80 year old conduit

[philoÂÂ]

After some wiring upgrades in my house I went around with an outlet tester to confirm all polarities and grounds were correct.

All tested good.

Later, doing some plumbing work, I noticed that on one run of conduit (from 1932) is loose at the junction box due to stripped threads.

Even though the ground on the circuits associated with this run test OK with a circuit tester, with my ohm meter it shows 200 ohms and I don't like that.

I took two ground clamps and connected them to either side of the poor junction and wired them together and the ground at the outlets shows about one ohm which should be OK.

My question is:

Is it permissible to leave things like that? If not I might as well replace the entire run...which is going to be a PITA.

Otherwise, since there are just a few lamps on these circuits, can I use a two prong outlet...the type with no ground? I see they are still being sold so presume there are some uses for them.

[dpb]

On 08/06/2014 12:57 PM, philo wrote: ...

Certainly. Can't fathom stripped threads on a conduit connector. What kind of "conduit" are we talking about, specifically? If thin wall (EMT), can't see why it would be any biggie to simply replace a connector at the box if really need be--they're just compression fit to the conduit and threaded inside the box.

[philoÂÂ]

The conduit is circa 1932, it's almost like water pipe.

The ends are threaded and it's fastened to the junction box by one nut inside and one out. I think the nut itself is stripped as it just turns and does not tighten.

To replace it I'd have to open the junction box and disassemble the wires. Back in those days they did not use wire nuts...the wires are twisted, soldered and taped. If I was going to take it apart and try to fix this, I'd be better off just replacing the run with all new Romex.

BTW: That old wire does not appear to be copper. It may be steel...I don't know but it's very stiff.

[gfretwell]

That is a bonding jumper, it is legal. You should be getting less than an ohm.

[dpb]

OK, that's RMC (rigid metallic conduit), then.

There's a lot of stuff that old and older here on the farm -- I've never had any trouble in just clipping the ends and having enough remaining to then use wire nuts.

But, I don't see any issue with the workaround you've installed either functionally or any Code prohibition.

I'm not sure on the wire itself, I've wondered a couple of times on some of this if it might not have been Cu-plated but haven't ever gone to the effort to really find out.

[clare]

80 years old I suspect would be "ridgid" conduit - with threaded ends.

[philoÂÂ]

After the electricians put in the new , 200 amp panel I've spent two weeks adding new circuits and bringing all my "slap-dash" work up to code...so I don't feel like doing any more wiring right now.

The wiring itself seems to be OK and even the old insulation has held up pretty well....so for now I'm going to leave things as they are.

[philoÂÂ]

Yep. that's it...now do you know what the wire is made of?

It's not solid copper...possibly steel with a copper coating?

[philoÂÂ]

Thanks for the info.

Now that I know that it's legal I think I'll clean up the conduit and see if I can get a connection closer to zero OHMs.

It looks like there are several other spots I should bond.

[gfretwell]

I only know of 2 kinds of wire, copper and aluminum. The aluminum might be copper clad but aluminum showed up in the late 60s in 12-10 sizes. By 75 it was pretty much gone in new construction.

[clare]

My suspicsion is hard drawn copper. When copper is drawn it is "work hardened" and very stiff. To make it easier to use, modern copper wire is fully annealed.. Some older copper is not oxygen free and 99.9% pure, and it precipitation hardens - over a long time it gets hard. This wire also tends to get a verdigris colouring to it with age.

This is just my "educated guess" and there are half a dozen guys on the list that will tell me I don't know anything about electrical and don't know what I'm talking about. I do have a copy of the very first electrical standards handbook published in the USA in 1914 handed down through generations of electricians from my great grandfather's brother-in-law who was one of the first electricians in Waterloo County, ending up in my father's hands -I'm part of the first generation since NOT to make my living as an electrician although I did a lot of work with my dad as a youngster.

[philoÂÂ]

Definitely not aluminum, if it was I'd replace it at once

[clare]

Another intersting tidbit about old copper wiring. Early rubber insulated wire used real gum rubber - which needed to be vulcanized to make it hard - and one of the chemicals used to vulcanize rubber is sulphur - which is very corrosive to copper. The wires were "tinned" before insulating to protect them from the sulphur.

also interesting is the way wire size is measured. Wire is made by drawing it through a series of increasingly smaller dies or ?draw-plates? to create its final size. It is believed that wire gauge numbers were originally based on the number of dies that the wire was drawn through. For example, No. 1 was the original rod, and if it was drawn through 12 dies it became 12-gauge wire. If two more dies were added, it became 14-gauge wire, etc. Thus, the larger the gauge number, the larger number of dies it was drawn through, and the smaller the wire. This was the original Brown & Sharpe standard that morphed, more or less, into the American Wire Guage standard used today.

[philoÂÂ]

It may be some type of hardened copper ?

[philoÂÂ]

Very interesting.

I am going to do my best to get the ground circuit down to less than one ohm. If I can't do so, I'm going to rip out the old wiring and re-do the whole mess.

[gfretwell]

If you have a raceway system, you should be able to pull out that antique wire and pull in THHN. I would go ahead and pull in a green wire ground and that problem you have becomes less critical.

[clare]

It becomes a total non-issue, electrically.

[gfretwell]

Raceway systems are still supposed to be bonded (to ground) but if you have a grounding wire, bonding the raceway is less critical because you are not using it as the fault path to equipment.

You still do not want a "hot" raceway.

[philoÂÂ]

If I cannot get this fixed by using clamps and bonding around the hi-resistance areas...and now it seems there are four of them... I am just going to Romex everything. The conduit in the basement is perhaps 25 feet long and from there, a short run of BX goes up to a three outlets at various places along the run.

[Stormin Mormon]

Does it stick to a magnet?