What is Knob and Tube Wiring
March 8, 2008 · Filed Under Home Inspections and Home Maintenance
I’ve recently witnessed knob and tube wiring in some downtown St.
John’s homes. It’s not a common sight, but when things are uncommon
and unknown a lot of questions arise.

So, just what is knob and tube wiring?

Knob and tube wiring is found in older homes dating back to the
1940’s. It was the electrical wiring choice at the time due to being
inexpensive and practical. Knob and tube is a two wire system
consisting of a ‘hot’ and a ‘neutral’ wire – no ground wire. When the
wiring was run through floor joists it was placed in a ceramic tube to
prevent the wires from chafing.

If you happen to notice knob and tube in a home you are purchasing
(hopefully you have a Home Inspector) asks lots of questions.

In the “older days”, this method was quite adequate for the electrical
loads being produced in a house hold. However as computers, plasma
TV’s and microwaves became the new way of life, the increase is
amperage (electrical current) to run these devices posed a problem for
knob and tube wiring. It became subject to repeatedly blowing 15mp amp
fuses. Quick fixes allowed homeowners to over-fuse circuits (changing
the 15amp fuse to a 20 or 30amp fuse) which in turn caused heat damage
to the wiring due to higher levels of current.

Some insurance companies in St. John’s will still insure knob and tube
wiring but they require an electrician to inspect the house to make
sure that there are no circuits over-fused. Of course there are some
insurance companies in St. John’s that refuse to insure knob and tube
wiring. No insurance = no mortgage.

Tags: downtown St. John's, electrical, home inspector, homeowner, knob
and tube