How to Troubleshoot Knob and Tube Wiring in Your Old House

Knob and tube wiring was commonly installed in homes built before 1950. This old electrical system can be dangerous if not properly maintained. Here is how to troubleshoot knob and tube wiring in your old house.

Identifying Knob and Tube Wiring

Knob and tube wiring has a distinctive appearance:

• Wires are separate hot and neutral wires, not bundled together like modern wiring. The hot and neutral wires are run through ceramic knobs attached to beams or studs.

• Wires are surrounded by tubes when passing through open spaces like wall cavities. The tubes protect and separate the wires.

• Wires are often wrapped with cloth insulation. This insulation has likely deteriorated over time.

• Wires are attached to ceiling rosettes instead of junction boxes.

Check your attic, basement, and inside walls for these signs of knob and tube wiring. Unfamiliar wiring in an old home is likely knob and tube.

Dangers of Knob and Tube Wiring

Knob and tube wiring poses several safety risks:

• Fire hazard - The old, dried-out insulation can crack or split, exposing bare wires that may spark and ignite flammable materials.

• Shocks and electrocution - Damaged wires with exposed metal conductors increase the risk of shocks, especially in damp areas.

• Insufficient capacity - These systems were designed for lower electrical loads. Adding appliances may overload the system.

• Unsupported wires - Loose, hanging wires move and rub, causing damage to the insulation.

Any signs of scorched or melted wires indicate an immediate fire hazard. Exposed metal wires also present electrocution risks.

Inspecting and Testing Knob and Tube Wiring

Carefully inspect the knob and tube wiring throughout your home:

• Check for cracked, damaged, or deteriorated insulation on wires. Any exposed metal conductors are extremely dangerous.

• Look for hanging, sagging, or poorly supported wires. Movement can damage insulation.

• Note any splices connecting knob and tube to modern wiring. These are potential weak points.

• Verify sufficient wire gauges for circuits, especially those serving major appliances.

Use a non-contact voltage tester to identify any live wires. Turn off power before touching any wiring. Also turn off all fuses/breakers and unplug all appliances prior to performing insulation resistance testing on wiring. Measure insulation resistance between hot wires and neutral/ground wires. Any very low or infinite readings indicate faulty insulation.

Upgrading Old Wiring

Ideally, any knob and tube wiring should be replaced by a licensed electrical contractor. Upgrading provides:

• Safety - Modern wiring is well-insulated and properly grounded.

• Capacity - New wiring supports today's electrical loads and new appliances.

• Convenience - More circuits allow connecting devices anywhere without extension cords.

• Efficiency - New wiring enables upgrading electrical panels and adding high-efficiency appliances.

If replacement is cost-prohibitive, you can implement temporary safety measures:

• Use overcurrent protection devices like fuses or circuit breakers on all circuits.

• Reroute extension cords and appliances to avoid overloading circuits.

• Where wires are cracked or exposed, carefully cap them with wire nuts or electrical tape.

However, I recommend saving up to eventually upgrade old knob and tube wiring for lasting safety.

When to Call an Electrician

Consult a licensed electrician immediately if you discover:

• Exposed hot wires
• Signs of burnt or melted wires
• No overcurrent protection devices
• Frequent popped fuses/tripped breakers
• Sparks or flickering lights
• Fixtures/outlets getting hot
• Tingling sensations from appliances/fixtures

The electrician can conduct thorough diagnostic tests and provide fix or replacement options. They can also ensure your electrical panel is adequately sized for your home.

Do not take risks with old wiring yourself. Hire a pro for both inspection and upgrades to protect your home and family.

Conclusion

Knob and tube wiring can be dangerous if left alone. But with diligent inspection, testing, and eventually upgrading the system, you can make your old house electrical safe. Be vigilant in watching for any signs of deterioration. Consider an upgrade sooner rather than later. With the right preventative measures, you can safely keep the charm of your old home.