Grounded neutral in an old sub-panel

On Tue, 04 Dec 2007 21:55:12 GMT, snipped-for-privacy@milmac.com (Doug Miller) wrote:


310.15(B)(4) ?
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Whoops, you're right. Forgot about that one.
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Doug Miller (alphageek at milmac dot com)
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Actually, it *is* an uninsulated neutral (because it's carrying return current). He has no ground.
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Doug Miller (alphageek at milmac dot com)
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On Mon, 03 Dec 2007 19:50:47 GMT, snipped-for-privacy@milmac.com (Doug Miller) wrote:

Yer correct, I stand (OK sit...) corrected.
Regardless his posts trouble me... <g>
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Well, yeah, me too -- a bit. At least he recognizes that he has some things to learn, and is trying to learn them. I'll take that over an "already know everything" attitude _any_ day.
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|>>Since the neutral conductor is uninsulated, it is in contact with the |> |>No, that is not an neutral conductor. It is a ground conductor. | | Actually, it *is* an uninsulated neutral (because it's carrying return | current). He has no ground.
It is physically wired LIKE a grounding wire. It is apparently used LIKE a neutral wire. It is wrong no matter which way you look at it.
But if you think of what is there now AS a grounding conductor, and if a new insulated current carrying conductor can be added to the existing conductors correctly (I don't know if that is the case), then that new one can be marked (white taped) as neutral and used that way, using the old uninsulated conductor as ground instead (if it is physically wired right for grounding).
Consider an old electric dryer circuit wired with 2 insulated conductors and one uninsulated conductor, terminating at a NEMA 10-30R outlet. You could replace the 10-30R with a 6-30R and make it legal (if the origin is a subpanel, be sure that ground wire is on the separate grounding bus). Of course the big problem is very few things work on 240 volt 30 amps. Maybe an arc welder. I wish they would make all dryers 240-volt-only in the future (they'd still work on a 14-30R circuit and be safer on the old 10-30R circuits).
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| Phil Howard KA9WGN (ka9wgn.ham.org) / Do not send to the address below |
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Code violation. The grounded (neutral) conductor is required to have *continuous* white or gray insulation. White wires are permitted to be marked black, red, blue, etc. to identify them as ungrounded (hot), but not the reverse.
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Miller) wrote:

Sorry, my fault. Not a violation in this case. That requirement applies only to conductors 6AWG and smaller, and we're talking about at least 3AWG here.
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Doug Miller wrote:

(Mental picture of someone painting overhead high tension lines... <smile> )
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Guy Macon
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In alt.engineering.electrical Guy Macon <http://www.guymacon.com/ wrote: | | | | Doug Miller wrote: |> |>Doug Miller wrote: |> |>>Code violation. The grounded (neutral) conductor is required to have |>>*continuous* white or gray insulation. White wires are permitted to be |>>marked black, red, blue, etc. to identify them as ungrounded (hot), |>>but not the reverse. |> |>Sorry, my fault. Not a violation in this case. That requirement applies only |>to conductors 6AWG and smaller, and we're talking about at least 3AWG here. | | (Mental picture of someone painting overhead high tension lines... <smile> )
Those are governed by a separate code: the NESC
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(Doug Miller) wrote:
|>>But if you think of what is there now AS a grounding conductor, and if a |>>new insulated current carrying conductor can be added to the existing |>>conductors correctly (I don't know if that is the case), then that new |>>one can be marked (white taped) as neutral |> |>Code violation. The grounded (neutral) conductor is required to have |>*continuous* white or gray insulation. White wires are permitted to be marked |>black, red, blue, etc. to identify them as ungrounded (hot), but not the |>reverse. | | Sorry, my fault. Not a violation in this case. That requirement applies only | to conductors 6AWG and smaller, and we're talking about at least 3AWG here.
I believe it is "smaller than 6AWG" (e.g. 8AWG or smaller) based on the availability of insulation colors in a variety of sizes.
BTW, this is a rule that I would like to see another exception made for:
Using a cable assembly with conductors colored white,black,red,blue and in a dwelling building supplied only with single phase, the blue conductor may be marked white and used as a separate neutral paired to the red conductor.
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| Phil Howard KA9WGN (ka9wgn.ham.org) / Do not send to the address below |
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"An insulated grounded conductor of 6AWG or smaller shall be identified by a continuous white or gray outer finish..." [2005 NEC, Article 200.6(A)]
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Doug Miller (alphageek at milmac dot com)
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| |>| Sorry, my fault. Not a violation in this case. That requirement applies only |>| to conductors 6AWG and smaller, and we're talking about at least 3AWG here. |> |>I believe it is "smaller than 6AWG" (e.g. 8AWG or smaller) based on the |>availability of insulation colors in a variety of sizes. | | "An insulated grounded conductor of 6AWG or smaller shall be identified by a | continuous white or gray outer finish..." [2005 NEC, Article 200.6(A)]
Great! You looked it up faster than I did. But now we know you have a copy of the code and know how to read it. So after you review 310.15(B)(4) regarding the exemption of the neutral from being counted in the multiple conductor adjustment factor, you can take a look at 250.30(A)(1) exception number 2 before hunting for that code you think prohibits bonding of the neutral of a separately derived system to the grounding electrode of the feed to the transformer primary side.
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| Phil Howard KA9WGN (ka9wgn.ham.org) / Do not send to the address below |
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[...]

Maybe you see something there that permits that. I don't.
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Doug Miller (alphageek at milmac dot com)
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| [...] |> take a look at 250.30(A)(1) exception |>number 2 before hunting for that code you think prohibits bonding of the |>neutral of a separately derived system to the grounding electrode of the |>feed to the transformer primary side. | | Maybe you see something there that permits that. I don't.
Maybe you can explain how you would wire it up any other way that is safe and compliant.
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| Phil Howard KA9WGN (ka9wgn.ham.org) / Do not send to the address below |
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Doug Miller snipped-for-privacy@milmac.com posted to sci.electronics.design:

BTW #2 AWG is cheaper and easier to get.
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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.
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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.

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| PeterD snipped-for-privacy@hipson.net posted to sci.electronics.design: |
|> 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.
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| Phil Howard KA9WGN (ka9wgn.ham.org) / Do not send to the address below |
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snipped-for-privacy@ipal.net snipped-for-privacy@ipal.net posted to sci.electronics.design:

It doesn't sound all that difficult. The existing system has no effective ground. Thus that is a neutral conductor.

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.
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