Ground Ring requirement for electrical room espansion

[Smart $]

Ok so even if the building only has one panel it still is required to have a GES. I assume this would apply any sort of structure as well such as a metal structure you may find on an industrial site?

Correct... other than where supplied by a branch circuit.

So every building or structure must have its own GES located at that building or structure within reasonable distance (say 10ft or so) and connect back to a remote GES located elsewhere to meet the requirements of a local GES?

There is no requirement to connect back to the remote GES by way of a GEC or bonding jumper. The connection is made through the EGC run with the feeder.

Yes there will be EGC's run with the MCC feeder and size accordingly per 250.122. It looks like from reading 250.32 these EGC's will tie into the MCC ground bus and the ground bus must in turn connect to the GES in the building. Is this correct?

Correct.

 

[Smart $]

... Is making a new CEE a better option than simply installing a ground rod in option #1?

It's a better electrode and quite easy to install provided you are there at the appropriate time. To install one rod will essentially require a second unless you due a bonafide ground resistance test proofing the one has 25 or less ohms to earth.

These appear to be the options to satisfy the GES requirements for the existing building. No matter what option is chosen the GES will have to connect to the equipment grounds in the MCC's correct?

At the building disconnecting means... and I take that to be the MCC's.

Now in terms of the building expansion we will have the luxary of installing a new GES. With this new GES we can then try to tie it back into the existing building. I suppose we could tie the new expansion GEC to a common ground bus on the wall and then connect this ground bus to the MCC grounds in the MCC's? Or does the GEC need to go right from the GES to the MCC (I'm a bit confused on the order of things)

Since you have multiple disconnecting means you can run the GES(s) to a common bus, then run taps to the individual disconnects.

Can a GEC be run inside of RMC conduit? For instance lets say we install a ground rod outside the exiting building. When the GEC enters to room can it be run in RMC to the MCC's to connect to the ground bus?

Yes... but you will have to bond the GEC to the RMC where it enters the RMC. If the RMC connects to the MCC enclosure its been debated whether or not it is reuired to be bonded there also. I'm on the 'not' side of that fence as long as the GEC is bonded to the enclosure by any approved means.

 

[Smart $]

Maybe I am reading it wrong but you can not supply a building with two feeders per 225.30 other then special conditions mentioned in 225.30(A) which mentions:Fire pumps
Emergency systems
Legally required standby systems
Optional standby systems
Parallel power production systems
Systems designed for connection to multiple sources of supply for the purpose of enhanced reliability

You can supply a building with up to six service disconnecting means and they can be supplied by conductors connected together at the source end but land in six different disconnecting means at the building served, but you can only run a single feeder when supplying a building with a feeder so if you are in compliance with that - there is no second place to have to worry about where to tie a GEC to. You could have one feeder to the building though with up to six disconnecting means at the building, in that case the GEC would need to connect to some "common" point in the supply, like wherever the feeder branches into the multiple disconnecting means.

Noteworthy point.


Perhaps one feeder then tapped to supply the MCCs...???

 

[don_resqcapt19]

Maybe I am reading it wrong but you can not supply a building with two feeders per 225.30 other then special conditions mentioned in 225.30(A) which mentions:Fire pumps
Emergency systems
Legally required standby systems
Optional standby systems
Parallel power production systems
Systems designed for connection to multiple sources of supply for the purpose of enhanced reliability ....

I have never been in an industrial plant with multiple buildings that did not violate that rule.

 

[philly]

Noteworthy point.


Perhaps one feeder then tapped to supply the MCCs...???

As I mentioned earlier this is an industrial site with multiple buildings On-Site which contain electrical equipment.

The building in question has two MCC's which connect together through a NO Tie breaker. Both of these MCC's have feeders from switchgear in a separate building which is also MTM switchgear.

So in this case it appears that both MCC's will be considered the disconnecting means and must be bonded to the GES.

Most industrial sites I have been two have buildings which contain equipment which is fed from different upstream sources. Wouldn't this also be the case with some commercial buildings such as a room in a hospital that had equipment fed from different emergency and standby distribution feeders?

 

[GoldDigger]

As I mentioned earlier this is an industrial site with multiple buildings On-Site which contain electrical equipment.

The building in question has two MCC's which connect together through a NO Tie breaker. Both of these MCC's have feeders from switchgear in a separate building which is also MTM switchgear.

So in this case it appears that both MCC's will be considered the disconnecting means and must be bonded to the GES.

Most industrial sites I have been two have buildings which contain equipment which is fed from different upstream sources. Wouldn't this also be the case with some commercial buildings such as a room in a hospital that had equipment fed from different emergency and standby distribution feeders?

All of the situations you mention seem to call within the special conditions of 225.30(A) as paraphrased by don.

 

[Smart $]

All of the situations you mention seem to call within the special conditions of 225.30(A) as paraphrased by don.

Specifically in this case, being MTM, 225.30(A) "Systems designed for connection to multiple sources of supply for the purpose of enhanced reliability".

 

[philly]

After this great discussion we are planning on implementing the following:

Install a 4/0 ground ring around the new building expansion with ground rods set each of the corners. We are also going to tap the ground rods at 2 of the corners to tie into the rebar in the new slab.

Along the new ground ring we are going to tap the 4/0 wire and run a 4/0 bare wire to a copper ground bus mounted on the wall in the new expansion. From this new ground bus we will run two GEC's to the two MCC ground buses in the existing building to satisfy 250.32. I'm assuming these GEC's are sized according to 250.66. With that being said I believe these GEC's would need to be 4/0 per 250.66 since the mcc feeders are 6 sets of 600mcm. We would plan on running these 4/0 GEC's in 2" RMC and ensure that the GEC is bonded to the conduit.

We are also going to add a second ground bus in the expansion room near where new panels and dry type xfmr will be located to connect the GEC to the transformer and panels. Any issue with having a second ground bar in the room? Any special bonding requirements? This ground bar will also be tapped with 4/0 from new ground ring.

If possible we will also try to tie the existing foundation rebar into the new ground ring if any Rabat becomes exposed during expansion process.

Does this sound like a sound plan? I appreciate all the helpful responses.

 

[Smart $]

...

Does this sound like a sound plan? I appreciate all the helpful responses.

I have to wonder how you're going to run a ground ring just around the expansion. To qualify as a ground ring, it has to run around the entire building. EVen if you manage to do this just for the 'expansion', then the 'expansion' would have to qualify as a separate building and its GES would not qualify as the GES for the existing [separate] building...???

Also, providing the transformer is SDS, the GEC(s) is(are) run either to the transformer or system disconnecting means, wherever the system bonding jumper(s) is(are) located.

 

[kwired]

I have to wonder how you're going to run a ground ring just around the expansion. To qualify as a ground ring, it has to run around the entire building. EVen if you manage to do this just for the 'expansion', then the 'expansion' would have to qualify as a separate building and its GES would not qualify as the GES for the existing [separate] building...???

Also, providing the transformer is SDS, the GEC(s) is(are) run either to the transformer or system disconnecting means, wherever the system bonding jumper(s) is(are) located.

I see nothing that violates NEC, though he does not have a ground ring that complies with NEC ground ring - nothing in NEC requires a ground ring either. So unless the ground ring is the only electrode I don't see how it can be wrong because if it were the only electrode then it would need to comply with NEC specs for a ground ring. He did say there was going to be some ground rods connected to this "semi" ground ring, so if anything he just has multiple ground rods with larger then the minimum required conductor run to them.

 

[Smart $]

I see nothing that violates NEC, though he does not have a ground ring that complies with NEC ground ring - nothing in NEC requires a ground ring either. So unless the ground ring is the only electrode I don't see how it can be wrong because if it were the only electrode then it would need to comply with NEC specs for a ground ring. He did say there was going to be some ground rods connected to this "semi" ground ring, so if anything he just has multiple ground rods with larger then the minimum required conductor run to them.

I agree with your assessment.

 

[iwire]

I agree with your assessment.

That is a relief, I was worried OP was going to be jailed for illegal electrode removal.

 

[Smart $]

...
I was actually able to make it out to the site to inspect the existing building that is being expanded only to find that there does not appear to be an existing ground ring or really any grounding electrode for that matter. We were told there was an existing ground ring but when contractor started excavating around building there was no ground ring to be found, so I apologize for stating that assumption.
...

That is a relief, I was worried OP was going to be jailed for illegal electrode removal.

I think we're well past that possibility.

 

[kwired]

I think we're well past that possibility.

Now we need to find the copper thieves that took the ring that is supposed to be there.