How to Solve Dangerous Knob and Tube Wiring in Old Homes
Knob and tube wiring was commonly installed in homes built before 1950. While it was suitable for the electrical needs at the time, this old wiring can be dangerous by today's standards. Replacing knob and tube wiring completely is the safest option, but requires a significant investment. There are also some less expensive steps you can take to improve safety until you can budget for a full rewire. Here is an in-depth look at the risks of knob and tube wiring and how I have worked to make my old house safer.
What Is Knob and Tube Wiring?
Knob and tube wiring consists of insulated copper wires running through porcelain knobs and tubes. It was the standard wiring method for homes in the early 20th century.
Some key features of knob and tube wiring:
No ground wire - There are only hot and neutral wires, no ground. This makes it more prone to shocks and fire hazards.
Run through open air - Wires are separated by knobs and tubes and do not run through protective conduit. Exposure can lead to insulation breakdown.
No protection from overloads - Older fuses and breakers may not trip with wiring overloads the way modern ones would.
Difficult to inspect - Wires hidden in walls are not easily accessible to inspect condition and make repairs.
While once considered safe, knob and tube wiring is now seen as a fire and shock risk and is no longer used in modern homes.
Dangers of Knob and Tube Wiring
There are several serious dangers posed by aging knob and tube electrical systems:
Fire hazard - Degraded insulation can allow wires to overheat and ignite nearby combustible materials. This can lead to electrical fires.
Shock hazard - Without a ground wire, a short makes metal parts electrified. You could get a serious shock from a metal appliance or lamp.
Overload - An overload on one circuit can overheat wires and start fires since fuses/breakers may not trip.
Insurance issues - Many insurers won't cover homes with knob and tube wiring or charge higher premiums.
Resale value - Knob and tube wiring can make it difficult to sell your home and lowers property value.
While the risks are real, it is possible to improve the safety of your wiring incrementally while you save up for a complete rewiring project.
Options for Improving Safety
Here are some options I considered for making my knob and tube wiring safer:
1. Add GFCIs
Installing GFCI (ground fault circuit interrupter) outlets on all circuits adds protection from shocks. GFCIs detect abnormal current flows and quickly cut power during a short. This adds a major safety improvement for a few hundred dollars.
2. Upgrade electrical panel
Replacing an old fuse panel with a modern circuit breaker panel gives you better overload protection. Breakers also make it easier to isolate and shut off troublesome circuits. Panel upgrades run $1000 or more.
3. Prioritize high-risk circuits
Kitchen and bathroom circuits pose greater risks due to their exposure to water. Focus on replacing these first before circuits in less risky locations like bedrooms.
4. Reroute accessible sections
For any sections of knob and tube that are accessible in basement or attics, it can be safer and cheaper to reroute small sections in conduit rather than a whole house rewire.
5. Add arc fault breakers
Arc fault breakers provide protection against dangerous arc faults which can occur in old wiring. Upgrading breakers to combination arc fault models adds another layer of safety.
6. Remove unnecessary loads
Eliminate any high wattage appliances like window AC units to reduce the overall load on the old electrical system. This reduces risk of overloads.
My Experience Improving Knob and Tube Wiring
When I bought my 1920s home, the knob and tube wiring was antiquated and frankly scary. Here is what I have done over 5 years to improve safety:
Added GFCI outlets throughout the house - Made this my first priority for shock protection.
Upgraded electrical panel from 60 amp fuses to 200 amp breakers - Added overload safety.
Rerouted attic wiring from knob and tube to modern NM cable - Eliminated exposed wiring in high-risk attic space.
Removed window AC units - Reduced electrical load by switching to portable units when needed.
These upgrades made me feel much safer while I save up to have the rest of the wiring replaced. Improving old knob and tube wiring requires both patience and persistence, but it can be made safer. My next goal is to replace all the wiring in the kitchen, which I hope to accomplish over the next year.
When to Call An Electrician
While DIY improvements can help, it's safest to have electrical issues addressed by a licensed electrician. I recommend calling an electrician for:
Inspecting your knob and tube wiring system.
Installing GFCIs and upgrading electrical panels.
Rerouting or replacing any wiring inside walls.
If you ever experience flickering lights, shocks or other electrical concerns.
Getting professional help gives you peace of mind that any repairs were done safely. Be sure to get quotes from multiple electricians before starting significant projects.
Replacing knob and tube wiring completely can be expensive. But with some interim safety improvements, you can buy yourself time to save up for the ultimate solution - rewiring your home according to modern electrical code. With persistence and the right professional help, you can make living with knob and tube wiring manageable while you work towards rewiring your historic home.