Home Inspection San Antonio
                     Home Inspection Reveals Aluminum Wiring: Problem or 
 Not?
Does a Home Inspector Check for Aluminum 
 Wiring?
We inspect a lot of homes in San Antonio, and it’s not uncommon to find segments of the electrical wiring that
are made of aluminum, especially in the older areas closer to the city center. Aluminum wiring isn’t inherently
dangerous by just existing, and in fact it’s still used today for service conductors, but the way that aluminum 
 wiring is installed and the precautions that must be taken into account for it can lead to problems when  
everything isn’t in place. home inspection san antonio
What is Aluminum Wiring, and Why Was Aluminum Wiring Used?
During the early 1960’s, the price of copper rose significantly in a short period of time. Multiple factors  
contributed to the steep increase in copper prices, including the Vietnam War, a housing boom, and a  
production limit set in place by producers to raise profits. As electrical wiring is a necessary material for new
housing, increased copper prices increased the price of building a home, and a cheaper alternative was
sought.
Aluminum wiring was the answer to soaring copper prices. Although aluminum is only 60% as effective at
conducting electricity as copper, the reduced density of aluminum made the wire lighter, and aluminum is  
significantly more abundant and thus cheaper than copper. The decreased conductivity required the use of
more metal to be used in the wiring, increasing the gauge (or size) of the wires, but at the time, the cost of  
aluminum was so cheap that it just made economic sense to work with aluminum instead of copper, and  
manufacturer’s did so. An estimated two-million homes were built primarily with aluminum wiring between 1965  
and 1972.
Why is Aluminum Wiring A Problem?
As mentioned earlier, aluminum wiring is not inherently a problem, so long as the the differences between it  
and copper wiring are accounted for. All the overhead wiring used by power companies in San Antonio has  
been aluminum for decades due to its low-cost and light weight, and aluminum is still used for the incoming  
service conductors on homes built to this day.
The issue is that these differences weren’t accounted for in the installation of aluminum wiring in the 1960’s and
1970’s.
Aluminum Wire Deforms and Arcs
For instance, the almost pure-aluminum alloy used in large overhead wires carrying huge amounts of energy  
expand and contract at a much higher rate than copper. As energy passes through the wiring, the wire’s  
temperature increases due to electrical resistance, and as the temperature of the metal increases, so does it’s  
size. The copper wire does not have as much electrical resistance as aluminum, so it doesn’t heat up as much, 
 and thus it doesn’t expand at nearly the same rate.
The expansion and contraction of the aluminum wiring, known as “creep”, caused problems when used on
connections designed with the properties of copper wiring in mind, such as receptacles. This wire creep and  
deformation could actually cause the wire to become loose from the connection over time, which further
increases the electrical resistance and would eventually lead to “arcing”, creating an ignition source for fire.  
This meant that over time, any connection made between aluminum wire and another component not  
specifically designed for aluminum wire could be a fire hazard.
Aluminum Wire Corrodes
Aluminum wire is also much less resistant to corrosion than copper. Over time, exposed copper wiring with  
energy flowing through it could corrode in the presence of simple water vapor, such as from a room humidifier  
or even cold-air leaking in from an exterior wall. These corroded wires are much more resistant to the flow of  
electricity than non-corroded wires, creating more heat and eventually an ignition point.
Aluminum Wiring and Home Inspections
Yes, any aluminum branch wiring discovered during the course of a home inspection in San Antonio will get
documented on the report. At that point, we will always recommend that a licensed electrical contractor  
evaluate the extent that aluminum wiring was used throughout the house and make recommendations as to the
solution.
As a home inspector in San Antonio, we are required to check that any aluminum wiring connections are made
with an anti-oxidant paste (typically black in color), in order to minimize the oxidation at the contact point. In this
case, we most often see aluminum wiring in main breaker panels or breaker sub-panels, used as service
conductors leading into the panel.
Does Your Home Have Aluminum Wiring?
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