80 year old conduit

That's shocking, but not surprising.

Nice to fix the problem.

I bet the threads were stripped when they put it in in 1932.

I bet you are right...interesting to see the old technology

I don't know but I'm glad it's fixed. There is nothing grounded on any of those outlets...but knowing it was bad...I was not going to leave it alone...even though it's probably been bad for 80 years.

The basic derating rule is here

Table 310.15(B)(2)(a) Adjustment Factors for More Than Three Current-Carrying Conductors in a Raceway or Cable

Number of conductors and derating factor

Then you go to the derating adder for ambient temperature at the bottom of 310.16 They also derate for raceways on roofs exposed to sunlight and cables penetrating top plates through insulation. (basically do not bundle a bunch of cables in the same hole) You do not have to derate a nipple less than 24"

Because of the limitations of 240-4(D) (the 14 ga -= 15a, 12ga = 20a rule) when you are using THHN you really do not end up derating until you are over 9 conductors in most cases. You derate from 310.16 90c column. Those numbers are high enough that 70% is still within the

People have gotten killed from 115vac!

You got that dead to rights.

On 08/07/2014 6:41 PM, snipped-for-privacy@aol.com wrote: ...

Granted for a practical case of this magnitude it's generally not an issue becase most of the old lower temp-rated styles are no longer around so one doesn't run into the limitation since the higher-rated wire covers the situations.

I was thinking simply of the generality of the overall process...not a specific case and shouldn't have use TH in the wording owing to it being higher-rated and therefore immune.

Well, there is one place that has a junction box that can reach w/o a ladder so I 'splored some--w/o disconnecting anything, I have convinced myself it is _not_ ferromagnetic via the magnet test. So, I think it's confirmed it is _not_ steel core; what it is, actually, I don't know.

I'll try to do some more digging thru the loft next time I'm up there -- there's almost bound to be a remnant or two but it could be buried pretty deeply...

It is most likely hard drawn copper. I had some feeding a house as the main. It was an old house so the wire was not at all very thick - maybe 10 gauge (probably a 30 or 40 amp main!) and it was really tough to cut.

We are already getting pretty pedantic but "TH" is not enough. You really need to see "xHHx" THWN is a 75c conductor and dual rated THHN/THWN when used in a wet location is now 75c too. Silly, maybe but that is what the code says.

Interesting, good to know. I stand corrected.

I have pulled romex through short runs of conduit but they were generally under 5' long and straight. Pulling stiff cable through bends would be very difficult.

Anthony Watson

On 08/07/2014 9:12 PM, Pico Rico wrote: ...

That's the point; it is _not_ Cu--a freshly cut end face reveals that it is copper-plated with a silverish colored interior. It isn't particularly hard nor stiff--of course, it's only 12 ga. Anyway, it's not copper-colored; can't say it's not some alloy but I've no klew as to what. If and when I find a chunk I'll clean up an end and try to get a magnified end picture that shows the face...

Been a couple years now since I added that switch in the garage so memories are a little fading but I don't recall making the connections being difficult to work with just the peculiarity of the look when one clips off the ends of the old joints to make a new connection.

I had a thought in passing that it might have been some wire provided by the REC when they were new but think that can't be right either as this surely predated their existence being as the old farrowing house is wired with it, too...and it was almost new in the early '30s from which have an entry form granddad filled out for a Farm Bureau "Operation Enhancement" annual award from which can tell he was obviously pleased as punch with it... :)

Now that I finally have all the wiring done I decided to check one last thing.

The electrician put in two new 8' ground rods, he said a total of 16' of ground is the new requirement.

All that was left on the old ground rod was my telephone/internet connection.

I decided to see how good the original ground was and got a rather poor connection. Nearly 600 ohms between the two grounds!

I decided I better tie the old rod into the new one.

It's surprising the electrician left them unconnected. which AFAIK is a code violation.

That sounds like good wisdom. Much safer.

No code violation.

He left the old ground rod disconnected from the AC input panel... he used the /new/ ones he installed of course.

The code does say you bond all available electrodes but he may have assumed that one was so ineffective it wasn't an electrode anymore.

It is required that the phone, satellite and cable TV be connected to the service electrode system tho. If not, any gradient between them will be resolved in your equipment ... kaboom.

They can't be left unconnected. The ground for the telephone, internet (cable?), must be the same grounding system that is used for the service. They can't be on their own separate ground. Back in the day, that was allowed. But not today and since he changed the grounding system, that is now a requirement.