Potential Fire Hazard: Aluminum Wiring
By James A. "Buck" Durham, P.E. of Jade Engineering.
If you're dealing with a home built, added on to, or rewired between 1965 and 1972, aluminum
wiring might be a problem for you. Research by the U.S. Consumer Safety Commission revealed
that homes wired with aluminum wire manufactured before 1972 are 55 times more likely to have
one or more connections reach fire hazard conditions than homes wired with copper.
Aluminum wire manufactured after 1972 was somewhat improved, though the introduction of
aluminum alloys did not solve most of the connection failure problems, and aluminum use for
branch wiring, that is wiring to receptacles and switches, ended by the mid seventies.
Now forbidden by building codes for internal branch wiring, aluminum wiring is still used for such
applications as residential service entrance wiring, or single-purpose higher amperage circuits,
including 240-volt air conditioning and electric range circuits. For these applications, a
heavy-gauge aluminum wire can be used, eliminating the hazard created by the smaller-gauge
branch wiring.
Aluminum wiring use started in 1965 as a cheap alternative to copper wiring. Its cheapness,
observed one builder, was evidenced by the fact that no one came to a home building site to pick
up aluminum wire scraps as they had always done with copper wire. Within a few years, however,
the less expensive wire proved itself to be a weak substitute for copper.
One common problem with aluminum wire is that it more easily corrodes at connections than
copper. Such corrosion increases resistance and this increased resistance causes overheating
of the wire at connections with switches or outlets, or at splices.
Another problem arises because aluminum wiring expands more than copper during the
expansion and contraction that carrying electricity causes wire to go through. The constant
expansion and contraction can eventually loosen the screws holding the wire onto the light switch
or receptacle, or loosen at a spice, causing the electricity to arc in the wall at the loose
connection. Such an arc is like a flint rock being struck and making a spark inside the wall,
eventually finding surrounding building material that will serve as tinder.
If you are not sure whether a home has aluminum branch wiring, you might be able to tell by
looking at the markings on the surface of cables left exposed in unfinished basements, crawl
spaces, garages or attic. Aluminum wiring will have "Al" or "Aluminum" marked every few feet
along the length of the cable. Copper-coated aluminum wire does not present the fire hazard of
plain aluminum wire. It is marked CU-clad or Copper-Clad.
Although not all failing aluminum wire connections give any tell-tale signs of their eminent
demise, there are sometimes warning signs. These include warm-to-the-touch face plates on
outlets or switches, flickering lights, non-functioning circuits and the smell of burning plastic at
outlets or switches.
The "feel the faces" advice, though often given, is ineffective and potentially dangerously
misleading since the person doing the feeling often has no idea how much current, if any, a
receptacle's connections have been carrying, and for how long, prior to being "tested" in this way.
A better method is to turn off the power to the outlet at the main power breaker, remove the
cover plate, and then, using a bright flashlight, inspect the area of each wire terminal. Look for
charring or discoloration of the plastic wiring device body around the screw terminals, abnormal
tarnishing or corrosion of wire and screw terminal, melting, bubbling or discoloration of the wire
insulation.
Also keep in mind that such inspection can reveal only what has happened, not what might
happen. An aluminum wire connection might not have overheated in the past because no
significant current was ever flowing in its part of the circuit. It can look "like new" but overheat to
hazardous levels when a new load, such as a television, portable heater or cooking appliance is
plugged in.
If you have determined that the branch wiring in a home is aluminum, it should probably be
replaced with copper wiring throughout the home and the disconnected aluminum wire left in the
walls. If this is financially unrealistic, a form of patching can be done at receptacles, switches and
splices. This, however, is exacting work and should be carried out only by a certified electrician.
There is always risk of property damage, injury and death associated with working on the
electrical system of a home. It is not a job for do-it-yourselfers. Disturbing such connections
without fully knowing what you are doing can often make them more dangerous.
A practical approximation to rewiring can be achieved by a method known as "pigtailing." This
entails using a specially-selected connector and installation method to splice a short length of
solid copper wire to each aluminum wire end. The copper wire "pigtail" is then connected to the
switch, receptacle, circuit breaker, light fixture, etc.
In the meantime, a fire hazard can be lessened by removing from around aluminum-wired
receptacles and switch boxes anything that might ignite, such as bits of wallpaper, wood dust/saw
dust, insulation. Also keep stacks of storage boxes or furniture away from such receptacles. Both
ASHI (American Society of Home Inspectors) and UL (Underwriters Laboratories) have extensive
information about aluminum wiring on their websites. ASHI can be accessed at www.ashi.com and
Underwriters Laboratories at www.underwriterslaboratories.com
A conscientious effort has been made by the authors to provide accurate information; however,
neither the authors nor Alabama Residential Inspection Services, LLC will assume any liability for
its use. Readers are advised to perform additional research, seek other professional advice, and
to act on the information provided, herein, very carefully.
By James A. "Buck" Durham, P.E. of Jade Engineering.
If you're dealing with a home built, added on to, or rewired between 1965 and 1972, aluminum
wiring might be a problem for you. Research by the U.S. Consumer Safety Commission revealed
that homes wired with aluminum wire manufactured before 1972 are 55 times more likely to have
one or more connections reach fire hazard conditions than homes wired with copper.
Aluminum wire manufactured after 1972 was somewhat improved, though the introduction of
aluminum alloys did not solve most of the connection failure problems, and aluminum use for
branch wiring, that is wiring to receptacles and switches, ended by the mid seventies.
Now forbidden by building codes for internal branch wiring, aluminum wiring is still used for such
applications as residential service entrance wiring, or single-purpose higher amperage circuits,
including 240-volt air conditioning and electric range circuits. For these applications, a
heavy-gauge aluminum wire can be used, eliminating the hazard created by the smaller-gauge
branch wiring.
Aluminum wiring use started in 1965 as a cheap alternative to copper wiring. Its cheapness,
observed one builder, was evidenced by the fact that no one came to a home building site to pick
up aluminum wire scraps as they had always done with copper wire. Within a few years, however,
the less expensive wire proved itself to be a weak substitute for copper.
One common problem with aluminum wire is that it more easily corrodes at connections than
copper. Such corrosion increases resistance and this increased resistance causes overheating
of the wire at connections with switches or outlets, or at splices.
Another problem arises because aluminum wiring expands more than copper during the
expansion and contraction that carrying electricity causes wire to go through. The constant
expansion and contraction can eventually loosen the screws holding the wire onto the light switch
or receptacle, or loosen at a spice, causing the electricity to arc in the wall at the loose
connection. Such an arc is like a flint rock being struck and making a spark inside the wall,
eventually finding surrounding building material that will serve as tinder.
If you are not sure whether a home has aluminum branch wiring, you might be able to tell by
looking at the markings on the surface of cables left exposed in unfinished basements, crawl
spaces, garages or attic. Aluminum wiring will have "Al" or "Aluminum" marked every few feet
along the length of the cable. Copper-coated aluminum wire does not present the fire hazard of
plain aluminum wire. It is marked CU-clad or Copper-Clad.
Although not all failing aluminum wire connections give any tell-tale signs of their eminent
demise, there are sometimes warning signs. These include warm-to-the-touch face plates on
outlets or switches, flickering lights, non-functioning circuits and the smell of burning plastic at
outlets or switches.
The "feel the faces" advice, though often given, is ineffective and potentially dangerously
misleading since the person doing the feeling often has no idea how much current, if any, a
receptacle's connections have been carrying, and for how long, prior to being "tested" in this way.
A better method is to turn off the power to the outlet at the main power breaker, remove the
cover plate, and then, using a bright flashlight, inspect the area of each wire terminal. Look for
charring or discoloration of the plastic wiring device body around the screw terminals, abnormal
tarnishing or corrosion of wire and screw terminal, melting, bubbling or discoloration of the wire
insulation.
Also keep in mind that such inspection can reveal only what has happened, not what might
happen. An aluminum wire connection might not have overheated in the past because no
significant current was ever flowing in its part of the circuit. It can look "like new" but overheat to
hazardous levels when a new load, such as a television, portable heater or cooking appliance is
plugged in.
If you have determined that the branch wiring in a home is aluminum, it should probably be
replaced with copper wiring throughout the home and the disconnected aluminum wire left in the
walls. If this is financially unrealistic, a form of patching can be done at receptacles, switches and
splices. This, however, is exacting work and should be carried out only by a certified electrician.
There is always risk of property damage, injury and death associated with working on the
electrical system of a home. It is not a job for do-it-yourselfers. Disturbing such connections
without fully knowing what you are doing can often make them more dangerous.
A practical approximation to rewiring can be achieved by a method known as "pigtailing." This
entails using a specially-selected connector and installation method to splice a short length of
solid copper wire to each aluminum wire end. The copper wire "pigtail" is then connected to the
switch, receptacle, circuit breaker, light fixture, etc.
In the meantime, a fire hazard can be lessened by removing from around aluminum-wired
receptacles and switch boxes anything that might ignite, such as bits of wallpaper, wood dust/saw
dust, insulation. Also keep stacks of storage boxes or furniture away from such receptacles. Both
ASHI (American Society of Home Inspectors) and UL (Underwriters Laboratories) have extensive
information about aluminum wiring on their websites. ASHI can be accessed at www.ashi.com and
Underwriters Laboratories at www.underwriterslaboratories.com
A conscientious effort has been made by the authors to provide accurate information; however,
neither the authors nor Alabama Residential Inspection Services, LLC will assume any liability for
its use. Readers are advised to perform additional research, seek other professional advice, and
to act on the information provided, herein, very carefully.
ALUMINUM WIRING PROBLEMS
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