Evaluation of the safety of aluminum electrical wiring:
Is un-repaired aluminum electrical wiring in a home ever "safe"? In response to inquiry by owners or buyers of homes served by aluminum electrical wiring, we receive occasional reports that some building inspectors, electricians, building code officials, industry representatives, express the view that "Aluminum wiring in your house not likely to be a real problem," or words to that effect.
Watch out: The condition and safety of aluminum electrical wiring and devices in specific individual homes cannot be reliably assured by someone who has not examined it! General "opinions" that an un-studied installation of aluminum electrical wiring is "safe" are thus nonsense. And the safety of an un-repaired aluminum-wired building cannot be reliably ascertained by inspection & test methods typically used by electricians or home inspectors.
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The condition of aluminum electrical wiring connections varies over an very wide range from building to building and among individual circuits and devices within specific buildings. It is possible for very unsafe conditions to be present, but not visible.
It is inaccurate and dangerous for anyone to make any representation about the condition of aluminum wiring in a specific property "over the telephone," and without on-site specific inspection and testing by a qualified expert who is familiar with aluminum wiring issues.
In explanation, we've attached the text portion a 2/3/94 letter from an expert on aluminum wiring, addressing this problem. The author, Dr. J. Aronstein, can be contacted at firstname.lastname@example.org, or contact me, Daniel Friedman. Extensive information about identifying and repairing aluminum wiring safety hazards is at ALUMINUM WIRING HAZARDS & REPAIRS.
February 3, 1994 (original addressee info) (deleted by DJF) Subject: Aluminum wiring (deleted ) Dear Mr. (deleted) You requested my comments on the safety of the aluminum wiring at (deleted) and my review of the written materials provided. The question to be answered is this - are the connections to the aluminum wire at (deleted) safe? Without determining what types of connections are in the system and how they were made, nobody can answer the question. Are the receptacles back-wired or screw-terminal wired? If screw-terminal wired, how is the wire placed under the screw (straight in or wrapped around)? Are the screws steel or brass? Are the screws plated with zinc on the neutral side? What kind of splicing connectors exist in the system? If twist-on connectors ("wire nuts"), are they the live spring or restrained spring type? Did the installer abrade the aluminum wire before connecting to remove the oxide? Were the spliced wires pre-twisted together? Was a corrosion inhibitor used on all connections? Given the answers to these questions (from direct observations), an evaluation of the relative safety of the wiring system at (deleted) can be made.
The information that they were provided with misleads as often as it informs.
What the committee was given, for the most part, was organizational positions rather than useful information.
For instance, references to aluminum cable being used in the Boeing 747 at the World Trade Center and in overhead power distribution are not relevant, since the connections systems used are quite different from those installed at (deleted).
What the NEC, the UL standards, local codes, and the wiring practices were at the time of installation and how they have changed makes for interesting discussion but sheds no light on whether or not there are serious electrical safety defects at (deleted), and, if there are, how they should be corrected.
I am concerned that a proper assessment of the state of the wiring system at (deleted) has not yet been made. The question electrical fire safety cannot yet be answered with any degree of certainty.
Yours truly, J. Aronstein, Ph.D., P.E. JA/lsr ######
Reader question: I was reading some of your information regarding Aluminum wiring. A question if I may, can a licensed electrician certify that a structure with Aluminum wiring is currently safe? Possibly via thermal imaging instruments, etc? If so, do you know if one would do so? - D.C.12/31/2013
Thank you for the interesting aluminum wiring safety question - it helps us realize where we need to work on making our text more clear or more complete.
What follows is my OPINION based on more than two decades of experience & research in topic of aluminum wiring hazards, and I am informed by others more expert than myself, but I have no approval authority and I am not an electrical engineer.
I want to answer with care, which involves some semantics and picky discussion of wording, even the use of "can" and "may".
Regarding the word "may" - to my knowledge there is no authority such as local or national electrical codes that regulate or authorize an electrician to certify the safety of an electrical system. Even a "certification" that a building is in compliance with electrical codes would be of little use where special hazards such as solid aluminum branch conductor wiring or FPE electrical panels are in place, as those hazards are not explicitly called out in most codes.
An electrician "can" do anything s/he wants by way of certification of the safety of a building's electrical system, though I would be surprised to find that any knowledgeable electrician would do something so dangerous to himself/herself or to others - as I will explain below.
And I caution that should you encounter an electrician who is willing to make such a certification, presumably for a fee, I would not only not trust the value of such a certification one iota, but I would presume that there would be absolutely no useful recourse should there later be a problem or worse a fire or injury or death in the building attributed to aluminum wiring. So what would be the value of such a certification? None.
Attempts at testing aluminum electrical circuit resistance to claim that there is or is not evidence of an overheating problem when the circuit is not under load are made by some home inspectors and possibly some electricians. This approach is fundamentally unsound - the level of electrical resistance that can actually cause overheating and a fire in aluminum-wired circuits is below the range of error or precision of all but specialized electrical test instruments.
Dr. Jess Aronstein has performed such testing, but then he is a PhD forensic engineer specializing in electrical hazards, with decades of experience, and he used detailed instrumentation of all of the connections in the circuit being tested - an approach that requires a great deal of expertise and one that is considerably beyond the scope, training, certification, and equipment held by a normal licensed electrician. Aronstein's approach monitored temperature rise at each connector or device and was able to guard against a fire - not something within the scope of the home inspector or electrician tests offered using devices that simply measure resistance.
Aronstein's approach might be used in a large complex (as might other methods such as history taking and visual inspection for obvious overheating examples) to choose the order of repair of aluminum-wired circuits for the case in which the work required is so extensive that it cannot be completed in a short time.
Simply measuring resistance in a circuit as a guess at electrical safety of an aluminum wired circuit fails to account for very significant changes that can occur in the circuit performance following a simple act such as jiggling an electrical receptacle while plugging in a vacuum cleaner, moving the location at which an electric heater is connected, or jiggling a light switch a few more times when switching it on and off.
Thus a circuit that might test as "OK" may the next day overheat.
Watch out: Worse still, attempts at testing electrical circuit operating characteristics while under load could, if not expertly performed, set a building on fire.
I would agree that thermal imaging could detect and thus permit reporting of active locations where overheating is occurring, but while such an approach could lead to reporting of an immediate hazard, should thermal imaging fail to detect overheating that is not a reliable assurance that the circuit is safe.
Thermal imaging can only detect overheating if overheating happens to be occurring during the time of inspection. The same variables I listed above could mean that a circuit that looks "OK" right now might overheat and cause a fire tomorrow, simply due to variations in the environment or in how a circuit is being used.
In short, absence of evidence of a hazard is never acceptable proof that a hazard is not present.
That is, as a fundamental logical principle, absence of evidence is not evidence of absence.
I understand the concern raised when there is a costly hazard that needs to be addressed and the discomfort that arises when one points out that overheating and failures do not occur in 100% of circuits and cases. An apparently-rational approach argues: if we could we would just repair the unsafe circuits. But this is an unsound and unsupportable approach.
Especially for the case of aluminum electrical wiring, the failure rate of these circuits is described by a "bathtub-shaped" curve. There were plenty of early failures attributed to poor installation. Those were detected early. Then there may be few failures for many years. But as a circuit ages and is used more over time the probability of a failure increases continuously and more rapidly. And as I argue above, a simple change by a new occupant, such as plugging in an electrical device where none was connected previously can completely change the risk picture.
In conclusion, my opinion is that there is no practical, safe way to test an aluminum-wired building that would let any knowledgeable, responsible party promise that the building is safe other than to assert that the aluminum wiring has been either completely replaced with copper or that absolutely all of the aluminum wired-circuits have been completely repaired - that is, that every electrical device, splice, connection, has been located and repaired using one of the two US CPSC recommended methods.
From the point of view of an insurance company, it might on further discussion, be decided that we could specify a level of inspection of a properly-repaired aluminum-wired building that would make the insurer acceptably confident that a proper repair has been made without having to literally find and re-visit every single connector - a procedure that would itself be quite costly.
Ultimately we'd be specifying a combination of historical research of the repair records (invoices, purchase records for the number of repair devices bought and presumably installed) along with specifications of the building electrical system (number of circuits and devices involving solid conductor aluminum wiring) along with a statistically sound sampling plan that chose an adequate number of devices as well as certain strategically-selected inspection points that I could specify.
It would be wise to include an inspection for the presence and operation of properly located & installed smoke detectors as well.
If you decide to pursue that approach I would be glad to offer or to find others to help offer more specific suggestions.
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