QUOTE (Olek @ Jan 19 2008, 10:06 PM) Thanks very much Jonathan and Mike!
Really appreciate your input...
Have a great weekend!
Olek
Hi Guys,
I have recently purchased a home in Calgary with Aluminum wiring and I have run into a few road-blocks, but each has been overcome. I`ve also spent a considerable time researching why Aluminum wiring can be dangerous and I will share my findings with you in this post.
House Insurance:
The first issue was finding an Insurance company that provided Guaranteed Replacement Cost (GRC) insurance for a home with Aluminum Wiring. Most insurance companies will either, not insure a home with any aluminum wiring OR will only provide a fixed amount of insurance, so if your home costs more to rebuild than you had it insured for, you are out of pocket for the difference.
I contacted the following companies and was turned down by all of them for GRC Insurance because of Al Wiring: Meloche Monnex, Wawanesa*, AMA, and State Farm. I then called 5 separate Insurance Brokers and only 2 were able to find me GRC insurance. The company I ended up going with was SGI Canada, because they did not require an electrical inspection. (SGI Canada is a saskatchewan based government insurance company that is licensed to provide insurance in 7 provinces across Canada).
*The only other choice I had was Wawanesa... I know I already wrote that they turned me down, but it seems an Insurance company has some discretion with the underwriters if you have had a policy with them and demonstrated a track record. However, Wawanesa wanted an electrical inspection completed a.s.a.p. and a commitment that I would replace the Al within 6 months. FYI: rewiring a home with copper (Cu) is cost prohibitive unless you are doing an extensive renovation where you will be exposing all of the wire behind the drywall and to the light fixtures.
Is Aluminum Wiring Safe? Yes, if you respect it:
The best source of information I found is detailed in a report called "Reducing the Fire Hazard in Aluminum-wired Homes" written by J. Aronstein, a professional engineer who has been researching Al wiring for 25 years. I suggest you read this and verify it with what others are saying on the internet.
You can find a copy of this report here:
http://www.inspect-ny.com/aluminum/alreduce.htm
or download the pdf at
http://www.inspect-ny.com/aluminum/alreduce.pdf
And for those who are interested, I will now subject you to my opinion on why Aluminum wiring is dangerous. Note: this opinion has been formed by reading as much information as I could get my hands on via the internet.
First of all, I do not believe that Aluminum wiring is dangerous because it expands and contracts more than copper. The coefficient of thermal expansion for copper is 16.5 micrometers per meter per Kelvin whereas the coefficient of thermal expansion for aluminum is 23.1 micrometers per meter per Kelvin. A difference that I think is too small to be significant. I think the loosening of wires that some sites talk about is more related to the fact that Aluminum has different properties with regard to creep.
I believe Aluminum wiring can be dangerous because of aluminum oxide, I`ll explain:
Aluminum is a great material because it doesn`t continue to corrode (or oxidize) at standard conditions for temperature, pressure, and relative humidity, because it passifies in the normal environment your home is at. What this means is that the exposed layer of Aluminum has corroded (in the case of iron we call it rust) but this layer of corrosion acts as a shield to slow any further corrosion so much that one could consider the corrosion to have stopped. This passive layer is no longer pure Aluminum, it is Aluminum Oxide (Al2O3). Al2O3 is an excellent electrical insulator. This is bad.
Think of a regular light bulb. The filament in the light bulb is made of tungsten, this has an electrical resistivaty of 52.8 ohm-meters. Meaning when you pass electricity thru this thin piece of metal, it resists the flow of electrons so much that it glows yellow-white and generates an extreme amount of heat and a little bit of light. Now lets compare this with copper and aluminum.
Copper has a resistivity of 16.78 nano-ohm-meters which is 0.00000001678 ohm-meters, so really it doesn`t put up much of a fight for those electrons and consequently doesn`t generate much heat. Aluminum has a resistivity of 26.5 nano-ohm-meters which is more than copper which means you require a larger cross sectional area of wire to transmit the same current, but again this difference is negligable in my opinion. However, Aluminum Oxide (Al2O3) has an electrical resistivity greater that 1 tera-ohm-meter or 1,000,000,000,000 ohm-meters. This is HUGE! So if you try to pass electrons through Al2O3 you are going to generate a lot of heat!
So, aluminum wiring, if not properly installed can either have a thin layer of Al2O3 on the exposed metal right at the point where the wire connects to the electrical fixture (be it a light switch, a receptacle, a light fixture, a marrette, etc), or it could oxidize for several reasons over time. But if you have this layer, you essentially have a really hot point in your electrical circuit. And if this heat source has the two other things it needs to start a fire -fuel, and oxygen - you have a pretty dangerous situation.
Is it really that scary? Yes and no, read the report I mentioned above. I`ve checked a few of my junction boxes and found the aluminum that is under the terminal screw to be bright and shiny meaning it is free of oxide. If the aluminum wire is a dull grey, you`ve got oxide and you should remove it, again instructions to do so are contained the report.
To put things in perspective, the thickness of the aluminum oxide is on the order of angstroms or 1x10^-10 meters... meaning it is REALLY thin. And when you connect your electrical component to the aluminum wiring, the tightening of the terminal screw is enough to scrap away that oxide layer and allow you to have a connection that won`t be a heat source causing your home to burn down. However, you still must exercise caution. Homes have burnt down, and it has been linked to aluminum wiring. If you are in doubt, have an electrician check it out.
If you have any questions or concerns, please let me know!
