Neutrals and ground on same bus in sub panels.

[ren ramsey]

1.Can someone tell me why in older homes I see so many subpanels with the neutrals and grounds not o separate bus bars. Did that use to be acceptable. 2. Why are neutrals suppose to be under separate screws. It is my understanding that is to keep one circuit from being energized by the other breaker if one breaker is turned off for work occurring on that circuit. If that be true, would not the connection on the bus not cause the same issue?

[John Kogel]

1) You see a lot of errors in sub (sorry, JP) panels because they are often installed after the fact by people who don't understand grounding and bonding. IMO. Never was permitted, AFAIK.

2) I believe the philosophy behind only one connection per screw is simply to ensure a solid connection for each neutral conductor. One neutral could come loose inadvertently if it shares a screw with another conductor.

[Jerry Peck]

Each neutral being in its own terminal was 'never permitted' but it was not always specifically addressed as such in the code - it was addressed for a very long time by virtue of it not being allowed (not necessarily 'not permitted', but not stated as being 'allowed') in the listing and labeling and instructions. The code finally caught up with the errors and the code specifically says that each neutral requires its own terminal.

If there are two hot wires in a terminal designed for two conductors, and (for whatever reasons) one becomes loose, that circuit is either dead or has an intermittent connection. When one goes to work on a dead circuit (no voltage on it) the circuit has is not 'unsafe' (other than the fact that the loose connection could make connection again, but one should start at that beginning point anyway).

If there were two neutral wires in a terminal and (for whatever reasons) one becomes loose, the circuit may no longer work, but the circuit is still live and unsafe to work on.

I'm not saying that is a reason even considered for that requirement, only that it is logical and makes sense that working on a circuit which does not work because the neutral is loose is like switching the neutral - unsafe - it leaves the circuit hot and energized (live) to shock, injure, kill (electrocute) anyone working on it.

[Gary Burnett]

Attached is your answer to #2