How to Rewire Your Home With Obsolete Knob and Tube Wiring

Introduction to Knob and Tube Wiring

Knob and tube wiring was commonly installed in homes built before 1950. It features:

• Wires running through open space in walls and attics rather than through protective conduit
• Wires attached to ceramic knobs or run through porcelain tubes
• No ground wire, relying on air as an insulator
• Wires coated in cloth rather than plastic or rubber insulation

While knob and tube wiring was suitable when first installed, it can become unsafe over time as insulation breaks down. Rewiring provides modern safety with grounded wires, but requires understanding how to integrate new wiring with the old.

Dangers of Obsolete Knob and Tube Wiring

Knob and tube wiring poses several fire and shock hazards:

• Cloth insulation can become brittle and crack over time, exposing live wires
• Wires run through open spaces where they can be easily damaged by rodents or homeowners
• No ground wire and outdated fuses increase risk of shock and fire from faults
• Inability to handle today's higher electrical loads and devices

These risks are compounded by DIY modifications over the years as homeowners add new wiring without removing the old. I recommend completely rewiring homes with knob and tube unless it has been unusually well-maintained.

Preparing to Rewire with Knob and Tube

Proper planning makes a knob and tube rewiring project safer and helps avoid costly mistakes:

• Hire a licensed electrician to ensure the job is done safely and correctly
• Have the electrical system inspected to identify all knob and tube wiring and any DIY modifications
• Create a rewiring plan determining new circuit layout, wiring routes, and timeline
• Obtain all necessary permits for the rewiring project
• Turn off power at the main panel before starting and verify it is off
• Inform your insurance company in case adjustments to coverage are needed

Rewiring is disruptive, so also plan how to manage lighting, appliances, and lifestyle during the process.

Installing New Grounded Wiring

When ready to start, the general process is:

1. Run new cables along planned routes from the main panel to devices, lights, and switches
2. Carefully remove devices and join their wires to the new cables
3. When all wring is complete, attach cables to the circuit breakers
4. Disconnect and remove obsolete knob and tube wiring
5. Patch walls/ceilings and restore surfaces along wiring paths

I recommend:

• 12/2 NM cables for 15-20 amp small appliance circuits
• 12/3 NM cables for 20 amp circuits with shared neutral
• 10/2 NM cables for 20 amp laundry, kitchen etc.
• 8/2 NM cables for 30-50 amp large appliances

Follow codes for cable sizing, wire connections, grounding, and more. Aim to reuse existing boxes but replace if damaged or insufficient.

Verifying Successful Knob and Tube Rewiring

Once the new wiring is installed and knob and tube removed, thorough testing should be performed:

• Verify zero voltage on all disconnected knob and tube wires
• Check voltage and polarity at each receptacle and switch
• Test GFCIs and AFCIs function properly by pressing test buttons
• Inspect wiring connections for tightness and no exposed copper
• Turn on all lights, appliances, and equipment to confirm proper operation
• Check for signs of loose connections like dimming lights

This ensures your rewiring and removal of knob and tube has been completed safely and successfully. Maintaining the new electrical system with periodic inspections will keep it running safely for decades to come.

Summary

While rewiring for obsolete knob and tube can seem daunting, careful planning and installation allows integrating modern, grounded wiring. Hiring professional electricians ensures the tricky removal and integration work is done properly. Taking time to verify fully successful rewiring makes sure your home's electrical system is safe and meets today's needs.