neutrals and grounds at main disconnect .

[Gaston]

" Celtic " , responded to " mshields " , with a picture of a correct path to earth of a ground fault , on a question regarding bonding at the load of a service . Perhaps some of you might remember . ( I tried to insert the picture but I was un able to do so ) . I found the picture self explanatory . But it still leaves me with the question of the neutrals and grounds at the main disconnect . As we all know , at the first mean of disconnect we must bond or ground the load beyond that piont . though the path in the picture , " Celtic " displayed , shows it being correct ; what happens when we are connecting them at the main disconnect when we have the main breaker at the panel.?

 

[roger]

Gaston, what was the name of the thread?

Roger

 

[ryan_618]

I am having a hard time following your question. Are you asking what happens if you bond nuetral to case at the service, as well as a downstream panel?

 

[Dennis Alwon]

I believe this is the thread
http://forums.mikeholt.com/showthread.php?t=87053&page=2&highlight=grounding

Is this the picture

 

[celtic]

what happens when we are connecting them at the main disconnect when we have the main breaker at the panel.?

Assuming the N-G connection at the Main Disco Panel (MDP).,....
Assuming you don't make a N-G connection at the MCB..all is well.
Assuming you do make a N-G connection at the MCB - Parallel paths..NFG.

In the image Dennis posted, imagine for a moment that the "load" with the fault is just another panel, all paths back to the MDP can be subject to objectionable current.

 

[haskindm]

If you have a main disconnect ahead of the distribution panel the distribution panel is a sub-panel. The presence of a "main breaker" does not change this. Perhaps it should be called a "Master Breaker" in that it would disconnect all of the circuits in the sub-panel. The Main Disconnect would still be the Main Disconnect and that is where the neutral/ground connection would be. I hope I am understnding your question correctly.

 

[George Stolz]

Gaston, I think of it this way: The service is usually the first point that the NEC has full control of an installation. They want the equipment grounding system (the system to provide an effective return path for a ground fault) to start as soon as possible, and then be seperate from the neutral current path.

Essentially, every point after the service disconnect should be bonded using the EGC, there shouldn't be a neutral connection to the exposed metal of an electrical system after that point. (There are a few exceptions to this general rule.)