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What you need to know about surge protectors

By Sloan Schrage, KSL TV | Posted - May 15, 2019 at 11:31 a.m.

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SALT LAKE CITY — We often link lightning strikes to power surges, but they’re not the only cause. A mishap by the power company during maintenance, or even an A/C unit or refrigerator motor can create a damaging spike in power.

Surge protectors are an inexpensive way to protect your electronics from getting fried by random surges. But they are not all the same.

“If it doesn’t say surge protector on it, it’s probably not a surge protector,” said electrical engineer John Palmer, an associate professor at the University of Utah’s Electrical and Computer Engineering department.

Palmer said many people are actually buying power strips instead of surge protectors. They look very similar and they are often sold side-by-side, but only the protector will guard your gear against surges.

Power strips and surge protectors are often sold side-by-side and look very similar, but only the protector will guard your gear against surges.

“All too many of us just go in and look. We see something that looks like what we want with a low price and that’s what we grab,” Palmer said. “But the difference between them is worth taking a minute or two to read labels and understand what it is we are purchasing.”

A power strip is essentially an extension cord with additional outlets. It offers no extra protection against a spike in voltage. But a surge protector can handle that random surge in power.

“It has an added feature such that when the power system has a voltage surge on it, or a momentary increase in voltage, it limits the energy transfer so that the surge doesn’t get into your high-end electronics,” Palmer explained.

Surge protectors are rated in joule — that tells you how strong of a punch of extra electricity it can take. The higher the number of joules, the bigger the surge a protector can absorb.

Electrical engineer John Palmer explains why the terms ‘power strip’ and ‘surge protector” are not interchangeable.

Below a thousand joules works great for electronics like small appliances, cellphones and battery chargers. Experts recommend at least 2,000 joules for more expensive and sensitive electronics.

“If I’ve got a high-end stereo system that’s, you now, worth several thousand (dollars) or more, then I want to invest in a more expensive (protector) and higher joule rating,” Palmer said. “Some of the higher-end surge protectors will have as many as 5,000 Joules.”

Another thing to consider besides joules is the protector’s clamping voltage. That is the threshold of excess voltage it takes for the protection components to go into action.

“The clamping voltage is the absolute maximum that the device will ever allow,” Palmer said. “In general, that’s only going to be when you have the very worst surges. Usually, it (the surge protector) will hold the voltage down to less than that clamping voltage.” The lower the voltage, the better.

Also, look for the protector’s response time, usually listed as nanoseconds. This rating shows how quickly it reacts to excess voltage. Here again, the lower the number the better the protection.

“When you have, for example, a lightning strike that may happen in your neighborhood, this pulse voltage comes in. It can be very high, but it’s a very short duration,” explained Palmer. “So, if you don’t have a good response time on your surge protector, then the initial part of that surge my actually make it through your device (surge protector) before it responds and pulls that voltage down.”

Palmer also recommended buying protectors with more outlets than you need. You should never plug a power strip or another protector into an existing protector to get more outlets. Not only will it likely void the manufacturer’s warranty on the protector, but it could spark an electrical fire.


Sloan Schrage

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