to ground and cause less damage, I have a really nice bridge in Brooklyn I will sell you.

The science behind this dates back perhaps 100 years. It’s discussed in the IEEE green book. There is likely an IEEE research paper you can obtain.