Internachi certified professional inspector
According to the InterNACHI Standards of Practice, we are required to check for and report as in need of correction “the presence of solid conductor aluminum branch-circuit wiring”. Does this mean aluminum wiring in a home is dangerous? Not necessarily.
Let’s first back up to the 60s. While that timeframe might bring images of Woodstock, counterculture or political change to a home inspector a different type of change comes to mind: that of a switch from copper (CU) to aluminum (AL) wiring due to the skyrocketing cost of CU wires in the mid-1960s. Until about 1973 this type of wiring was almost exclusively used in branch circuits, which are the wires that go to individual outlets and switches.
Why is this type of AL wiring a concern? There are several reasons:
AL Wiring is More Malleable
Another way to say this is to say it is damaged easily. As it is a softer metal, it can be nicked or damaged far easier and a more amateur installation can greatly reduce the ability of the wire to safely carry electricity (and heat).
AL Wiring Expands/Contracts Easily
The #1 issue with AL wires is the significantly increased fire risk. The biggest danger comes from connections can come loose that can build up heat and eventually lead to an electrical fire.
AL is an Inferior Conductor
Compared to CU wiring, AL is not as good of a conductor of electricity. In most cases this is not a problem as an electrician knows to account for this but amateur DIYs might not realize the size difference between CU and AL. To give you an example of what I mean, below is a sample chart of the proper types of wire to use. Remember as the gauge gets smaller the wire gets bigger. As you can see AL is one size bigger in almost all conditions.
AL wiring was never discontinued or banned and is still widely used to this day. Due to its low weight, it is the preferred material for outdoor transmission lines and is frequently seen inside homes as the material the main service conductors are made of. As well, post 1973 aluminum wiring is of a much higher quality and generally does not have the safety issues just mentioned to nearly the same degree.
To summarize, while widely used, AL wiring can be considered dangerous in certain circumstances, especially if installed from 1965 to 1973. A home inspector can identify if you have this type of wiring and if so, will recommend an electrician evaluate the system to see if any corrective action needs to be taken to ensure the system is safe and functional for years to come.
If you have ever looked at your electric panel, you might see a label similar to this. If you are like most homeowners, you have no idea what all the circled numbers and letters mean. Let us take a quick look at each one:
125 AMP MAX
This is a measure of the maximum amperage rating. Simply put, this is a measure of the flow of electricity. Most modern houses have a 200-amp service although I have seen service as low as 100 amp without issue. There are systems that are smaller than 100 amp but in general, many insurance companies will not insure a home with less than 100 amp mostly due to the fact these are generally older systems and do not meet a modern family's needs.
This means that this panel can use either copper or aluminum conductors. You may have heard that aluminum wires are a major fire hazard and while that can certainly be true, there are many situations where they may be used safely. Your home inspector should be able to tell you if you have aluminum wiring and if so, whether an electrician should be consulted.
This is a measure of the voltage (pressure) this system is designed for. Well over 99% of homes in North America use what is known as a split phase system that uses two 120V service wires (120+120=240). While there are some properties that use just one 120V (mostly very old homes or cottages), I have never encountered one in the field. Fun fact: you may have heard that high voltage is very dangerous and while in most cases this is true, there are some ways that getting shocked with high voltage can be perfectly safe. Did you know that a simple static shock can deliver between 20,000 to 30,000 volts?
This is an acronym for alternating current in both English and French. I could write several essays on alternating vs direct current (DC) and why we receive power as AC yet use DC in most appliances and gadgets but, with the exception of solar systems, nearly every home receives power from the utility as AC and this is a standard designation.
This refers to the fact that this panel is designed for single phase power. To make a complex concept simple, there are two types of phasing used: single phase and three phase. Almost all homes and small businesses use single phase and three phase is used in large buildings. The way inspectors tell single from three phase power is the number of hot service wires, which brings us to our last point.
This means that is designed for 3 wires from the utility: 2 hot (usually black and red) and 1 neutral (white) wire that services the home. Three phase systems usually have an extra hot wire (any color except white or green but usually blue) and are extremely rare in homes.
Still confused? Let me quickly summarize: the only thing you need to worry about as a new or existing homeowner is the amperage, which usually varies from 100 to 200 (and up) amperes. The rest is standard to nearly every home and any deviation should be investigated by an electrician.