Bonding - service panels & sub-panels

[hardworker]

I understand the sub-panel rules of bonding the ground bar, isolating the neutral bar, removing the connector link between the two, and keeping the neutral wires and the ground wires tabbed to the appropiate bar.

I understand the service panel rules of bonding the neutral bar, and keeping the connector link in place.

Please explain to me, why the sub-panel separation is not affected by the non-separtion of the service panel wire diagram. If the sub-panel and the service panel are connected by metal conduit, it seems to me their wire diagram becomes one in the same.

What am I missing?

 

[raider1]

Could you maybe clarify your question?

I am having a hard time understanding what it is you are asking.

Thanks,

Chris

 

[hardworker]

How does the sub-panel wiring stay isolated, when the sub-panel and the service panel are connected via conduit? Bonding connects the ground bar to the chassis of the panel and the conduit connects the sub to the service panel. The service panel is bonded to the neutral bar. It all seems to be tied together.

 

[Buck Parrish]

I understand the sub-panel rules of bonding the ground bar, isolating the neutral bar, removing the connector link between the two, and keeping the neutral wires and the ground wires tabbed to the appropiate bar.

I understand the service panel rules of bonding the neutral bar, and keeping the connector link in place.

Please explain to me, why the sub-panel separation is not affected by the non-separtion of the service panel wire diagram. If the sub-panel and the service panel are connected by metal conduit, it seems to me their wire diagram becomes one in the same.

What am I missing?

The neutral and equipment ground are still connected , but not at the sub panel.
One reason , So a fault current can take the quickest path back to ground.

 

[hardworker]

Ok, thanks for that explanation. Why is the sub-panel bonded differently than the service panel? How does that affect a fault current?

 

[RUWired]

The sub panels have the neutral and grounds seperated because if they were bonded together as in the main panel, the equipment ground conductor or metal conduit could and will carry some amount of neutral current. The objective is to keep all current off the equipment ground conductors for safety reasons and for GFI breakers to work properly.

 

[hardworker]

Very good. Thank you for that clear explanation.

 

[Charlie Bob]

hardworker, maybe you'd like to get the Mike holt grounding and bonding book and Soares grounding and bonding as well they are exelent books.They did a whole lot for me.