Knob & Tube wiring

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shepelec said:
I've seen house built in the late 30's using BX. So it could have been a slow change over.
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It's trill being USED today... Installed as extentions, and repaired in kind TODAY...

But if you mean in popular use - well that depends... In many areas of the country Late 30's some places 40's

SF CA - clear untill the early 70's... THW in 3-wire circuits...
 
My last house was built in 1951, and it had knob and tube wiring. The house I'm in now (built in 1959) has the 'cloth' romex with no ground (until I replaced it all). So my answer to this question has always been 'some time in the early-fifties'.
 
According to an article I have by David Dini P.E. from UL Knob and Tube began to be phased out in the thirties and was no longer used for new installations by mid seventies.
 
Knob& Tube was the only permitted single family wiring method in the county where I served my apprenticeship in the 60s.
 
Warning - boring post ahead. :)

In my travels doing residential work, this is the general transition of wiring methods I've observed in dwelling units built over the last 100 years. If someone could add some dates for these transitions that would be nice. :)

K&T > BX (no bond wire) with rubber insulated conductors > clothed covered 2-wire romex with rubber insulated conductors > cloth covered 2-wire romex with thermoplastic insulated conductors (type TW) > cloth romex with reduced ground wire > plastic romex with reduced ground > plastic romex with full sized ground (NM) and TW conductors > modern NM-B and THHN conductors
 
peter d said:
, this is the general transition of wiring methods I've observed in dwelling units built over the last 100 years.
K&T > BX (no bond wire) with rubber insulated conductors > clothed covered 2-wire romex with rubber insulated conductors > cloth covered 2-wire romex with thermoplastic insulated conductors (type TW) > cloth romex with reduced ground wire > plastic romex with reduced ground > plastic romex with full sized ground (NM) and TW conductors > modern NM-B and THHN conductors
Click to expand...

That not only sounds right, if you were to look at the furnace circuit in my basement, you would see just about all of those, in that order, starting at the service area and running to the furnace. The transition from K & T to BX is a running splice with lots of tape for protection. The lack of ground wire isn't an issue as there is no place to connect one as there is no GES anywhere for the entire house.

The new service and complete rewiring of the house is in the planning stages.:D
 
peter d said:
Warning - boring post ahead. :)

In my travels doing residential work, this is the general transition of wiring methods I've observed in dwelling units built over the last 100 years. If someone could add some dates for these transitions that would be nice. :)

K&T > BX (no bond wire) with rubber insulated conductors > clothed covered 2-wire romex with rubber insulated conductors > cloth covered 2-wire romex with thermoplastic insulated conductors (type TW) > cloth romex with reduced ground wire > plastic romex with reduced ground > plastic romex with full sized ground (NM) and TW conductors > modern NM-B and THHN conductors
Click to expand...

We rewired a old restaurant a few years back that had every wiring method you just mentioned. During the demo one of the old locals stopped by the job site to check out the new construction. He said the building use to be a brothel for the loggers back in the 30's and 40's. During the demo the GC found some old red velvet wallpaper under some of the existing paneling and sheetrock. If the walls could talk!
 
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