Engineer Problems: Multiple Grounding Electrode Conductor Connections

[al]

Situation: Separate electrical equipment building with service,MCC, VFD's, etc. Design engineer shows a Ufer ground and a perimiter ground ring with the GEC connected to the service disconnect. They also show a connection from each VFD enclosure to the ground ring. Obviously this is a code violation but looking for the code references.

 

[ptonsparky]

Is there also an EG to the service or MCC from the drives?

Not sure if this is exactly a code violation but I do not believe it is the way the drive mfgs like to see them grounded. In that case it would be a violation in that instructions for installation were not followed.

 

[iwire]

I agree with Tom.

 

[augie47]

The EGC may be of little use in this case, but, it seems that 250.134 & 250.110 would require an EGC, but I see no violation as to the equipment being connected to the GEC also.

 

[al]

Is there also an EG to the service or MCC from the drives?

Not sure if this is exactly a code violation but I do not believe it is the way the drive mfgs like to see them grounded. In that case it would be a violation in that instructions for installation were not followed.

Yes there is an EGC in the pipe from the MCC to the VFD.

Al

 

[mcclary's electrical]

Yes there is an EGC in the pipe from the MCC to the VFD.

Al

IMO, in that case, the extra bond is not a violation, but a design issue that needs to be clarified by the manufacturer, as they may not like this connection

 

[al]

So, to use a residential example, If I run a single conductor bonded to the frame of a range or dryer, run it to the grounding electode conductor this is not a code violation as long as there is a EGC in the branch circuit conductors??

 

[ohmhead]

Well on most projects i do we must run a separate ground to every motor frame all feeders out of MCC have a ground wire in conduit then attached to motor .

Then we cadweld one more ground wire bond to frame attached to grounding ring or matt its just a extra bond if ground is lost and keeps everyone equal.

Conduit is not a good ground connection and can vibrate lose or chemical connections by products flow rust or corosive stuff over time and grounds get lost sometimes.

Mostly in a sewage plant or like fruit packing plant pepsi plants are the worst .

 

[iwire]

So, to use a residential example, If I run a single conductor bonded to the frame of a range or dryer, run it to the grounding electode conductor this is not a code violation as long as there is a EGC in the branch circuit conductors??

That is correct.

 

[ptonsparky]

So, to use a residential example, If I run a single conductor bonded to the frame of a range or dryer, run it to the grounding electode conductor this is not a code violation as long as there is a EGC in the branch circuit conductors??

Only if it is a 4 wire branch circuit and the neutral is not bonded to the frame.

edit: Yea, like you said

 

[al]

In some fashion we now have an EGC in parallel with a GEC. Doesn't this violate 310.4? 310.4(E) allows a size in accordance with 250.122 but there is no mention of an GEC.

 

[pete m.]

As long as there is no violation of 250.6 and the manufacturers installation instructons are followed there should not be an issue.

Pete

 

[benaround]

Al'

Think about all the conduits that are fastened to the metal parts of the building and those

metal parts are all connected to the GEC in one way or another, this is just once more.