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  1. #1
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    Default home surge protection

    A good friend of mine had an incident where a huge electrical surge (probably lightning) pretty much destroyed most of the home electronics, electrical appliances , HVAC, and other electrical devices causing a few thousand dollars of damage to the equipment with some being damaged beyond repair.

    The equipment that was attached to the (point of use) common type of surge protectors’ (suppressors) people mostly use didn’t help. These were the typical power bars with surge protection that we all blindly put our faith into. So in researching why these wouldn’t help I ran across information forgotten over the years also some interesting facts.

    Surge suppressors are not all they're cracked up to be. Most surge suppressors employ a device called an MOV (Metal Oxide Varistor). MOVs are variable resistors, typically made of zinc oxide (ZnO), and are very cheap to produce. Surge suppressors generally work by shorting voltage spikes directly to ground. This can, by the way, cause severe damage to any unprotected equipment that happens to be on the same circuit.
    Some MOV surge protectors short hot to neutral instead of shorting hot to ground, and while this may be somewhat safer, it is still not an ideal situation.

    Each time this happens, the MOV degrades, and it will eventually cease to perform. Depending on conditions, this can occur after only one or two lightning strikes or other power fluctuations, yet there is little or no indication that there is a problem.
    In some types the little light only indicates that the protector is still in-line and its internal fuse has not blown. It provides no indication as to the health of the MOV.
    Having a UL listed surge protector does not guarantee better protection. The UL listing for surge protectors does not test how well the MOVs will work, but only assure you that the MOVs will not burn down your building when they fail. Failed MOVs can cause fires; that's why most of them are now fused.

    Now it’s not to say these types of surge protectors shouldn’t be used. Rather than relying on this point of use surge protectors for abnormal surges from lighting or power line surges they seem to be fine for conditions that exist in the home. These would be normal or common mode surges or spikes from things like HVAC , fridges , freezers, washers , hair dryers , etc.

    So … in thinking about better protection from abnormal surges from lighting and power lines had led me to the direction for point of service type of protectors. The research I’ve come across seems to be agreed upon by different sources.... the point of service is the most effective means of protection. There are two types of these where one is mounted to the electrical service panel (example here) and the other is located at the meter box (example here). There is one utility company here offering these to people.
    Depending on the cost with this type of protection may have some financial benefit of insurance premiums being affected by claims and if the cost would offset the deductibles.

    I invite any comments or input to this.
    Last edited by canuk; 10-19-2007 at 11:48 PM. Reason: oops ... spelling errors

  2. #2
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    Default Re: home surge protection

    Great post.

    I do not do residential electrical projects but in commercial applications I see TVSSís specified on well over 50% of new panel installs associated with feeding computers or electronics. These are panel mounted TVSSís.

    I donít really know what brands or models are available for this type of application because the only type of TVSS I have ever seen specified is the Liebert AccuVar series of TVSS. We are talking about hundreds of different projects here.

    I donít know, maybe all of those engineers know something I donít.

    http://rmg.liebert.com/assets/produc...t/sl_22040.pdf

  3. #3
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    Default Re: home surge protection

    Kent , at what voltage does that suppressor " clamp " ?
    The problem with a lot of those strip type units is that they
    will pass 250 - 300 volt surges without reacting . The best protection for a computer is a UPS system . APC makes some great ones .

  4. #4
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    Default Re: home surge protection

    Quote Originally Posted by djohns View Post
    Kent , at what voltage does that suppressor " clamp " ?
    .
    .......I don't know, I'll fire an email to my Liebert rep with the question.

  5. #5
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    Default Re: home surge protection

    kent... how do they normally get wired to the panel?

    From what I've seen they are wired in after the main to 20 amp double pole breakers which I assume would be for each line leg ... so would they be the first breakers in the panel ? I'm guessing they would be the first ones so they would feed directly to the surge unit before the branch circuits .

  6. #6
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    Default Re: home surge protection

    Quote Originally Posted by canuk View Post
    kent... how do they normally get wired to the panel?

    From what I've seen they are wired in after the main to 20 amp double pole breakers which I assume would be for each line leg ... so would they be the first breakers in the panel ? I'm guessing they would be the first ones so they would feed directly to the surge unit before the branch circuits .
    I don't think you would want to put a circuit breaker in series with the suppressor . Connect it line to ground and " Let the hair go with the hide " .

  7. #7
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    Default Re: home surge protection

    I don't think you would want to put a circuit breaker in series with the suppressor .
    djohns ... check this link to see what I mean.
    http://www.sycomsurge.com/pdf/TC%20Wiring%20Diagram.pdf
    You'll see that it's wired to breakers which seems to be a common thing with others I've check on as well.

    Actually the hair has gone by the wayside



    The best protection for a computer is a UPS system .
    Uninterrupted Power Supplies are indeed the best protection though most are Standby Power Supplies ... that's a different topic.
    Last edited by canuk; 10-17-2007 at 11:18 PM.

  8. #8
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    Default Re: home surge protection

    An MOV is a variable resistor that changes resistance with voltage. Another type of varistor's change resistance with temperature. In almost all surge suppressors they are rated at 130vac so their resistance changes to maintain a differential of no more that 130vac. The big problem with MOV's is that their switch time is about 10ms and a lighting strike is about 10ns much to fast for the MOV to even react.

    The TVSS's clamp at + or - 15% nominal line voltage, that would be + or - 18vac for a 120volt unit and + or - 36vac for a 240vac unit. Switch time is 5ns

    UPS's (uninterpretable power supplies) come in two types one the load runs off the line until power is lost and then the inverter converts the batteries output to ac the second type the load is always running off the inverter and batteries the line only furnishes power to keep the batteries charged. The first can cause problems due to the switch time and because you are running off the line is only as good as the filters that are also in the unit. The second has 0 switch time and does the best job of filtering the power but are more expensive.

    There is absolutely nothing made that can guarantee protection from lightening. Lightening can jump across open switches and damage equipment that is not even on. Lightening is unique in that it can even come in on the ground line. The second UPS and possible the TVSS can only minimize chances.
    Jack
    Last edited by JLMCDANIEL; 10-18-2007 at 12:21 AM.
    Be sure you live your life, because you are a long time dead.-Scottish Proverb

  9. #9
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    Default Re: home surge protection

    Canuck , It appears that the manufacturer is more worried about protecting the suppressor than the equipment attached to it .
    If you want to insert a weak link into your protection circuit , have at it .

    JL , my computer has been running trouble free on an APC ,
    UPS system for years . When the power goes out , the computer never see's the interruption . I wouldn't be without one .

  10. #10
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    Default Re: home surge protection

    Thanks guys on the comments and input.

    That's the purpose of this discussion .... to feel out whether or not this is a direction to investigate.


    There is absolutely nothing made that can guarantee protection from lightening. Lightening can jump across open switches and damage equipment that is not even on. Lightening is unique in that it can even come in on the ground line.
    Jack,
    Absolutely agree about direct strikes , nothing will withstand that. Considering the arc flash seen from lightning that can be hundreds of feet long.

    It's more about the induced surge that occurs in the power lines from lightning and utility line issues. For example in rural areas where power fluctuations occur from agricultural and commercial equipment causing in-rush surges on power lines. These can originate from huge motors used in their operations when they first start them. I know of situations where these types of operations are restricted to when and how frequent they can start their equipment otherwise they are penalized by the utility companies. This can occur in urban centers where there are large commercial or manufacturing facilities as well.

    A lightning EM induced surge could originate anywhere upstream or downstream on the power lines. As you know this induced surge will act like a tidal wave moving in either direction ( up and/or downstream) and depending where you are along that line will determine the impact on you.

    These are the most common issues that would be addressed with suppressors.


    If you want to insert a weak link into your protection circuit , have at it .
    djohns,
    Curious .... why is it you feel the TVSS is a weak link.
    I'm interested in your thoughts.

    My personal feeling is they are no worse than the point of use surge protectors and if they provide the suppression at the service panel < 5ns.... that's quicker protection than allowing that surge to spread into the home.

    My original thought is the suppression located at the meter box minimizing the chance of the surges reaching the service panel ... this makes sense to me preventing the surges entering the home. At this point I haven't come across any pricing for these types.

    The TVSS which are at the service panel seem to be cost effective averaging between $250 - $350 considering that my insurance deductible is $500. So ... if they are indeed effective then it becomes economically feasible.



    JL , my computer has been running trouble free on an APC ,
    UPS system for years . When the power goes out , the computer never see's the interruption . I wouldn't be without one .
    Yep ... wouldn't be without one.
    The intention is back up power for sags,brownouts,total power loss of line power and depending on the type of unit will only provide the same surge protection as a typical point of use suppressor like a power strip. Like Jack mentioned there are different types that offer different degrees of protection.

    The common economical (SPS) standby power supply ... which is very similar to those back up light systems used in commercial buildings .... will have the same MOV surge protection as the power strips use. Since these types are on line during the normal operation the surge protection is only as effective as a power strip would be.
    An exception would be a form of (SPS) standby power supply known as ferro-resonance. They are similar to the common type of SPS though instead of a switch for providing battery/inverter power it utilizes a transformer for the switching. They will still have the common MOV suppression but ... the big difference is that the standby UPS's transfer switch that selects between power sources has been replaced by a ferro-resonant transformer. Since transformers have isolation and filtering characteristics these add to the filtering and suppression at the output.

    The true on-line interruptible power supply (UPS) are indeed the best type and offer the best protection though these are high end units. Since they are providing battery/inverter power output continuously and combined with the MOV suppression isolates the equipment plugged into them.

    Geez ... really taxing the old brain cells
    Last edited by canuk; 10-19-2007 at 11:51 PM. Reason: darn spelling

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