Lightning protection system

I’m looking for reliable information about a diy lightning protection system. Separate and apart from the solar system and electrical system of my cabin. Though providing the possibility of protection for both.

I’m seeing a lot of snake-oil type sales stuff. Shirley this is something that can be a diy project. It seems pretty simple in concept. Particularly as I have a flat, square roof about 30 feet above my array.

Has anyone been down this path? I suspect the materials cost will be significant.

Thanks

Very expensive.
Cheaper to replace damaged equipment, at the residential level.

I was thinking more of protecting the building itself. It stands pretty tall compared to the surrounding forest.

Bluedog225 said:

I was thinking more of protecting the building itself. It stands pretty tall compared to the surrounding forest.

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Brief overly simplified description:
Air terminals spaced about every 20', around the perimeter of the roof.
A 3/0 fine strand braided copper conductor ran down to ground level from each to a ground rod.
A loop of the same conductor connecting all air terminals together.
Another loop connecting all ground rods together.
The entire system is electrically isolated from the building and building systems. With the exception of one #6 GEC from the electrical system ground rod to the nearest lighting protection systems ground rod.

It's expensive to control a lighting bolt.

Thanks. Interesting that there is a point of connection between the electrical system ground rod to eh lightning protection ground rod.

Alternatively plant highly invasive giant bamboo close to the house within a few years you will have eco lighting rods that explode when hit, that's what we have...

Bluedog225 said:

I’m looking for reliable information about a diy lightning protection system. Separate and apart from the solar system and electrical system of my cabin. Though providing the possibility of protection for both.

I’m seeing a lot of snake-oil type sales stuff. Shirley this is something that can be a diy project. It seems pretty simple in concept. Particularly as I have a flat, square roof about 30 feet above my array.

Has anyone been down this path? I suspect the materials cost will be significant.

Thanks

Click to expand...

Just used Midnite Solar SPDs and hoped for the best..

Not sure lighting arrestors ( those that look like dandelions on a pole) to ground help or hurt?

Bluedog225 said:

Thanks. Interesting that there is a point of connection between the electrical system ground rod to eh lightning protection ground rod.

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This makes the lighting protection system electrically safe.
(Everything conductive must remain safe to touch)

timselectric said:

This makes the lighting protection system electrically safe.
(Everything conductive must remain safe to touch)

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I think it defeats the whole purpose of the lightning protection system to connect it to the very system you are trying to protect.

Quattrohead said:

I think it defeats the whole purpose of the lightning protection system to connect it to the very system you are trying to protect.

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A bonding connection is necessary for personal safety.
The reason that it's connected in this manner (rod to rod) is so that it doesn't defeat the purpose.
The goal of a lightning protection system is to direct lightning around and away from the things you want to protect, instead of through them.

Personally, I find that lightning is rather hard to predict, and doesn't always strike the most obvious place. E.g., big oaks on the top of a ridge are spared, while smaller trees a third of the way down the slope get blasted. We've had lightning damage in more than one piece of equipment, in more than one house, yet never from a direct strike.

I'd argue Tim is right, and it's easier to replace equipment than to attempt an elaborate system. Drive your ground rods in, hook everything to them properly, and pay your insurance premium, is our approach. BTW, current project is building a 36x44 gambrel roof barn, built with wood framing but wearing an enormous metal "coat" as exterior cladding, sitting in the middle of a field. Now where did I put those rubber-soled boots?...

There are so many overpriced products in this space you can spend a lot and still have crap protection if your surge protection system is not done correctly. I highly suggest reading this document https://www.eaton.com/content/dam/e...arthing-surge-protection-application-note.pdf

Even if you don't use Eaton products.

I can't say anything about the American market, but at least here in EU we broadly have 3 types of SPD (surge protection devices). Within these classes there are also voltage levels to pay attention to. Personally (being EE educated, but not working in this area) I'm perfectly happy with typical Type 1,2,3 SPDs from any reputable manufacturer. No need to be going to various pretty/expensive devices with blinking lights etc (although ability to see the status clearly is definitely a good thing). The types are not better/worse. Broadly speaking they offer protection at different levels like this:
- type 1 - protects cabling insulation from breakdown (compulsory in EU for any building with lightning protection)
- type 2 - protect insulation within appliances like electric motor windings, simple electric devices. (combined with type 1 most often and installed as Type 1+2 in the electric panel)
- type 3 - protects specific devices like PCs, electronics. Most often installed at the device being protected, for example on the generator input of a an AC charger, but devices that combine Type 1+2+3 exist for panel mounts. Sometimes Type 1 is called B, Type 2 C and Type 3 D.

The bottom line, your SPD's will be only as effective as the quality of your grounding. The key to the game is to lower the impedance. However if you have to protect a single point grounded system you can often make do with less than ideal ground - the document linked described how. With multiple buildings and additional comms wires things get complicated quick.

timselectric said:

A bonding connection is necessary for personal safety.
The reason that it's connected in this manner (rod to rod) is so that it doesn't defeat the purpose.
The goal of a lightning protection system is to direct lightning around and away from the things you want to protect, instead of through them.

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I agree but still don't like it.
If the spikes are on the roof and the copper braid/wire is insulated running from the roof to the ground rod, that should satisfy the safety aspect.

Ultimately, Mother Nature will answer these questions in her own time and way.

Quattrohead said:

I agree but still don't like it.
If the spikes are on the roof and the copper braid/wire is insulated running from the roof to the ground rod, that should satisfy the safety aspect.

Ultimately, Mother Nature will answer these questions in her own time and way.

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I don't think you can get insulated coarse-weave copper. You need the coarse weave to limit skin effect IIRC.

Directly connecting the two at the ground rods posesl the lowest risk. If you are going to spend the money you might as well do it right.

The "streamer terminal" snake-oil solutions are actually widely used in many countries and are pretty effective if properly installed and maintained. Another approach is to go for a catenary wire system for complete isolation from the structure, but that is an order of magnitude more expensive.

This is the streamer terminals in action; each of the strikes is to one of the terminals and it helps to dissipate the energy. Not my photo, but I worked on the project a long time ago.

Are you at a location that this is a concern? I've spent tens of thousands of dollars of other peoples money on lightning protection but these were radio towers on mountain tops. We used to call some of them the county lightning rod. Unless you're on an exposed hill in a lightning prone area, the risk is actually quite small that you'll ever experience a direct strike. Quality surge suppressors on the AC mains will catch anything from near earth strikes that gets inducted in to the grid. My go to surge suppressor products have been Atlantic Scientific (now Eaton) for AC and DC circuits ans Polyphaser for RF.

I wonder why 3/0 is needed per air terminal when solid bare #4 copper will handle multiple 50kA strikes without melting. Is this code being unreasonably overkill again?

In terms of where you spend your money, I'd vote to spend it this way first:

1. SPD at load panel, protecting all circuits (level 2 SPD - load panel level)
2. SPD at (expensive) electrical devices/appliances, protecting that device/appliance (level 3 SPD - device level)
3. SPD to protect from grid (if grid-connected), SPD on your inverter (if off-grid, and inverter supports) (level 1 SPD - grid/inverter level)
4. LPS if there's some reason for it (ham shack full of $1000's of gear, money to burn, etc.)

Most danger is surge from the grid (this is most likely source, not lightning), next danger is a surge from "nearby" lightning strike (through the earth to your wiring, this is less likely than the grid, but every area of the country is different in lightning strike potential), next danger is micro-surges from every other device in your house (too many devices, too many standards, too many manufacturers of dubious quality).

Because many vendors offer it, you can throw an SPD directly on your inverter (my pre-wired magnum has two midnite solar SPD's wired in). Takes some homework to figure out why you have these, and the scenarios where it is helping you. Midnite solar SPD's are effective and *visual*, so you know if they're still good and effective, whereas I have to open up the load panel to see if my level 2 SPD is still effective (check the led's). As in my case, these came pre-wired, so it was my first occurrence of SPD at that level, in my home wiring ... inverter went in, SPD was there. Only later did I chase down info on surges, and got the other levels in.

In America, we also have a tiered system of SPD's, although a homeowner would have to hunt the information down. Electricians know about it, and codes speak to it (I believe #1 is now in the electrical codes). There are also descriptive/install documents on LPS's, but you'll have to hunt those down as well.

I learned about SPD while chasing down THD. It turns out that surges are a big problem (and we can easily do something about it), and THD pales in comparison (as in, we can't do anything about THD). We can also do something about LPS, but at some amount of cost.

Still pondering LPS, but only because I do have some ham shack gear, electronics workbench gear, etc. Just lacking in the "money to burn" category.

You can't do enough homework ... perhaps if you buy your electrician a beer, you could pump them for their take on these subjects!

Hope this helps ...

Quattrohead said:

I agree but still don't like it.
If the spikes are on the roof and the copper braid/wire is insulated running from the roof to the ground rod, that should satisfy the safety aspect.

Ultimately, Mother Nature will answer these questions in her own time and way.

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The problem is that if the ( un bonded) lighting protection system somehow inadvertently becomes electrified. A person could be on the roof, maybe making repairs.
And if they touched an air terminal, while holding a piece of equipment that is (should be) grounded/bonded, they would be shocked.
Even a small shock on a roof, can lead to death from falling.
The most important thing about electricity is safety. And anything that can be touched, should always remain safe to touch.

AntronX said:

I wonder why 3/0 is needed per air terminal when solid bare #4 copper will handle multiple 50kA strikes without melting. Is this code being unreasonably overkill again?

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I’ve seen alu wire offered.

AntronX said:

I wonder why 3/0 is needed per air terminal when solid bare #4 copper will handle multiple 50kA strikes without melting. Is this code being unreasonably overkill again?

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I really don't know if it was a code requirement. I don't know anything about lightning protection system codes. They were all engineered systems, and I just followed the drawings.
I just know that it's what we always used. Maybe it was just the industry standard. Or maybe it was the most readily available.

AntronX said:

I wonder why 3/0 is needed per air terminal when solid bare #4 copper will handle multiple 50kA strikes without melting. Is this code being unreasonably overkill again?

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Skin effect. High frequency current travels in the outermost part of a solid conductor. A lighting strike transient is in the megahertz range, so the impedance of the conductor is ~250x higher. You manage this to a degree with course braided conductors, but you need more copper no matter what.