Grounded neutral in an old sub-panel

In alt.engineering.electrical whit3rd wrote: | On Dec 3, 11:06 am, snipped-for-privacy@ipal.net wrote: |> In alt.engineering.electrical JoJo wrote: |>

|> | The existing (old) sub-panel is fed by 2 phases and an uninsulated neutral |> | conductor... stapled to the flat roof under the roof's insulation & paper | |>

|> Another alternative: install a 240 to 120/240 volt transformer and derive a |> new neutral at the subpanel. | | Yes, that is an excellent way to deal with the problem at the | subpanel. The wire-buried-in-roof-insulation is, however, | ALSO problematic. It scares me. | | In rewiring some of my basement sockets, I once found | vinyl-sheathed cable sandwiched in paneling, with nails mainly missing | the | cable (four penetrated) and penetrating nails mainly not hitting | more than one conductor (though one nail was melted in half, and | made sparks when I pulled the halves...so I couldn't be sure) : -D

That would be a situation that calls for tear-out and re-wire.

JoJo snipped-for-privacy@planetslkenv.jo posted to sci.electronics.design:

Well you have walked straight into a very specific and detailed NEC class question. Without knowing much more, i cannot possibly offer a reasonably close to correct answer. It can be especially difficult as it seems to involve grandfathered installations and modifications of them.

snipped-for-privacy@aol.com snipped-for-privacy@aol.com posted to sci.electronics.design:

This is not a new installation , it is a modification.

Doug Miller snipped-for-privacy@milmac.com posted to sci.electronics.design:

For new installations. For modifications it is a bit more complex.

Doug Miller snipped-for-privacy@milmac.com posted to sci.electronics.design:

Hmmm. That abandon has different meanings in different jurisdictions. Get a local electrical contractor to check the local variation for you.

PeterD snipped-for-privacy@hipson.net posted to sci.electronics.design:

Wrong.

That is the question. Exactly how to apply the code, no where enough enough information has been supplied yet to answer that question.

Part of my point exactly; it may well be to Code by "grandfathering". Making modifications can be extremely touchy. That is one of the reasons i have the the current NEC (2005) as my personal property.

Doesn't matter whether it's new work or a mod. It's still a Code violation to run a neutral separate from the hot leads or to use the bare wire as a neutral.

Care to elaborate on that?

Fiddlesticks. Disconnect all conductors from everything at each end and leave it there. NEC doesn't apply to wiring that isn't connected to anything.

Just curious... if you think this "may well be to Code by 'grandfathering'", then what edition of the Code, exactly, do you suppose it was which *ever* permitted using an uninsulated neutral to feed a subpanel?

In alt.engineering.electrical JosephKK wrote: | snipped-for-privacy@aol.com snipped-for-privacy@aol.com 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). |>>

|>>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). |>>

|>>Since the neutral conductor is uninsulated, it is in contact with |>>the sub-panel (it is in the conduit bringing the feed conductors |>>into the sub-panel). In a sub-panel the neutral and ground are not |>>supposed to be connected. |>>

|>>My question is this: |>>How do I install this new sub-panel and new ground conductor such |>>that the neutral and ground are separate? |>>

|>>JJ |> |> The short answer is no. Run a new feeder. |> You can't run a neutral separate from the hot leads and you can't |> use the bare wire in your existing cable for a neutral. | | This is not a new installation , it is a modification.

However, if a new wire is run, it becomes an installation subject to the current code. At the very least, that new wire itself is considered and one wire alone doesn't meet code. If you get to elect to include the other wires then they all together have to meet the code for the new wire to be considered compliant. Actually, you don't get to elect that if the other wires are part of the circuit of the new wire. So if you do this kind of work, the whole thing must meet current code.

If a new wire is not run, but a new sub panel is added, that sub panel must meet code. It must be fed with a feeder that is correct for the type of ciruit or electrical system involved. In the case of the OP's wiring, it _appears_ to be suitable for _only_ circuits that are 240V only. Connecting a neutral wire of a branch circuit to that uninsulated feeder wire would make the sub panel itself non-compliant with current code. Only the 240V circuits would have a chance to comply because they have no neutral that needs to be connected (AFCI and GFCI protected circuits would not be able to be operated unless their operation can be done on 240V but such devices are not currently manufactured as far as I know).

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.

|>>sub-panel (it is in the conduit bringing the feed conductors into |>>the sub-panel). In a sub-panel the neutral and ground are not |>>supposed to be connected. |>>

|>>My question is this: |>>How do I install this new sub-panel and new ground conductor such |>>that the neutral and ground are separate? |> |> Install it according to code. There is no other alternative. | | That is the question. Exactly how to apply the code, no where enough | enough information has been supplied yet to answer that question.

This is common on Usenet (not enough info). The simple answer is that everything new must comply with the code. In many ways, such compliance requires considering what the existing wiring is (how it is installed, not how it is improperly used). A _new_ sub panel may have to treat the uninsualted feeder conductor as a grounding wire.

|> That |> includes getting that non-code, hazardous, existing wiring under the |> roofing removed, and replaced with soemthing that meets code. | | Part of my point exactly; it may well be to Code by "grandfathering". | Making modifications can be extremely touchy. That is one of the | reasons i have the the current NEC (2005) as my personal property.

It could be grandfathered by leaving it alone. If the existing sub panel has space to add new circuits, they _may_ be able to be added. But new circuits _must_ meet current code when installed. And such installation requires doing things in certain ways that may not be available. The big thing is there is NO NEUTRAL AVAILABLE at that sub panel right now. There is a mis-used grounding wire. So a new circuit would have no _legal_ source of neutral connection, limit such new circuits to line-to-line 240 volts.

Doug Miller snipped-for-privacy@milmac.com posted to sci.electronics.design:

The existing wiring may be that way. The new wiring will not be "up to snuff" if done that way. The only bare conductors still allowed are ground conductors and not all of them are any more.

Doug Miller snipped-for-privacy@milmac.com posted to sci.electronics.design:

BTW #2 AWG is cheaper and easier to get.

In alt.engineering.electrical JosephKK wrote: | JoJo snipped-for-privacy@planetslkenv.jo posted to sci.electronics.design: | |> 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). |> |> 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). |> |> Since the neutral conductor is uninsulated, it is in contact with |> the sub-panel (it is in the conduit bringing the feed conductors |> into the sub-panel). In a sub-panel the neutral and ground are not |> supposed to be connected. |> |> My question is this: |> How do I install this new sub-panel and new ground conductor such |> that the neutral and ground are separate? |> |> JJ | | Well you have walked straight into a very specific and detailed NEC | class question. Without knowing much more, i cannot possibly offer a | reasonably close to correct answer. It can be especially difficult | as it seems to involve grandfathered installations and modifications | of them.

The OP apparently wants to treat the feeder as grandfathered. He may be able to. But as soon as the old incorrectly wire sub panel is removed, the feeder has to be considered in the way it is physically wired. If it is sourced from a main panel, then there is no distinction that the uninsulated wire is specifically a neutral or a grounding wire. So the new sub panel going in at the end has to consider what the existing wires are in terms of the way they are installed. That uninsulated wire is thus only a grounding wire in terms of how the new panel is allowed to be wired up. No neutrals may be connected to it in the new panel.

The existing feeder may well be fully in compliance with current code as a feeder for 240-volt-only circuits. This is where more information is needed to be sure all aspects of the circuit allow its _utilization_ in a new installation (the new sub panel is the new installation).

The wiring _may_ or _may_ _not_ be able to have a neutral added to it under the current code. More information is needed.

Apparently a transformer can probably be connected to derive a new system and thus have a neutral as part of the new system. An auto-transformer cannot be used due to the requirement to have a neutral in common in such a connection (can't do that with no neutral coming in).

snipped-for-privacy@ipal.net snipped-for-privacy@ipal.net posted to sci.electronics.design:

It may have been compliant when built. Rewiring the feed must be done to current code.

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 Paul Hovnanian P.E. |> wrote: |> |> | It sounds like you have a subpanel feeding only 240V loads, with |> | no neutrals and what you have is no _neutral_ bus. The bare |> | conductor being a ground. Either that, or this is not in |> | compliance with current code. |> |> It sure sounded like a 240V only sub to me. But I bet it got used |> for |> 120V loads (out of compliance and likely dangerously). That's one |> reason I offered the transformer suggestion (isolation only, an |> autotransformer would not meet code there as it could still have |> ground currents). |> | | It may have been compliant when built. Rewiring the feed must be done | to current code.

But it may be possible that the existing uninsulated wire is usable as the grounding wire. That depends on other details about the installation work and quality that we cannot see and was not provided in the post. Only a qualified electrician or electrical inspector on site could be sure. But it is a possibility. Still, that wouldn't be useful unless the OP can also install an insulated single wire neutral. And that could be difficult to do in compliant with current code. If the existing wires are a cable, then likely not. But that may be allowed if they singles in a conduit (just add he new neutral into the same conduit, if there is room ... another issue).

Doug Miller snipped-for-privacy@milmac.com posted to sci.electronics.design:

Be careful about making too global of claim with that assertion. Just the same; replacing the feeder connection definitely comes under "upgrade to meet current standards" in this case.

Doug Miller snipped-for-privacy@milmac.com posted to sci.electronics.design:

I happen to live and work in a jurisdiction where it requires attempting to remove the conductors (getting a good piece out is good enough sometimes) and crimping the conduits closed. That is why i brought it up.