Utility companies have used Aluminum in their
transmission lines since early 1900. It is still the preferred transmission and
distribution wiring material for distributing companies because Aluminum offers
cost and weight advantages over copper.
This blog is focussed on Aluminum wiring from Home Inspection point of view thus we will talk about its use in houses only.
In North America Aluminum wiring was used in houses
between 1960 and late 1970. The cost of copper was much higher compared to
aluminum. Therefore, to save money Aluminum was used as an alternative to
copper. It is estimated that there are around 450,000 houses in Canada which
are wired with Aluminum wiring. Insurance companies are becoming more and more
wary of the houses with aluminum wiring due to associated fire hazard and
require inspection and a certificate of safety from the licensed electrician
before issuing or renewing insurance policy for the houses with Aluminum
wiring. As per US product safety commission Homes with aluminum wiring are 55
times more likely to have one or more connections reach Fire Hazard Condition
than a home wired with copper.
Problems with Aluminum
wiring
1. Aluminum wire in itself is not a fire hazard its
only when the termination were not properly done it becomes loose, overheat which
can cause arching which can start the fire.
2. Aluminum oxidises more than copper which forms a
layer of aluminum oxide on top of wire. The layer although very thin is non-conductor
of electricity. The current carrying capacity of the wire is then reduced which
overheats the wire.
3. Aluminum expands and contracts more than copper so
if the connections are not made properly overtime the connections become loose
and arching can occur.
4. The problem in aluminum wiring is mostly for the
single strand wiring circuits used for 15amp and 20 amp branch circuits, although
all the circuits need to be inspected by licensed electrician.
5. Aluminum has a higher resistance to current flow
which means to carry same amount of current aluminum wire has to be thicker
than that of copper.
6. Aluminum is more malleable thus it is more sensitive
to compression. If the screw has been over-tightened on Aluminum wiring, the wire
will continue to deform after tightening has stopped. This deformation creates
a loose connection and reduces the current carrying capacity of the wire.
How to locate aluminum
wiring
The best place to check whether your house has Aluminum
wiring is to look for visible wiring in attic, basement and crawl space or at
the service panel. The wiring should be marked with the word Aluminum, ALUM,
AL, ALUM ACM, AL ACM. During home inspection the inspector will open the main
distribution panel (if accessible and safe). Aluminum wires can be spotted at
splices near the breakers or fuses.
Furthermore, following symptoms that indicates aluminum
wiring!
1. Flickering lights.
2. Static on the radio, computer or TV
3. Circuit breakers or fuses that trip for no apparent
reason.
4. Odor similar to that of burning plastic around
switches and receptacles.
5. Discolored or warm switch plates and receptacles covers.
6. Plugs that do not work even with the circuit
energized.
How to fix Aluminum
wiring problems
To fix aluminum wiring problems hire Licensed Electrical
contractor to inspect your house and to get advise about what needs to be done to
ensure the safety. Every house is different and the solution to the aluminum
wiring varies.
Following is few fixes that a licensed electrical
contractor can propose!
1. The best and permanent solution is to replace
Aluminum wiring with the copper wiring.
2. Cut back the damaged aluminum conductors and join
these to a copper tail using a connector approved for use with aluminum. Such
connectors are colored brown or purple (depending on the manufacturer). The
copper tail is then terminated at the terminal screws of an ordinary devise
(which includes approved receptacles, etc.)
3. Cut back damaged aluminum conductors and
re-terminate a new device bearing the marking CO/ALR (copper aluminum revised).
