Knob & Tube
Knob and Tube wiring was used up into the early 1950's.It consisted of singular-insulated copper conductors run within wall or ceiling cavities,
passing through holes drilled in joists and wall studs via
porcelain insulating tubes that
resemble a "hollow piece of chalk", and suspended between
nailed-down porcelain insulators
which resemble "spools of thread" on long runs. The wires
were encased by flexible cloth insulating sleeving called "loom". The first insulation was asphalt-saturated cotton
cloth, then rubber became common. Wire splices in such installations were twisted together, then soldered and wrapped with
friction tape. Rarely were wire splices made inside metal junction boxes pre 1950.
K&T relied on
fast heat dissapation and the correct installation had the wires routed on the "rake"
part of the roof system and not on the ceiling joists, however, many homes were wired that way also. One of the problems is
attic insulation covering the K&T wiring, it prevents heat dissapation. One of the first things a person did / does in
older homes is improve the attic insulation, because way back when, 2" inches of Vermiculite (Asbestos) was all that
in attics as insulation. Most "Batt" type insulation has a paper backing called"Kraft
Paper." If the K&T becomes exposed due to rodents or overheating, you now
have live wires in contact with a combustible
material. Overheating was also caused by homeowners placing a "Penny" in the
"Fuse block" and putting the burned out fuse
back in the Fuse block. The Penny completed the circuit once again, but without any
amperage regulation. Without amperage regulation, the excessive heat flowing through
the K&T hardens the "Asphalt-saturated Cotton Cloth and Rubberized
Loom" that encases the wire, which makes it brittle and allows it to flake off. This could have already occurred, or
may occur in walls and inaccessible areas of the attic and crawlspace.
Zinsco / Zinsco-Sylvania Electrical Panels
Zinsco and Zinsco-Sylvania electrical panels are discovered in buildings they should be replaced to reduce some very real
fire and shock hazards.
Where Zinsco electrical
panels and Zinsco circuit breakers are in use, arcing, contact-point burn, and even circuit breaker case blow-out have been
observed in the field. A principal Zinsco™ circuit breaker (or Sylvania™ or GTE-Sylvania™ or Kearney™
electrical panel using this circuit breaker) point of failure appears to be at the point of contact where the circuit breaker
contacts clip onto the electrical panel bus, combined with the use of an aluminum electrical panel bus. Expert testing on
this equipment has shown that circuit breakers do not trip about 25% of the time when exposed to overcurrent - risking overheating,
fire and other hazards. The failure rate of competitive-brand circuit breakers is much less than 1%. For more info on Zinsco
/ Zinsco-Sylvania Electrical Panels, visit this "Zinsco" link.
Federal Pacific / FPE Electrical Panels
Pacific Electric Company (FPE) was one of the most common manufacturers of circuit breaker panels in North America
from the 1950s to the 1980s. Millions of their panels were installed in homes across the country. Yet, as the
years passed, electricians and home inspectors often found Federal Pacific Electric panels failed to provide proper
protection to homeowners and their families. Experts now say that FPE panels can appear to work fine for years,
but after one overcurrent or short circuit, they can overheat and become fire hazards.
In a class action lawsuit, a New Jersey State Court ruled that the Federal Pacific
Electric (FPE) Company “violated the Consumer Fraud Act because FPE knowingly and purposefully distributed
circuit breakers which were not tested to meet UL standards…” (To see the Class Action Settlement
Notice issued for New Jersey Residents, click here.) An expert who investigated the potential hazards of Federal Pacific Electric panels stated under UL 489 test
conditions, that FPE panels fail to trip at a much higher rate than standard panels.
When a breaker fails to trip, an extreme amount of power from the outside electrical supply surges into a
home’s panel and circuits. Once that happens, it cannot be stopped or shut off manually. Electricity will
burn until it runs out of fuel or the wires melt. The panel could overheat and catch fire, causing serious harm
to a home and its occupants. Many Federal Pacific Electric panels and breakers can operate properly for years.
But if and when they do malfunction, a disaster could occur.
When the price of copper was at a premium
due to the War in Vietnam (1964-1975),
manufacturers and contractors sought a less expensive alternative to copper wiring
thus Aluminum Wiring was the result. Between 1965 and 1973, use of aluminum wiring
in new construction, additions
and remodeling projects was most active.
Aluminum is softer than copper and reacts (expands and contracts) to fluctuations
temperatures. Because aluminum is more reactive than copper, there is a higher
probability the electrical connections
made in your home will become loose. When
connections are loose, they create a safety and fire hazard.
What Homes are Affected?
Homes built before 1965 are not likely to have aluminum branch circuit
built, rooms added, and circuits rewired or added between 1965-1973 and some post
-1973 houses may
contain aluminum wiring. I have observed firsthand, 110v aluminum branch
circuit wiring in a home built in 1975.
Electricians that were on top of their game used to use 10.ga Aluminum Wire
because they knew of the heat issue, but, most light switches, receptacles and fixtures -
were not rated for use with Aluminum Wiring back then.
important to note that aluminum wiring is still permitted and used for certain
applications, including residential service
entrance wiring (the wiring that enters your
electrical panel) and single-purpose higher amperage circuits such as 240V
Furnace, Electric Water Heater and Electric Range circuits. The electrical fire hazard
lies in the 110v
branch circuits that go from your electrical panel to each room and
other areas in your home.
copper to aluminum is a common fix to the aluminum wiring issue, but, there
are only "two acceptable means"
to do so correctly and safely due to joining two
dissimilar metals. One is the "Copalum Crimp" which is a
special device that is
extremely expensive. Copper is "Cold Welded" to the aluminum under 10,000 lbs of
pressure. The issue is the device is expensive and not many electricians have them.
The second and newer
method is to use "AlumiConn" connectors. These special
connectors are UL listed and approved by the Consumer
Product Safety Comission -
where as your typical "Wire Nut" is not rated for use with dissimilar metals. Go
following link to read more about the dangers of Aluminum Branch Circuit Wiring.
Puget Sound Home Inspection Service, Inc.
Thoroughness is My Trademark !
Jim Hintz - Owner / Inspector
Proud Member of Inter-NACHI
(Click InterNACHI Banner to verify)