How to Replace an Outdated Knob and Tube Wiring System

Introduction

Outdated knob and tube wiring can be a fire and shock hazard. Replacing it with modern wiring improves safety and allows for additional circuits to be added. This article provides a step-by-step guide on how I replaced the knob and tube wiring in my 100 year old house.

Dangers of Knob and Tube Wiring

Knob and tube wiring consists of individual wires run through ceramic knobs and tubes, usually in unfinished spaces like attics and basements. It has the following drawbacks:

Overload risk - The wiring is not designed to handle the electricity needs of modern homes. Running too many appliances can cause dangerous overheating.
Exposed wires - The insulation on old wiring often cracks and falls off, exposing bare wires. This creates a serious shock and fire hazard.
Difficult to modify - It is hard to tap into knob and tube circuits to add additional outlets. This often leads to unsafe DIY modifications.
Insurance issues - Many insurance companies will not issue policies on homes with knob and tube wiring. Those that do often charge a much higher premium.

Preparing for the Replacement Project

Before starting, I took the following preparatory steps:

Had a professional home inspector confirm that all wiring was knob and tube and should be replaced.
Had an electrician install a new breaker panel sized for the number of circuits I planned to run.
Reviewed the proposed new wiring plan and got necessary permits from the town building department.
Purchased the necessary supplies - romex cable, junction boxes, receptacles, etc.

Removing Knob and Tube Wiring

With preparation complete, I was ready to remove the old wiring:

1. Turn Off Power

The first step is to shut off power to the circuits at the breaker panel. I also turned off the main breaker to be extra safe when working.

2. Remove Wiring from Attic

I was able to access most of the wiring in the unfinished attic. I removed the old wiring from the ceramic knobs. I also cut back wiring to junction boxes and removed any spliced connections.

3. Remove Fixtures/Outlets

Next I removed all light fixtures, outlets, and switches from walls so I could access the wiring. I labeled each to make reinstallation easier.

4. Pull Wiring from Walls

For wiring inside walls, I shut it off and disconnected it from the breaker panel. I then carefully pulled it out by accessing the basement and attic.

5. Remove Wiring to Outbuildings

Any old wiring extending to outbuildings like garages and sheds was also removed. These were replaced with new circuits as well.

Installing New Wiring

With the knob and tube fully removed, I was ready to install the new wiring:

1. Run Cable

I ran the appropriate gauge romex cable for each circuit, securing it with insulated staples. I made sure to leave extra length at ends to simplify making connections.

2. Install Junction Boxes

I installed new junction boxes, making sure each was accessible for future maintenance. Junctions were made inside boxes with wire nuts.

3. Connect Devices

I connected the wiring to all the fixtures, outlets, and switches I had previously removed. Everything was labeled which made this straightforward.

4. Connect to Breaker Panel

Finally, I connected the wiring to the new breakers in the panel, matching the circuit plan I created earlier.

5. Test Circuits

With everything connected, I turned the power back on and tested each circuit using a non-contact voltage tester.

Finalizing the Replacement Project

With all new wiring installed and tested, I finished the project with:

Patching drywall at junction boxes and along wire runs.
Replacing insulation disturbed by the wiring replacement.
Having the completed system inspected by the town inspector.
Disconnecting the old fuse box which was made obsolete by the new breaker panel.

Replacing the knob and tube wiring took time and effort, but it was one of the most important upgrades I have made to my home. It has made the house much safer and easier to maintain and improve.