Even if there are no obvious flaws, danger may be lurking within your Zinsco brand electrical service equipment.
Your service equipment includes the switches, or breakers (and fuses in older homes), that can be used to disconnect a home from its electrical service at the customer’s end. Taken as a whole, it is colloquially referred to as your electrical panel (sometimes service panel, or just panel). Other roles of your electrical panel include splitting your electrical service into multiple circuits, such that no one circuit gets overloaded.
Because a home inspector is essentially a safety inspector, he or she does not even need to look at anything beyond the Zinsco label in order to write up the panel as in need of replacement. Let’s take a look at several reasons these Zinsco service panels can be dangerous:
First of all, the most notorious Zinsco panels were installed during the 1960s and 1970s, making the youngest models at least 40 years old. In that time, there have been numerous updates to the National Electric Code (NEC). Panels of that age often have too few circuits for a modern home and they may also not be supplied with enough amperage for a modern home (just think of all the electronics and appliances we use today that were not in frequent use during the 70s). This is a common occurrence in older homes that can be experienced by any brand of electrical panel.
The bus bars (the connection point for the breakers) used in these panels can create unsafe conditions that can lead to electrical arcing (when electricity “jumps” through the air between two conductive surfaces). This is how an electrical fire begins. Specifically, the parallel orientation of the bus bars and dual connection points means a breaker can slide out of place, leaving a gap that can lead to arcing. Additionally, the aluminum alloy used is inferior to the alloy used by manufacturers today and may corrode or become pitted, which can also cause arcing.
In connection with the above issues, the breakers themselves may suffer internal damage due to heat buildup. This damage can be difficult or impossible to see from the outside, especially when the breakers are installed. That is why even experienced electricians cannot always identify defective breakers. Affected breakers may not trip during an over-current event. Research suggests that as many as 25% of Zinsco breakers may be unable to trip. Further, damage may allow the breaker to display the OFF and still be passing current through to the circuit. This is a serious danger to homeowners and electricians.
Now that you understand the reasons that Zinsco panels are considered unsafe, would you still want one in operation at your house, even if everything “seems fine” when inspected? These panels are so notorious that some insurance companies will not cover a home that functions on a Zinsco electrical panel. Others will provide coverage, with an increased premium.
I like to think of it like this: Imagine a certain tire brand had to recall one model of tires because 25% of them failed, and your car has those tires. You’ve got 4 tires on your car, so statistically speaking, one of them is likely to fail. Would you continue driving on them, because they “seem fine so far”? Would you wait until you have an issue, and then replace them? No, you would pay a couple hundred bucks for new tires. That would get you peace of mind for today, and you would have new tires that will last you probably a few years. And they cost less than getting a new car.
The same is true of your service equipment. Yes, it may seem like a lot of money now, and electrical panels aren’t as fun as new kitchen cabinets or a big screen TV, but it will improve your safety and will last for decades.
One final word of caution: If your electrician says he can “fix” the panel, or “clean” the bus bars, or find “reconditioned” breakers or that everything in your Zinsco panel “seems fine,”... Get a new electrician!