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How To Upgrade Old Knob and Tube Electrical Wiring

By Dave Rongey - Summary:

How to Fix Old Electrical Wiring Problems: Guide for Repairing Old Wiring, Upgrading Knob and Tube Wiring and a Fuse Box

Guide for Repairing and Upgrading Old Electrical Wiring

Electrical Question: My 1907 house has a 200 amp service, and the kitchen has been upgraded with new circuits.

  • Lights and Outlets on One Circuit
    Trouble is, the remainder of the house, the lights in all the remaining rooms along with the outlets are all on one circuit. In the middle of this circuit, there remains a small fuse box, with four fuses, three are active, but I can only identify two of them. Last week, the circuit blew, and I flipped the breaker.
  • The upstairs portion of the circuit regained power, but the lower portion, the outlets in the first floor have no power. I checked the fuse box for that circuit, and none were burned.
  • Old Fuse Box Panel
    I moved fuses around to see if possibly that was the problem. no luck.
  • I can get to most of the bottom floor outlets, from the basement, but my house is solid masonry and of course, where the wires are run are in the plaster and lath interior walls.
  • Circuit Wiring
    My question is, can I change the portion of the circuit that is currently not working, upgrade the outlets that I can reach and still keep the lighting (functioning) portion of the circuit in tack?
  •  I haven’t been able to find diagram of how to do this. Do you have suggestions?
  • Unfortunately, I am have no income, so calling an electrician is a last resort.

Any help will be greatly appreciated!

Background: Rebecca, a Handy-woman from Jackson, MO.

Additional Comments: Thanks for your site, and thanks for your help!

Dave’s Reply:
Thanks for your electrical wiring question Rebecca.

home electrical rewiring

How to Fix Old Electrical Wiring Problems

  • Identifying the existing wiring circuits and access to the wiring is the key factor when upgrading old electrical wiring.
  • Even though the finish walls are lathe and plaster it may be possible to fish new wiring in to upgrade the wiring to existing outlets.
  • One barrier may be fire blocks, which were commonly placed about four feet from the floor and were installed in each wood framed stud bay or section cross-ways, from side to side.
  • This block of wood prevents fishing a new wire down to the existing outlet box unless that portion of the wall is opened enough to drill a hole through the block, intercept the wire and continue feeding it down to the outlet box.
  • Its a time intensive and messy job, however it is possible and an alternative to removing all of the existing lathe and plaster.

Upgrading Knob and Tube Wiring and a Fuse Box

  • Replacing the Fuse Box
    When upgrading the existing knob and tube style wring it is important to disconnect the existing portion of the circuit that has been replaced with new wiring, and it is best to remove any old or abandoned wiring.
  • Replacing the existing fuse box with a new sub-panel with circuit breakers would be advisable, and most likely necessary to eliminate the possibility of complications with fuses and connections within.
  • The sub-panel must have a separate ground wire that is bonded back at the main electrical panel.
  • The sub-panel ground wire must not be bonded with the neutral wire inside the sub-panel, the two must be separate and isolated from each other.
  • The ground and neutral wires are only bonded together at the main electrical panel where the ground bond is required.
  • While your at it, I would strongly suggest that consider installing smoke detectors in the home that are hard-wired with battery back up and inter-connected together so that if one goes into alarm, they all do.

Totally separating the new circuits from the existing circuits would be best, then as more upgrading is performed the new outlets can be added to the new circuit as they are removed from the old existing wiring.

I have provided the following links that lead to fully detailed information on this website that will assist you with your electrical question:

More about Knob and Tube Wiring

Knob and Tube Electrical Rewiring

Electrical Junction Boxes
Electrical Code for How Many Wires in Junction Boxes

Circuit Wiring
Electrical Panel Circuit Listing

Kitchen Electrical Wiring

For more information about Circuit Wiring
Circuit Wiring
Circuit Wiring
Electrical Circuit Wiring
This article looks at common 120 volt and 240 volt house wiring circuits and the circuit breakers that are installed identifying the types and amperage sizes used in most homes.

This link is helpful as a Handy woman
Do-It-Yourself Electrical

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2 Responses to “How To Upgrade Old Knob and Tube Electrical Wiring”
  1. Bob says:


    I was told that pulling a wire for a sub panel would be the best way to get power above the rooms that presently have knob and tube wiring. I need to know how do I determine what size wire to buy for this run. I have a Cutler Hammer 100 amp CH7 and 4 of the breakers, one 20 amp and three 15 amp are wired with knob and tube. The local inspector said that I could leave the knob and tube and that there isn’t any reason to install Romex unless I really want to.

    • Dave Rongey says:

      Hi Bob,
      The size of the wire or cable would depend on the size of the panel that would be installed, and this can only be determined by knowing what the load will actually be. If you are just replacing the bedroom circuits as mentioned then the actual loads of these circuits will need to be evaluated. The loads should also take into consideration all appliances that are plugged in during the year, including space heaters and room air conditioners. Also consider any additional loads or dedicated circuits that may be added. After this is known then the panel size and cable size may be determined.


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