How to Replace Your Home's Knob and Tube Wiring
Replacing old knob and tube wiring in your home can seem like a daunting task, but with proper planning and precautions, it is very doable as a DIY project. Knob and tube wiring was commonly installed in homes built before the 1940s and can pose safety risks due to degraded insulation and improper grounding. By taking the time to educate yourself on the process and following important safety steps, you can help bring your home's electrical system up to modern standards. In this guide, I will walk through all the key steps involved in replacing knob and tube wiring in a safe and effective manner.
Dangers of Knob and Tube Wiring
Before jumping into the project, it's important to understand why knob and tube wiring needs to be replaced in the first place. Here are some of the main risks posed by this old wiring method:
Fire hazard - The insulation on old wiring can break down over time, exposing bare wires that could arc and spark. This can ignite nearby combustible materials.
Insufficient capacity - Knob and tube circuits are often 30 amp systems or smaller. This limits the amount of electricity that can be safely drawn to power modern devices and appliances.
No equipment grounding - Knob and tube systems typically do not include a ground wire. This can lead to an increased risk of shocks and damage to electronics.
Insurance issues - Many insurance companies will not cover homes with knob and tube wiring, or charge a higher premium. Replacing it can avoid headaches down the road.
Difficulty with renovations/upgrades - Any electrical upgrades or renovations are complicated by the presence of knob and tube wiring. It's wise to get ahead of the issue.
So while the wiring may seem to be working fine currently, it makes sense to preemptively replace knob and tube wiring before any of those risks above turn into reality.
Preparing for the Project
Replacing the wiring in an entire home is not something to be approached haphazardly. Proper planning, precautions, tools, and know-how are needed to ensure a successful result. Here are some key steps to take in preparing for a full rewiring project:
Assess Scope of Work
- Carefully survey your home to map out all locations of knob and tube wiring. Attics, basements, and crawl spaces need to be checked closely.
- Also note where all electrical panels and junction boxes are located.
- Create a plan for routing updated wiring to replace the old.
Have Electrical Panel Evaluated
- Consult with a licensed electrician to assess if your main electrical panel is sufficient for updated wiring.
- It may need to be replaced or upgraded to a 200 amp panel or larger.
- Discuss your overall project plans to get feedback.
Acquire Proper Materials
- For most DIYers, copper wiring will be the optimal choice for durability and electrical capacity.
- You will need various sizes of Romex copper wiring - 12 gauge and 14 gauge for circuits.
- Also have on hand electrical boxes, junction boxes, connectors, conduit, and other wiring supplies.
- Turn off power at the main electrical panel and use a contact voltage tester to confirm it is off.
- Post warning signs so no one inadvertently turns power back on.
- Wear insulated gloves and other safety gear when handling wires.
Hire Electrician If Unsure
- If any part of the rewiring project seems beyond your skill level or comfort zone, hire a licensed electrician to take over. Safety should be the top priority.
Removing Knob and Tube Wiring
Once preparations are complete, it's time to remove the old wiring. Take it slow and exercise caution when taking the following steps:
Locate All Access Points
- Attics, crawl spaces, and basements are common access points. Remove covers or drilling access holes as needed.
- Disconnect the old wiring from electrical panels, outlets, switches and junction boxes.
- Twist wires together and tape ends to mark as abandoned wiring.
Remove Knob and Tube Components
- Unscrew or pry off old porcelain knobs attached to joists or studs.
- Pull out old rubber-wrapped wires from knobs and access holes.
- Remove any conduit or armored cable housing the wires.
Check for Hidden Wires
- Old wires are sometimes hidden in walls. Check thoroughly for any remnants before insulating or sealing access holes.
Dispose of Old Wiring
- Properly dispose of all removed knob and tube components to avoid any risk.
- Copper can be recycled for scrap value.
Follow all local regulations when disposing of old electrical wiring and hardware.
Running New Wiring
With the old wiring fully removed, it's time to run updated replacement wiring throughout the home:
Plan Circuit Layout
- Use your earlier scoping notes to plan what size wire should run to each room.
- Group rooms into circuits appropriately, using 12 gauge for 20 amp circuits and 14 gauge for 15 amp circuits.
Run Wiring Through Access Points
- Carefully feed new wires into attics, crawl spaces, and walls via access holes and conduits.
- Use staples as needed to tack wires against walls and joists for support.
Update Electrical Panel
- Connect new wiring to appropriate breakers in the main service panel.
- Ensure the panel has sufficient capacity for added circuits.
Install New Electrical Boxes
- Replace old junction and outlet boxes with new ones where needed.
- Feed new wiring into boxes and secure with cable clamps.
Connect Devices and Fixtures
- Connect wires to all electrical outlets, switches, and permanent fixtures.
- Install wall plates when complete.
Label New Circuits
- Clearly label each new circuit at the service panel to identify rooms served. This aids troubleshooting down the road.
Take care to insulate and secure all connections properly per code. Never splice wires outside an approved junction box.
Wrapping Up the Replacement Project
After all new wiring is installed and connected, there are still some final steps to take:
Seal All Access Holes
- Seal any holes in walls, floors, or ceilings with cement, insulation, or drywall. This helps fireproof and stabilize the new wiring.
Confirm No Stray Current
- Carefully check for any stray electrical current from old wiring using a non-contact voltage detector. Removes hazards.
- Contact local permit office to have wiring replacement project inspected before re-energizing. Ensures compliance with code.
Turn Power Back On
- If wiring passes inspection, turn main power back on at the service panel. Then test outlets, switches, and fixtures.
Replacing the knob and tube wiring in a home with modern wiring greatly improves electrical safety and functionality. Paying close attention to details in the planning, removal, installation, and inspection stages helps ensure a successful project free of any lingering hazards. With some perseverance and care, you can avoid the risks of knob and tube wiring.