Help Me Understand, and Choose, a Whole Home Surge Protection Device.

[A.Justice]

We have a ton of big storms with lots of lightning, and live on the highest point in the area. I also play with things that plug into the grid, so a local surge is always possible as well, and in fact might be more probable than a lightning strike.

I've been looking at the Siemens and Eaton whole home SPD's that wire into the breaker panel. They come with different interrupt ratings (60 70 100 140 160 250ka), and while I understand what that means, I have no idea which size is appropriate for what I need, and I can't find any documentation from the manufacturers that explain it clearly. They just show maps that tell you what you need. If that's the case, fine, but I'd really like to know WHY I need that size. Plus, there's a good deal on one of the smaller (60ka) ones locally, and I'd like to use that if possible.

I would also like to know if that style of SPD even works, there's really no tests, or way to test, for an average person. The few that are available on YouTube test at very low currents, and obviously can't simulate a lightning strike.

If anybody has one of these devices, or knows more about them, I would definitely appreciate some feedback!

 

[MurphyGuy]

SPD's have two important ratings. The first is the amount of current they can shunt to ground, the second is their reaction time.

Contrary to what a lot of folks thing, SPD's don't act like fuses or breakers where they trip and open if there's a spike. What they do is the exact opposite, they basically connect your 120 volt line directly to ground to direct the current away from your appliances, but that connection to ground is something that only lasts for stupidly short time frames.

When your power line experiences a spike, that spike is a rise in voltage to a level much higher than the typical 120 volts that supposed to be on each leg. Thing is, that rise in voltage only lasts for a very short time, typically measured in microseconds or milliseconds.

The first variable, the amount of current they can sink to ground, is based on the size of the spike you expect. No SPD will stop a direct hit from lightening, but most appliances damaged by lightening aren't damaged by direct strikes, they're damaged by a strike that is several hundred yards away (or more) and migrates into the house, or one that maybe strikes a highly conductive object on your house which sends most of the energy straight to ground and only a small fraction makes its way into your wiring.

The best SPD on the current market for residential applications is the Siemens FS140, which is what I have in my house. It has a response time that is fast enough to stop a conductive spike from a Nuclear EMP at only 1 nanosecond. That is way way faster than what is needed for lightening.

The Eaton units, SquareD, and most of the others, have response times in the low microsecond range, which is plenty fast enough for lightening, but not nearly fast enough for a conductive Nuclear EMP.

You are not limited to a single SPD. You can connect as many of them as you wish.

If you have something really important (like a home computer that supports your livelihood), you should put it on its own quality uninterruptible power supply instead of depending on an SPD, or in conjunction with the SPD.

My suggestion is not to screw around.. Get the Siemens FS140

 

[A.Justice]

I appreciate the advice. I did some research and that seems like the best option for me as well. More importantly, my wife agrees that it's a good idea.

 

[svetz]

When I looked at this before I liked the Midnight SPDs, but your power utility probably sells one (mine did... and found one already installed ; -)
There's also a basic thread on surges you might enjoy too.

 

[A.Justice]

It took me a while to get one (sold out everywhere), but I am now the proud owner of an installed Siemens FS140.

I appreciate the advice.

 

[MurphyGuy]

It took me a while to get one (sold out everywhere), but I am now the proud owner of an installed Siemens FS140.

I appreciate the advice.

Damn, I just looked at the price on those FS140's. When I bought mine in 2019, I paid about $160, they're $300 now. WTF?

You know what else is sold out of stock everywhere? Geiger counters.

I've also been building Faraday cages for people lately and am having a hard time getting the special conductive seals now.

 

[A.Justice]

Damn, I just looked at the price on those FS140's. When I bought mine in 2019, I paid about $160, they're $300 now. WTF?

You know what else is sold out of stock everywhere? Geiger counters.

I've also been building Faraday cages for people lately and am having a hard time getting the special conductive seals now.

Yeah, it was hard to stomach paying that much, I think I ended up paying like $340 shipped. Still worth it if it protects even one device though.

There's definitely a concerning amount of prep and military surplus items disappearing. People are starting to wake up.