Grounding vs Neutral path

[AES1005]

I find a lot of load center's that have the neutral (white) wires and the bare ground wires on the same terminal screw. I know these are bonded together, my question is, could this configuration cause resistance issue's? The earth ground being 25 ohms if the path is kept series/parallel or would attaching these on the same bus bar same screw terminal matter?

 

[al hildenbrand]

The amount of current going into the 25 Ohm earth connection is tiny, when compared to the amount of current in the small fraction of an Ohm in the neutral service conductor.

The bonding of the equipment grounds with the branch circuit neutrals is not a problem.

That said, though, you will want to be certain that the terminal with two conductors is listed by its manufacturer to actually have two conductors under it.

 

[dereckbc]

What does earth resistance have to do with anything? It has no function in any part of the circuit.

What you describe is quite a common practice, as long as the device is listed to used as such, no problem.

 

[George Stolz]

I find a lot of load center's that have the neutral (white) wires and the bare ground wires on the same terminal screw.

Do you mean the same bar, or actually under the same screw? A neutral conductor is not supposed to share a screw with any other conductors, 408.41.

I agree with Al and Dereck about the resistance issues. It is just the same as a person touching the service enclosure - no appreciable amount of current travels through the person to the earth, back to the source, because the resistance of the person, the earth, the ground rod at the transformer and the GEC to the transformer is a far higher resistance path than the neutral to the same location.

As the neutral resistance increases (due to deterioration, poor installation, etc), then the path through the person would see more current, but the neutral must become very resistive to start looking less appealing than a 1000 ohm person.

 

[Jljohnson]

I agree with what has been said so far but will add... If this is a sub-fed panel then the Neutrals and grounds must be terminated on seperate bars. It is only acceptable to use the same bar if the panel has Neutral and ground bonded in that particular enclosure (IE the main breaker is located there,or "A" main breaker if this is a seperatley derived system). Also, George, stop in the office sometime soon. I want to put an ohmeter on you and see if you measure 1000 ohms : ).

 

[AES1005]

Thanks, that helps clear things up.

Thanks, that helps clear things up.

From what I have gathered, The only problem is bonding the two wires under the same terminal screw on the same bar, In the main service panel. As george brought out (408.41).

Thanks again for everyone's input

 

[JohnJ0906]

Depending on the manufactuers instuctions, it is sometimes permissable to place 2 ground of the same awg ( 2-#14 or 2-#12) under the same terminal. Check the sticker with all the torque settings

 

[don_resqcapt19]

it is sometimes permissable to place 2 ground of the same awg ( 2-#14 or 2-#12) under the same terminal.

It is often permissible to put 2 and sometimes even 3 grounding conductors under the same screw on the bar, but it is never permissible to put more than one grounded conductor under the same screw.
Don