Seperate Ground for a Building with Seperate Service

[Electriman]

Hi friends,

I just have a quick question.

I know based on NEC we need to bound all the ground together or in other word we cannot have a separate ground and all the ground wires need to be connected.

But I have a special case on which I would like to get your opinion.

I have a plant. Inside a plant there is a building which is far from the rest of the plant (around 200'). This building has a separate service point. Am I allowed to used a separate ground for that building because the service point is different from the plant service point?

 

[petersonra]

Hi friends,

I just have a quick question.

I know based on NEC we need to bound all the ground together or in other word we cannot have a separate ground and all the ground wires need to be connected.

But I have a special case on which I would like to get your opinion.

I have a plant. Inside a plant there is a building which is far from the rest of the plant (around 200'). This building has a separate service point. Am I allowed to used a separate ground for that building because the service point is different from the plant service point?

Is this a feeder or a service that supplies the separate building?

In either case you need a grounding electrode system (GES) at the separate building.

If it is being fed from a different utility service than the rest of the plant, no connection to the GES of the rest of the plant is required.

If it is fed from the same service as the rest of the building it is a feeder and you need to run an equipment grounding conductor with the feeder that is connected to the grounding electrode system at the separate building.

There are exceptions for older installations where this was not required by earlier code versions.

 

[Electriman]

Is this a feeder or a service that supplies the separate building?

In either case you need a grounding electrode system (GES) at the separate building.

If it is being fed from a different utility service than the rest of the plant, no connection to the GES of the rest of the plant is required.

If it is fed from the same service as the rest of the building it is a feeder and you need to run an equipment grounding conductor with the feeder that is connected to the grounding electrode system at the separate building.

There are exceptions for older installations where this was not required by earlier code versions.

Thanks Bob it is a separate service point. But the utility provider is the same company for both service points.

 

[charlie b]

I am a bit confused. What do you mean by “plant”? Are you saying that you have a building (with its own four walls and a ceiling or roof) that is located entirely inside another building?

If so, then I believe that whatever grounding electrodes you install for the “inner building” must be bonded to the grounding electrode system for the “outer building.” Reference 250.50. For your installation, any electrode that you use for the “inner building” would necessarily be “present” with respect to the “outer building,” in the context of 250.50.

 

[petersonra]

I am a bit confused. What do you mean by “plant”? Are you saying that you have a building (with its own four walls and a ceiling or roof) that is located entirely inside another building?

If so, then I believe that whatever grounding electrodes you install for the “inner building” must be bonded to the grounding electrode system for the “outer building.” Reference 250.50. For your installation, any electrode that you use for the “inner building” would necessarily be “present” with respect to the “outer building,” in the context of 250.50.

Does this require its own GES when installed inside of a building?

http://www.zoro.com/porta-king-modu...JG-zqEwhu8B688BVpyhlzxoCLGLw_wcB&gclsrc=aw.ds

How about this?

http://www.grainger.com/product/3EP...3EPN8&ef_id=Unu@mwAAABREBh0R:20151006203343:s

What if they had their own services?

The requirement to have a GES is dependent on it being a separate structure. I don't see how anything inside another structure is "separate".

 

[Electriman]

I am a bit confused. What do you mean by “plant”? Are you saying that you have a building (with its own four walls and a ceiling or roof) that is located entirely inside another building?

If so, then I believe that whatever grounding electrodes you install for the “inner building” must be bonded to the grounding electrode system for the “outer building.” Reference 250.50. For your installation, any electrode that you use for the “inner building” would necessarily be “present” with respect to the “outer building,” in the context of 250.50.

The plant is a petrochemical plant that has 12.47 kV service point. the plant is 500'x500' big. There is a control building inside the plant near one of the corners which is kind of far from the rest of the equipment. This building has a 120/208V separate service point.

Do you still think that 250.50 applies to this project?

 

[Smart $]

The plant is a petrochemical plant that has 12.47 kV service point. the plant is 500'x500' big. There is a control building inside the plant near one of the corners which is kind of far from the rest of the equipment. This building has a 120/208V separate service point.

Do you still think that 250.50 applies to this project?

Interconnection of grounding electrode systems of separate buildings and structures is never required. However, interconnection happens inadvertently through EGC's when the different systems supply the same building or structure.

 

[charlie b]

I don't think we need to think about the "inner building" as being a separate structure. I see this as being similar to a building that is large enough to need two 2000 amp services, or a building that gets both 480/277V and 120/208V services from the utility. The main service equipment to which each set of utility service conductors is brought will need to be grounded, in accordance with 250.20(B). That means that each service will have an associated GES. That is when 250.50 comes into play, and requires that the GES associated with the first service be bonded to the GES associated with the second service. The present situation is no different. Here we have Service 1 brought into a main electrical room, and Service 2 brought into the Control Building. We could have another building with 2000 amp Service 1 brought into the North Main Electrical Room and 2000 amp Service 2 brought into the South Main Electrical Room. In either case, all grounding electrodes present must be bonded together.