Surge Protection 101
Surge Protection Devices (SPDs) are a recent addition to many local and national electrical codes. They protect equipment from voltage spikes caused by nearby lightning strikes, utility lines shorting together due to damage, or a nearby abrupt cessation of a large load. But how they work and why they’re needed is not always clear. Let’s go over the basics.
There are four types of SPDs. Broadly speaking, the type is determined by the kind of faults it can handle, which in turn determines where in your electrical system it can be installed.
Type 1 surge protection devices are installed on the line side of, that is before, the first disconnecting means of the service they protect. This is not something that will be common on your typical residence.
Type 2 surge protective devices are installed after the first disconnecting means. This type is by far the most common, and like the type 1, it usually protects every device in a whole building.
Type 3 SPDs are portable, essentially. A common example of a type 3 SPD is the power strips that offer their own surge protection.
Type 4 SPDs are inherent to a piece of equipment. They are always installed during manufacturing.
Surge protection devices work by detecting a rise in voltage above a certain threshold, and then shorting together conductors inside the device. This causes the breaker or fuse ahead of the SPD to open, stopping the flow of electricity at the wrong voltage. For most off-the-shelf SPDs, this results in the destruction of the device, but this is normal. They usually have a small light on it that indicates whether or not the device is still operating correctly.
Finally we get to the why. When I first started hearing about SPDs, it was not clear why they should be needed. They’re not expensive, but they’re not cheap either, and they take up two spaces in your typical home panel, which doesn’t usually have two spaces to give. However, the purpose of electrical codes is the practical safeguarding of people and property, so how do SPDs do this? It’s one thing to try and protect your computers and TVs, but that’s not really a life safety issue. The important circuits and equipment that SPDs protect are things like fire alarms, GFCIs and AFCIs, and even standard breakers can be damaged by voltage spikes. These things serve an important purpose, and the cost of SPD could not only save thousands of dollars on technology, but also your home and your life.
Surge protection devices prevent a lot of potential problems in your home. They protect your property and the lives of the people around you. You might live in your house your whole life and never even have to think about it. After the adoption of the 2020 National Electrical Code (NEC), SPDs are required on all new one and two-family dwellings, whether it’s new construction or just a new service. But beyond that, I personally recommend putting an SPD in your house if you don’t have one.
