In alt.engineering.electrical JosephKK wrote: | snipped-for-privacy@ipal.net snipped-for-privacy@ipal.net posted to | sci.electronics.design: | |> In alt.engineering.electrical JosephKK |> wrote: |> | PeterD snipped-for-privacy@hipson.net posted to sci.electronics.design: |> | |> |> On Sun, 2 Dec 2007 22:26:03 -0700, JoJo |> |> wrote: |> |> |> |>>The existing (old) sub-panel is fed by 2 phases and an |> |>>uninsulated neutral conductor. There is no ground bus, return |> |>>conductor to the service entrance, nor connection to a ground |> |>>rod. The conductors are in conduit when leaving the main panel |> |>>and arriving at the sub-panel, but not in between (they're |> |>>stapled to the flat roof under the roof's insulation & paper). |> |> |> |> You are kidding, right? Run, run away fast... Totally replace the |> |> existing setup, get those wires off the roof! |> |> |> |>>
|> |>>I want to replace the sub-panel with a modern one with safe |> |>>breakers and add a ground conductor, which will be run via |> |>>another route (I want to keep the project manageable, so don't |> |>>want to run new conductors). |> |> |> |> The current system is a hazard, and needs full replacement. If |> |> you touch it, do it right. If you don't do it right, and later |> |> there's an accident (and there *will* be) you will be held |> |> responsible. |> |> |> |>>
|> |>>Since the neutral conductor is uninsulated, it is in contact with |> |>>the |> |> |> |> No, that is not an neutral conductor. It is a ground conductor. |> | |> | Wrong. |> |> Would you like to try to convince anyone? It fits the description |> of |> a grounding conductor installation. The fact that it is |> (improperly) used as a neutral conductor doesn't change the way it |> is installed. | | It doesn't sound all that difficult. The existing system has no | effective ground. Thus that is a neutral conductor.
If the feeder connects to the main panel (as opposed to some other sub panel) and if that main panel has the neutral and ground bond in the panel, then the wire that is connected to the grounded bus bar in the main panel is the effective ground. If this feed goes to a separate building, adding a grounding electrode or two at the separate building will make it effectively grounded.
It is neither a neutral nor a grounding wire if it is not connected to any circuit or load, when fed from a main panel. A main panel can intermix neutral and ground wires (but no more than one neutral per screw hole in the box) on the bus or busses. A sub panel would have to keep them separate. A circuit from the main panel that includes an uninsulated wire attached to such a mixed bus does not determine that said wire is a neutral or a grounding wire in terms of how it is connected into the main panel. That it is uninsulated would, in terms of today's code, make it a grounding wire. What makes the big difference is how it is connected at the load end and used. If it is used to maintain current balance on a pair of 120 volt L-N loads or circuits, then it is being used as a neutral. But it could just as well be used as a grounding wire as long as all aspects of how it is installed meet the applicable code (which would be today's code if the circuit is upgraded to include another wire).
| One thing is clear, OP is in way over his head and needs to get a | competent contractor to inspect and produce a statement of | requirements and an estimate. Nor will this service be free in most | cases.
Agreed.