Electrical surges

Recently I learned some very useful info related to electrical surges and surge protection. An electrical surge can be described as additional voltage and/or current above and beyond the expected amounts. These surges can come from two main sources, outside your house (e.g. lightning strike) or inside your house (more on that later). Regardless of the source, a surge could easily damage newer electronic devices which are very sensitive to surges. Despite common believe, fuses do not protected against surges. Fuses only protect against too much current (amperes) not too much voltage.

Before I discuss protection, I wanted to talk a little more about surge sources. It's easy to understand surges external to your house - the most obvious example would be lightning strike. But surges generated inside your house are a little more difficult to understand. I won't go into the electrical science, but the short answer is any large inductive device has the potential to create voltage surges. The most common inductive device capable of generating large surges is large electrical motors. Whenever you turn off an electrical motor it creates a voltage surge on the household circuit on which it's connected. And yes you read that correctly, the surge is created after the motor is turned off, not before or during. This is one of the main reasons why refrigerators, washer and dryer, and air conditioners are typically on their own circuit. If other appliances were connected to the same circuit as these appliances they would get a surge every single time the motor switches off. There is however one large motor in your house which is not on a dedicated circuit - your vacuum cleaner. Vacuum cleaners have deceptively large powerful motors in them. It's not uncommon for a vacuum cleaner to pull 12 amps or more. That is a lot of power! So if you plug your vacuum cleaner into the same circuit as your expensive TV or computer, when you turn the vacuum off you're subjecting those devices to a surge. After vacuum cleaners, the next biggest source of surges would have to be fans (both those plugged into the wall and ceiling fans).

Now that we know the sources of surges, what can we do about it? Obvious you say, we use a surge protector. Well yes and no. The answer is a surge protector, but not all surge protectors are created equal. Most people refer to the following item as a surge protector:

This may be a surge protector, but chances are good it's just a power strip. A power strip is nothing more than multiple outlets with an on/off switch. It offers zero protection against over-voltage or over-current. A true surge protector is usually a little larger in size and costs more. The only way to tell them apart is to either open them up and look on the inside, or read the specs that came with the product. Chances are if you spent less than $10 or $20 on it, then it's probably a power strip not a surge protector. Probably the most respected name is APC, they make high-quality devices. There are other good brands as well.

Even if you have good-quality surge protectors, you may not be covered. As it turns out surge protectors breakdown over time. In effect they can only protect against a certain number of surges before they fail. When they fail the surge protector will still provide power, but the surge protection aspect is gone.

So what's the take-away from all this.

1. Identify the circuits on your house with expensive electronic items (TVs, computers, etc.). Never use a vacuum cleaner on these circuits. Also, if possible avoid fans on these circuits.
   
2. Buy and use good quality surge protectors NOT power strips.
   
3. Even if you have good-quality surge protectors, don't assume you're safe as they have a limited lifespan.
   

If you really want to know more on this, I recommend you watch this video in which he does a great job of explaining inductive spikes. Also, the following article dissects a surge protector and goes into more details.