Knob and tube wiring

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domnic

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When did nickel plated copper wire used for knob and tube wiring in homes . start?...................
 
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Do you think it might be tinned copper as opposed to nickel.

At some point (1925 ish) it was discovered the sulfur in the rubber insulation damaged the copper in K&T wiring and the wire was plated in tin.
 
Tin plating is still common with some conductors where the insulation has a high rubber content, DLO for example.
 
Hadn't really thought about it but most of the K/T wiring I ever saw was tinned too. I did about 10 whole house rewires, removing K/T and BX. BX was the worst IMHO.
 
I thought somewhere along the line that the tinning was for a couple other reasons,
1- was to help aid in keeping the rubber from sticking to the copper which was a pita to remove.
2- aid in the soldering of splices.
 
Have any of you seen old type-R conductors that are not tin plated? That would be interesting to see right up there with mystery wires like NM-A or XHHN. My guess is the tin plating started in the telegraph era well before the before the knob-n-tube era.
 
tortuga said:
Have any of you seen old type-R conductors that are not tin plated? That would be interesting to see right up there with mystery wires like NM-A or XHHN. My guess is the tin plating started in the telegraph era well before the before the knob-n-tube era.
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Good question. I'll bet someone here knows.
 
augie47 said:
Do you think it might be tinned copper as opposed to nickel.

At some point (1925 ish) it was discovered the sulfur in the rubber insulation damaged the copper in K&T wiring and the wire was plated in tin.
Click to expand...
Thanks for great explanation of why the copper wire in knob & tube was tin plated. Was told back in the 1960's is was plated to make it easier to solder. Probably been 50 years since I had to work on knob & tube.
 
ramsy said:
Anyone who's seen cloth NM cables from the 1950's should recognize it.

See Link description beginning with paragraph titled Cloth Braiding:
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Yeah I can see a 1950's NM cable not having a non tinned conductor. But I have never seen knob and tube type "R" conductors that are not tinned. Other than someone using a newer TW type conductor.

Well I checked and going back to at least the 1899 NEC all rubber covered conductors (type R) were required to be tinned
41. Rubber-Covered –
a. Copper for conductors must be thoroughly tinned.
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That also is rule 50a in the 1911 NEC
I imagine this was in the NEC until 1965 as type R was removed from the NEC in 1968, but perhaps they lifted the tinning requirement at some point.
 
So I got curious on this question and dusted off the old code books, the last rule I can find 602(c) requiring tinned rubber 'type R' is in the 1928 and appears to have been removed from the NEC in the 1930 edition.
 
Side note on old cloth covered Ronex. Can remember paying maybe $8 or $10 for a 250' box of cloth covered 14/2 Romex back in 1967. Only goid thing about it it had type TW insulation on the conductors. Was a dirty job pulling it thru joists in hot weather. Hands would have tar on them. For only fifty cents or maybe a dollar more supply house had plastic jacketed romex.
 
garbo said:
Side note on old cloth covered Ronex. Can remember paying maybe $8 or $10 for a 250' box of cloth covered 14/2 Romex back in 1967. Only goid thing about it it had type TW insulation on the conductors. Was a dirty job pulling it thru joists in hot weather. Hands would have tar on them. For only fifty cents or maybe a dollar more supply house had plastic jacketed romex.
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That must have been the last days of cloth Romex. I never saw any new rolls of it. When I started in 1976, plastic was the only option. It also had TW conductors. I left the trade a few years later, came back to it in 1995 and by then it had THHN conductors. Big improvement. 2002 or 2003, jacket colors came along. I liked that a lot too. # 10 was always easy to ID but 12 & 14 a little harder. Stiffness varied brand to brand, easy to grab the wrong roll. Colors simplify things a bit and I like that.
 
jmellc said:
That must have been the last days of cloth Romex. I never saw any new rolls of it. When I started in 1976, plastic was the only option. It also had TW conductors. I left the trade a few years later, came back to it in 1995 and by then it had THHN conductors. Big improvement. 2002 or 2003, jacket colors came along. I liked that a lot too. # 10 was always easy to ID but 12 & 14 a little harder. Stiffness varied brand to brand, easy to grab the wrong roll. Colors simplify things a bit and I like that.
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There was a earlier effort to color code romex I remember #14 with a light blue jacket and #12 with a black jacket do you remember that stuff?
Unless I am mistaken they don't really use actual "THHN" in the romex today, with the old romex really had "TW" it was printed on the conductor.
 
tortuga said:
Unless I am mistaken they don't really use actual "THHN" in the romex today
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Yes they do, but most of the time it is not MARKED as THHN on the individual conductors so if you strip it out if the jacket, you can’t use it as such. People have posted examples of individual cases where the conductors WERE marked inside, the speculation being that for a production run of NM, they just used excess inventory if marked THHN solid (which is probably not a big seller and sits around in inventory too long).
 
tortuga said:
There was a earlier effort to color code romex I remember #14 with a light blue jacket and #12 with a black jacket do you remember that stuff?
Unless I am mistaken they don't really use actual "THHN" in the romex today, with the old romex really had "TW" it was printed on the conductor.
Click to expand...
I recall seeing just a little of the light blue and black but can't recall if it was 12 or 14. I thought then it was just an odd brand or maybe a slight manufacturing defect, such as too little or too much of a dye, etc.

I also recall seeing a bit of Romex with an insulated ground, seems like reduced ground and cloth jacket. Existing wiring, not new. I would like to see insulated grounds across the board. I've seen bare grounds hit switch and receptacle terminals more than once in crowded boxes. For this reason, I always tuck the ground splices first, then cover with neutral and line splices, so only the ground leads needed come to the front.
 
tortuga said:
There was a earlier effort to color code romex I remember #14 with a light blue jacket and #12 with a black jacket do you remember that stuff?
Unless I am mistaken they don't really use actual "THHN" in the romex today, with the old romex really had "TW" it was printed on the conductor.
Click to expand...
In the mid and late 80's here romex came in black and white. No size relation 12/2, 14/2, 14/3, 10/2, 10/3 came in both colors. (I didn't pay close attention, it was probably based on manufacturer. It was also boxed in 250' coils, not plastic wrapped.) I do remember light blue 14/2 from earlier days, and I assumed it was just one mfg's choice. UF used to come in white or black, not gray. I hated when the white/ yellow/ orange colors came in the early 2000's. I liked the all white scheme. I also liked when the Arlington Black Buttons were white....
 
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