GEC for transformer in MCC

[acebradley]

I am looking at a specific installation where I am wondering if art. 250.30(A)(5) Exception 2 would apply. The installation in question is an MCC with a transformer and panel integral with the equipment. The transformer has a factory installed lug to accommodate a grounding conductor and the factory wired Neutral connection and factory installed jumper. There is no accommodation for a GEC for the separately derived ssystem grounding requirements. The feeders are hard piped all the way to the equipment. Would the grounding conductor ran with the feeders be considered a GEC if ? :

1. It is sized accordingly &
2. The conduit is considered to be the equipment ground &
3. The ground bus in the equipment is sized not smaller than the required GEC &
4. The equipment is listed and identified for use as service equipment

The MCC is European manufactured I believe. Some of the grounding terminals are labeled PEC

I have never dealt with something like this before, so I thought I would see if anyone else out there has.

 

[don_resqcapt19]

Is the equipment used as service equipment?

 

[acebradley]

No. Just being used as an MCC.

 

[Smart $]

Is the equipment used as service equipment?

The equipment is not required to be used as service equipment. However the problem when not used as service equipment is no grounding electrode conductor will be brought to the equipment. Only an EGC will be brought to the equipment.

With that said, the 2011 NEC 250.121 prohibits the use of an EGC as a GEC. In editions prior to 2011 and, as it appears, the 2014 edition, such is not prohibited, providing all requirements for both GEC and EGC are satisfied.

 

[petersonra]

A transformer like this is an SDS.

It has to have a GEC coming into it.

It is not the responsibility of the MCC maker to do this. The installer has to bring in the GEC.

I would suspect there is some place in the MCC where a GEC can be landed.

It does not matter if it is service equipment or not. An SDS requires a GEC.

 

[don_resqcapt19]

The equipment is not required to be used as service equipment. However the problem when not used as service equipment is no grounding electrode conductor will be brought to the equipment. Only an EGC will be brought to the equipment.
...

That was the reason for my question.

 

[petersonra]

That was the reason for my question.

It does not matter if the MCC is service rated or not. The installer still has to bring in a GEC if it has an SDS associated with it.

Incidentally, a service rated MCC does not require a GEC unless it is actually being used as service equipment.

 

[Smart $]

It does not matter if the MCC is service rated or not. The installer still has to bring in a GEC if it has an SDS associated with it.

Incidentally, a service rated MCC does not require a GEC unless it is actually being used as service equipment.

True, but....

If it is service rated and not being used as service equipment, a factory supplied bonding jumper for the SDS transformer to grounding bus does not need to be replaced (because of sizing and type requirements) and the GEC or EGC/GEC combo can be landed on the grounding bus.

 

[petersonra]

True, but....

If it is service rated and not being used as service equipment, a factory supplied bonding jumper for the SDS transformer to grounding bus does not need to be replaced (because of sizing and type requirements) and the GEC or EGC/GEC combo can be landed on the grounding bus.

I do not think it matters if it is service rated or not. I think you bring the GEC on to the ground bar. just like a UL508a panel.

 

[Smart $]

I do not think it matters if it is service rated or not. I think you bring the GEC on to the ground bar. just like a UL508a panel.

The point is whether the factory supplied system bonding jumper can remain or has to be replaced. Where the GEC lands is dependent on this. A GEC is required to be connected to the grounded conductor in a grounded system. It is only by exception that a GEC can be connected to the grounding bus and that is dependent on the SBJ meeting NEC size and type requirements. In many cases, it has to be a wire type SBJ. While the listing says a factory supplied bonding strap is sufficient for ground when used as service equipment, it very well may not meet the the requirements of an SBJ in many cases where not used as service equipment... and if so, the GEC must be connected to the grounded conductor, not the ground bus... unless you replace the SBJ.

 

[Smart $]

PS: Refer to 250.30(A)(5) and it's Exception No. 1

 

[don_resqcapt19]

It does not matter if the MCC is service rated or not. The installer still has to bring in a GEC if it has an SDS associated with it.

Incidentally, a service rated MCC does not require a GEC unless it is actually being used as service equipment.

Yes a GEC is required for the SDS, but if the MCC is service equipment, the SDS GEC can be connected to the service GEC in the MCC. If the MCC is not service equipment, then there would be no GEC in the MCC to connect to. That would bring up the question as to the use of the EGC as a combination GEC/EGC, unless you are on the 2011 code where you can't do that.

 

[petersonra]

Yes a GEC is required for the SDS, but if the MCC is service equipment, the SDS GEC can be connected to the service GEC in the MCC. If the MCC is not service equipment, then there would be no GEC in the MCC to connect to. That would bring up the question as to the use of the EGC as a combination GEC/EGC, unless you are on the 2011 code where you can't do that.

Just because it is not service equipment does not mean there is no GEC.

It is still required, even if the electrician forgot it.

The GEC for an SDS is required to be run to a specific GE. It is quite possible that the GEC that is brought in for the service does not meet the requirements for an SDS GEC. Wouldn't that require what amounts to a second GEC in the MCC?

 

[Smart $]

Just because it is not service equipment does not mean there is no GEC.

It is still required, even if the electrician forgot it.

The GEC for an SDS is required to be run to a specific GE. It is quite possible that the GEC that is brought in for the service does not meet the requirements for an SDS GEC. Wouldn't that require what amounts to a second GEC in the MCC?

Hmmm... seems you two are talking "chicken vs. egg" :slaphead:

 

[petersonra]

Hmmm... seems you two are talking "chicken vs. egg" :slaphead:

not sure what Don's point is.

It seems to be that he is trying to claim it is not the fault of the electrician for failing to bring in a GEC to an SDS because the MCC is not labeled as service equipment, even though the two situations are not directly related. The MCC could be both service equipment and have an SDS.

It could also be labeled as suitable for use as service equipment and not used that way. It would still need a GEC if it had a SDS.

 

[don_resqcapt19]

My point is if the MCC is used as the service equipment, there is no need to bring a second GEC into the MCC. The GEC that is required for the SDS is permitted be connected to the service GEC that is already in the MCC, of course the service GEC would have to be large enough for the SDS, but the transformers that are installed as part of the MCC are not usually very large. It is very likely that the service GEC is of suitable size for the SDS that is installed in the MCC.
250.30(A)(5) Exception #2.

 

[petersonra]

My point is if the MCC is used as the service equipment, there is no need to bring a second GEC into the MCC. The GEC that is required for the SDS is permitted be connected to the service GEC that is already in the MCC, of course the service GEC would have to be large enough for the SDS, but the transformers that are installed as part of the MCC are not usually very large. It is very likely that the service GEC is of suitable size for the SDS that is installed in the MCC.
250.30(A)(5) Exception #2.

I did not have my code book handy but are you claiming the exception allows you to not run a GEC from the closest available GE to the SDS because it is service equipment?

 

[Smart $]

I did not have my code book handy but are you claiming the exception allows you to not run a GEC from the closest available GE to the SDS because it is service equipment?

He's saying when the MCC is service equipment, the GEC is already connected to the grounding bus (either direct or through the main bonding jumper). As such, the factory supplied system bonding jumper for the SDS (grounded conductor to grounding bus) is compliant under the exception.

 

[don_resqcapt19]

I did not have my code book handy but are you claiming the exception allows you to not run a GEC from the closest available GE to the SDS because it is service equipment?

Yes, I am saying that the GEC for a SDS that is part of the service equipment it not required to directly connect to a grounding electrode. It is permitted to connect to the GEC for the service and in some cases to the equipment grounding bus in the service equipment.

 

[petersonra]

Yes, I am saying that the GEC for a SDS that is part of the service equipment it not required to directly connect to a grounding electrode. It is permitted to connect to the GEC for the service and in some cases to the equipment grounding bus in the service equipment.

You previously referred to 250.30(A)(5) Exception #2.

It does actually say that.