Introduction
Knob and tube wiring was commonly installed in homes built before 1950. While it was suitable for the electrical loads of the time, knob and tube wiring can be dangerous by today's standards. Rewiring a home with knob and tube wiring is highly recommended for safety, but it can also be complicated. This article will discuss some key considerations for safely rewiring your home while working around the existing knob and tube wiring.
Dangers of Knob and Tube Wiring
Knob and tube wiring has several inherent dangers that make rewiring advisable:
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Overloading circuits - The wiring is not designed to handle the higher wattage of modern appliances and devices. This can lead to overheated wires and fire hazards.
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Exposed wires - Knob and tube wires are separated and suspended between ceramic knobs, with tubes protecting wires through joists and studs. Age and damage can leave wires exposed.
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Lack of grounding - There is no equipment grounding conductor in knob and tube wiring. Ungrounded electrical systems can lead to shock hazards.
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Inadequate wiring - Old wiring is often undersized for today's larger homes and expanded electrical needs. Voltage drop and dimming lights can occur.
Preparing to Rewire with Knob and Tube
Careful planning and preparation is required when rewiring a home with knob and tube wiring:
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Consult an electrician - Only take on what you are comfortable doing. Have a licensed electrician handle all main electrical panel work.
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Check attic and basement - Look for accessible knob and tube wiring runs that can be removed.
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Get necessary supplies - Have on hand electrical boxes, receptacles, cable, wire strippers, voltmeter, etc.
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Label circuits - Note what each existing circuit powers before disconnecting it.
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Take safety precautions - Wear insulating gloves, goggles, etc. Turn off power at the main breaker before working.
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Develop a plan - Rewire by location or circuit. Prepare new wire runs along planned paths.
Running New Wiring
When running new wiring, there are approaches to make the rewiring proceed efficiently and safely:
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Fish wires through walls instead of in open cavities. Use fiberglass fish tape. Avoid contact with live knob and tube wires.
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Run cables through basement and attic to limit cutting into walls. Use protective wire molding.
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Overlap new wiring and old - Keep existing circuits live as long as possible.
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Label everything thoroughly - Note locations and connections of old and new wires.
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Mount new boxes - Securely fasten new receptacle and switch boxes.
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Connect new ground wires - Ground all outlets and light switches for safety.
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Make final connections - With power off, remove knob and tube and connect new wires.
Removing Knob and Tube Wiring
As you finish each circuit, focus on safely removing the old knob and tube wiring:
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Disconnect at terminals - Remove knob and tube wires from any devices and splice points.
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Remove accessible portions - Take down knob and tube runs that are available. Leave wires in walls alone.
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Cap dead ends - Properly terminate any remaining wires that are disconnected.
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Check with inspector - Your work may be subject to inspection before renovation continues.
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Dispose properly - Knob and tube wiring is typically considered hazardous waste. Follow local regulations.
Summary
Rewiring a home with knob and tube wiring takes time and care, but is extremely worthwhile for safety. With proper planning, safe procedures, and attention to detail, you can remove hazardous old wiring and modernize your home's electrical system. Hire and consult with licensed electricians when needed, and always place safety first.