h2. Understanding Knob and Tube Wiring
Knob and tube wiring was commonly installed in homes built before 1950. This type of wiring consists of individual hot and neutral wires that are separated from each other, rather than bundled together like modern electrical cables.
The hot and neutral wires are supported along their length by ceramic knobs attached to framing members or tubes through which the wires are threaded. The key advantage of this type of wiring was air circulation, which kept the wires from overheating. However, knob and tube wiring lacks a ground wire, which can be a safety hazard.
While properly maintained knob and tube wiring can be perfectly safe, it does become less reliable as it ages. The insulation material tends to become brittle and fall apart over decades. This exposes the dangerous live wire inside. I chose to rewire my home's old knob and tube system to take advantage of safer, higher capacity modern electrical wiring.
h2. Planning the Rewiring Project
Before beginning a knob and tube rewiring project, it's important to educate yourself on electrical basics and safety. Working with electrical wires comes with fire and shock hazards. I invested in a good multimeter to test wires and circuit breakers. I also downloaded reference materials on home electrical systems.
It's also wise to consult with a professional electrician, at least for advice if not to hire them directly. An experienced electrician can audit your existing wiring and provide guidance on the new wiring plan. They may also pull permits and handle any utility work.
To plan the rewiring, I created a diagram of my home's circuits, marking all outlets, switches, and light fixtures. I also noted the location of the electrical panel and all knob and tube wiring. This gave me a blueprint to work from.
h2. Running New Wiring
With the project planned, it was time to run the new wires. I chose Romex brand NM-B 12/2 with ground cable. For each new circuit, I ran the cable from the breaker panel to the first outlet box, then from box to box, leaving extra length for slack.
Running cables through finished walls can be tricky. I used a flexible drill bit and long fish tape to route my cables through stud and joist bays. Having access to a finished attic or basement is very helpful. I was also able to remove flooring as needed to drill holes.
Here are some tips for smoothly running new wiring:
- Carefully measure wire runs to buy the correct length of cable
- Maintain at least 1/4" clearance from other wires and use cable staples
- Write circuit number on both ends of each cable as you go
- Attach cables to the sides of outlet and switch boxes, not the rear
h2. Replacing Outlets and Switches
Once the new wiring cables were run from the panel to all locations, I was ready to start replacing the old outlets and switches. I turned off the power and removed the old devices.
When installing each new outlet, I connected the new NM cable to the outlet and secured it firmly to the box. I used the included wire nuts to join the hot, neutral, and ground wires. For switches, I connected the new cable hot wire to one screw terminal and the switch leg to the other.
It's crucial to attach the ground wires to all outlets and switches, which helps prevent shocks. I also made sure new and old wires were fully separated from each other. Outlet and switch styles can be updated at this point to match your home's decor.
h2. Connecting the Panel and Finishing Up
With all the new outlet and switch boxes wired up, the final step was connecting everything back to the main panel. I turned the main breaker off for safety. I then removed each old circuit from the panel one at a time and wired up the new circuit in its place.
It's important to carefully label each new circuit in the panel so current and future uses are clear. I grouped the wires neatly and secured them to the panel box.
Once all circuits were connected, I turned the main breaker back on and tested each outlet and switch. I also checked for properly grounded outlets and correct polarity. After confirming everything was working correctly, I buttoned up the outlet and switch plates.
Some final steps include:
- Update any affected wall plates, trim, insulation, etc
- Properly cap unused wires from old system
- Check that all junction boxes are properly closed
- Hire electrician to validate completed system if desired
While rewiring a home's electrical system is a major project, it brings your home's wiring up to modern safety standards. Taking the proper precautions makes the process straightforward. Just be sure to do your homework before getting started.