Prebricated Building Grounding Plans

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That would be part of the E sheets. Are you doing the electrical design or a shell?
 
Malteser said:
I am designing a prefabricated building underneath a long major bridge. Do I need to provide a grounding plan for the prefabricated building?
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That depends on what you call a grounding plan.
My company builds prefabricated buildings and it can be as simple as providing a grounding electrode conductor for connection to the grounding electrode system to as complicated as a halo ground around the interior of the building that everything gets bonded, grounded to.
What is the use of this building?
what is your customers specs?
 
Thank you for your help.

I am an electrical designer making plans that will require a prefabricated building. I'm designing a prefabricated building to be installed in Pennsylvania. The building will contain electrical equipment to feed roadway lighting in Pennsylvania and roadway lighting in New Jersey. The building will have electrical equipment such as service entrance equipment (main disconnect switch), panels, transformers, automatic transfer switches, a generator, a disconnect for a redundant feed from NJ, and a docking station for maintenance to plug in their own generator. The voltage is 480Y/277V.

I sized all of the "Equipment Grounding Conductors" (ground wires) correctly in accordance to NEC Table 250.122.

My questions are as follows:
1. For the grounding plan, should I provide a grounding electrode conductor for connection to the grounding electrode system or as a halo ground around the interior of the building that everything gets bonded, grounded to? What factors go into this decision? My client doesn't have any specs or standards regarding this. The installations just needs to be in accordance to NEC and pass local inspection.
2. Personally, I prefer the grounding electrode conductor connection to the grounding electrode system. I interpret this to mean sizing the grounding electrode conductor per NEC 250.66 then connecting to a ground rod (at the location of the service entrance equipment.) How do I know what ground rod size, diameter, length and how deep it needs to go?
 
It seems to me that as the designer of the building you should be in a position to know this stuff already.

if you do not know, perhaps you should hire someone who does.
 
Will the prefabricated building be set on a poured concrete slab?
If it will be, then a Concrete Encased Electrode may be the best ground you can provide, and may be required.

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Malteser said:
...
1. For the grounding plan, should I provide a grounding electrode conductor for connection to the grounding electrode system or as a halo ground around the interior of the building that everything gets bonded, grounded to? What factors go into this decision? My client doesn't have any specs or standards regarding this. The installations just needs to be in accordance to NEC and pass local inspection.
2. Personally, I prefer the grounding electrode conductor connection to the grounding electrode system. I interpret this to mean sizing the grounding electrode conductor per NEC 250.66 then connecting to a ground rod (at the location of the service entrance equipment.) How do I know what ground rod size, diameter, length and how deep it needs to go?
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A grounding halo around the interior of the building has nothing to do with the grounding electrode system. While the halo can serve as, in part, a grounding electrode conductor bus, you'll still need one or more grounding electrode conductors to connect to the electrodes.

In effect, the halo would just be an extraneous and unnecessary expense, as it does not negate the requirement for equipment grounding conductors run with circuit conductors... which can effectively be used to bond all non-current-carrying metal parts... unless the building also contains non-electrical metallic equipment.
 
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