Knob & Tube Wiring Replacement

Electrical Service Pros specializes in knob & tube wiring throuhgout Massachusetts.

What Is Knob & Tube Wiring?

From 1880’s it was widely used through the 1930’s. In some locations throughout Massachusetts, it has been installed into the late 1950’s. Years ago there were few electrical appliances, electricity usage and loads were limited. Knob & Tube was the best and only option.

The wires were spliced and soldered together inside walls, without junction boxes and then wrapped with electrical tape. Wiring was rubber and cloth covered #14 copper mounted on porcelain Knobs nailed to the wood studs and joists. When required to pass through these members porcelain Tubes were inserted in holes with the conductors inside. Knob and Tube wiring therefore never touched the wood structure or plaster. Heat from load or overload dissipated in the air space between rafters and partitions. These circuits originally could be fused by 20 Amp plug fuses. Do not use fuses or breakers over 15 Amp today.

Visual inspection of conductors and splices can determine state of K&T integrity nowadays. Conductors with bare or dry, crumbling or stiff insulation should be replaced. These conditions resulted from over-current, shorts, improper fusing, or high temperatures. Problems are usually found in switch, plug, and junction boxes, in attics, furnace or boiler rooms and above the lights especially.