How to Troubleshoot Old Knob and Tube Wiring

Introduction

As a homeowner with an older house, I often have to deal with old knob and tube wiring. This type of electrical wiring was commonly used in homes built before 1950. While it can still be functional, knob and tube wiring often needs repairs and upgrades. In this article, I will provide a step-by-step guide on how to troubleshoot and safely repair old knob and tube wiring.

Understanding Knob and Tube Wiring

Knob and tube wiring consists of individual wires that are run through open air, on porcelain knobs, and through porcelain tubes. It does not have a ground wire and the wiring is often brittle or cracked from age. Some key facts about knob and tube wiring:

• Used in homes built before 1950
• No ground wire, just a hot and neutral
• Wires run through open air, not inside conduit
• Knobs hold wires off surfaces; tubes protect wires through framing
• Can be functional but prone to problems from age
• Difficult to repair; replacement often recommended

Signs You May Have Problems with Knob and Tube Wiring

Some common signs of problems with knob and tube wiring include:

• Frequent tripped circuit breakers or blown fuses - This often indicates damaged or frayed wiring.
• Discolored or warm outlets or switches - Can signal unsafe connections or overload.
• Lights flickering or dimming - Damaged or deteriorated wiring may cause poor connections.
• Buzzing, humming, or sizzling from outlets - Noisy electrical components can indicate arcing wires.
• Odd odors from outlets - Burning smells signal major safety issues.
• Shocks or sparks from outlets - Exposed wire from age causes shocking/sparking.
• Full or partial power outages - Wiring may be damaged or overloaded.

If you notice any of these warning signs, it's important to thoroughly inspect and troubleshoot your old electrical wiring.

Safety Tips for Inspecting Old Wiring

When dealing with knob and tube wiring, safety should always be your top priority. Follow these tips to safely inspect old wiring:

• Turn off power at the main panel - Shut off all power before doing any electrical work.
• Use a non-contact voltage tester - Verify power is off with a voltage tester before touching any wires.
• Look for exposed wiring - Damaged insulation can expose live wires and pose a serious hazard.
• Check joints for deterioration - Brittle, cracked joints may fail under load.
• Use caution near knob insulation - The old insulation can easily crumble and expose live wires.
• Avoid overloading circuits - Capacity limitations can cause overheating.
• Consider upgrading - If wiring is in poor condition, replacement may be necessary.
• Call a professional if unsure - Do not take risks with old electrical wiring.

Inspecting Visible Wiring and Components

Once you have safely powered off the circuits, start inspecting any visible knob and tube wiring:

• Carefully examine the knob and tube insulation for any cracks, deterioration, or exposure. Tap gently to check for crumbling.
• Look for splices, joints, or junctions that may be compromised. Signs include charring, poor connections, or cracked insulation.
• Check where wiring enters electrical boxes and fixtures. Insulation damage is common at these points.
• Verify that connections are secure at devices. Loose screw terminals can cause arcing.
• Scan for any signs of modifications or amateur repairs. These often violate safety codes.
• Note locations with excessive bending or stretching of wires. This can stress connections.
• Watch for nails, screws, or staples piercing old wiring. This can create hazards.

Also inspect light fixtures, switches, outlets, and junction boxes for problems. Signs of issues include overheating, odors, discoloration, noise, and sparks.

Checking Wiring Condition in Walls

While much of the knob and tube wiring may be hidden in walls, there are ways to inspect it:

• Carefully examine the interior sides of electrical boxes for cracked or fraying wire insulation.
• Use an inspection camera to look for wiring inside finished walls and ceilings.
• Check for discolored or warm walls which may indicate overloaded circuits inside.
• Consider cutting small access holes to inspect wiring in problematic areas.
• Remove baseboards, outlets, or switches to check wire insulation behind them.
• Consult an electrician about using special tools like insulation testers or ground fault detectors.
• For difficult access areas, wiring may need to be disconnected and pulled out for inspection.

Finding deterioration or violations in hidden wiring can indicate a need for full replacement.

Testing Circuits and Troubleshooting Problems

To thoroughly troubleshoot old wiring, testing of individual circuits is needed:

• Turn off all power and verify it is off before testing wiring.
• Start at the main panel and map out each circuit. Note wire material, gauge, and breaker amperage.
• Test each circuit individually - Turn on the breaker, energize the circuit, and check for problems.
• Check for any drop in voltage along a circuit length - Can signal excessive resistance from damage.
• Use a thermal camera or probe to check for hot spots and overheating.
• Test each outlet's wiring for proper polarity and grounding. Reverse polarity or open grounds are hazards.
• Check circuits with inductive loads like motors for noise or voltage drops.
• Evaluate the condition and capacity of the main service wires and panelboard. Overloads can cause failures.
• Document all issues found and prioritize repairs based on severity. Label dangerous areas.

Considering a Knob and Tube Wiring Replacement

If old knob and tube wiring is deteriorated or improperly modified, full replacement is often necessary:

• Replacement improves safety with modern grounded wiring and circuit protection.
• It allows for capacity increases to serve larger loads and new appliances.
• New wiring enables electrical system upgrades like AFCI and GFCI protection.
• Proper installation meets the electrical code and passes inspections.
• Removal restores full use of walls for insulation, low voltage wiring, plumbing, etc.
• It increases home value for resale over an obsolete electrical system.

Replacement does come at a significant cost - often $8,000 to $15,000 on average. Get quotes from licensed electricians to determine the investment.

Working Safely with Electrical Professionals

With safety as the priority, partnering with qualified electricians is highly recommended:

• They have the training, tools, and expertise to thoroughly evaluate old electrical systems.
• Professionals follow established safety procedures and use PPE for hazardous electrical work.
• Licensing verifies their qualifications to legally perform electrical repairs and upgrades.
• They know how to work on old wiring in a way that prevents damage to your home.
• Electricians can advise when repairs are possible or replacement is needed.
• For DIYers, they can provide guidance to ensure work is done properly.

Proper repairs or replacement of old knob and tube wiring improves safety and reliability. By following safe practices and working with professionals, you can tackle this electrical upgrade project confidently. Let me know if you have any other questions!