Two neutral to ground bonds

[encoreman]

I told my customer that I had to install a neutral to ground bond at the first disconnect after the meter which is on a pole 100 feet away from his small building. He wanted me to make the neutral to ground bond at the panel inside the building. I explained to him that it had to be at the disconnect because the local jurisdiction adopted the 2008 NEC.

He was not happy, but did not argue. I returned to the building several months later and found he had grounded the neutral at the panel. The ground at the panel connects to an extensive ground grid surrounding the building and has a physical copper underground connection to the ground at the disconnect. There is also an equipment ground wire from the disconnect to the panel.

I explained to him that he was in violation of the code and he could suffer liability damages if there was ever an incident that could be traced back to the illegal neutral to ground bond.

He wanted to know why the second neutral to ground bond could cause a problem. I did not have an answer that satisfied him.

Does anyone have an explanation as to what kind of problems he could experience? (electrical problems not legal problems). I told him I could not work on his premises until he rectified the problem. I suspect he will disconnect the neutral to ground before he calls me out and will reconnect it after I leave. I need a practical answer so he will leave the neutral to ground bond only at the disconnect.

Thanks!

Jack

 

[charlie b]

Your customer might be right on this one. I don't think a disconnect that is 100 feet away from a building can be credited as the required main disconnecting means. I think the main breaker inside the panel would be the main disconnecting means, and the N-G bond needs to take place close to that location (i.e., within that panel). I would be interested to see if others have a different opinion.

 

[Smart $]

...

Does anyone have an explanation as to what kind of problems he could experience? ...

Creates a parallel path for neutral current.

If the feeder neutral faults open, all neutral current will flow on grounding conductors and not trip any overcurrent devices.

Neutral current on grounding conductors can create voltage gradients with shock potential on grounded non-current-carrying metal parts.

 

[augie47]

Smart$ provided the info requested and, as you noted, per today's Code he is in violation.
The fact that he has provided a good ground system and since prior ot '08 the install would in have legal in many situations, I would not make it a major issue.

 

[Rick Christopherson]

If the feeder neutral faults open, all neutral current will flow on grounding conductors and not trip any overcurrent devices.

This is actually the reason why you would not want the bond 100 feet away in the disconnect. If he lost either the ground or neutral in the distance between his disconnect and the OCPD, it would never clear a ground fault inside the building.

 

[G._S._Ohm]

Creates a parallel path for neutral current.

If the feeder neutral faults open, all neutral current will flow on grounding conductors and not trip any overcurrent devices.

Neutral current on grounding conductors can create voltage gradients with shock potential on grounded non-current-carrying metal parts.

You could draw out the equiv. circuit and run the numbers.
Almost everyone puts more credibility on numbers. It turns matters of opinion into matters of fact (which can then be proven or disproven).

 

[A/A Fuel GTX]

Your customer might be right on this one. I don't think a disconnect that is 100 feet away from a building can be credited as the required main disconnecting means. I think the main breaker inside the panel would be the main disconnecting means, and the N-G bond needs to take place close to that location (i.e., within that panel). I would be interested to see if others have a different opinion.

Charlie, are you thinking 230.82(3) would apply here? Would that make the the run from the meter to the load center service entrance conductors and eliminate the need to do the NG bond at the meter disconnect? If so, how is a meter disco different from a main disco?

 

[encoreman]

Thank you for your replies!

Thank you for your replies!

I've been on an out-of-town job and not able to join the discussion. From what I understand from the discussion so far, I should just ignore the modifications my customer made and continue to do work at this facility since the two neutral to ground bonds appear to fall in a "gray" area.

Thank you all for your contributions.

Jack

 

[don_resqcapt19]

I think the code is very clear that this is a code violation.

I just don't see it as big deal as this is one of the cases where the code says that the electrons behave differently if they are on the line side of the service equipment then they do on the load side. On the line side, multiple neutral to ground connections are not only permitted, but in some cases required. As soon as we get to the load side these connections are dangerous and prohibited:happysad:

 

[A/A Fuel GTX]

I think the code is very clear that this is a code violation.

I just don't see it as big deal as this is one of the cases where the code says that the electrons behave differently if they are on the line side of the service equipment then they do on the load side. On the line side, multiple neutral to ground connections are not only permitted, but in some cases required. As soon as we get to the load side these connections are dangerous and prohibited:happysad:

Just like a parallel path is considered legal on raceways containing service entrance conductors.