Surge Protectors?

Are surge protectors useful? What size do you need for desktop PCs?


They fit squarely into the “can’t hurt” category.
They will not help during a lightning strike, but might provide some protection from a smaller power surge. I use a UPS with built-in protection, but if you don’t want to spend that kind of money, you could just get a decent power strip.

yes they can be.

it is ‘you get what you pay for’ deals. cheap ones may only protect at too low and level and do so only once. this about $25 before they get good.

much better is a UPS (uninterruptable power supply) which has better surge protection circuitry and a battery backup to allow you to shut down your computer if the power fails. this about $60 for lower end.

i would only use a UPS.

Surge protectors are certainly useful, though they only protect against certain types of things. How useful they are depends on the power in your area and whether or not you live in an area that gets a lot of lightning.

A surge protector won’t protect your PC from a brownout or an intermittent connection that keeps making and breaking. If you want to protect yourself from these types of faults then you need a UPS combined with a surge protector (most UPS units will have a surge protector built into them).

Also, nothing that you can reasonably buy can protect you from a direct lightning strike. There’s just way too much energy in a lightning bolt for that.

The first thing you want to look at is how much energy the surge protector can handle, usually rated in joules. The higher the number, the better. Your typical power strip type of surge protector will probably have a rating of several hundred to maybe a couple of thousand joules. A whole house type of surge protector will probably be higher, maybe several thousand to a few tens of thousands of joules. To put it in perspective though, a lightning bolt contains a few billion joules of energy. Now you can see why blocking a direct lightning strike is so difficult.

The next thing to look it is how much current the surge protector can shunt, and again, the higher the number, the better. A cheaper surge protector may be a few thousand amps. A really good unit may be 50,000 to 100,000 amps or higher.

Next you want to look at the clamping voltage. For this, the lower the number, the better. A cheapie power strip might clamp at 500 volts. A better surge protector might clamp at only 300 volts. The higher the voltage that it lets through, the more damage can be done to your PC, so the lower number is better in this case.

Another thing you want is some sort of visual indication that the thing is working. One of the key elements of most surge protectors is called a metal oxide varistor, or MOV. The MOVs are designed to turn on and short circuit once the voltage gets above the clamping voltage. This usually will blow out the MOVs and destroy them, but the idea is that you destroy the MOVs and not your PC. With the cheaper units, you have no way of knowing if a surge already took out your MOVs or not. Better units will have an LED or a light that indicates that the MOVs are still working properly. If the light goes out, you know you need to replace the surge protector because it has been blown.

You also want to look for protection from any line to any other line. The three lines are the hot, neutral, and ground, often abbreviated H, N, and G. A good surge protector will have MOVs installed between all three conductors. Cheaper ones may only have one or two sets of MOVs.

Better surge protectors and especially better UPS units will also have noise filtering on the line.

As you start comparing specs, you’ll quickly see that the cheapies don’t really provide much protection.

Yes they can be an advantage.
Let me describe a situation that happen in the building I use to work at.
I got a call that a tenant was having electrical problems in their suite. When I got there they sure enough had problems. The building had three phase 120/208 power. I checked one of the outlets and got 190 VAC. The neutral wire to that suite had come loose at the electrical panel. ( A Zinsco panel, can you say junk?). They had cheap surge protectors and good (expensive) APC surge protectors. We bought new computers that they were using the cheap protectors on and new APC protectors where they were being used. Fried the APC protectors and protected the computers at 190VAC.

Most modern computers will work from 100-250v with no problems.

Good write-up, ECG. But a couple nitpicks:

The MOV (and it’s high-tech cousin, the TVS) is actually a clamping device, not a crowbar device. GDTs are crowbar devices.

It’s true MOVs can and do fail. (Sometimes spectacularly.) Every time it goes into “clamping” mode it degrades a little. The damage is cumulative, and it will eventually fail. A big voltage surge - such as that from a close lightning strike - can make an MOV fail immediately. Sometimes it will fail open (and thus offer no more protection) and sometimes it will fail short (smoke & fire).

What kills most computers and phones is the ground potential surge in the vicinity of a lightning strike rather than an actual strike.

The surge comes in on the power lines and the phone lines. Normal MOV surge protectors handle this quite well.

You ideally want the type that protects one power point and one phone line at once. They are very cheap and quite effective. Use it primarily for your internet modem and any cordless phone base points. Having more than one for different devices causes no harm.

You can if you wish buy much more expensive units with more bells and whistles but the cheap ones work fine.

The only other thing to consider is a surge protector in the power switchboard. That handles surges that might blow up your TV or microwave.

I think most computers work on 120 or 250 volts. But I am not a computer guy.

What about people who get their internet connection via cable (Comcast or other evil corporations)? Presumably those connections, running on the same poles down the alley, are also vulnerable to lightning strikes & similar surges. Are there devices that protect these connections?

a whole house surge protector (mounted at your main circuit breaker box) can protect phone, cable and power for the house. get one that includes those functions.

Whole house surge protectors are generally better (just watch the specs though, I’ve seen some that were basically worthless), but they do sell power strip type surge protectors that also have a place to plug in other things like your coax or ethernet cable so that it can protect those lines as well. They also sell individual surge protectors for things like phone lines and ethernet cables.

There’s a pretty wide variety of stuff out there.

Yes. Many of your better surge protectors and UPS have protection for coax cables on them.

Side story: I once supported a PC that was used to control the automatic watering of a golf course. This was years ago and it used the serial cable to connect to the watering system. Sure enough the computer got fried by a lightning strike that came through the serial port. They do make surge protectors for serial ports also.

there are still some cheap PC power supplies which still have a switch for input voltage, but pretty much any modern switch-mode power supply should be able to work between 90 and 250 VAC, either 50 or 60 Hz.

For well over 100 years, the proven solution has always answered by a simple question. Where do hundreds of thousands of joules harmlessly dissipate?

Start with specification numbers for power strip protectors. What happens when that protector tries to absorb a potentially destructive surge? Well, if a surge is too tiny to overwhelm protection already inside appliances (ie computer), then that current, passing through both protector and computer, can destroy that grossly undersized protector. Undersizing gets a majority to recommend a grossly undersized protector with obscene profit margins.

Worse are other problems created by an adjacent protector. It can give a surge more paths to find earth destructively via that appliance. In rare cases, it can (and often has) create house fires. In fact, recently listed were some APC protectors so prone to fire that these must be removed immediately.

Again, protection is always about where hundreds of thousands of joules harmlessly dissipate. Your cable TV, telephone and satellite dish were required by standards, codes, and government regulations to have this solution. Unfortunately, many installers only have an electrician’s knowledge. May not install or may compromise these proven solutions.

Most common source of surges to a structure is averted by earthing a lightning rod. Then direct strikes occur without damage. Most common source of surges to appliances is avert by earthing a ‘whole house’ protector. Every facility that cannot have damage uses that solution. Your telco’s $multi-million computer, connected to buildings all over town, typically suffers about 100 surges with each storm. How often is your town without phone service for four days after each storm? Never? Because the proven solution has been used for over 100 years. That means protectors connected low impedance (ie ‘less than 10 feet’) to single point earth ground. And without protectors adjacent to electronics.

Again, protection is always about where hundreds of thousands of joules harmlessly dissipate. Cable TV connects that surge direct to earth with a hardwire. AC electric and telephone cannot connect direct to earth. So a protector does what that hardwire does better. Then hundreds of thousands of joules harmlessly dissipate outside a building in earth. Then even direct lightning strikes do not cause damage.

Again, this is 100+ year old technology. This is the only solution found in facilities that cannot have damage - even from direct lightning strikes. This solution is provided by companies with superior integrity including Ditek, General Electric, Polyphaser (an industry benchmark), Syscom, Siemens, ABB, Intermatic, Square D, and Leviton. A Cutler-Hammer sells in both Lowes and Home Depot. Not listed are APC, Belkin, Tripplite, Panamax, or Monster. But again, that is only a protector. Most of your attention must focus on what actually does protection - single point earth ground. Since protection is always about where hundreds of thousands of joules are harmlessly absorbed.

Did it? Surges are electricity. That means it must have an incoming path and another outgoing path. If a surge was incoming to a serial port, then some other outgoing path must have also been damaged - using your reasoning.

A surge is a connection to earth. Most common incoming path is AC electric. Incoming on AC mains. Outgoing to something connected to earth via that serial port. Damage is often on the outgoing path.

First a surge connects a cloud to earthborne charges. That electric current exists everywhere simultaneously in that path. Then later, typically one weakest part in that path fails. Serial port would have been a weakest component is a path that connected cloud to earthborne charges. To say more, identify everything in that path.

Again, facilities that cannot have damage earth a surge BEFORE it can enter a structure. Cable TV, phone, and satellite dish should already have this. Only incoming wires, not required to have this solution, is AC electric. See a previous post for how direct lightning strikes without damage are routine. For about $1 per protected appliance.

I think you’re missing the point here.

Pretty much nothing can handle the power of a nearby lightning strike. Nothing that the average homeowner can economically do to protect his PC, unlike the phone company’s mainframe computers.

But a surge protector, or better yet, a UPS device can protect your PC from the myriad of small surges & dropoffs that occur every day in our electrical supply. These happen because everybody else is connected to the same main electrical lines, and their activities can affect your electricity.

Modern computers are built so they can handle a lot of this without damage to the machine – but they can often cause it to re-boot … and then you lose everything you were working on unless you remembered to save it recently. A couple of incidents like that, and you’ll find the cost of a UPS quite reasonable!

Routine everywhere (even in homes) is a direct lightning strike without damage. Even basic numbers make this obvious. For example a direct lightning strike may be 20,000 amps. So a minimal ‘whole house’ protector (about $1 per protected appliance) is rated at 50,000 amps. Because even a protector must remain functional.

Protectors that protect that $multi-million computer are similar to what is also installed at each subscriber interface - at each home. Only difference is the only item that defines quality of protection. Telcos install a better earth ground. Meanwhile, even informed residential owners suffer direct strikes without damage … when they do not use that near zero power strip or UPS. And when they properly earth what does (according to an IEEE Standard) 99.5-99.9% of the protection.

Surges and dropoffs have no place in the same discussion. Since they are two completely different anomalies. Are not avert by same hardware. One is potentially destructive and the other causes no electronics damage.

Add the word small. Then no appliance is damaged by surges or dropouts. Since that ‘fear’ only exists among many without basic elevctcrical knowledge - who are educated by advertising myths and hearsay. All electronics are so robust as to even consume small surges as electricity to power its semiconductors. Routine is to convert those spikes into well regulated low voltage that is called 5 and 12 volts.

Due to myths promoted without numbers, then many assume a vacumm or washing machine creates surges that destroy electronics. If true, then every homeonwer is trooping to the hardware store daily to replace clocks, GFCIs, smoke detectors, and the TV. All electronics (even semiconductors in LED and CFL bulb) are so robust at to make the ‘feared’ small surge irrelevant.

Only concern is the rare transient that causes damage. That occurs maybe once every seven years. That protection means the informed consumer knows where hundreds of thousands of joules harmlesslyl dissipate. Only scammed consumers spend tens or 100 times more money for the near zero protection in a UPS or power strip. The informed consumer spends about $1 per appliance by earthing one ‘whole house’ protector. Then even 20,000 amp lightning strikes harmlessly dissipate outside (are never inside the house) via a 50,000 amp protevctor - that does not fail.

Protection was never provided by that UPS or power strip. Protection is always about where hundreds of thousands of joules are harmlessly absorbed. A protector is only as effective as its earth ground - which neither UPS nor power strip provide. And the manufacturers will avoid all discussion to protect obscene profit margins.

All this was well understood 100 years ago when even direct lightning strikes were harmlessly earthed - caused no damage. Unfortunately too many are only educated by hearsay. And never learn critically relevant numbers above.