How to Troubleshoot an Obsolete Knob-and-Tube Electrical System

Introduction

Knob-and-tube wiring was commonly installed in homes built before the 1940s. While obsolete, many homes still have remnants of these old electrical systems. Troubleshooting knob-and-tube wiring can be challenging, but with some knowledge and caution, homeowners can safely identify and resolve issues. In this article, I will provide an in-depth guide on troubleshooting knob-and-tube electrical systems.

Understanding Knob-and-Tube Wiring

Knob-and-tube wiring consists of individual wires run through ceramic knobs and tubes. Wires are separated from each other and do not have grounding. There are several key characteristics of knob-and-tube systems:

• Wires are single conductors, not bundled together like modern Romex cable
• Ceramic knobs separate and route wires through open stud bays
• Tubes protect wires through joist and stud crossings
• No grounding wire
• Wiring is prone to deterioration over time

Knob-and-tube wiring does not meet modern electrical code requirements. It lacks safety features like circuit breakers and grounding. However, with caution and proper maintenance, knob-and-tube systems can be reasonably safe for continued use.

Signs of Problems with Knob-and-Tube Wiring

There are several signs that may indicate issues with old knob-and-tube wiring:

• Frequent tripped circuit breakers or blown fuses - This can indicate overload or short circuit in the wiring
• Discolored or warm electrical outlets - Sign of unsafe connections causing overheating
• Flickering or dimming lights - Can mean loose, damaged, or deteriorated wiring
• GFCIs or AFCIs tripping frequently - Arcing or ground faults in the knob-and-tube wires
• Vermin infestation - Rodents or insects damaging insulation

Any of these signs mean knob-and-tube wiring repairs are needed. It is not safe to ignore problems with obsolete electrical systems.

Inspecting the Wiring

Thoroughly inspecting the knob-and-tube wiring allows you to locate points of deterioration or damage. Here are some inspection tips:

• Check wiring in unfinished basements or attics for insulation damage
• Remove outlet and switch covers to inspect connections
• Check walls and ceilings for discoloration from excessive heat
• Locate splices and examine condition of connections
• Verify separation between knob-and-tube wires

Use a non-contact voltage tester to identify live wires during inspection. Look for signs of insulation cracking or fraying on old cloth-insulated wires. Also check for junctions pulled loose from ceramic knobs.

Testing the Circuits

You can perform some basic tests to diagnose problems with knob-and-tube circuits:

• Use a multimeter to check for voltage drop along circuit conductors
• Verify circuits have proper polarity and are correctly wired
• Check circuits for ground faults using a GFCI outlet tester
• Load test circuits by turning on all lights and outlets to check for malfunctions
• Use an ammeter to measure circuit loads exceeding capacity

Compare readings across circuits to identify any with abnormal voltage, excessive loads, or faulty wiring. This helps pinpoint trouble spots.

Repairing Unsafe Conditions

Any identified safety hazards with knob-and-tube wiring must be addressed immediately. Here are some repair tips:

• Reroute or splice damaged sections of wire
• Replace deteriorated insulation with electrical tape or heat shrink tubing
• Resecure any loose wire connections at outlets and junctions
• Confirm proper circuit overload protection with correctly sized fuses or breakers

For excessive splicing or deterioration, replacement of entire circuits may be necessary. All repairs to knob-and-tube wiring should only be performed by qualified electricians. Never exceed your skills.

Upgrading from Knob-and-Tube Wiring

Ideal long-term solution is to completely upgrade electrical system by:

• Installing new grounded Romex cables and outlets
• Replacing fuse boxes with modern circuit breaker panels
• Providing grounding and GFCI protection
• Removing old knob-and-tube wiring when able

Upgrades can be done gradually by hiring an electrician to replace one circuit at a time. Though expensive, this provides modern safety while preserving structure. Get quotes from contractors experienced with knob-and-tube upgrades.

Maintaining Safety with Old Wiring

When stuck with knob-and-tube wiring, focus on safety:

• Use surge protectors and avoid overloading circuits
• Do not run high-wattage appliances on old wiring
• Never install insulation in contact with knob-and-tube wires
• Perform regular inspections to catch any deterioration
• Always turn off power at main panel before any work

With diligence and proper precautions, knob-and-tube systems can be maintained reasonably safely. But upgrades should be planned when possible.

When to Call an Electrician

It is wise to call a professional for:

• Inspections revealing major deterioration or damage
• Any signs of burning, arcing, or short circuits
• Faulty connections at junction boxes or devices
• Significant voltage drop across circuits
• Upgrading old wiring and installing new grounded systems

Do not attempt repairs beyond your skill level. Licensed electricians have the training to work safely on knob-and-tube wiring.

Conclusion

Troubleshooting knob-and-tube electrical systems presents challenges, but armed with the right knowledge homeowners can identify issues. Thorough inspection, testing for faults, and safe repairs can extend the life of old wiring. However, upgrading to modern wiring should be considered whenever feasible for maximum safety. With proper precautions, knob-and-tube wiring can be maintained but should eventually be replaced by a professional.