Trevor Tremblay, Technical Advisor at Electrical Safety Authority, highlights some of the trends he’s seeing within the field and addresses your questions about emerging challenges.
Knob and tube wiring might sound like a relic from a bygone era, but it remains a common sight in many older homes. In this episode, Karen Ras and Trevor Tremblay, Technical Advisor at the ESA, explain best practices for LECs dealing with knob and tube wiring to ensure safety and follow regulations, including some common circumstances electricians may find knob and tube wiring in, and the safest approaches to maintain wiring.
History and Identification
Knob and tube wiring dates back to the early 20th century and was widely used until the 1950s. This system is characterized by ceramic knobs, which hold and support the wires, and ceramic tubes, which protect the wires as they pass through wooden structures. It consists of two conductors with insulation made from a rubber-like material that can become brittle over time.
If your basement is unfinished, identifying knob and tube wiring is straightforward.
“It’s very easy to determine if you have a knob and tube. Just go downstairs, look up,” Trevor explains. “You'll see the white tubes, you'll see the knobs. You'll see the insulated conductors, hopefully with insulation on it.”
However, if the wiring goes up into the walls, further inspection might be necessary.
“In an older home, you're going to have multiple generations of wiring as their needs increase. You'll see aluminum extending from the knob and tube, which is not allowed, and you'll see new wiring methods intermixed so it could become a problem over time.”
Common Issues
While knob and tube wiring can be safe if properly installed and maintained, Trevor describes that over time it can become a problem as newer wiring methods are intermixed and the system deteriorates.
Older homes typically have fewer circuits, leading to multiple high-demand devices (like fridges and microwaves) sharing a single circuit. This can cause overloading and the dangerous practice of increasing fuse sizes to prevent blowing, which is unsafe.
Upgrading two-prong outlets to three-prong ones without proper grounding is common, and homeowners might assume the outlets are grounded when they are not, which can be hazardous.
Updating and Maintaining Knob and Tube Wiring
Regular inspection of these systems is crucial. Contractors should check visible sections of the wiring for insulation integrity, ensure connections are secure, and verify that circuits are not overloaded. For any modifications or extensions, ensuring compliance with modern safety standards is essential.
Replacing knob and tube wiring is generally not as expensive as one might think, especially if the basement is unfinished. Contractors can often replace wiring without a complete teardown, typically by cutting small access holes to run new wires.
In older homes, walls might contain asbestos. It’s important to identify and manage this hazard during any rewiring project.
Homeowners should inform their insurance companies about the presence of knob and tube wiring. Some insurers might require an upgrade to qualify for coverage or lower premiums.
Trevor also suggests that contractors could benefit from specializing in knob and tube replacement. There’s a substantial market in older neighborhoods, and by advertising this expertise, licensed electrical contractors can tap into a niche that promises steady work.
Knob and tube wiring, while a hallmark of historical homes, requires careful attention and expertise to maintain safety and functionality in modern times. Whether you’re a homeowner or a licensed electrical contractor, understanding the intricacies of this system is vital. For contractors, this knowledge not only enhances safety but also opens up lucrative business opportunities.
More information on Knob & Tube Wiring is available on our website.
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