March 1948 Radio-Craft
Wax nostalgic about and learn from the history of early electronics.
See articles from Radio-Craft,
published 1929 - 1953. All copyrights are hereby acknowledged.
Aluminum wire's role in electronics
and electrical service systems is an interesting case study. Early on, as this
1948 Radio-Craft magazine
article reports, aluminum was seen as a panacea for harder to find copper sources
and attendant price increases. Back in the early 1970s when I first began working
as an electrician while taking vocational courses in high school, aluminum wire
was being installed in low-end tract homes, apartments, and townhouses in order
to save a little money. Usually, you needed to go one size up (12 ga. for
15 A circuits instead of 14 ga.), but the cost was still less. The
National Electric Code (NEC) permitted it at the time
because it had not been in service long enough for its cold flow nature to manifest
itself through loosening connection interfaces and eventual fires due to sparking
under load. Brittleness after repeated stressing also caused arcing and resulted
in fires, as did corrosion brought on by dissimilar metals interfaces between the
aluminum wire and the brass connection screws on receptacles and switches. The
situation was/is so dire that some insurance companies will not cover homes
built during the brief aluminum wire era unless it has been re-wired with copper.
Not willing to totally surrender the use of aluminum, manufacturers began producing
copper-clad aluminum wire for residential use. It, too, eventually proved unsafe
and the industry returned to what is today's standard. These days copper is
used almost exclusively for 10 AWG and smaller wire (30 A circuits), while
8 AWG and larger is most often multi-conductor aluminum. The service entrance
cable to your home is almost certainly aluminum, as is the 50 A
(or greater) line to your electric stove, the
40 A (or greater) line to your air conditioner
compressor, but they are stranded and the device terminals are designed to
work with aluminum.
Aluminum Wire is likely to increase greatly
in popularity in the next few years, the American Society of Agricultural Engineers
was told last month. Wartime improvements in manufacture and use of aluminum
and the increase in price of copper wire were given as reasons.
Aluminum wire is half as expensive as copper, and its light weight makes
it especially desirable for many applications. Its conductivity is lower - it
has a specific resistance of approximately 17 as compared with 10.4 for copper
- but its lighter weight permits running larger conductors.
Posted February 3, 2021(original 12/30/2014)