How to Replace an Outdated Knob and Tube Electrical System
I know from experience that replacing an old knob and tube electrical system can seem like a daunting task. However, with proper planning and by following important safety precautions, it is possible for a determined do-it-yourselfer to upgrade to a modern and safer electrical system. Here is my guide on how I was able to successfully replace the knob and tube wiring in my own home.
Assessing the Existing Knob and Tube System
The first step is to thoroughly inspect the existing knob and tube electrical system in place. Look for:
- Locations of the ceramic knobs holding the wires
- Tube protectors covering wires where they pass through walls and studs
- Wires connected to fuse boxes or breakers
Make notes on the routing of the wiring through the house. Knob and tube wires are often spliced and travel unexpected paths. Understanding the full scope of the existing system is crucial before developing a replacement plan.
Pay special attention to any splices, deteriorated insulation, or other damage. Problems will need to be addressed as part of the replacement project.
Developing a Replacement Plan
With an understanding of the existing wiring, I could start mapping out a plan for the new electrical system. Key factors to consider:
- The amperage of the existing electrical service and if an upgrade is needed
- Desired locations for the main panel and any subpanels
- Where to physically run the new wiring – often easiest to follow existing routes
- Which circuits should be on which breakers based on load
- All applicable electrical codes for my area
I drew up rough plans showing all the new wiring I needed to install. Having a good map was invaluable during the actual work.
Removing Old Knob and Tube Wiring
With my replacement plan ready, it was time to remove the old knob and tube wiring. Safety first - I made sure to turn off the main breaker before starting any work.
I removed each ceramic knob and tube protector, being careful not to damage surrounding surfaces. For walls and ceilings, I cut holes to access the wiring.
As the old wires came down, I fully disconnected any spliced connections. I wanted to completely clear out the old system.
Removal was tedious at times, especially fishing wires out of tight spaces. But taking it slow and steady got the job done.
Installing New Wiring
The fun part was finally installing the new wiring through the house. I ran NM cables from the main panel to all the locations on my plan, using the existing routes where possible.
For any new routes, I drilled holes and used protective bushings. I carefully pulled the cables through each run, leaving plenty of extra wire at the ends for connections.
I made sure to follow code for properly securing the new cables. I used staples approximately every 4-6 feet along runs.
At the endpoints, I prepared the cable sheathing and wires to be terminated. The new circuits were starting to take shape!
Connecting the Wiring to Panels and Devices
With all the cable runs complete, it was time for the big connections.
I terminated each cable at the main panel, carefully matching the wires to the appropriate breakers. Neutral wires, ground wires, and any bonding screws were all double checked.
I also terminated runs at subpanels, allowing whole sections of the house to go online.
At each Fixture - lights, switches, outlets - I used wire nuts to join the new cables to the device. Everything was securely fastened and carefully labeled.
Seeing those first devices illuminated with the flip of a modern breaker switch was an amazing moment!
Wrapping Up the Project
To finish the project, I buttoned up all the holes and verified full functionality of every circuit. I also had the completed work inspected by the local building department to receive an official certificate of approval.
Replacing my knob and tube wiring took planning, patience, and attention to safety. But now my home's electrical system is far more modern, efficient, and most importantly - safe. The peace of mind is well worth the effort!