Thunderstorms, do I always need to unplug?

You should go out in a lightning storm with a kite, and place a key on the string. Have a Leyden jar connected by a string to absorb the energy from the lightning strike. This will protect your home and audio equipment inside.

This isn’t true. Lightning takes the point of least resistance and at the sort of current it has, the material doesn’t matter much. The height and geography of the immediate area is more a factor.

For example, metal clad houses don’t get struck any more often than surrounding wood or masonry structures.

The main thing with lightning rods is that they are durable to wind, last long and are connected to ground.

Similar to the reply by Richard D, a few years back we had a lightning strike several hundred metres from the house yet it still damaged wiring in the house despite a very modern consumer unit. I’d unplugged almost everything beforehand and was glad I had but since I didn’t unplug the phones and broadband box it wrecked those.

The power of lightning strikes was illustrated for our family some 40 years ago. My younger brother was living with our parents in Dorset (Southern England). He was a farm worker and watched two cows in a field being killed by lightning strikes. He went home to find my parent’s house surrounded by firefighters. The incoming mains supply had taken a direct hit. The roof caught fire and despite the best efforts of the fighters, the house was largely destroyed.

I agree. Searched first the statistics on damaged electrical equipments by thunderstorms, but couldn’t find. They certainly occur much more often than physical damages on persons.

When I worked at the Naim factory I certainly saw a number of pieces of equipment come into the service department that had been damaged from the effects of a lightning strike on or near the property. I’m sure @NeilS can confirm.

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While non-metallic materials can be struck by lightning, it will follow the path of least resistance, and that will tend to be whatever metal it finds. Otherwise lightning conductors wouldn’t work and connected electrical devices wouldn’t be the most commonly damaged items.
Most lightning damage is not caused by direct hits. When it gets into the ground it can enter buildings by following metal pipes or cables, and exposed overhead cables can also carry a close strike into a building.

Thats not so far from the truth. You can get lightning ‘poles’ here for country places with enough land to plant one in. Stick a metal cone on a tall stick and ground it.

When I was young my house was hit. The flash and sound was incredible, it lit the whole garden up. It hit my amateur radio antenna and melted the plug, which I’d unplugged, which shot across the room narrowly missing my brother. When we went outside half of our neighbours were in the street already. There was very little left of the antenna and in my bedroom half the electrics were destroyed. I unplug every time now

That doesnt sound dangerous at all

Having spent hours discussing the ins and outs of building materials, cladding and so forth with our structural engineers and cladding specialist none of that appears to be true. Electrical devices are damaged because of their proximity to a strike and the fact they are conductive. Collateral damage if you will. They don’t increase the chance of strike itself or invite it. Lightning rods use the best and most affordable material that can stick up high and be resistant to the elements, and be connected to ground, so metal is chosen.

If your house is clad top to bottom with metal and surrounded by wooden houses, it won’t get struck more than them unless it is also taller. To offer meaningful lower resistance via material, you really need to be talking about a massive iron girder like in a sky scraper. This is why corner flats of high rises get struck more often than the roof with the lightning rod.

The distance (or closer proximity) provides less resistance than the choice between a conductive and poorly conductive material. If you stand in a field in a lightning storm next to a flat iron plate on the ground, you’re far more likely to be the path of least resistance than the plate.

Least resistance is never dictated by material unless all other variables are equal.

Isn’t that why lightning does actually strike twice ( or multiple times) at the same place. Positive charges built up on the ground then provide the path to the negative in the clouds. Its the ground positives that dictate the lightning path, and are often generated in the same place.

Lightning conductors are not only arranged to be above the highest point of the building, but they invariably end in spikes. That is a key factor in their effectiveness in attracting lightning to then, more so than the fact that they are connected directly to a good earth by a metal bar. The physics is interesting - established recognised by Benjamin Franklin - invented the first lightning conductors to protect buildings, and have been used ever since.

The spike effect may explain why aerials are may attract lightning.

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Basic physics. Positive ions/charge gather at the pointed part of a body.

Lightning occurs when the positive ions at ground level are massed enough to provide a superior path or route to connect to negative charges in the air. Higher the pointy bit the nearer it is to the negative charge in the atmosphere.

So if you can provide a high spikey metal cap with a good connection to ground, but far away enough from the house to not have the charge run through the ground and the house, then Bobs your wotsit.

That doesn’t help most of us though. Just unplug to be safe, or have good insurance.

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The simple fact is that devices with a connection to a copper cable, whether Ethernet, mains power, TV aerial or whatever, are far more likely to attract a lightnjng strike and be damaged than one that is not connected. If you think it’s OK to disregard Naim’s advice to unplug your HiFi you are free to do so. I shall be continuing to unplug mine when electrical storms are forecast. I’ve had my house hit by lightning 3 times that I’m aware of, and on each of those occasions connected devices have been damaged. Unconnected electrical devices have not - I don’t think that will come as a surprise to most people.

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We do see a few from time to time, damage can range from just the input transistor pair to complete devastation.

I remember a network player coming in from Germany (I think), together with the router. The Ethernet cables were welded into their sockets.
We also had an incident where a tuner suffered a strike (probably not a direct one) while on soak at the factory - it left a scorch mark on the shelf above.


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When my fried Unitiserve went back to Naim to see what could be salvaged it looked perfectly OK from the outside apart from some slight charring on the Ethernet socket. The rebuild cost was almost as much as replacement, so I didn’t bother.

Er… but isn’t that about 15 grand?!!

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@frenchrooster is very skilled at finding exotic things on the internet - and presenting them as normal things! Some of them undoubtedly would make for good ways to use a good lottery win!


I’ve not said that. You’ve misunderstood my post.