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Surge Protector Question

 
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vickyg2003
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Joined: 20 Mar 2004
Posts: 6946
Location: Florida

PostPosted: Sun Jul 01, 2012 4:10 pm    Post subject: Surge Protector Question Reply with quote

I use power strips that say they are surge protectors. I had a really bad surge problem the other week. When it was passed several pieces of equipment were acting totally weird. My Magnavox DVR wouldn't power on, and the TV channels were not working correctly on one of my TVs. All that stuff has been worked out with a bunch of reset procedures. But this makes me question whether my surge protectors are any good. My SurgeMaster used to have a green light on it that said protected, but that doesn't light up any more. I always thought that these would just power off like a bad fuse if they were not working. Now I'm not so sure.

If a power strip still works, does that necessarily mean that the "surge" protector is still working? Anybody know?


Next Question, if the lights not working means the surge protecting powerstrips are not functioning, does anybody have a recomendation for replacements, because I just went and checked and only the strip with the fuse seems to be functioning correctly. Nothing else is lit up anywhere.
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zaphod7501



Joined: 02 Aug 2004
Posts: 528
Location: Peoria Illinois

PostPosted: Sun Jul 01, 2012 5:01 pm    Post subject: Reply with quote

Short answer, the strips are probably bad and should be replaced. Long answer .....

If a power strip was wired in a "proper" manner, then any surge will render it completely dead, requiring an immediate replacement or a breaker reset. While I have seen some single plug/outlet protectors wired this way, I have rarely seen a strip wired "correctly".

The active device in a strip is an "M.O.V." (metal oxide varistor) It mimics the characteristics of an old style power transformer. It will absorb an electrical shock in one of three methods. It can absorb the shock and recover, it can open up, or it can short out.

If it recovers, the strip will have done its job and will continue to work, possibly with a breaker reset.

If it opens up, it may have done its job, the strip will still be live, but no longer a protective device.

If it shorts out, it will also have done its job but will trip the house breaker as long as its plugged in. Consequently, they are usually designed with a fuse or breaker. A breaker can be reset and a fuse can be wired in two ways. One way will kill the entire strip (correct wiring) or the fuse will only remove the MOV from the circuit the same as if it was open. (incorrect but most common wiring method) Neon lamps can be added in various configurations to indicate "good" or "bad".
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vickyg2003
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PostPosted: Sun Jul 01, 2012 5:08 pm    Post subject: Reply with quote

Thanks Steve, as always you provide information in a way that I can understand it.

So basically I need to replace a boat load of surge protectors, because the cheapies didn't have a fuse, and they didn't stop working after the surge. Yikes, I thought I was protected, but I'm not. Only one of my surge protectors has the fuse, and seems to be functioning correctly.

I guess I should be looking for APC or TripLite?
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zaphod7501



Joined: 02 Aug 2004
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Location: Peoria Illinois

PostPosted: Sun Jul 01, 2012 9:20 pm    Post subject: Reply with quote

Well, power strips (I refuse to call them surge protectors since they protect against spikes, not surges) are of debatable value. They ALL use the same 25 cent MOVs as their active component, so brand has no relationship to function. The fancy "filtering" some offer is normally supplied by simple capacitors. A useful filter has some form of coil or "choke" included; (a copper wire coil with iron core - large, expensive, hot, and not energy efficient) and it still won't protect against a "surge". Good luck finding any actual specifications on what is inside of a "surge suppressor" - trade secret, proprietary, patented, etc.

A surge is a condition where the line voltage (nominal 117 VAC) changes to something else for a measurable period. (135 VAC for 2 seconds, 80 VAC for 1/2 second, etc) A spike, or transient, can run 1000's of volts but lasts a nanosecond or so. They require two different kinds of protection. A surge requires a "power line conditioner" for protection while a transient can be controlled by so-called surge suppressors/power strips. Power line conditioners are sized by the wattage they supply and can run about a dollar a watt. (total the watts needed, double the number, and that is the size of the conditioner you need)

Obviously you got hit with a hard spike (500 volts or more) and they did their job.

They are fairly useful in lightning prone areas. (and lightning DOES tend to strike in the same places, over and over again) Power outages, brownouts, lights flickering, and the like - they are useless since they don't trigger until the spike/surge hits 300 volts or more. To be effective against an actual "surge" they would need a "clamping voltage" of about 135 volts - but there would be so many spikes at that level that they would only last about a week at a time before self-destructing.

The most useful part of a power strip is the switch to disconnect the devices from the AC line voltage.

A power line conditioner regulates the incoming power to a fixed output over a large input range, typically 80 - 135 volts locked to 117 volts. Some one gave me a 450 watt conditioner. It was 8 inches wide, 10 inches tall, 18 inches long, weighs 25 pounds, hums constantly, and draws 2 amps at idle with nothing plugged in. Newer ones are better, but you get the idea. It is very difficult to actually protect typical consumer electronic devices. Full protection can cost more than the devices you are trying to protect.

Personally, I would try to find the cheapest strip with some form of good/bad indicator. The indicators are just cheap neon lamps wired to specific points in the wiring, nothing sophisticated about their implementation, so they shouldn't add any significant cost to the strip.
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vickyg2003
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PostPosted: Mon Jul 02, 2012 9:22 am    Post subject: Reply with quote

Hmm, so I should replace the strips, but they don't do much good.

Of course they don't act like a line conditioner. Is my battery backup a line conditioner? I've been sitting here listening to it go click, click during the peak power times, which seems to indicate that its trying to level out the power to my PC. That was a rather expensive purchase.

But back to my power strips, since I can't see the indicators, I'd want one that powers itself off and has the reset switch. Everything that was on the strip that powered off was working fine and gave me warm and fuzzy feelings about being protected, even though its not much protection. Although I wonder if the rest of the family could possibly figure out what is going on if one of the power strips fail somewhere..... Rolling Eyes They are so clueless. They all gave up trying to understand anything once the digitial TV made viewing so difficult.
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zaphod7501



Joined: 02 Aug 2004
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Location: Peoria Illinois

PostPosted: Mon Jul 02, 2012 7:34 pm    Post subject: Reply with quote

Some battery backups offer some line conditioning, often in 5-10 volt increments. (your clicking) They are useful to protect costly items like computers. They do have weakness in that, if you have other things connected to the device (antennas for TV tuners, network cables, stereo systems, etc) you will have bypassed any spike protection since the spike can come in from the other wiring or in the power line and out through the other wires bypassing even the most sophisticated AC line protection equipment.

Strips fall in the "better than nothing" category and are useful for true lightning strikes even if they don't help much with surges.

Most modern electronic devices actually have MOVs, noise chokes/coils, and spark gaps built in to them. This serves to reduce the internal damage in case of storms. Of course, you need a service company with decent ethics to fix them afterwards, since the set will usually be dead after they do their job and you need someone who will replace the $1 parts instead of the $300 circuit boards.

While it is possible to design a strip with a relay that has to be reset after a power interruption, (self energizing relay) in practice, there are none outside of industrial situations (usually in the form of a "contactor"). I have a 50's era pinball machine with one inside. Your battery backup will power down after the battery runs down and will not restart until you force it back on. Some backup supplies can be tied to the PC in such a way that the computer will shut itself down gracefully when running on battery and then turn off the backup device itself.
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