Just clearing the air.

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mopowr steve

mopowr steve

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Electrical contractor
Is knob and tube wire considered copper-clad-aluminum?

And if so, use that column for breaker sizing?
 
I've never seen any that wasn't copper. Plus all I have see were sizes 14-10 and if protected by today's Code 240.4(D) would limit your breaker size to the 60° rating.
 
I've always wondered but never rose my hand. As sometimes when stripping the insulation off the knob and tube the copper appears to have some cladding to it, maybe it is lead but I don't know for sure.
So what is this copper-clad-aluminum spoke of in the ampacity chart? Don't know if I've ever seen it, maybe some older tw wire that when stripped resembles it?
 
augie47 said:
I've never seen any that wasn't copper. Plus all I have see were sizes 14-10 and if protected by today's Code 240.4(D) would limit your breaker size to the 60° rating.
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It is aluminum wire which has a thin layer of copper over it in an attempt to reduce the high resistance connection problems with early aluminum wire.
It does not allow you to use it with Cu-only devices though.
mopowr steve said:
I've always wondered but never rose my hand. As sometimes when stripping the insulation off the knob and tube the copper appears to have some cladding to it, maybe it is lead but I don't know for sure.
So what is this copper-clad-aluminum spoke of in the ampacity chart? Don't know if I've ever seen it, maybe some older tw wire that when stripped resembles it?
Click to expand...
 
mopowr steve said:
Is knob and tube wire considered copper-clad-aluminum?
Click to expand...

That old wire is tinned- they did that a long time ago for protection against the corrosive properties of the old rubber insulation, iirc.
Scrape some of tinning and you will see copper. The dead giveaway for tinned vs copper clad is the insulation type of the wire: If rw or rubber like in texture or "feel" it's going to be tinned copper almost certainly- by the time cc al hit the scene rw had been replaced by tw.

To further complicate stuff, I believe that tinned nm with tw insulation was made briefly same as cc al nm . To tell the difference maybe just look at the jacket- if its braided clothy tarry stuff, its most likely tinned copper. If its a slick plastic jacket, probably cc al, as most braided jackets were gone too, afaik, by the time cc al nm came out in late 60's- early-'70s. CC al is also not the silver color of tinned k&t.
 
Anybody got a picture of it?

Thanks I have never heard that before. I've come across aluminum nm but never what you have described.
 
mopowr steve said:
... knob and tube the copper appears to have some cladding to it, maybe it is lead but I don't know for sure. ...
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I'm almost certain it's "tinned" copper wire. Soldering was the standard connection method at the time.
("tinned": plated with solder, an alloy of lead & tin, usually 63% Pb / 37% Sn for electrical work)
 
mopowr steve said:
Anybody got a picture of it?

Thanks I have never heard that before. I've come across aluminum nm but never what you have described.
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No pictures that I can find anywhere of the tinned nm but from what I understand it did exist, at least in very, very old nm.
 
user 100 said:
No pictures that I can find anywhere of the tinned nm but from what I understand it did exist, at least in very, very old nm.
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I have some in my scrap collection.

Here is a pic (not so great) from the 'net

Wiring_Fabric_Rubber_PHG_239_DJFss.jpg


From the article:

Tinned Copper Electrical Wire Identification


http://inspectapedia.com/electric/Tinned_Copper_Electrical_Wire.php

Here is tinned KT

kt_conductor.jpg
 
Well, tinned k&t all makes more sense now!
Since the method of connecting and splicing was soldering anyway, and as stated earlier as a barrier from rubber.

Still would like to see some copper-clad-aluminum though, inquiring minds need to know---ya know.
 
Since this thread contains good information regarding different conductor types I've moved here where it's more relevant.
 
mopowr steve said:
Well, tinned k&t all makes more sense now!
Since the method of connecting and splicing was soldering anyway, and as stated earlier as a barrier from rubber.

Still would like to see some copper-clad-aluminum though, inquiring minds need to know---ya know.
Click to expand...

copper clad aluminum to my knowledge was used briefly during the 1970's in romex, when they had
this spiffy idea that skin effect and the copper plate would make it as good as solid copper for house
wiring.

the practice ended when it was discovered that copper clad set houses on fire as well as straight aluminum.
it was all the rage in 1977 when i started as a muppet. started about 1975, and the show was over by 1980.
 
I remember seeing "use copper, or copper clad aluminum only" on wiring devices, & always thought CU clad AL's purpose was the "economy" of aluminum, and the ease of termination of copper.
 
When I was in grade school, my grama sold a section of land to the Hatler Bros. who turned it into the very first subdivision/housing development in our area. Anyway, the contractors would let me pick up scrap wire for helping clean up around the site. I learned pretty darned quick the difference between copper nm and copper clad nm, the main difference to me at the time being that copper clad didn't buy many ice cream cones:weeping:!
 
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