The trustworthiness of surge-protector power strips

So I work a remote job online from home, and the forecast is for thunderstorms for a few hours - unfortunately, I cannot avoid working during those hours. I do have my computers and router/modem etc. hooked up to surge-protecting power strips, but are those really dependable (except for a direct or nearby lightning hit; nothing can save that?)

I rent, don’t own, my apartment, so I can’t hook up the entire apartment to a house-saving surge protector either.

Yesterday there was a crash of thunder and one computer made a bit of a burnt smell but still operates just fine, wonder how?

Plug into an inverter during the storms. Keep a spare marine battery and recharge it while not using it. Use wifi to get to the internet if needed. Complete isolation from incoming power. Even better than an isolation transformer.

We’ve used the Belkin line of products throughout our offices, both hard-walled offices and trailers.

The surge protectors have always worked for us. The battery backup version are a bit expensive, but for some of our jobsite trailers, they’ve kept the power clean and steady, even coming from a generator.

If you can get the Belkin line where you are, its a good, reliable system.

Or a back-up battery system that is always making the power for it’s load so it it has to pick up a load when the surge protector cuts in or the power fails someway, it is always already working. These are not the cheap set ups.

If you are not running a big system but say a laptop or something without heavy current draw, then what “PoppaSan” said is probably cheaper and doing a WiFi connection by unplugging from the router really is a good idea. I need to set this up for when we travel because I already have an power supply that will carry our laptops and all I need is a good battery. Hummmm Thanks for the idea “PoppaSan”…

IMO, the whole system needs a sacrificial cheap surge protector at the wall & the good one/ones between that and your equipment and then battery backup if you can afford it. But that is big desk tops, printers and other stuff running a lot & you really need to stay online during storms.

The cheap surge protectors (not UPS battery systems) contain ‘sacrificial’ components that can be killed by surges, but which prevent the surges from going beyond into your equipment. Quite possible that the burnt smell you noticed was such a component giving its’ life to save your equipment.

Unfortunately, after such an incident, the device no longer is able to provide any protection from surges. It does keep working, but functions only as a multi-plug power strip. (Because customers would really object if it stopped working after a surge.) I suppose it could be designed with a warning light that goes on or off after its’ surge protecting feature is gone, but the manufacturers don’t do so. Probably because of cost, or because it would happen so soon, maybe in the first thunderstorm.

There are surge protectors and there are surge protectors. They are not all created equal.

The power strip type generally use metal oxide varistors (MOVs) for protection. These are devices that remain “off” until the voltage gets too high. Once the voltage gets too high, they turn “on” and essentially create a short circuit, shunting the incoming spike to ground. The energy dissipated generally blows the MOV, so it’s a one-shot deal.

The el-cheapo surge protector strips will only have an MOV between the hot wire and ground. A good surge protector will have MOVs between all wires, hot, neutral, and ground. That way any type of spike that comes in will get stopped.

The higher the joule rating, the better. An el-cheapo surge protector may only be rated for a couple hundred joules. A decent one will be in the range of a couple thousand joules. A good whole-house unit may be a few tens of thousands of joules. For the benefit of others who might be coming into this thread, there are some whole-house cheapies that don’t offer any more protection than what you can find in a power strip.

To put it in perspective, a lightning bolt has a few billion joules of energy in it, which should make it obvious why nothing that you can afford to buy will protect you from a direct strike. If you are interested in how they protect buildings like radio station transmitters from lightning strikes, google Ufer grounds, halo/ring grounds, and Faraday cages.

Another important rating is the amp rating. There are actually two amp ratings. One is for the standard power that the power strip provides, which will be something like 10 to 15 amps. If you plug a lot of computers and other things into the power strip you’ll want to be on the high end of this. The other rating is how much current the surge protector can shunt to ground, and this will typically be something like 50,000 amps. Again, the higher the number the better.

Next you want to look at the clamping voltage. This will typically be something like 300 or 400 volts. The LOWER the number, the better. If you have a 350 volt spike coming down the line, the 300 volt surge protector will clamp it, and the 400 volt surge protector will let the entire 350 volt spike through.

Another thing to look at is the response time, typically measured in nanoseconds. The lower the number, the better, as this means that the surge protector responds more quickly to a spike.

A good surge protector will also have indicator lights on it that will tell you if the MOVs are intact or if they have been blown. That way you know if the MOVs are still protecting you or if they already blew out in a previous spike.

As has already been mentioned upthread, a UPS gives even better protection, though it costs a lot more. A good UPS also has surge protection built into it, and the same specs above also apply. You also want to consider things like battery life with a UPS, and you want one with an inverter that puts out as close to a sine wave as possible. Some of the cheapies put out very square-ish waveforms, which effectively makes your AC line a bit noisy. Most equipment these days can handle that, but you may find that it causes some issues, like maybe extra annoying hum in your sound output.

I had a computer’s power supply killed even though the computer was plugged into a surge protector. The guy who fixed the machine told me he’d seen it before.

Many years ago during some electrical work, a contractor connected my office building’s normal 120 volt single phase circuit to a 480 volt 3 phase generator. Of the random grab bag of power strips and surge protectors we had, the APC surge protectors were the only ones which successfully protected the equipment plugged into them. As expected, the non-surge suppressing power strips prevented nothing. The non-APC power strips that were called surge suppressors also protected nothing. All of the APC surge suppressors died (and were replaced free by APC), but the equipment, mostly computers, plugged into them survived.

I know that sounds like an ad for APC, so let me clarify, the surges suppressors fell into two categories: a widely known name brand (APC) and non-name brand ones. Other name brand (or simply high quality) surge suppressors probably would have also been good protection, but we didn’t have any of those, because at the time we could get the APC stuff cheaply under GSA contract.

Anyway, the point of all that is, not all surge suppressors are created equal. It is easy for a manufacturer to write “surge suppressor” on the side of a package. Engineer_comp_geek’s seems like a good guide to finding high quality ones. I have no idea how the APC surge suppressors would have handled a lightning strike.

There are several lines of inexpensive UPS available just about anywhere. I like to get mine at Staples or Office Depot/Office Max. $50-$75 gets you a whole lot of peace of mind.

Note that UPSs are generally not isolated from the incoming AC.

I’ve used a UPS for a number of years, and it has always done the job. The last one I bought was around $100, money well spent when you consider the alternative.

Are you saying that a surge protector is redundant with a UPS (i.e. “standard practice is not to add a surge protector”), or that you need to add a surge protector (i.e. “most models don’t have any protection in the input side”)?

In a proper UPS’es (all but the really cheap ones) the output ALWAYS comes from the internal battery. That battery is being simultaneously recharged from the building’s power (e.g. from a wall socket).

Sorry, but that is not true.

“Line Interactive” UPSs are isolated from incoming AC, and have no switchover time, but they are substantially more expensive than your consumer-grade UPSs, and are not the cheap units that people have been recommending.

From here.

UPSs come with and without surge protection.

There are also two basic types of UPSs. There are those that are always powered off of the inverter, and therefore offer a bit more isolation from the incoming AC line. There are also UPSs that work on more of a standby type of system. As long as the incoming AC line is up, the UPS output comes from that. If the incoming AC line fails, then the UPS inverter switches on and takes over. This type obviously has much less isolation from the AC.

The better (and more expensive) ones have both surge protection and are always powered off of their inverter.

Our generator supplied server and charger trailer was powered up with the generator set to the wrong voltage.
Most of the equipment is supplied by high quality UPS of the isolation type. The incoming AC is converted to DC. Then used to charge the UPS batteries and converted to clean AC for the equipment.
It took far too long to detect the problem. The smell of burning equipment.

But the UPS systems did the job. The AC input sides ranged from repairable with new parts to charred craters in the circuit boards. But the downstream equipment suffered no over voltage damage at all. A full server with 24 bay internal and external raids. Multiple network switches. AC to DC power supplies.

On the other side of the trailer were the battery chargers. The AC to DC power supplies were protected with external MOVs and the internal protections of the manufacturer TDK Lamda. Lots of MOVs blew. Several power supplies died forever. Some were revived.

Isolated UPS is your best protection. But it too may give it’s life to save your goodies.

You also have to consider that lightning can follow in through the modem also. We were hit through the phone lines when I was young. I’m not sure of what happens with fiber lines though.

I feel obligated to point out that having one surge protector plugged into another is dangerous. You risk overloading a circuit and starting a fire. Also, plugging one into another may cause one to prematurely trip its protection, shutting everything down. It’s a bad idea and always discouraged.

Plugging one surge protector into another isn’t dangerous as long as the total current draw for each surge protector does not exceeded its current rating. (Which means, of course, the total current draw for the surge protector plugged into the wall receptacle must include the total current of the other surge protector.)

What type of protection are you talking about? Over-current protection? Or something else? And why would one surge protector trip the protection circuitry in the other?

I’m an IT professional and a state employee at an agency that (among other things) regulates workplace safety. Daisy-chaining surge protectors and/or power strips is a big no-no. It’s against OSHA, NFPA, and UL safety regulations.

OSHA Standard 29 CFR 1910.303(b)(2)

Installation and use. Listed or labeled equipment shall be installed and used in accordance with any instructions included in the listing or labeling.

OSHA Standard Interpretation

In an OSHA interpretation regarding power strips, an OSHA Director, Richard Fairfax, included this statement: “Manufacturers and nationally recognized testing laboratories determine the proper uses for power strips. For example, the UL Directory contains instructions that require UL-listed RPTs to be directly connected to a permanently installed branch circuit receptacle; they are not to be series-connected to other RPTs or connected to extension cords.”

NFPA 1 Standard 11.1.4
Relocatable power taps shall be of the polarized or grounded type with overcurrent protection and shall be listed.
The relocatable power taps shall be directly connected to a permanently installed receptacle.
Relocatable power tap cords shall not extend through walls, ceilings, or floors; under doors or floor coverings; or be subject to environmental or physical damage.

UL 1363 1.7

A cord-connected RPT is not intended to be connected to another cord-connected RPT.

UL White Book (2015-2016)

The UL White Book states this: “Relocatable power taps are intended to be directly connected to a permanently installed branch-circuit receptacle outlet. Relocatable power taps are not intended to be series connected (daisy chained) to other relocatable power taps or to extension cords.”

For some discussions on daisy-chained surge protectors interfering with each other, and the danger of overloading circuits:

Honestly though, just Google it. You’ll be overwhelmed with information. Don’t daisy-chain.

I know many organizations prohibit it. Daisy-chaining power strips is prohibited at my workplace, too. None-the-less, I still stand by my statement: