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I want to make my whole house surge protected, there are several solutions available

  1. You can install MOV based surge protection on the entire house in line entry point - first line of defense
  2. You can use socket surge protection, MOV based as well - third defense line, protecting individual appliance
  3. Junction box SPD if such a thing exists - second line of defense.


How much of such defensive layers of surge protection makes sense to install from economical and technical point of view?

kreuzerkrieg
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  • I don't know if layers are as important as the overall ability to absorb energy (usually measured in kA). Redundancy may be another issue altogether. – BrownRedHawk Mar 09 '15 at 20:47
  • 3 levels of redundancy? it is not military application :) As I understand, once the energy cannot be absorbed you get catastrophic failure in MOV or anywhere else in SPD and your appliances are safe. but the line will be in unusable state until you replace the SPD, so where the redundancy matters here? – kreuzerkrieg Mar 09 '15 at 20:54
  • It's possible for the MOV to fail open, so you'd be unprotected without another level of protection. – Johnny Mar 09 '15 at 21:28
  • This may shed some light; nothing really deals with a direct strike. http://diy.stackexchange.com/questions/51897/what-does-a-surge-protector-do-that-a-breaker-doesnt/51903#51903 – Ecnerwal Mar 09 '15 at 23:36
  • economical/technical point of view? That depends on the value of items you need to protect, the likely hood of surges and the amount of insurance coverage you have. If you have something that can not be lost, I would consider a dedicated offsite/offline backup first. As a surge is only one of many ways that data loss can happen. – diceless Mar 10 '15 at 04:49
  • @Johnny AFAIK MOV fails short and this is the point of good SPD - it will never leave your appliances unprotected – kreuzerkrieg Mar 10 '15 at 05:19
  • @kreuzerkrieg - if a surge overloads a MOV, it can [physically split open](http://www.zerosurge.com/technical-info/truth-about-movs/) and unless you were there to smell the smoke when it happened, you may never know that you're unprotected. [Wikipedia](https://en.wikipedia.org/wiki/Varistor#Hazards) also says: *If excessive current is conducted by a MOV, it may fail catastrophically, keeping the load connected, but now without any surge protection. A user may have no indication when the surge suppressor has failed.*. I've seen the split MOV in a number of failed surge protectors. – Johnny Mar 10 '15 at 15:37
  • @Johnny, some SPD manufacturers claim that in case of catastrophic failure the SPD will not supply a current to appliance. Namely APC and Belking. So I guess there are means available to detect MOV failure. – kreuzerkrieg Mar 10 '15 at 16:13
  • @kreuzerkrieg - they are all supposed to have overcurrent protection that will blow (and sometimes auto-reset) before the MOV does. That's not always the case. Indicator lights are also unreliable, especially on cheap consumer surge protectors. – Johnny Mar 10 '15 at 16:40

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Before you even start on surge protection, look at your service entrance ground and consider adding to it if it's inadequate by current standards (it may well have been adequate by code when it was built, and still be underbuilt by current standards.)

For instance, if there's a single ground rod, you might consider adding 1, 2 or even 3 more spaced 8-10 feet apart. An effective ground is the backbone on which anything else you do to deal with surges rests - if it's not good, nothing else will work very well.

The answer I linked in the comment explains pretty much what I do, which is a somewhat layered approach. I guess I can link it again here. What does a surge protector do that a breaker doesn't?

The version of "whole house" protection I use is not a "plugs into the panel like a set of breakers" thing, so you could run a second set in a (preferably steel) junction box closer to the end-use point if you wanted to. I think they fit inside a 6x6x4 box.

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Ecnerwal
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