Knob and tube

sw_ross

Senior Member
once again I'm rewiring a house that has a decent amount of k&t. It's a basic layout with kitchen/dining/living plus bath on the main level and bedrooms and bath on second level.
Some of it has been changed out, but the upstairs (attic, bedrooms and bathroom), and the ceiling portion of the main level are predominately k&t.
The attic has blown in insulation (thankfully not vermiculite) so it's challenging to see the runs of k&t.

Does anyone one have any diagrams as to how a house is typically wired using k&t? I want to abandon all that I can, but I don't want to start chopping wire without knowing how it's run.

i already fished wire up into the attic from the basement. That will replace the k&t for lites and receps in the upstairs area (I'll fish down from the attic).

Its that transition between the main floor ceiling and the upper floor that I have limited access to.
Wishing I had more knowledge about how the wires are run in this transition area....
 

480sparky

Senior Member
There's only one way K&T was run.... however it was easy & cheap. Every house will be different.
 

ptonsparky

Senior Member
Yes, it’s different at each house and just like today some done better than others. I’ve been able to pull some of it out and new in. Others tied nice and tight. We have taken the upstairs floor loose In places. New siding? Hand holes in the outside walls.
 

hbiss

EC, Westchester, New York NEC: 2014
Me, I wouldn't care how the old stuff was run and it wouldn't matter if it was K&T, BX or Romex. What difference would it make? You are doing a complete rewiring from scratch, run that where and how you have to.

-Hal
 

sw_ross

Senior Member
Me, I wouldn't care how the old stuff was run and it wouldn't matter if it was K&T, BX or Romex. What difference would it make? You are doing a complete rewiring from scratch, run that where and how you have to.

-Hal
Have you worked in homes that had k&t?
Am I supposed to force the HO to gut their home so I can rewire it? There's portions of the house that aren't slated to get opened up.
 

al hildenbrand

Senior Member
Am I supposed to force the HO to gut their home so I can rewire it? There's portions of the house that aren't slated to get opened up.
I've worked with K&T my whole career. I've rarely had any homeowner gut a room solely to assist with rewiring.

Back in the early years of my career I read The American Electrician's Handbook to learn about tools and materials, but what I took away was fishing techniques. When faced with a K&T replacement, the fishing techniques, many times, are the same techniques that were used to install the original wiring (to update to electricity from the old gas lighting).

Identify the existing receptacle outlets, lights and switches that are on the K&T, and then fish in new Chapter 3 wiring. Definitely labor intensive.
 

electrofelon

Senior Member
Have you worked in homes that had k&t?
Am I supposed to force the HO to gut their home so I can rewire it? There's portions of the house that aren't slated to get opened up.
My policy is all or none. With all the buried splices, you would end up having to leave most of the old stuff energized to leave even a few non upgraded locations. You hardly have to gut a place for a rewire. Drill 4" holes for access points, smoke detectors can fill some of them. Most houses really don't take that many holes. It doesn't cost much to have a painter/drywall guy patch 20 4" holes.
 

hbiss

EC, Westchester, New York NEC: 2014
Have you worked in homes that had k&t?
Am I supposed to force the HO to gut their home so I can rewire it? There's portions of the house that aren't slated to get opened up.
Like I said, doesn't matter what the old wiring method is. As others have said, you don't have to gut the house to rewire if you know how to fish.

Maybe your problem is that you are trying to follow the old wiring routes? Don't. Just make like it never existed.

-Hal
 

david

Senior Member
How do you patch 20 year old birch paneling , or gain access to the second floor joist when the carpet is wall to wall or lamented flooring put in less than a year old

there are some homes where fishing just isn't an option unless the home owner agrees to except damage to the finish that will be left behind.

Even small vibration on 150 year old lath will cause large sections of old plaster to let loose
 

LarryFine

Master Electrician Electric Contractor Richmond VA
Like Al, I, too, have worked on K&T homes. Some wired when built, mixed with black-steel conduit and/or BX, but plenty retro-wired after construction.

The popular retro-wiring method involved prying up a pair of floor-boards front-to-back in the upstairs hallway, giving access to the downstairs central wall for switches and receptacles, and the downstairs ceilings for lights. The rest was usually accessed from the attic and crawl spaces.
 

sw_ross

Senior Member
How do you patch 20 year old birch paneling , or gain access to the second floor joist when the carpet is wall to wall or lamented flooring put in less than a year old

there are some homes where fishing just isn't an option unless the home owner agrees to except damage to the finish that will be left behind.

Even small vibration on 150 year old lath will cause large sections of old plaster to let loose
This does have wood paneling and a fair amount of tongue and groove walls. Most of the lathe and plaster is in reasonable shape.
Obviously, I can't just go cutting 4" round holes in various locations damaging the plaster.

The HO (young couple with kids) just purchased the home, so they don't have a lot of spare change.

One plus is they're gutting the kitchen which gives me some access to that area walls and ceiling.

I definitely want to get rid of the k&t. There are just parts of the house that I don't have easy access to.
I'll just take it a piece at a time.
 

growler

Senior Member
My policy is all or none .
Here if you pull a permit to "rewire" a house then you are expected to replace all existing wiring and bring everything up to code. If you are only going to replace portions of the wiring you must permit it to repair as needed.

You can find houses where they are being sold as rewired and they have not been.
 

sw_ross

Senior Member
How how would they have done a 3-way switching setup with k&t?
Would they still do it like current methods?

Power & Travelers at Sw#1 => Travelers => Sw#2 has Travelers & Load?

I assume they'd use any available neutral that was available...

The specific location I'm pondering is the stair-light, 3-way'd from front door to upstairs hall.
 

Knuckle Dragger

Master Electrician Electrical Contractor 01752
Like the others have said there is no typical wiring diagram on where the K&T is run throughout the house.
I don't know of any rule that forces a GC or home owner to open up the walls for a rewire. That would be so helpful.:)
This kind of work is what I do close to 50 percent of the year.
If your plan is to get rid of all the K&T you could start at the panel, look all around the basement for transitions from K&T to RX/BX and vise-versa do the same in the attic, open up every receptacle,switch, fixture and box and check.
Don't get hung-up on how the K&T is wired like three-ways and such because you are installing new wiring to accommodate the new home owners needs.
Older 100 year old + houses for the most part are much easier to snake than new construction (much larger chases for plumbing and chimneys that lead to the attic.
Like electrofelon mentioned they will be drywalling the kitchen so don't be afraid to cut out holes or carefully pry off floor boards/ baseboards for snaking, be sensitive to unique moldings and wood work (I'm very comfortable with this if you are not maybe you shouldn't do it)
If I can't get to an area to install a receptacle to meet code requirement for whatever reason I typically don't worry about it because I am adding receptacles and making it better and most AHJ realize this and if you have to satisfy the code then "so be it" find a way you are a professional.
Try to utilize all the open walls you can.
I make holes in the less fancy ceilings adjacent to the rooms I am wiring when possible like closets, pantrys, back hallways.
When cutting out boxes I look for the stud and mount it up against it. If the wood lath/ plaster fails you could always zip a screw to it. (I know someone will object to this but so what)
 

LarryFine

Master Electrician Electric Contractor Richmond VA
How how would they have done a 3-way switching setup with k&t?
Would they still do it like current methods?

Power & Travelers at Sw#1 => Travelers => Sw#2 has Travelers & Load?
Yep. You'd typically find a hot, a neutral, a switched leg, and a pair of travelers along the pathway.

I assume they'd use any available neutral that was available...

The specific location I'm pondering is the stair-light, 3-way'd from front door to upstairs hall.
Since there was usually only one circuit, or one circuit per floor, there was only one neutral to use.
 

kwired

Electron manager
How how would they have done a 3-way switching setup with k&t?
Would they still do it like current methods?

Power & Travelers at Sw#1 => Travelers => Sw#2 has Travelers & Load?

I assume they'd use any available neutral that was available...

The specific location I'm pondering is the stair-light, 3-way'd from front door to upstairs hall.
Can vary some but was pretty common to bring L1 and L2 to each switch, and common off each switch goes to the light, this method left you with reversing the polarity of the lampholder depending on switch positions. When the light was "off" it either had L1 or L2 to both common leads at the time.

Was typical to run L1 and L2 in somewhat close proximity from lighting location to lighting location, taps to switch loops went wherever was convenient, not a lot of receptacles were needed back in K&T days, but when they were supplied tapped of those main runs where ever was convenient at the time as well.

Multi floors you likely have one circuit in the ceiling of each floor.

In rural areas a lot of this wiring was installed before there was utility power, they may have had wind generators initially. I don't think those systems were 110VAC so probably was limited mostly to lighting being the only loads supplied.
 

480sparky

Senior Member
How how would they have done a 3-way switching setup with k&t?
Would they still do it like current methods?

Power & Travelers at Sw#1 => Travelers => Sw#2 has Travelers & Load?

I assume they'd use any available neutral that was available...

The specific location I'm pondering is the stair-light, 3-way'd from front door to upstairs hall.
Again, there's not one single way it was done.

Google 'California 3-way", 'Farmer 3-way', 'Power Beyond 3-way', 'Chicago 3-way'.
 

al hildenbrand

Senior Member
Again, there's not one single way it was done.

Google 'California 3-way", 'Farmer 3-way', 'Power Beyond 3-way', 'Chicago 3-way'.
And don't forget the "Carter 3-way." The 3-way switching method Kwired is describing in Post #17 (lampholder polarity switching) is a "Carter". Occasionally one will find a modern 3-way switch that momentarily shorts the two traveler terminals, and when connected in a true Carter circuit will blow the overcurrent circuit protection every time one flips the switch.
 

480sparky

Senior Member
And don't forget the "Carter 3-way." The 3-way switching method Kwired is describing in Post #17 (lampholder polarity switching) is a "Carter". Occasionally one will find a modern 3-way switch that momentarily shorts the two traveler terminals, and when connected in a true Carter circuit will blow the overcurrent circuit protection every time one flips the switch.
They're all the same..... just different names.
 
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