Knob and Tube, Doom and Loom

Submitted by DonHester on Tue, 10/23/2012 - 15:31.

Knob and Tube, Doom and Loom- Wenatchee and Leavenworth Home Inspection Services

It is very common in older homes up to about 1950 to find Knob and Tube wiring. Knob and Tube get its name from the porcelain Knobs (holders) and Tubes that run through framing members to protect the wires.

Knob-and-tube wiring systems starting going by the way side after the 1930’s due to the growing popularity of non-metallic and armored cable systems for homes.

As home inspectors we will find this style of wiring quite often when inspecting homes in the pre-1950 era.

Knob and Tube (K&T) had some advantages that modern wiring does not. It was an open air system and as such was able to dissipate heat much better. Heat is the enemy of all electrical systems. This is why service conductors from power poles are often smaller than the service entrance conductors.

The problem with many of these older wiring systems is that they were never designed for our modern lifestyles.

Knob-and-tube wire, properly installed, is not inherently a problem. While opinions regarding the safety of knob-and-tube wiring vary widely, the concerns are not with the original wiring, but rather with what has happened to it after the fact.

Improper Knob and Tube Splices- Wenatchee Home Inspection

(These holders are the knobs)

When knob and tube are spliced or connected to junction boxes, fixtures or lights it must have what is called loom. Loom, special water resistant cotton braid tubing, is used to cover the wire. This provides the conductors protection when entering devices such as junction boxes etc…

Knob and Tube Loom

This is the same as cable covering in modern “Romex” style of wiring. The cable cover needs to enter the junction box to protect the wires.

Improper Knob and Tube splice and Loom- Wenatchee Home Inspection

When evaluating knob and tube wiring it is important to look for how any connections are performed and that the loom is in place. Circuits with K&T wiring should be on 15 amp circuit breakers only.

“A shocking occurrence ceases to be shocking when it occurs daily. “

Alexander Chase

NCW Home Inspections, LLC is a Licensed Washington State Home Inspection service located in Wenatchee Washington serving Chelan County, Douglas County, Kittitas County, Okanogan County and Grant County Washington and the cities of Wenatchee, Leavenworth, Cashmere, Oroville, Cle Elum, East Wenatchee, Quincy and many more…

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Knob and Tube, Doom and Loom