Grounding 2 point test result failed

[PowerdT]

What are the reason for the resistance to be this high? What could be the problem?

Test results (used 2 point method)
1st ground rod result 0.4 ohms

Ground rod to server room busbar resulted 16 ohms

Ground rod to server room busbar resulted 210 ohms

 

[Joethemechanic]

Are these 3 different ground rods? Are they in different locations?

 

[PowerdT]

Are these 3 different ground rods? Are they in different locations?

No. There is only one ground rod. The 2 point was between the ground rod to bus bar

 

[Dennis Alwon]

1st ground rod is from rod to what?

Are the grounding electrode conductor's tied to the ground rods?

 

[PowerdT]

1st ground rod is from rod to what?

Are the grounding electrode conductor's tied to the ground rods?

From transformer N-G GEC to main panel. From main panel to main busbar, from main bus bar to the ground rod.

 

[don_resqcapt19]

Sounds like some type of isolated grounding system was installed for the server room and there is no physical connection to the electrical grounding system.

 

[PowerdT]

Sounds like some type of isolated grounding system was installed for the server room and there is no physical connection to the electrical grounding system.

is it normal to get like result above if the server bus bar is terminated in #6 EGC?

 

[Joethemechanic]

is it normal to get like result above if the server bus bar is terminated in #6 EGC?

If they are all tied together with #6 at some point, No

#6 copper only has a resistance of 0.3951 ohms per 1,000 feet

 

[Dennis Alwon]

Are you trying to see if the bussbar is connected to the ground rod. Is this bussbar not the neutral Bus? Are there breakers installed in the panel? I assume everything is not energized.

 

[PowerdT]

Are you trying to see if the bussbar is connected to the ground rod. Is this bussbar not the neutral Bus? Are there breakers installed in the panel? I assume everything is not energized.

Yes I am trying to find out if the Busbar in server room are connected to ground rod

And everything is energized

 

[Dennis Alwon]

Is the busbar the neutral buss that you are testing? I have never done a continuity test with a circuit energized.

 

[PowerdT]

Is the busbar the neutral buss that you are testing? I have never done a continuity test with a circuit energized.

No what is measured is the ground rod and the server busbar

 

[Dennis Alwon]

No what is measured is the ground rod and the server busbar

It's like talking to a brick wall. I kept reading server but was thinking service.....doh Sorry.

 

[PowerdT]

It's like talking to a brick wall. I kept reading server but was thinking service.....doh Sorry.

lol.

 

[PowerdT]

So how do you guys size server/telecom busbar for grounding?

 

[don_resqcapt19]

Yes I am trying to find out if the Busbar in server room are connected to ground rod

And everything is energized

With the resistances you posted, it is clear that the busbar is not connected to the electrical system ground rod. When was this system installed?
A number of years ago, you would find IT and other electronic systems installed with a completely isolated grounding electrode. That was never permitted by the code, but from your numbers, I still think that is what you have.
Can you physically trace the wire that is connected to the server room bus?

 

[don_resqcapt19]

So how do you guys size server/telecom busbar for grounding?

100% a design issue as the code does not even require that grounding busbar.

 

[PowerdT]

With the resistances you posted, it is clear that the busbar is not connected to the electrical system ground rod. When was this system installed?
A number of years ago, you would find IT and other electronic systems installed with a completely isolated grounding electrode. That was never permitted by the code, but from your numbers, I still think that is what you have.
Can you physically trace the wire that is connected to the server room bus?

That’s is correct there is design issue. I didn’t believe there is one ground reference point for the building.

I can’t trace the green wire bonded to the server busbar. However I suspect that they used #6 EGC. It seems to be coming from sup panel.

 

[PowerdT]

A

With the resistances you posted, it is clear that the busbar is not connected to the electrical system ground rod. When was this system installed?
A number of years ago, you would find IT and other electronic systems installed with a completely isolated grounding electrode. That was never permitted by the code, but from your numbers, I still think that is what you have.
Can you physically trace the wire that is connected to the server room bus?

Another test we did in same building

Transformer N-G —>rod —>busbar.

The rod measures 1ohms. Then, When we measure the resistance between rod and busbar result is around 10ohms.

 

[suemarkp]

Divide and conquer. What is the resistance from the rod to the panel ground bus? What is the resistance from the panel ground bus to the grounding bar? Can you see a wire on that ground bar going somewhere? Is it going to the panel ground bus, building steel, something else? Is there a system bonding jumper at the transformer or first disconnect?