EEVblog Electronics Community Forum
General => General Technical Chat => Topic started by: Storeinfinity on November 07, 2011, 08:27:18 am
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Power strip:
according to Wiki.org,(http://en.wikipedia.org/wiki/Power_strip (http://en.wikipedia.org/wiki/Power_strip)) "In 1972, the electrical "power-board" was invented by Australian electrical engineer Peter Talbot working under Frank Bannigan, Managing Director of Australian company Kambrook. The product was hugely successful, however, it was not patented and market share was eventually lost to other manufacturers."
I've seen some really good designs yet still am using traditional old ones.
(http://www.popgadget.net/images/T12-power-strip.jpg)
(http://cdn.freshome.com/wp-content/uploads/2010/06/power_strip_r7_around_stool.jpg)
(http://www.wired.com/images_blogs/gadgetlab/2010/02/multi-tab-power-strip-by-soon-mo-kang.jpeg)
Anyone tried stuff the same or similar?
I would like to know some popular options when it comes to power oscilloscopes and multimeters etc.
Many Thanks and Wish you all the best.
By the way
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Worldwide muslims celebrate this every year for three days.
As a Kazakh this festival is pronounced into Kazakh as ?????? ??? (Qurban ayt).
See more: http://en.wikipedia.org/wiki/Eid_al-Adha (http://en.wikipedia.org/wiki/Eid_al-Adha)
http://www.timeanddate.com/holidays/us/eid-al-adha (http://www.timeanddate.com/holidays/us/eid-al-adha)
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http://nation.com.pk/pakistan-news-newspaper-daily-english-online/Regional/Lahore/07-Nov-2011/Eidul-Azha-being-celebrated-today (http://nation.com.pk/pakistan-news-newspaper-daily-english-online/Regional/Lahore/07-Nov-2011/Eidul-Azha-being-celebrated-today)
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I'm using APC (American Power Conversion) brand. I have a unit bought sometime 1998 still working fine 8)
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i like the Tripplite PS3612. nice spacing for wall warts. power switch guard. lifetime warranty. the mounts aren't that great, but they work.
-sj
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For general purpose power strips the best quality use metal casings for long term durability, but it cost so much more because the contacts have to be isolated from the chassis and the chassis grounded for protection. Plastic thus are just as fine and can last decades so long as its kept away from sunlight, as UV causes many plastics to degrade unless they are UV treated, which just prolongs its lifespan not last for lifetimes such as an all metal case.
http://www.rutlandplastics.co.uk/plastics_additives_stabilisers.shtml (http://www.rutlandplastics.co.uk/plastics_additives_stabilisers.shtml)
Less moving parts, and single long strip is the most hardy kind. Even no name Chinese label ones are fine, I pick them up for $1-2 each during special deals and all have universally a circuit breaker that also doubles as an on-off switch.
A power strip is a separate issue from a surge protector.
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i like the Tripplite PS3612. nice spacing for wall warts. power switch guard. lifetime warranty. the mounts aren't that great, but they work.
-sj
I freaking love these. They have a whole range of sizes. I didn't like the mounts at all when I first saw them, but they hold much better than I expected. I have always considered that I could email Tripplite and get extra ones for more stability if I wanted to, and probably at no cost to me. They're a reputable company.
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Go for the max joules for the buck. then make sure it can hold wall warts. like this: http://www.walmart.com/ip/Belkin-BE112234-10-SurgeMaster-Professional-12-Outlet-Surge-Suppressor/13073631 (http://www.walmart.com/ip/Belkin-BE112234-10-SurgeMaster-Professional-12-Outlet-Surge-Suppressor/13073631) 3960 joules for $25.00
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The belkin looks nice with a good price, however if we're talking about more joules, this is probably a better deal for a few dollars more. Same # of jacks (12) but goes to 5000 joules instead:
http://www.amazon.com/MonsterDigital-PowerCenter450-HPM-MDP-450/dp/B002RL9XQM/ref=sr_1_1?ie=UTF8&qid=1320979009&sr=8-1 (http://www.amazon.com/MonsterDigital-PowerCenter450-HPM-MDP-450/dp/B002RL9XQM/ref=sr_1_1?ie=UTF8&qid=1320979009&sr=8-1)
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The belkin looks nice with a good price, however if we're talking about more joules, this is probably a better deal for a few dollars more. Same # of jacks (12) but goes to 5000 joules instead:
http://www.amazon.com/MonsterDigital-PowerCenter450-HPM-MDP-450/dp/B002RL9XQM/ref=sr_1_1?ie=UTF8&qid=1320979009&sr=8-1 (http://www.amazon.com/MonsterDigital-PowerCenter450-HPM-MDP-450/dp/B002RL9XQM/ref=sr_1_1?ie=UTF8&qid=1320979009&sr=8-1)
Agreed, I actually have a 5000 joule phillips unit but I could not find it for the post. You did a better job of searching than I did.
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High joule rating for a surge protector is a misconception. Here's a thread on it from a year ago.
https://www.eevblog.com/forum/index.php?topic=381.msg19635#msg19635 (https://www.eevblog.com/forum/index.php?topic=381.msg19635#msg19635)
http://en.wikipedia.org/wiki/Surge_protector#Joules_rating (http://en.wikipedia.org/wiki/Surge_protector#Joules_rating)
Based on work done by NIST, a joule rating of over 100 is adequate. Over 300 joules allows for a 3x derating is likely more you'll ever need.
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High joule rating for a surge protector is a misconception. Here's a thread on it from a year ago.
https://www.eevblog.com/forum/index.php?topic=381.msg19635#msg19635 (https://www.eevblog.com/forum/index.php?topic=381.msg19635#msg19635)
http://en.wikipedia.org/wiki/Surge_protector#Joules_rating (http://en.wikipedia.org/wiki/Surge_protector#Joules_rating)
Based on work done by NIST, a joule rating of over 100 is adequate. Over 300 joules allows for a 3x derating is likely more you'll ever need.
Would the higher capacity in joules (more or larger MOV's) equate to yielding a longer life?
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Hi robrenz,
It could. But its hard to say what will happen.
MOV work by shunting the surge current to ground; if the ground is somehow removed [ that's why good surge protectors have a ground fault light] the MOV will absorb the energy.
A high joule rating [ akin to a high watt rating on a resistor] will then absorb more energy before it blows, and MOVs that blow are like a flare and very hot. At worst it can melt plastic cases and if it breaks through, can burn the surrounding area of the surge protector, like a carpet or a sofa. These high joule MOV are best in all metal cases. If the MOV absorb the energy and do not blow, then nothing likely will happen, and the good news is the partially damaged MOV will likely blow at lower energy at the next surge, whenever that is. The downside is that high joule rating MOV are a fire risk.
To avoid this, plastic cased surge protectors are best with small joule MOV, so they will die quickly and not have too much energy to dissipate. Many surge protectors from reputable power product companies like APC bypass the hype and usually just have 300-500 joule MOV inside them and will offer a lifetime guarantee on the product, because surges that damage protectors are fairly rare and the cost to replace the unit truly small.
To get higher joules some surge protectors makers either parallel multiple 100-500 joule MOV or use one of the newer premade single unit parallel MOVs.
MOV are non-linear and when faced with surge voltage, identically label MOV will not act identical, some will have let through voltages lower or higher than spec. This causes one of the units in parallel to blow sooner than others, so you don't have the violent burn expected of a single high joule MOV.
Alas, better designs include a thermal fuse in series with the MOV. If the MOV overheats, the fuse will blow, cutting off the MOV from the line thus preventing an explosion. If this design is used, all the joule ratings become moot, because the thermal fuse is often designed to trip before the MOV can explode, making high joule ratings unnecessary.
Better designs have MOV also linked by a thermal fuse to the HOT side of the AC line. If the MOV overheat, the HOT line thermal fuse will blow, killing all power to units serviced by the the surge protector, again preventing a MOV fire but also killing the whole protector.
Thus, in the end high joule ratings are a fire risk, and if thermal fuses are used, will unlikely provide the benefit of making the surge protector last longer against surges.
Based on work done by NIST, a joule rating of over 100 is adequate. Over 300 joules allows for a 3x derating is likely more you'll ever need.
Would the higher capacity in joules (more or larger MOV's) equate to yielding a longer life?
High joule rating for a surge protector is a misconception. Here's a thread on it from a year ago.
https://www.eevblog.com/forum/index.php?topic=381.msg19635#msg19635 (https://www.eevblog.com/forum/index.php?topic=381.msg19635#msg19635)
http://en.wikipedia.org/wiki/Surge_protector#Joules_rating (http://en.wikipedia.org/wiki/Surge_protector#Joules_rating)
Based on work done by NIST, a joule rating of over 100 is adequate. Over 300 joules allows for a 3x derating is likely more you'll ever need.
Would the higher capacity in joules (more or larger MOV's) equate to yielding a longer life?
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Thanks saturation, very informative. I never thought about the fire risk of the plastic cased units.
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You're welcome. Here are some links to discussions of surge supressor fires. With thermal fusing, these events are fairly rare, unless the surge protector manufacturer doesn't use them. I open mine to insure they are built this way.
http://www.nmsu.edu/safety/news/lesson-learned/surgeprotectorfire.htm (http://www.nmsu.edu/safety/news/lesson-learned/surgeprotectorfire.htm)
Fowler is an investigator and focuses on fires caused by surge protectors and power strips:
http://www.sfowler.com/investigations/Surge%20Protectors.htm (http://www.sfowler.com/investigations/Surge%20Protectors.htm)
this is how violent a MOV fire is when faced with large surges:
Varistor - SloMo Explosion (https://www.youtube.com/watch?v=fzSjK9Nz44w#ws)
Thanks saturation, very informative. I never thought about the fire risk of the plastic cased units.
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Thanks for the info saturation, don't you think this is worth putting on EEVBlog's wiki?
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you're welcome. I didn't know there was a wiki, feel free to copy it there and I'll edit it if needed.
I helped write the Wikipedia one, but the other contributors fixed it up nicely.
You're more than welcome to add more or ask more about them; I spent time talking to Francois Martzloff at NIST, the 'surge god' and then Robert Standler, about some of the industry 'wierdness' about the consumer side of this industry. The professional side is ok but what they do for consumer products is certainly worth an expose.
For more details, read this review on an APC surge protector, as the details also discuss the strange activities in the industry:
http://www.epinions.com/review/APC_11_OUT_SURG_W_TEL_COA_EA_APNP11VNT3_Surge_Suppressor/content_453665328772 (http://www.epinions.com/review/APC_11_OUT_SURG_W_TEL_COA_EA_APNP11VNT3_Surge_Suppressor/content_453665328772)
Thanks for the info saturation, don't you think this is worth putting on EEVBlog's wiki?
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For my bench, noise filtering is usually the number one concern, second is number of outlets and spacing. Its nice to see strips come with spacing for bricks now and rotating/swiveling sockets as well. The I find the cheap home strips need to replaced occasionally as I find the surge protection becomes inadequate over time (perhaps a few years). I live in an area with fairly noisy lines with frequent transients so this may play a part.
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Yes, it certainly can. I rarely have mine blow, I had one APC fail explosively after 12 years, and it was over 12 years old.
If you replace them frequently, a MOV only costs about 50c, a thermal fuse MOV combo about $1.60, and if they failed but the associated fuses are intact, you can replace them cheaper than buying a new surge protector.
If you buy an APC model they have a good history of honoring the lifetime warranty on failed SPD's for free for life, AFAIK. After my APC blew, I contacted APC and they sent me a new one in the mail even before I mailed mine out.
(http://ecx.images-amazon.com/images/I/31YBTYDMqiL.jpg)
http://www.amazon.com/review/RX94MQ90PBJM8/ref=cm_cr_pr_perm?ie=UTF8&ASIN=B00000J3WW&nodeID=&tag=&linkCode= (http://www.amazon.com/review/RX94MQ90PBJM8/ref=cm_cr_pr_perm?ie=UTF8&ASIN=B00000J3WW&nodeID=&tag=&linkCode=)
An example of a bad experience with a surge:
http://www.amazon.com/Belkin-F5C895-TEL-SurgeMaster-8-Outlet-Protector/dp/B00000J1RU/ref=wl_it_dp_o_npd?ie=UTF8&coliid=I3RZVU2J95MR80&colid=EIWMTQB99Q0R (http://www.amazon.com/Belkin-F5C895-TEL-SurgeMaster-8-Outlet-Protector/dp/B00000J1RU/ref=wl_it_dp_o_npd?ie=UTF8&coliid=I3RZVU2J95MR80&colid=EIWMTQB99Q0R)
UL 1449, the spec for SPD, changed recently, and any home SPD over 10 years old is obsolete, if they don't have thermal fusing it should be upgraded or modded by the owner otherwise its a fire risk.
For my bench, noise filtering is usually the number one concern, second is number of outlets and spacing. Its nice to see strips come with spacing for bricks now and rotating/swiveling sockets as well. The I find the cheap home strips need to replaced occasionally as I find the surge protection becomes inadequate over time (perhaps a few years). I live in an area with fairly noisy lines with frequent transients so this may play a part.
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MOV work by shunting the surge current to ground; if the ground is somehow removed [ that's why good surge protectors have a ground fault light] the MOV will absorb the energy.
Sorry for thread necroing, but this is interesting. Often there are places with no grounded outlets whatsoever, so I'm forced with this temporary handicap. So my question is: Does any kind of surge protector work this way (MOV energy absorbtion) without a grounding?
What you're saying is quite positive considering what all the naysayers on the interwebz are claiming
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TrippLite Isobar has been an industry standard surge suppressor.
I know this is a marketing picture but I can't say that it should be too far off...
(http://g-ecx.images-amazon.com/images/G/01/electronics/detail-page2/tripplite_isoultra_parts2.jpg)
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Sorry for thread necroing, but this is interesting. Often there are places with no grounded outlets whatsoever, so I'm forced with this temporary handicap. So my question is: Does any kind of surge protector work this way (MOV energy absorbtion) without a grounding?
Are surges really your biggest worry if the installation lacks any ground connection? I would avoid using any IEC class I equipment, like desktop computers and oscilloscopes, which rely on a solid ground connection for safety in case of faults. Using a class I appliance without ground connection will often result on a high-impedance mains/2 voltage on the case due to the capacitive divider in the EMI filter and can expose the user to mains voltage after a single fault, as opposed to class II equipment or class I with ground connection, which is designed to be safe in the case of a single fault. Class II appliances don't require (or have) a ground connection, so they should be safe.
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Sorry for thread necroing, but this is interesting. Often there are places with no grounded outlets whatsoever, so I'm forced with this temporary handicap. So my question is: Does any kind of surge protector work this way (MOV energy absorbtion) without a grounding?
Are surges really your biggest worry if the installation lacks any ground connection? I would avoid using any IEC class I equipment, like desktop computers and oscilloscopes, which rely on a solid ground connection for safety in case of faults. Using a class I appliance without ground connection will often result on a high-impedance mains/2 voltage on the case due to the capacitive divider in the EMI filter and can expose the user to mains voltage after a single fault, as opposed to class II equipment or class I with ground connection, which is designed to be safe in the case of a single fault. Class II appliances don't require (or have) a ground connection, so they should be safe.
So basically you want to avoid desktop computers ? ::) Sadly people still want to use desktop computers , unless you live in a cave .
But i would question whether you typed that on a laptop or a desktop :-X
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Sorry for thread necroing, but this is interesting. Often there are places with no grounded outlets whatsoever, so I'm forced with this temporary handicap. So my question is: Does any kind of surge protector work this way (MOV energy absorbtion) without a grounding?
Are surges really your biggest worry if the installation lacks any ground connection? I would avoid using any IEC class I equipment, like desktop computers and oscilloscopes, which rely on a solid ground connection for safety in case of faults. Using a class I appliance without ground connection will often result on a high-impedance mains/2 voltage on the case due to the capacitive divider in the EMI filter and can expose the user to mains voltage after a single fault, as opposed to class II equipment or class I with ground connection, which is designed to be safe in the case of a single fault. Class II appliances don't require (or have) a ground connection, so they should be safe.
I prefer power strips with individual switches.
Hello alm,
can you please elaborate further regarding these class II equipment? What are the common class II equipment and how do we tell them apart without looking at the wiring?
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I'll give another vote to the Tripplite units. They really should throw a couple extra mounts in the box, but the units themselves have fantastic build quality. I've always plugged them into cheaper 2 outlet surge protectors hoping it would sacrifice itself in case something really bad happened and save the Tripplite. So far that's worked quite well.
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I'm really not keen on having surge protectors in power strips for a few reasons:
- Combining the two means you'll be making compromises with both
- I hate the idea of having distributed fire starting boxes around my house
- In London, power is very, very clean in terms of surges and overvoltage. The maximum overvoltage we have had is around 12V in the last 2 years. I don't measure for quick transients, but have no reason to suspect there are any. Benefits of underground cables.
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So basically you want to avoid desktop computers ? ::) Sadly people still want to use desktop computers , unless you live in a cave .
Then have an electrician install grounded sockets.
But i would question whether you typed that on a laptop or a desktop :-X
On a battery powered laptop without any mains or ground connection, your point being?
can you please elaborate further regarding these class II equipment? What are the common class II equipment and how do we tell them apart without looking at the wiring?
I'm talking about IEC protection classes (http://en.wikipedia.org/wiki/Appliance_classes). The most common by far are class I and class II.
Class I equipment, which always has a grounded plug, requires only single isolation for any conductor, but relies on a grounded case to prevent a single fault from being harmful. A fault (eg. damaged insulation) will result in a short to ground, which will blow the fuse or GFCI. Without ground, it would result in the case being elevated to mains potential.
Class II always has an ungrounded plug, and relies on double insulation instead of grounding. Clearances and creepage distances are doubled, and conductors might have two layers of insulation or reinforced insulation around conductors. This makes the chance of someone coming into contact with hazardous voltages equivalent to the occurrence of two faults.
Class II equipment is becoming more and more common since it's still safe in the absence of a ground connection.
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A well made PSU for most devices can take more abuse than most folks know, and there is logic to having your device die from a surge rather that risk a fire from MOV overload; a poorly made surge protector is more a risk than a power strip, which is simply a set of conductors, circuit breaker and a switch [ just make sure they all look properly rated for load], I open strips and all my surge protectors and confirm they are well made and if a power strip alone, there are no MOVs in side:
http://www.avsforum.com/avs-vb/showthread.php?p=15356579#post15356579 (http://www.avsforum.com/avs-vb/showthread.php?p=15356579#post15356579)
Triplite used to be a great name in surge protectors, but after sampling there new isobars made in China they are made so badly, I wouldn't consider them in the same league as APC, which so far has been consistent since 1990s. I have not destructively tested any of them but just gauge their worth based on the assembly of the units and the 2 APCs that have actual died in surges.
I'm really not keen on having surge protectors in power strips for a few reasons:
- Combining the two means you'll be making compromises with both
- I hate the idea of having distributed fire starting boxes around my house
- In London, power is very, very clean in terms of surges and overvoltage. The maximum overvoltage we have had is around 12V in the last 2 years. I don't measure for quick transients, but have no reason to suspect there are any. Benefits of underground cables.
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It should be remembered that any device that is connected to two different ports, like an ADSL modem or so, it connects to electrical network and phone line. It can still be destroyed even if protected by SPD, if enough voltage develops between phone line and mains earth. Or if there are two computers interconnected via ethernet or something like that. It is imperative to ensure that those will see the same potential in event of surge.
So for that reason, I tend to think that proper surge protection is more system level issue, than per device issue.
I prefer at least two stages of surge protection, one heavy duty at distribution panel (levels 1 & 2), and then finer and faster near the equipment to be protected (level 3). Idea is to absorb bulk of the surge at beefier device. I had a close call last summer, a lighting stroke nearby and I heard a sharp snap from somewhere in mains outlet. We have underground low voltage 400 VAC cabling, but "mid-voltage" 20 kV distribution is mostly above ground. However I haven't observed any damage so far. After that I decided to have that distribution panel level SPD installed (levels 1+2 combo), a Phoenix Contact FLT-CP-3S-350. Although that is relatively expensive, it is still quite cheap (few hundred euros) when compared to most electronics devices, or some measuring equipment which can be easily destroyed by a surge pulse. Good thing in centralized SPD is that it ensures that ground potential will rise equally at all mains outlets, thus reducing damage potential for interconnected devices.
I know one case where our customer at work wondered why their equipment broke down at regular intervals at industrial building, it turned out that all breakdowns stopped when SPD was installed. It is not the mains frequency overvoltages that matter, but those microsecond-level surge pulses, which can reach levels of kV's. Switching large loads will generate surge pulses in mains.
Regards,
Janne
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Yes, your recommendation is the preferred method, jahonen.
I'm not sure if I linked this before, but here is a layperson geared brochure on total home protection, which incorporates level of protection at various junctions, from the supply line, distribution panel to the wall socket.
How much you need really depends on your risk for surges: where you live [ lightning prone or not] inductive loads at your location or nearby enough to couple into your wiring.
http://publications.usa.gov/USAFileDnld.php?Pub=pdf1329.pdf&PubID=1329&httpGetPubID=0&PHPSESSID=48kqd2tbjq3kp7t75qvvu90io4 (http://publications.usa.gov/USAFileDnld.php?Pub=pdf1329.pdf&PubID=1329&httpGetPubID=0&PHPSESSID=48kqd2tbjq3kp7t75qvvu90io4)
One thing that is often overlooked is EMF coupled into your structures wiring, it can induce surges that bypasses all mains protection, and thus the plug-in types are your last level of defense. Coupled EMF can enter through any lines: CATV or POTS telephone lines, even if the companies that provide such services already have system wide surge protection.
A practical problem is choosing a reputable surge protector, because you have to take it on faith that the maker makes good products, or do your own tear down analysis, since the only time you may know its not well made is when it fails to provide protection.
Folks who live in apartment complexes may not have to worry about surges, as many modern buildings provide whole building protection, but it can't hurt to have your own for those expensive items like large screen TVs or against EMF or inductive surges caused by other occupants.
It should be remembered that any device that is connected to two different ports, like an ADSL modem or so, it connects to electrical network and phone line. It can still be destroyed even if protected by SPD, if enough voltage develops between phone line and mains earth. Or if there are two computers interconnected via ethernet or something like that. It is imperative to ensure that those will see the same potential in event of surge.
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my ex gf called me up wondering why my tv wouldn't come on. so i checked it out and this is what i found... one mov failed closed and a blown hrc fuse. the rest of the components "survived", but instead of repairing i tossed the board and converted it into a 15a power strip. saved my 40" xbr, but two powered monitors (audio) were not so lucky. could have been unrelated though, as they have been known to have faulty power supplies. also not sure what she had the monitors plugged into. looks like the polyamide contained a good bit of the blast. anywho...
-sj
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Power strip:
according to Wiki.org,(http://en.wikipedia.org/wiki/Power_strip (http://en.wikipedia.org/wiki/Power_strip)) "In 1972, the electrical "power-board" was invented by Australian electrical engineer Peter Talbot working under Frank Bannigan, Managing Director of Australian company Kambrook. The product was hugely successful, however, it was not patented and market share was eventually lost to other manufacturers."
I've seen some really good designs yet still am using traditional old ones.
Just for the youngsters, here's one of the original Kambrook powerboards.
I've had this one since the mid 70's and it's still in use in the shed. The neon indicator stopped working long ago but otherwise, it will outlast me. :)
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Don't get too many post-mortems of SPDs blowing.
Who was the maker of the SPD? Do you know where the surge may have come from?
my ex gf called me up wondering why my tv wouldn't come on. so i checked it out and this is what i found...
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I have has MOV's as add ons for many years, and have had a few fail short circuit in that period. Luckily here the MCB has ruled supreme since the 1960's and earth leakage ( GFCI to the USA) has been a standard since then, only way you will not have one is if you bought a house in 1960 and never had any electrician out, or never replaced a socket outlet or light since then.
When they fail it just trips, and I need to go around and pull plugs until the circuit will reset, then replace the MOV's in the plugtop with new ones. They have saved a lot of equipment over the years from damage, even after lightning hit the building next door and blew a lot of electronics, never even knew anything had happened until I saw the pile of crisp at the bins. Dial up modem went through a surge suppression plugtop as well, it provided 2 levels of voltage protection to the phone line as well as more mains overvoltage filtering. I have a similar one on my ADSL line still, from old modems where the users refused to plug in the 2 leads to get the phone line protection, and had overhead phone lines. Might account for some of the 23.5 dB attenuation on the line, but still have a lot of margin. The record I know for that is lightning hit over 40km away and blew the entire exchange out. No phones for 2 weeks while it was ripped out and replaced entirely, nothing survived.
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Don't get too many post-mortems of SPDs blowing.
Who was the maker of the SPD?
Monster Cable PowerCenter AV800
Do you know where the surge may have come from?
lighting is very common here in Florida. most likely the source imo...
-sj
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Thanks sonicj; I've had 2 failures in my lifetime with a SPD, once in a Florida motel and another in the Pacific but never from Washington DC to Toronto.
Don't get too many post-mortems of SPDs blowing.
Who was the maker of the SPD?
Monster Cable PowerCenter AV800
Do you know where the surge may have come from?
lighting is very common here in Florida. most likely the source imo...
-sj
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On the subject of power strips, my Isobar has 3 different levels (50db, 75db, and 100db). Is there any real difference between these?
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First level is the incoming supply after the filter, between 1 and 2 they added an extra common mode choke assembly and so on for 3. They might have added extra X capacitors and MOV's in each stage, but they are limited in how much Y capacitors they can add before it will cause nuisance tripping due to earth line current.