Grounding had not been invented yet when K&T wiring was done. So there’s no standard way to ground it.
If the only wiring that is energized off of your electrical service is the NEW wiring, then all of your knob and tube is deenergized. You do not have to rip it all out - abandones is OK as long as you have chopped it up enough that the next owner cannot reuse it.
Theoretically, abandoned wiring could conduct electricity if it is accidentally energized but if you have chopped it up or better yet grounded out all of the abandoned wiring that cannot be removed similar to how when the power companies do deenergized maintenance the put grounding jumpers across all the wire you do not need to worry.
If you put in enough new wiring nobody will need to try to reuse the old K&T.
Mike Cole, Ohio electrical contractor license number EL45,008
I’ve worked for a general contractor who was also a licensed electrician. Really, it depends on the contractor if he’ll do the work himself or contract it out. Either way, ask for references, ask to see his/her contractor’s license, ask to see relevant permits, make sure the proper inspections are performed. You have a right to know who will be working on your property and their qualifications so feel free to ask about sub-contractors as well. A good and ethical contractor will not have a problem with any of that.
We had some customers who just up and left while we were working. We had others that were frequently dropping by/looking over our shoulders and asking the boss questions. We didn’t have a problem with either (well, OK, the boss did get testy about the one guy who was doing this to the point of disturbing/distracting the workers - not a good thing when you’re working on scaffolding with power tools), but really, it never hurts to double-check on anyone working on your home.
Pretty much the case in the US also, but code and permitting rules vary from city to city. Codes must meet or exceed the latest accepted national codes. Permits are dictated by the city/county rules where the work is being done. Where I am, if the electrician is merely extending an existing circuit, no permit is required. If he’s running a new circuit, a permit is required.
I had never heard of this wiring system before. I gather it must be at least 60 years old. On that basis alone I think that on safety grounds alone it should be ripped out as much as possible and professionally replaced with a complete modern circuit.
In the UK, a house with wiring that old would never qualify for a mortgage or get insurance. If anyone (visitor/friend/child) was electrocuted, the householder would be fully liable.
That said, I have no doubt that there are houses still in use with wiring even older. When the house my mother lived in was rewired prior to her moving in, some of the wiring was lead sheathed. The plumbing (one cold tap in the kitchen) and a flush lavatory) was entirely lead. Mind - the house was built in 1457. I guess it had no wires or plumbing then:)
In case you were wondering - Victoria County History
zombie or no
i think it has been denergized.
It varies in the U.S.
A lot of places will let you keep the knob and tube stuff. There’s no requirement to replace it, and technically it should be fine as long as it is properly maintained. If something breaks you can generally replace it with exactly what was there before, but in most places if you actually change something to something different then everything in the affected area has to be brought up to current code.
While the NEC and local codes may not require knob and tube wiring to be replaced, sometimes insurance companies will. I’ve known more than one person who had to have the wiring replaced because their insurance company refused to insure it as-is.
I’ve said this before in other threads, but personally, knob and tube wiring gives me the willies. If I moved into a house that had it, it wouldn’t be there for long.
ETA: And the proper way to handle unused wiring that has been left in walls is to short the two wires together (twist them together and wire nut it). Don’t ever leave bare wires hanging.
I also saw upthread somewhere a comment about using plumbing as an earth. Until recently that was common and in code in the UK. It was the advent of plastic plumbing pipes that triggered a new code which now requires a robust earthing circuit throughout the house.
I also saw where cables are routed underneath joists - in the UK they are required to go through the centre of joists.
I’m an electrician…if u have to question anything about what u r looking at…best advice is to. Leave it alone…and pay. Someone that knows what they r doing…getting shocked I’d least of ur worrys…can burn ur house down!!!
I have a good bit of electrical experience. Ive installed boxes, run emt and bx, wired all sorts of fixtures including 3 phase.
That said, I would not attempt to redo the KT in a house I owned. Let a pro do it and assume the liability.
There’s frugal and there’s foolhardy. Know when to spend the money.
As t-bonham@scc.net said:
“K&T wiring is safe, & works fine, as long as you leave it alone. Even if the insulation is old & brittle and falls off, the wires are physically separated and won’t touch each other to short out.”
I echo this. My previous house, built in 1924, had knob and tube throughout. When I hired the electrician to replace the main electrical panel and add a few circuits (1984) I asked about the strange wiring I had never seen before.
“It’s called knob and tube. It’s pretty safe because the wires are so far apart. In fact, I could still wire this house with knob and tube if you wanted to pay for it – it hasn’t been forbidden by the local code.”
Again, this was 1984. I decided in 1988 to replace the knob & tube with conventional wiring. The same electrician left all the old k&t in place but did indeed tie the clipped ends together and used wire nuts to prevent casual reuse.
Update: I sold the house. 