The condition of your electrical system probably doesn’t come to your attention until a breaker trips, lights flicker, you hear electrical humming or it just stops working. All of these symptoms are signs that there is something going wrong. Age, dangerous brands, capacity, and grounding all have a bearing on the safety and reliability of your electrical panel and meter.
Homes with pre-1970 electrical panels and meters have outdated and unsafe electrical systems. Meters from before 1970 do not have a main shut off switch on the outside meter, usually have no grounding and have an undersized wire leading into the meter.
Today we use more electrical devices drawing more power than 50 years ago. The electrical panels and meters in our homes are rated for a certain amperage. The standard today is 100 amps, but older homes commonly are rated for much less (70 amps were common). If you try to draw more power than your electrical system is rated for, a circuit breaker will be tripped.
When a circuit breaker is tripped it is because you are attempting to draw more power than the breaker is rated. If the breaker did not trip, and electricity continued to flow beyond what the breaker was designed for, it could cause an electrical fire. Homes that are built today are designed to handle 100 amps.
Another thing to check for in older homes is the number of circuits. Many older home’s electrical systems used only 2 or 3 circuits throughout the entire home. There are many devices that need to be on their own circuit, such as your furnace and air conditioner. Three circuits is insufficient with the demands of the average family’s power consumption.
If you have an older panel and meter you should have your electrical system inspected by a licensed electrician for many reasons. One of which is to ensure that your circuit breakers are still working. It is possible to have a circuit breaker fail and no longer prevent the flow of electricity beyond capacity, which could overheat the system and cause an electrical fire.
Zinsco and Federal Pacific manufactured electrical panels have proven to be dangerous and were the subject of class action lawsuits. If you have one of these dangerous panels it should be replaced immediately. These panels have a high circuit breaker failure rate, meaning that the breakers over time melt and will no longer trip so they do not prevent the flow of electricity. This has been the cause of many electrical fires.
Grounding of your electrical system is an important safety feature that older homes may lack. Grounding ensures that electricity will go to the ground if an electrical short or problem occurs. Without it, like most older meters, the electrical potential is left waiting for a means to travel to the ground–which could be through you via a deadly shock if you were to touch it.
Copper is one of the most conductive metals, is very durable, and not as susceptible to expanding and contracting with the change of weather. Copper has been used in electrical wiring since the 1820s. “Only in 1925 did half of all homes in the U.S. have electric power.” (https://www.nps.gov/edis/learn/kidsyouth/the-electric-light-system-phonograph-motion-pictures.htm)
Aluminum wiring was used on many homes between the mid 1960’s and the mid 1970’s when the price of copper was much higher. Aluminum wiring is still used today but can be problematic and requires more maintenance than copper. Aluminum wiring is softer, not as conductive, rusting is problematic, and the wire is prone to creeping.
Aluminum wire is softer than copper and not as strong, making it more prone to damage. Broken or damaged wires can create hotspots and pose a fire risk. But because the aluminum is softer it can be easier to install with significant cost savings. Though the savings may not be worth the risks and upkeep.
To compensate for the lower conductivity level of aluminum wires, a thicker gauge wire (12 gauge) is used to match the copper wire equivalent (14 gauge). Where the wiring is exposed and prone to rusting, conductivity issues arise. Rusty aluminum forms a white oxide which creates a problematic electrical connection. In contrast, rusty copper will remain conductive. Rust on aluminum wires can cause overheating issues which can lead to fires.
Another problem with aluminum wiring is that it expands and contracts more than copper does, and as such is prone to creeping. The aluminum wire can expand and contract so much that it can slip out from its connections which can cause sparking and lead to a fire.