Was Knob & Tube always soldered?

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brycenesbitt

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I've see a bunch of K&T, and the joints have never been a problem, so I can't say I've unwrapped and inspected many.

Today I encountered this, which appears to be an original (1920's era) K&T junction with no solder. It was covered with modern electrical tape, which had failed:

knob_and_tube_junction_no_solder.jpg

This appears to be historic 1920's era extension (it goes on a feet to reach the rear of the house). No functional problem was noted, and the voltage drop is lower than the modern circuits nearby.

Is no-solder K&T common?
 
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The Western Electric splice (similar if not identical to the photograph) was designed to provide a good electrical contact with wire to wire pressure as well as mechanical strength.
But I believe the standard was to solder too.
 
Being the company “vandal” (demolition) I made a plant safe for the wrecking ball to flatten.

Wired in the 20’s it was all K&T. All joints, tee offs, etc. were soldered and cotton taped.

Pity I wasn’t really interested in the history of our trade back then. The switchboard should have gone to a museum.
 
A number of long term studies have shown that unsoldered connections with 10 wraps actually has HIGHER reliability than soldered.

A major factor in that is operator error in soldering (e.g, wrong flux = corrosion; cold joint, etc)

If one looks at MIL-STD-217 on connections, the failure rate for crimped connectors is lower than for crimped and soldered.

One of the lowest failure rate connections is circuit board wire wrap - of course, those have square edged pins the wire is wrapped on.

I'd suspect that if you unwrapped part of the connection you show, some of the contact area will still show bright copper.
 
brycenesbitt said:
Today I encountered this, which appears to be an original (1920's era) K&T junction with no solder.
This appears to be historic 1920's era extension (it goes on a feet to reach the rear of the house). No functional problem was noted, and the voltage drop is lower than the modern circuits nearby.

Is no-solder K&T common?
Click to expand...
Over my career I've done a lot of work around, and, occasionally, on, historic K&T branch circuits. Infrequently I will find an unsoldered joint. I attribute it to the less than workman like accomplishments of those of our trade.

I can believe a common assembly was to install all the conductors, with mechanical splicing done, open and ready to solder, then taking the torch, iron or solder pot around to all the locations to solder tight the mechanical joints. Occasionally one would be missed.

I can't tell, is the second joint in your photo, the one in the background, is that one unsoldered as well?

The Holy Writ says:

110.14 Electrical Connections. . . . Materials such as solder, fluxes, inhibitors, and compounds, where employed, shall be suitable for the use and shall be of a type that will not adversely affect the conductors, installation, or equipment. . . .
(B) Splices. Conductors shall be spliced or joined with splicing devices identified for the use or by brazing, welding, or soldering with a fusible metal or alloy. Soldered splices shall first be spliced or joined so as to be mechanically and electrically secure without solder and then be soldered. All splices and joints and the free ends of conductors shall be covered with an insulation equivalent to that of the conductors or with an insulating device identified for the purpose. Wire connectors or splicing means installed on conductors for direct burial shall be listed for such use.
Click to expand...

394.56 Splices and Taps. Splices shall be soldered unless approved splicing devices are used. In-line or strain splices shall not be used.
Click to expand...
 
brycenesbitt said:
I've see a bunch of K&T, and the joints have never been a problem, so I can't say I've unwrapped and inspected many.

Today I encountered this, which appears to be an original (1920's era) K&T junction with no solder. It was covered with modern electrical tape, which had failed:

View attachment 13370

This appears to be historic 1920's era extension (it goes on a feet to reach the rear of the house). No functional problem was noted, and the voltage drop is lower than the modern circuits nearby.

Is no-solder K&T common?
Click to expand...

I don't think "just twisting" K&T joints ( or any other res wiring method for that matter ) was ever acceptable per the NEC. I agree with al hildenbrand in the post above this one about the sometimes poor workmanship- the guys that wired that place 9 or so decades ago may have simply skipped the solder for a joint or two, figuring the twist alone was good enough and besides, after it was wrapped w/ the rubber tape and then friction tape, who would know anyway?:D
 
brycenesbitt said:
Is no-solder K&T common?
Click to expand...
It is instructive to compare the most recent language in the Code that I have in my post above, with the language from the copy of the 1918 NEC that I have.
1918 National Electrical Code
Class C -- Inside Work
Rule 16. Wires
(c.) Must be so spliced or joined as to be both mechanically and electrically secure without solder. The joints must then be soldered unless made with some form of approved splicing device, and covered with an insulation equal to that on the conductors.
Click to expand...
 
Here in the Kansas City area, mostly KCMO proper, i have very rarely seen knob & tube wiring soldered.

So little, that i believe I could count them on one hand. And I have worked on older houses all over the area, in widely varying economic demographics (from the standpoint of original value).

900 sf bungalows, 2200 sf colonials, 3000 sf Victorians, 6000 sf Queen Annes....


I've said for a long time that Kansas City has a long history of inferior craftsmanship
 
I found some more recent work like that
 

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JoeyD74 said:
I found some more recent work like that
Click to expand...

At least they did a decent tape job, right? :)
It's always funny that you will see a mixture of old/new wiring like that, yet the splicing method will be old school- probably some old timer did it, believing that it was perfectly safe to tap like that-afterall they did it w/ K&T.:D
 
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