How to Replace Outdated Knob and Tube Wiring
Replacing knob and tube wiring can seem like a daunting task, but with the right preparation and safety precautions, it is quite doable as a DIY project. Knob and tube wiring was an early standardized method of electrical wiring used in North America from about 1880 to the 1930s. While it was safe when initially installed, this outdated wiring can be a fire hazard today due to deterioration over time. Replacing it completely with modern wiring enhances safety and allows your home's electrical system to be upgraded.
Reasons to Replace Knob and Tube Wiring
There are several important reasons to replace knob and tube wiring:
- The insulation on old knob and tube wires often breaks down over decades, increasing fire risk. This can allow wires to arc or spark.
- Knob and tube wires lack grounding, which is essential for safety with modern appliances. Ungrounded outlets can leak voltage.
- Outdated wiring lacks overload protection. Newer circuit breakers or fuses cut power if there's too much draw on the system.
- Knob and tube wiring was designed for simpler electrical loads. Today's homes have much higher power demands.
- Older fuse boxes often max out at 30 or 60 amps for the whole house. Modern homes often have 150 amp or more capacity.
- Rewiring allows you to add more circuits and outlets. This reduces the strain on each circuit.
Inability to Support Modern Appliances
- Many modern appliances like air conditioners, washer/dryers, and computers require a grounded outlet to function safely and properly.
New wiring allows you to add insulation, which can help reduce energy costs.
You can add modern conveniences like more abundant outlets, three-way switching, and built-in USB ports.
Develop a Wiring Replacement Plan
Careful planning makes a wiring replacement project go smoothly:
Consult local permit/inspection requirements. Most areas require permits and inspections for rewiring.
Decide how much you'll DIY vs. hiring an electrician. Some homeowners replace wiring themselves except for the main service panel. Others hire out the entire project.
Consider any house renovations planned. It can save time and money to replace wiring during other remodeling.
Account for any wiring quirks of your home. Adjust plans if previous owners made any unusual modifications.
Choose a realistic project scope. Rewiring the entire home is a huge endeavor. It often makes sense to start with one section or circuit at a time.
Plan around home occupant needs. Try to minimize disruption to daily life. For example, consider the best timing and order when rewiring different rooms.
Always make safety the #1 priority when replacing old wiring yourself:
- Turn off power at the main breaker before starting any electrical work. Verify it's off at outlets with a tester.
- Follow local electrical codes for materials, installation methods, and getting inspections.
- Wear eye protection, gloves, and non-conductive shoes when wiring.
- Keep a fire extinguisher and first aid kit handy.
- Beware of asbestos - some old wiring insulation contained it. Have any suspected asbestos tested.
- Work carefully with another person present. Never work on wiring alone.
- Handle exposed wires carefully. Even with power off, wires can still hold dangerous residual charge.
- Double-check all connections are tight and insulation intact before restoring power.
Removing Knob and Tube Wiring
The first step is removing the old outdated wiring:
Gather Necessary Materials
- Wire stripper
- Claw hammer or pry bar
- Ladder or scaffolding
- Receptacle and junction boxes
- Shop vacuum
Access the Wiring
- Remove cover plates from all outlets and switches.
- Open up access panels or remove ceiling/wall materials (plaster, ceiling tiles) to reach wiring.
At outlets: Remove the outlet completely from the box. Snip wires individually as close to the box as possible.
At switches: Detach switch from the junction box where multiple wires are joined.
Junction boxes: Disconnect knob and tube wires where they splice to newer wiring.
In walls/ceilings: Either pull wires out completely, or cut and leave them in if removal is difficult.
Knobs: Pry or hammer knobs off wood lath or framing.
- Take down light fixtures. Remove any knob and tube connections.
- Vacuum dust and debris thoroughly.
- Patch any holes or damage from removing wiring.
Installing New Wiring
Follow these best practices when installing replacement wiring:
Run All New Wire
It's usually not up to code to just remove the unsafe knob and tube runs and splice to newer wiring. Fully new runs are safer.
Use Proper Materials
Follow codes for approved insulation type, gauge wire size, junction boxes, and other materials. Using quality materials prevents dangerous shorts and fires.
One Circuit at a Time
Focus on removing the old wiring and installing new wire for one complete circuit before moving to the next. This organized approach prevents confusion.
Use colored tape and numbered tags to label each wire run and junction. This makes it far easier to match up when connecting fixtures and devices later.
Use Safe Installation Methods
Follow best practices like:
- Properly anchoring wire.
- Maintaining safe bending radius.
- Securing boxes and junctions.
- Keeping wire trimmed and connections tight.
Have an electrician or city inspector verify safety at key checkpoints like inspecting junction boxes before close-up.
Connecting Fixtures and Devices
Finish off by connecting all fixtures like lights, outlets, switches and appliances:
- Confirm all circuits are labeled correctly. Verify power is still off.
- Carefully join wires in junction boxes using proper connectors and splicing methods. Maintain continuity of grounding.
- Re-install fixtures and devices like outlets, switches and cover plates.
- Add any new fixtures or wiring features like new outlets, switches or light fixtures. Install to code.
- If wiring to the main panel, properly size and install breakers or fuses. Ensure suitable amperage rating for each circuit.
- Verify grounding and polarity is correctly maintained throughout.
- With assistance, turn power back on at the main breaker. Watch for any sparks or malfunctioning fixtures indicating issues.
- Test outlets and fixtures in each room to confirm proper function. Flip switches and circuit breakers on and off while testing.
Following safe practices and taking it step-by-step allows a homeowner to successfully replace old knob and tube wiring. The result is a safer, more robust electrical system ready to meet all your home's wiring needs.