Surge Protection Explained
Choosing the best surge protector for your computer, TV or gaming system
When it comes to power surges, most people think of external sources like lightning or a downed power line. But most power surges actually occur inside your home or office, for example, when a large appliance is turned on. When a voltage spike reaches something containing a microprocessor, like a TV or computer, the damage can be immediate and catastrophic. A simple and relatively inexpensive solution is to plug sensitive electronics into a good quality surge protector.
What is a Surge Protector?
A surge protector is designed to protect any device with a standard AC plug from potentially damaging and disruptive power surges, voltage spikes and line noise transferred through an electrical outlet. Think of a surge protector like an insurance policy. You hope you never have to use it, but you're very glad you have it when you need it.
Also known as a transient voltage surge suppressor, a surge protector may have a long power cord or it may plug directly into the wall, and it usually has multiple AC power outlets for connecting equipment. Some surge protectors also have built-in protection for data lines, including telephone, Ethernet network and coaxial lines.
Are surge protectors and power strips the same thing?
Be careful not to confuse a surge protector with a power strip. They can look almost identical, but a power strip does not provide protection against voltage surges and spikes. A surge protector should be labeled as a surge protective device or similar on its nameplate. In addition, the manufacturer's documentation will identify it as a surge protector or surge suppressor and provide specifications for the level of surge protection provided.
Why Do You Need Surge Protection?
A good quality surge protector is your best defense against AC voltage surges and spikes that can ruin your valuable equipment in a flash or build up damage over time.
What are power surges and voltage spikes?
An electrical surge, or power surge, is an intense, short-duration voltage increase that travels through electrical wiring or other cables that transmit power or data. Most homes and offices in North America have electrical wiring with a standard voltage of 120 volts. Essentially, voltage is a measure of electrical pressure. In the same way that higher pressure on one end of a hose pushes water to an area of lower pressure and makes it flow out of the hose, greater electrical potential energy on one end of the wire moves electric current to the other end where the pressure is lower. When there's too much pressure – in other words, when voltage significantly exceeds 120 volts – it can damage electronic equipment. If an increase in voltage lasts three nanoseconds (billionths of a second) or more, it is called a power surge or transient voltage. If the increase lasts less than three nanoseconds, it is called a spike.
What causes power surges and voltage spikes?
Common causes of surges and spikes include restoration of power after an outage, downed power lines, electrical grid malfunctions or accidents, on/off cycling of large appliances, wiring faults, tripped circuit breakers and lightning strikes. Very large surges, which are caused primarily by lightning and temporary interruptions resulting from storm damage, occur infrequently. They may happen a few times a year or several times a month, depending on the area. However, normal equipment operation may cause surges over 1,000 volts multiple times per day. The additional voltage in both surges and spikes generates extra heat that can seriously damage or completely destroy the circuit boards and other critical components in electronic equipment. The damage may occur all at once if the surge or spike is large enough, or equipment may be harmed incrementally over time by smaller, repeated power surges and spikes.
How Do Surge Protectors Work?
How do surge protectors protect against surges and spikes?
When the voltage rises above the accepted level, the surge protector suppresses the excess voltage to prevent it from causing harm. Internal components called metal oxide varistors (MOVs) absorb excess voltage and divert it to the ground wire, preventing it from reaching the connected equipment. To function effectively, a surge protector must be connected to a properly wired and grounded AC outlet. Some surge protectors include diagnostic LEDs that alert users to possible wiring problems.
What is line noise?
Surge protectors also protect against line noise. Line noise is caused by electromagnetic interference (EMI) and/or radio frequency interference (RFI), typically generated by operating other equipment on the same electrical system. For example, line noise may result from turning on fluorescent lights or a laser printer, or using a generator or appliance. People may recognize this as audio static or video snow.
Will a surge protector stop lightning?
When lightning hits the earth, a power line or building, most of the energy flashes to ground or is shunted through utility surge arrestors. The remaining energy that enters the building's AC power system is called surge current. When connected to a properly grounded AC outlet, a surge protector can prevent surge current from damaging connected equipment by diverting excess voltage to ground. If the surge is large enough to damage its internal protection circuitry, the surge protector may require replacement under warranty.
Direct lightning strikes are extremely rare. If they are a concern, however, a lightning arrestor can provide additional protection against this type of event.
How do surges and spikes damage surge protectors?
When the line voltage rises above the accepted level, the surge protector suppresses the excess voltage to prevent it from causing harm. Specifically, internal components called metal oxide varistors (MOVs) absorb the excess voltage and divert it to the ground wire, preventing it from reaching the connected equipment. When they absorb excess voltage, the MOVs may sustain damage. Over time, accumulated damage from multiple power incidents and/or a single very large incident can damage the MOVs to the point where they can no longer provide adequate protection.
How do you know if your surge protector is still protecting?
An automatic shutoff feature should permanently cut power to the outlets if the protection circuit is incapacitated, preventing equipment damage and indicating replacement is required. Most Eaton surge protectors also include a "Protected" LED indicating whether the protection circuit is still functioning.
When should you replace a surge protector?
Damaged by repeated surges, a surge protector will eventually lose its ability to protect connected equipment from additional surges. Like a bike helmet, once a surge protector has done its job, it needs to be replaced because it can no longer continue to provide the desired protection.
If the surge protector's automatic shutoff feature permanently cuts power to the outlets or the green "Protected" LED goes out, it is time to replace the surge protector. An Eaton surge protector can be replaced under its limited lifetime warranty. In addition, if a surge protector, its case or its cord become discolored, cracked, melted or otherwise damaged, you should unplug the surge protector immediately and replace it as soon as possible.
Buying a Surge Protector? What to Look For
Warranties and Connected Equipment Insurance
Most Eaton surge protectors can be replaced under their limited lifetime warranty if surge protection is no longer functional. In the unlikely event a surge protector fails to protect connected equipment, the connected equipment insurance covers replacement costs. Make sure the insurance amount is enough to cover the replacement cost of all your connected equipment. Eaton's connected equipment insurance is also called "Ultimate lifetime Insurance."
Types of Surge Protector
Surge protectors come in multiple styles, including direct plug-in, in-line, strip, under-monitor, bench mount and rack mount. There are even styles that clamp to flat surfaces or mount in desk or table cutouts. Some surge protectors also have built-in protection for data lines, including telephone, Ethernet network and coaxial lines. Other surge protectors include USB charging ports for charging smartphones, tablets and other devices.
See Also: Special Application Surge Protectors
Joule Rating
A surge protector's joule rating indicates how much energy it can absorb before it fails. The higher the number, the greater the protection provided. The type and value of the equipment are key factors in determining the optimal amount of protection, as is the region of the country where the equipment is located. If lightning storms are frequent occurrences, for example, a higher level of protection should be strongly considered.
The highest level of protection we offer is an audio video surge protector with a joule rating of 5100 joules.
Number of Outlets
Determine how many different items will be plugged into the surge protector, and invest in one with at least that many outlets. If some of the items include bulky transformer plugs (also known as AC adapters or power bricks) rather than standard ones, allow for possible outlet blockage or select a surge protector designed specifically to accommodate the wider plugs without blocking adjacent outlets.
Some industrial surge protectors have up to 24 outlets. (see products)
Cord Length
Make sure you select a surge protector with a cord long enough to reach a grounded AC outlet. If you want to place furniture flush against the wall in front of the AC outlet, choose a surge protector with a right-angle plug. Do not use an extension cord.
Eaton offers a number of surge protectors with 25-foot cords (see products)
Isolated Filter Banks
You often want to plug your computer or TV and associated peripheral devices into the same surge protector, but some devices may generate line noise that disrupts other equipment. A surge protector with isolated filter banks provides an extra measure of line noise filtering, eliminating disruptions generated by printers or other peripherals connected to the same surge protector as other equipment. Eaton's Isobar surge protectors include isolated filter banks.
Choosing the Best Surge Protector
Surge protectors come in many different shapes and sizes designed for different applications, but they all share the same core function: to prevent surges from damaging connected equipment. The best surge protectors have the following characteristics:
Low Let-Through Rating
The UL 1449 voltage let-through rating defines the average amount of voltage the surge protector "lets through" to the connected equipment following a surge or spike. The lower the let-through rating, the better the protection. The UL rating levels are 330, 400, 500 and 600 volts.
High Joule Rating
The joule rating of a surge protector indicates how much electrical energy it can absorb without failing. Choose surge protector joule ratings based on the value, importance and sensitivity of the equipment that will be connected. For more sensitive or costly equipment, such as computers, televisions, lab equipment and audio/video equipment, select a surge protector with a joule rating of at least 1,000.
Special Applications
Frequently Asked Questions
Will a surge protector work on an ungrounded outlet?
A surge protector designed for a standard AC power outlet requires a functional ground connection in order to work properly. The surge protector diverts excess voltage to the ground wire, preventing it from reaching connected equipment.
Can I plug a surge protector into an extension cord?
This is not recommended because the extension cord may not be robust enough to carry the current required by the surge protector safely. In addition, long cable runs increase electrical resistance, which can cause overheating and fire hazards. Instead, choose a surge protector with a long input cord designed to carry the required current safely, such as one of these models.
Can I plug an extension cord into a surge protector?
This is not recommended because long cable runs can cause overheating and fire hazards. Instead, choose a surge protector with a long input cord designed to carry the required current safely, such as one of these models.
Can I plug a power strip into a surge protector?
This is not recommended because long cable runs can cause overheating and fire hazards. Increasing the number of outlets also makes overloads more likely. Instead, choose a surge protector with a long input cord designed to carry the required current safely, such as one of these models.
Can a surge protector be used with a generator?
Yes. However, a surge protector should not be used unattended outdoors unless it is rated for continuous outdoor use.
Can a surge protector be used with a UPS system?
UPS systems have built-in surge protection, so this is unnecessary and not recommended. It also increases the risk of overloads.
If I have a fuse or circuit breaker, do I still need a surge protector?
Yes. Fuses and circuit breakers protect against current (amperage) overloads, but they do not protect against voltage surges and spikes.
Will a surge protector stop breakers from tripping?
No, tripping breakers are usually caused by current (amperage) overloads. Surge protectors protect against voltage surges and spikes.
Why does a breaker trip either on the surge or in my home?
Tripping breakers are usually caused by current (amperage) overloads. That means too much equipment is plugged into the surge protector or the outlet. Unplugging some equipment or replacing it with equipment that requires less power (wattage) may prevent the breaker from tripping. Other possible causes include a compromised breaker in the electrical panel that requires replacement or an appliance that draws too much amperage on startup, such as a heavy-duty power tool. High-amperage devices may require a 20 amp outlet instead of the typical 15 amp outlet. A 20 amp outlet can be combined with a 20 amp surge protector, such as one of these models.
My surge protector is buzzing. What does this mean?
This may indicate the surge protector is damaged or faulty. You should unplug the surge protector and replace it. If you still notice a problem, consult an electrician.
Can I plug a surge protector into a GFCI outlet?
Yes, but keep in mind that all the equipment plugged into the surge protector will lose power if the GFCI outlet trips.
How can I tell if an outlet strip has surge suppression?
A surge protector should be labeled as a surge protective device or similar on its nameplate. In addition, the manufacturer's documentation will identify it as a surge protector and provide specifications for the level of surge protection provided, including the joule rating and voltage let-through rating.
How does a surge protector differ from a power conditioner or automatic voltage regulation (AVR)?
A surge protector is designed to protect against very short-term and high-intensity voltage spikes and surges. A power conditioner is designed to protect against longer-term and lower-intensity voltage sags (brownouts) and swells (overvoltages). The automatic voltage regulation (AVR) feature of line-interactive UPS systems performs the same function as a power conditioner. Power conditioners and UPS systems typically include built-in surge protection in addition to their voltage regulation features.
How does a surge protector differ from a residual-current device?
A residual-current device, such as a GFCI outlet, monitors for leakage current to ground and interrupts the circuit when it detects leakage current. Interrupting or breaking the circuit prevents equipment damage and the potential for dangerous electric shocks. Rather than protecting against excessive voltages like a surge protector, it protects against current (amperage) leaking to the wrong place in the circuit due to a wiring fault or other problem.
Products Mentioned in this Article
Why Buy from Eaton?
We know you have many brands to choose from. On the surface, they may all seem alike. It's what you don't see that makes the difference. With Eaton, you get solid engineering, proven reliability and exceptional customer service. All our products undergo rigorous quality control before they are offered for sale, and independent testing agencies verify our products meet or exceed the latest safety and performance standards. Our commitment to quality allows us to back our products with industry-leading warranties and responsive customer service. It's the Eaton difference.
