I am going throught the Internachi res electric course and am confused on this. The writing in the course says grounds and neutrals should never share bus bars because it may allow current to flow to grounds; however, the video and some answers on forum express that they are allowed to share in the main service panel but not in sub panels. What is correct and why?
That is correct unless the sub-panel is in a detached outbuilding that has its own ground rod
Which one is right?
In sub-panels grounds and neutrals are isolated from one another. They are only bonded in the main panel. If this were not the case, the grounds between the two panels would become current carrying conductors.
Dennis is correct and let me add:
…and there is no other metal connection between the house and outbuilding e.g. phone line, metal water line, etc.
Chris, the only place where the grounded (neutral) conductors and the grounding (bare grounds) conductors can share a bus is in the 1st (and only) service disconnect after the meter. That may be a single breaker panel board outside next to the meter or inside. All other panel boards after the service disconnect are distribution panel boards and need to have the grounding and grounded wire separated with the grounded conductors (not bonded to the panel board) and the grounding (bare wires) bonded to each panel board.
I hope this is helpful.
The out buildings are a different story and if you are not sure you can refer it out.
OMG you’re going to upset the master sparky
To expand on what Dennis stated the exception for the detached building was removed in the 2008 NEC. You may still find old installations in detached structures with bonded neutrals that are providing the equipment grounding just like in a service. For installations under the 2008 NEC and beyond an EGC with the feeder is required and the neutrals and EGC’s are kept isolated from each other.
The part of your comment in Bold
Okay. Thank you.
The neutrals in a properly assembled residential electrical system are NEVER floating.
Thank you…my misuse of description was not good…CORRECTED.
A rod has nothing to do with bonding inside of a panel.
N/G connects after the main disconnect aren’t always a safety concern. They are always a code violation (since 1934 I believe).
What would be the better work other than floating?
Unbonded to the panel board…
And, IDK if there is one word to replace that.
How about isolated.?
Like Jim said I like the word isolated. If it’s a sub-panel and you use the word floating most will know what you mean even if it’s not exactly accurate. Also depends on how you use the term floating. If you said “in a sub-panel in relation to the metal equipment enclosure the neutral is floating” most would say that it means that they are not connected. It doesn’t mean that in that system the neutral and EGC aren’t connected by a main bonding jumper somewhere else.
I like that word…ISOLATED.
Thanks for the explanation, Robert. That helps me understand it better.