no ground wire inside conduit cable


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Old 05-21-24, 04:49 PM
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no ground wire inside conduit cable

I have Flex Metal Conduit from the 60s. 12/3 no ground wire.
After cutting it open, I see only a red, black and white wire.
I was going to use a metal junction box to help join two sides together after a bunch of slack is taken out.
If there is not ground wire inside the conduit, how do I ensure the box does not become energized?
 
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Old 05-21-24, 04:54 PM
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A system of spiral metal flex conduit and metal boxes itself does not count as the equipment grounding conductor unless there is a bare wire or strip, sized for the highers amperage branch circuit running inside, and itself running the full length inside the conduit, and outside any paper or other lining. This bare strip or wire does not have to come into each outlet box and be wire nutted to other equipment grounding conductors.

You may be able to disconnect and pull from the conduit the existing 3 wires and add a bare ground wire to match the ampacity of the circuit (here, 12 gauge for 20 amps) and pull that back into the conduit.

An otherwise ungrounded outlet box may be grounded by running a separate EGC, sized for the amperage of the circuit serivng that box,k running exactly, pproximately, or vaguely along the same routing, to the panel with the breaker for that outlet box. If said panel is ungrounded, the separate EGC must continue and sized for the amperage of the panel departed from, and reaching the next panel upstream. Should the separate EGC first reach a grounding electrode conductor ( fat ground wire from the first building panel to a ground rod or other grounding electrode), or (new) first reach some other properly outlet box, it may end and be clamped on there.
 

Last edited by AllanJ; 05-21-24 at 05:23 PM.
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Old 05-22-24, 04:25 AM
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Seems you are talking about a 1960 electrical code that didn't require box to be grounded and some later code that did. I don't see a problem making things safer electrically but don't know the ground rules or extent the change must be implemented.
 
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Old 05-22-24, 04:49 AM
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If this wiring is AC or BX cable with a bonding strip the outer jacket is the grounding path.

If this is Flexible Metal Conduit (Greenfield) then you should be able to add a ground wire in the conduit.

12/3 would tell me that this is a cable not conduit.
 
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Old 05-23-24, 08:41 AM
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I have this FLC ,Flex Metal Conduit, Greenfield, BX cable. So all the neames we have laid out.
The question I have is, can I splice this together inside a metal junction box with out a ground.
Red, Black, White. 12/3
Into Red Black White, 12/3. Same cable just further down the run, so we can remove excess metal cable.
I was not planning on running hundreds of feet of bare copper through conduit and junctions boxes all the way to the panel.
What is the typical solution here as I have only ever seen 12/3 with a copper wire and I ground everthing in my limited experience.
I had stated above this was all 1960's electrical.
I just want to make a simple splice. Something I have done with Romex in a junction box and grounded it.
But seeing no ground, humm? I am scratching my head a bit here. Maybe I use one plastic box for this splice? I do not know?
 
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Old 05-23-24, 11:11 AM
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This time just splice it back together, red to red, white to white, etc. inside a box. Okay for making a repair when, say, the cable got damaged. In the future, keep in mind that you may not add to (extend) the wiring without bringing it up to code. You can upgrade piecemeal, just the portions from the panel in the direction you are extending, if you choose.

Not worth the bother to make splices all over the place, each splice needing a junction box where none was before, to get rid of a little slack here, a little slack there.

Ground fault circuit interrupters will provide near perfect protection from accidental electrocution, with or wihout grounding.
 

Last edited by AllanJ; 05-23-24 at 11:41 AM.
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Old 05-23-24, 03:05 PM
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I just spoke to the electrician. He said that back in the day the Flex Metal Conduit I have, aka greenfield, aka BX cable.
He said back then the code was the flex conduit was the ground. So they did not run grounds for those back then. Obviously now a-days you can not use Flex Conduit as EGC. But I do not have to run a copper line through the house for this circuit.
Just connect the Red Black and white to the Red Black and white. Check the hot with the metal box to ensure it is at 120v (grounded). Check the neutral with the metal box, check the red with the metal box to get 120v. Check the red and black get 240. The metal box is the ground. The flex metal connectors and and cable and box all secure form the EGC. Which again is outdated code, but that is how they actually did it and that is how the entire place is wired.
Done and Done.
 
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Old 05-23-24, 05:51 PM
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BX cable is not the same as Greenfield/Flexible Metal Conduit/FMC. BX is a factory assembled cable, meaning the wires are already installed and you cannot add additional wires.

BX is actually a trade name and is most similar to Armor Clad (AC) cable. Most people associate BX as not having the bonding strip that creates the grounding path back to the source.

I agree with your electrician's recommendation in this case.
 
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Old 05-25-24, 09:57 AM
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Because old style BX isn't 100% reliable in terms of ability to carry fault current on the armor, it's recommended to use GFCI protection (e.g. when upgrading from 2 prong to 3 prong receptacles).
 
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Old 05-27-24, 04:44 AM
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"" I was not planning on running hundreds of feet of bare copper through conduit and junctions boxes all the way to the panel. ""

The branch circuits are grandfathered to the (pass/fail) condition they had when installed.

Note that rejoining the ends of the armored otherwise ungrounded cable where damage occurred using a plastic junction box will not qualify because the grounding provided by the armor, however insufficient by todsy's standards, is worse than before.

New electrical facts have been discovered over the years that have led to stricter codes for newer work. For example, spiral armor could oxidize in a manner that its spiral (coiled) nature becomes electrically significant, raising the resistance to the 60 Hz AC possibly to the point that it overheats during a ground fault flow and starts a fire. This added resistance, called inductance, does not affect direct current while the "normal" resistance of the metal spiral itself ,and of the lengthwise strip if any, affects AC and DC about the same. (Also some more AC/DC resistance from having to go around the spiral instead of jump from one loop to the next.) The term "impedance" refers to the different kinds of resistances discussed here collectively and in a general sense impedance is AC frequency dependent.
 

Last edited by AllanJ; 05-27-24 at 05:23 AM.
 

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