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What Are Surge Protectors and How to Choose One to Buy


If your shop is like most, you’ve got more things to plug in than outlets to put them in. And, in all likelihood, those things you need to power are expensive and difficult to replace. So, naturally, you need to add more outlets and you need to do it in a way that safeguards your critical equipment.

However, not all surge protectors are created equal. In fact, some can even do irreparable damage. Before you grab any old power strip, let Grainger give you the rundown on how to chose a surge protector.

What is a surge protector?

Electrical surges happen all the time, and they have a wide range of causes. Lightning strikes, tripped circuit breakers, large equipment on/off cycles and power outages can all wreak havoc, costing you thousands of dollars in a split second.

Surge protectors are designed to handle these irregularities and keep an even flow of power to your devices. Keep in mind that a surge protector and a power strip are two very different things. They may look alike, but a power strip will only add outlets; it won’t offer any protection.

Types of Surge Protectors

  • Surge Protector Strips plug into any standard outlet and let you plug in and protect several devices at one time.
  • Point-of-Energy Surge Protectors are designed to protect your entire facility from external surges.
  • Uninterruptible Power Supplies give your devices a safety net of battery backup at all times. If the power surges, dips or cuts, it will keep them running without interruption for a period of time.
  • Wall-Mount Surge Protectors have no cord. They plug directly into a power outlet and fit snugly against the wall, which is ideal for spaces that can’t accommodate a power strip.

Surge Protector Ratings

Here’s where surge protectors earn their keep. When you’re browsing for one, you’ll see a number of ratings and indications. Here’s what they mean:

What are Joules?

The joules rating tells you how much energy the unit can take before failing. This may be the most important factor in choosing a surge protector—the higher the number, the better your protection will be. For small electronics like clocks or lamps, anything up to 1,000 joules is fine. Power tools, routers and printers need something with a rating between 1,000 and 2,000, while computers, TVs and heavier equipment will require a rating of 2,000 joules or more.

What is Clamping Voltage?

Clamping voltage (sometimes called suppressed voltage or peak let-through) is the point at which the protector will kick into gear and start protecting your equipment. Unlike joules, you want a lower number here.

What are UL Standards?

Underwriters Laboratories has created a safety standard called UL 1449 Voltage Protection Rating (VPR). This indicates how much total voltage your protector will allow through to any connected devices. Again, the lower the number, the better your level of protection.

What is Response Time?

Surges don’t happen instantaneously; they can take up to a few nanoseconds. Response time tells you how many nanoseconds it will take for your protector to spring into action. You want to look for something with a response time of one nanosecond or less.

Other Considerations

  • Energy Savers. Some protectors allow you to save energy by “turning off” all the connected devices on standby that are drawing energy.
  • GFCI Protection. GFCI protection will automatically detect a short circuit and shut the power off, which could save your facility from an electrical fire.
  • Remote Control Surge Protectors. Often, surge protectors are located in hard-to-reach areas, so turning them off or on can be a hassle. If that’s the case, look for a one with a remote control, which can be mounted to the wall for easy operation.
  • Timers. Some protectors come equipped with timers you can program to switch on and off at certain times of the day or night.


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The information contained in this article is intended for general information purposes only and is based on information available as of the initial date of publication. No representation is made that the information or references are complete or remain current. This article is not a substitute for review of current applicable government regulations, industry standards, or other standards specific to your business and/or activities and should not be construed as legal advice or opinion. Readers with specific questions should refer to the applicable standards or consult with an attorney.