bonding seperate services together

[jessieman61]

two buildings on the same property with seprate service laterals from the same utility transformer. Do you bond the ground grid of each service together?

job engineer says yes, state job no inspector.

I think no, this will create a parrel path for the neutral current

 

[augie47]

Welcome to the Forum
250.50 requires all grounding electrodes that are present at each structure to be bonded together. In addition, 250.62(D) provides the rules for bonding multiple service disconnects. If you have more than one service disconnect they all must be connected to the grounding electrode system even though that sets up path between them.

 

[brian john]

1. Is it a common building or two separate structures.
2. Not code just something to think about common transformer they are connected there if there is any metallic connection between the two facilities, rebar, I-Beams, utility water service and the neutrals are connected there also so you have parallel neutrals with circulating current on the metallic components.
3. I really am not sure if it really makes a difference but as noted if a common structure it is NEC.
4. If it is a common structure it has a common ground by default as all metallic components are attached through various methods and through the slab.

 

[Pierre C Belarge]

If there are 2 separate buildings, the NEC does not require the 2 services of the different buildings to be bonded, regardless if they are supplied from the same transformer.

 

[augie47]

I am still learning to read. Somehow I missed the "two separate buildings". Pierre is correct.

 

[Pierre C Belarge]

I am still learning to read. Somehow I missed the "two separate buildings". Pierre is correct.

Augie
If you do not want to wear glasses, you can increase the font size of your screen.

 

[RICK NAPIER]

Pierre is right but nothing prevents you from doing it so if it is in the specs you may need to do it.

 

[SG-1]

Let me add to Brian's post that the shield on coaxial cable or telephone/data lines are a conductive path that may exist between the structures.

 

[Smart $]

Pierre is right but nothing prevents you from doing it so if it is in the specs you may need to do it.

If both services are fed by the same transformer, the two services grounding systems are bonded together via the grounded service conductors' connection at the transformer (I am assuming both are grounded systems). To do so otherwise would create a parallel path for neutral current.

 

[brian john]

If both services are fed by the same transformer, the two services grounding systems are bonded together via the grounded service conductors' connection at the transformer (I am assuming both are grounded systems). To do so otherwise would create a parallel path for neutral current.

I am missing something in your post how would not bonding the services result in a parallel path. If they are on the same bus (XO) in the transformer and there is any conductive path from the grounded conductor/bond/grounding electrodes in the two different structures you would have parallel conductors. The neutrals are common at bot ends.

 

[erickench]

NEC 250.30(A)(4) only permits a common earth ground if the systems are separately derived. Since these two service laterals are coming from the same utility transformer they are not separately derived. So I would not bond them together. Also, NEC 250.58 contains a reference to separate services connected to the same grounding electrode as a requirement. I would assume by "separate" they mean separately derived.

 

[don_resqcapt19]

NEC 250.30(A)(4) only permits a common earth ground if the systems are separately derived. Since these two service laterals are coming from the same utility transformer they are not separately derived. So I would not bond them together. Also, NEC 250.58 contains a reference to separate services connected to the same grounding electrode as a requirement. I would assume by "separate" they mean separately derived.

A service, by definition, cannot be a separately derived system.

 

[Smart $]

I am missing something in your post how would not bonding the services result in a parallel path.

You didn't miss it... I didn't discuss it.

If they are on the same bus (XO) in the transformer and there is any conductive path from the grounded conductor/bond/grounding electrodes in the two different structures you would have parallel conductors.

That is correct.

The neutrals are common at bot ends.

They should not be common by intentional bonding. Only through incidental bonding should or would the neutrals [grounded conductors] be common at both ends, such as those mentioned hereinabove by others.

250.6 covers problems arising from incidental bonding (aka objectionable current), and permitted alterations for prevention or remedy.