How to Safely Rewire Your Home Using Knob and Tube Wiring

Introduction

Knob and tube wiring was commonly installed in homes up until the 1940s. This old wiring system can be unsafe due to degradation over time. However, with proper precautions, I can safely rewire my home while leaving the existing knob and tube intact. Here is a comprehensive guide on how I plan to safely rewire my home while utilizing the existing knob and tube wiring.

Dangers of Knob and Tube Wiring

Knob and tube wiring has several inherent dangers that I need to be aware of:

• Overheating - The wiring is not designed to handle high amperages. Overloaded circuits can overheat, melt insulation, and cause fires.

• Unsafe connections - Loose connections can spark and ignite surrounding materials.

• Lack of grounding - Knob and tube has no ground wire, increasing the risk of shocks.

• Deterioration - Old, cracked insulation exposes wires to short circuits and shock hazards.

• Inaccessible wiring - Wiring run through walls is difficult to inspect for damage.

To mitigate these risks, I need to take the proper precautions when rewiring around old knob and tube wiring.

Pre-Rewire Inspection

Before beginning any rewiring project, I need to thoroughly inspect the existing knob and tube wiring:

• Check for damaged insulation on wires - cracked, frayed, or deteriorated insulation can expose live wires.

• Look for loose connections - these can spark and ignite fires.

• Identify any improperly overloaded circuits - this risks overheating wires.

• Note any modifications or splices - these are prone to failure.

• Verify wiring has not been chewed on by rodents - this damages insulation.

• Check that insulation is dry - moisture degrades insulation.

Any unsafe wiring I find will need to be replaced with modern NM cable before rewiring the rest of the home.

Install New Grounding System

Since knob and tube wiring has no ground wire, I need to install a new grounding system to lower shock risks:

• Drive a 5/8" x 8' ground rod 6 feet into the earth near the main electrical panel.

• Connect the ground rod to the main panel chassis and neutral bus bar with 6 AWG copper wire.

• Install a separate ground wire in all new NM cables I run through the house.

Properly grounding the system is crucial for safety. I may also need to install GFCI outlets in ungrounded areas for additional protection.

Running New Wiring

When running new NM cables, I need to take care to avoid contacting or damaging any existing knob and tube wiring:

• Keep new wiring at least 6 inches from any knob and tube runs. Closer proximity risks arcing.

• Do not use existing holes in framing - drill new holes at least 2 inches away.

• Avoid excessive pressure - use care not to stress or deform old wiring.

• When fishing cables, watch for snags that could damage old insulation.

• Label all new wiring at ends so it is identifiable.

Taking it slow and checking my work is key to preventing damage to old wiring during new installations.

Connecting New Wiring to Old Systems

I need to be extremely cautious when connecting new wiring to existing knob and tube circuits:

• Turn off power and verify it is off before working.

• Limit use of wire nuts - use terminal blocks or screw terminals instead.

• Avoid overloading circuits - balance loads across separate circuits.

• Cap all unused wires - prevent accidental contact.

• Double check all connections - verify tightness to prevent arcing.

• Insulate connections - wrap with electrical tape for added protection.

Rushed or improper connections can lead to dangerous shorts and fires. Meticulous work is essential.

Inspecting My Work

Once the rewiring is complete, I need to thoroughly inspect all of my work:

• Verify expected voltage on all circuits - irregular voltage can indicate a wiring problem.

• Check for hot spots along wire runs - use an infrared thermometer.

• Ensure all circuits are properly grounded. Test with a multimeter.

• Confirm no shorts are present - use a multimeter to check for continuity between hot and neutral or ground.

• Check all connections are tight and insulated.

• Ensure no wires were damaged during installation.

Taking the time to methodically inspect all my work allows me to identify and correct any potential hazards introduced during the rewiring process.

Conclusion

Rewiring a home while preserving old knob and tube wiring can be done safely, but requires great care in planning, installation, and inspection. With proper precautions, the inherent risks of knob and tube can be mitigated. Patience and meticulous work practices are essential to preventing electrical hazards. When in doubt, I should consult with a licensed electrician. But by following this comprehensive guide, I can rewire my home while protecting the original knob and tube system.