Hi CV:
The entire field of engineering dealing with this issue is called power quality. While the quality of the whole USA has risen considerably every year, what individuals actual get vary because of who delivers it, your local power company, contamination of the power lines by nearby industrial consumers, and then the quality of wiring in your home. For example, if you live in a neighborhood with overhead wiring, or if your home is older, both are prone to more problems with power quality. You may then need to add some power conditioners to get your 21st century gear to work with 20th century grade power.
In general, where the population is denser, you tend to have good power quality, just as with Internet connectivity, you get the fastest, latest and most reliable Internet speeds in more populated areas ... also good networks and servers need good power to run reliably.
A good plug-in MOV based surge protective device, SPD, if it had to work often due to bad power in your personal situation, will eventually fail and not work. A good suppressor should disconnect your equipment when it fails, and signal you with a light that it no longer works. So when the 'big surge' does occur and your SPD is broken, your equipment is effectively disconnected from the power already.
The problem with MOV base designs is that its so easy to make, so many companies are selling them but few are good designs: they sell based on a nice case, fancy plugs and colors, use questionable claims directed at the audio video market, but are not best made for surge protection. At the very least, I know APCs are well made, but other brands, even popular ones like Belkin and Philips, I've personally opened and examined, are very variably bad. You are looking to spend $10 for a basic power only SPD, $20 for one with phone line protection, and not more than $35 for one with coax, Ethernet, phone, and power protection.
Even if meant to disconnect your gear from power line, some MOV based designs do not disconnect your equipment after a failure, some designs do so unreliably, while few work very well.
Unfortunately, there are no studies or compilations of which brand MOV SPD protects equipment best, not even by Consumer Reports. There are a lot of anecdotes on the Internet of folks complaining, usually because the warranties were not honored. Assuming the poster isn't lying, this is one such report, its interesting because if true multiple devices were plugged into many SPDs:
http://www.amazon.com/review/product/B00000J1RU/ref=cm_cr_dp_all_summary?_encoding=UTF8&showViewpoints=1&sortBy=bySubmissionDateDescending
Of MOV based designs, APC, Panamax, Tripp Lite are very reputable, but I have not had a chance to dissassemble Panamax to examine their claims personally.
In surges, a series mode device assumes than the surges that enter your home are usually lower energy. The series mode devices are usually heavy duty 120V power line filters, that are made to take the worse case scenario of surges, which rarely if ever happens. However, if the surge energy is too great, then a series mode device once saturated will pass its energy onward to the plugged in device, with nothing typically should happen to itself, unless the insulation of the device is exceed and it breaks down.
We speak of surges as if they were one type of problem, its actually just a common name for 7 types of power line problems.
1.
Transients, random bursts of excess voltage in nanosecond durations; 2.
Interruptions, at least zero voltage at at least half of one AC cycle; 3. Sag /
Undervoltage, under 90% of rated voltage at at least half of one AC cycle; 4. Swell /
Overvoltage, above 110% of rated voltage at at least half of one AC cycle; 5.
Waveform distortion, any deviation from a pure sine wave; 6.
Voltage fluctuations, a periodic recurring combination of 3 & 4; 7.
Frequency variations, more than +/- 3 Hz.
SPDs cover items 1, 4, 5. 1 & 4 can damage home electronics quickly and
quietly, and thus should be suppressed to as near 120V as possible. The source for 1 & 4 include natural phenomena such as storms, and thus, cannot be controlled by power company's completely. SPDs will also control 6 when the fluctuation exceeds 120V.
5 typically causes performance degradation such as poor audio or video quality but in severe cases can cause overheating, its fixed by line regulators or an uninterruptible power supply, UPS. Often, 5 is caused from nearby industrial machinery.
Items 2,3,6 are tolerated by most home electronics well. If devices don't act erratically, they tend to turn themselves off due to the anomaly or after overheating. However, if it chronically reoccurs, it eventually can damage equipment, and the user should add a UPS or a voltage regulator.
7 is rare for home users, and commonly occurs from home power generators. Its more a problem for AC motors than run for long duration, causing them to run inefficiently and overheat.
Series mode devices only protect you from #1.
Quote:
Originally Posted by CajunViper /forum/post/15562650
I thought that the power supply through out the US is not that consistent. So wouldn't the shunt mode be deflecting small surges all the time. Then when the big surge hits it is worn out and your equipment gets fried. And I thought this would not happen with series mode.
Just wondering, I,m no sparky.
CV
