Building Ground Riser

[mbrooke]

Genuinely have no idea. What is the function and purpose of a building ground riser? I would think that a low impedance EG on every feeder and branch circuit would be sufficient IMHO?

 

[infinity]

We install them in poured concrete buildings where there is no building steel to connect transformer GEC's to. Run a #3/0 up through the building, add grounding bus on the wall and connect the transformers to it.

 

[mbrooke]

We install them in poured concrete buildings where there is no building steel to connect transformer GEC's to. Run a #3/0 up through the building, add grounding bus on the wall and connect the transformers to it.

Interesting.


But, what purpose does this serve for the electrical system?

 

[texie]

Interesting.


But, what purpose does this serve for the electrical system?

For grounding step down transformers typically.

 

[petersonra]

For grounding step down transformers typically.

I think the question is what good purpose does it serve other than being able to meet code.

 

[mbrooke]

I think the question is what good purpose does it serve other than being able to meet code.

Yes

 

[mbrooke]

For grounding step down transformers typically.

I would think the EGC serves this purpose?

 

[petersonra]

I would think the EGC serves this purpose?

It could

 

[infinity]

I think the question is what good purpose does it serve other than being able to meet code.

IMO it serves little purpose. The transformer has a system bonding jumper and an EGC that are connected together so what does the GEC connected to the common grounding riser actually do?

 

[electrofelon]

IMO it serves little purpose. The transformer has a system bonding jumper and an EGC that are connected together so what does the GEC connected to the common grounding riser actually do?

I agree. I don't see why the EGC that is serving the transformer can't just be the GEC. Or perhaps a better way to put it is, why does a transformer need a gec at all? This is one of those things in the code that makes no sense whatsoever, but the NFPA refuses to amend it.

 

[petersonra]

I agree. I don't see why the EGC that is serving the transformer can't just be the GEC. Or perhaps a better way to put it is, why does a transformer need a gec at all? This is one of those things in the code that makes no sense whatsoever, but the NFPA refuses to amend it.

I think it can be the GEC if it meets all the requirements.

 

[infinity]

I agree. I don't see why the EGC that is serving the transformer can't just be the GEC. Or perhaps a better way to put it is, why does a transformer need a gec at all? This is one of those things in the code that makes no sense whatsoever, but the NFPA refuses to amend it.

If the purpose of the GES is for lightning protection, line surges, etc. what does connecting the transformer on the 20th floor of a building to the GES actually do? IMO, 0

 

[electrofelon]

I think it can be the GEC if it meets all the requirements.

Yes, but are the special GEC installation rules necessary?

 

[mbrooke]

The extra copper could just be added to the EGC when needed. Other than that I see no reason for it a separate wire.

 

[electrofelon]

The extra copper could just be added to the EGC when needed. Other than that I see no reason for it a separate wire.

Code wise, see 250.30(A)(6) which is essentially what you describe in the OP