0

I was drawing a diagram of cable runs through my 1920s house as I am planning to replace knob and tube with romex. Some are completely buried in the walls so there's some guesswork involved. As I was in the attic, I was confused by several seemingly nonsensical runs - some through the joists below, some along the rafters, and what I found as I was testing current and shutting off circuits one-by-one, is that some cable is neutral-only. It has the cloth jacket, and a prior electrician created a run of new Romex that only joins the cable to white (all other cables were not joined, they weren't even capped!).

I am guessing that there is no reason to keep the wire runs this way, and I can completely redraw the plans to keep the wire runs with a single cable? Is this just an artifact or a history of wild electricians doing whatever feels right?

Improve this question
3
  • 1
    Key is the distinction between cables and wires. A wire is a single piece of copper or aluminum, possibly inside insulation (whether rubber, plastic or cloth). A cable is 2 or more wires inside an outer sheath. Each has its place, and the rules have changed a bit over time.
    – manassehkatz-Moving 2 Codidact
    Commented Jul 17 at 16:09
  • 1
    @manassehkatz-Moving2Codidact thanks for the distinction. I was indeed confused on this point, calling anything inside insulation/jacket "cable".
    – AdamO
    Commented Jul 17 at 16:30
  • K&T "multiwire branch circuits" has been described in some past posts, IIRC - where you'd have one neutral and a pair of hots, with the hots 240V apart - so 3 separate wires rather than just the usual 2.
    – Ecnerwal
    Commented Jul 18 at 0:54

2 Answers 2

Reset to default
3

K&T did route neutrals separately. If you have new NM cable being used the way you describe it is possible that someone made a repair to K&T using Romex cable, in a situation where the K&T was damaged and there was not a desire to rip down walls to install all new cabling. Whether the electricians were being "wild" or just pragmatic depends on the details of how they did it. Did they at least improve the overall safety of the bits that they touched? Or did they make it worse? Or tap off existing K&T to install new wiring improperly?

What you SHOULD do now depends on your renovation plans for the house. What kind of electric service do you have? Are you planning to upgrade that? Do you an have unfinished basement and/or attic? Are you planning any major renovations? If someone said "You should completely replace all wiring, and remove all possible traces of the K&T, breaking open any walls, ceilings and floors as necessary" would that fit somehow into your plans (say, 10-year) for the house?

Improve this answer
4
  • Good considerations. It's a 200 amp panel which is full of mostly 15A circuits. The future may include a new bathroom or air con/minisplit. I believe we can free up the necessary room by peanutting 15 and 20 amperage breakers rather meticulously balancing loads and merging circuits, so keeping all fixtures on the existing circuits seems OK. My rationale for doing this is safety. Neighbor's house burned down 4 years ago. My 10 year plan is not fighting insurance, and living in a hotel waiting for a new house to be built. (My region permits DIY electrical)
    – AdamO
    Commented Jul 17 at 16:39
  • Ok, a 200A panel "mostly full" means there's only some K&T still in use, probably upstairs and that some parts, probably at least the kitchen, are much newer. Am I on the right track?
    – jay613
    Commented Jul 17 at 16:46
  • 1
    That's right. Most light fixtures and outlets are still K&T, but the kitchen is redone and all runs exclusively romex.
    – AdamO
    Commented Jul 17 at 16:49
  • Insurance is sometimes the kicker: if you neglected to tell them about the k&t that had been touched in more recent times, it might play out badly in the event of a fire.
    – Aloysius Defenestrate
    Commented Jul 17 at 19:28
2

The preferred option with old knob and tube wiring is to rip it all out and redo it according to modern standards. Those modern standard include keeping the return path of the current (the neutral to the live and the switched live to the live in a switch loop) in the same cable/conduit as the outgoing.

It'll mean more runs to the main panel, but that's fine.

To do that you don't really need to know the current state of the wiring unless you need to preserve some part of it.

Improve this answer

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.