HACKER Q&A
📣 TowerTall

My house just got hit by lightning and it fried the PSU in my computer


If everything is wired correctly in my house, should all equipment attached to my UPS have survived this with no impact or is a direct lightning strike so powerful that even high-quality home-grade UPS must give up?

My computers were connected to an UPS surge projector. Various kitchen machinery and extension sockets that was not doesn't work anymore. The neighbor's TV blew.

There was a bright white flash inside of my living room, just under an open window and directly above the my UPS surge protector and then all my devices turned off including the surge projector. The PSU in one of the computers is gone, but not the motherboard and rest.

I was sitting on the concrete floor in the middle of the room watching it happen.

I live in Thailand in the middle of a big flat coconut groove with only two houses. Except for the palm trees, my house is the tallest structure in a 200 x 200 meters (300 feet)+ area and we have frequent huge thunder storms, but this one was in a category on its own. It made my concrete walls tremble. It was so intense. Spectacular show by nature.

Only two months ago, I bought a socket outlet tester. It reported that my sockets was not grounded. I got an electricians out to fix that. I suspect this is the reason why the lightning chooses me. We have frequent big thunderstorms and haven't had this issue before, but now there is a ground connection.

I don't know if there is a proper grounding rod. There is a cable going from the house into the ground, but I don't know what it is attached too. The rest of the electric installation is amateur's business so could be connected to nothing. The house is a long-term rental and the electric installation came with it, but I can change it regardless of it's is a rental.

The electricity doesn't even come directly from the power company's cables. It goes in to the owners house, where the meter is. From there they have pulled a 200 meter cable into ours. There is a fuse box in my house.

Any suggestions on what to do next? A big metal stick somewhere in the garden?


  👤 osamagirl69 Accepted Answer ✓
A lightning bolt carries a current upwards of 100,000 amps, and has upwards of 10 billion joules of energy.

A high end consumer grade surge suppressor might be rated for 1000 joules, and a few thousand amps of peak current.

If lightning directly strikes your house wiring, no amount of surge suppressors are going to save you.

For an idea of what a surge suppressor that can handle the blow of a full on lightning strike looks like, take a look at the units used by utility companies on their high tension lines. Typically they are about a 6" in diameter and often several feet long -- and those units still need to be replaced after a single direct hit! https://www.equipmentimes.com/product/details/Lightning-Arre...

The best thing that you can do to protect yourself in the future is to have a lightning rod network installed on your roof, which will shunt the current from the strike directly to the ground. Otherwise the only failsafe alternative is to completely unplug sensitive equipment (still OK to run from battery but with all ethernet etc cables unplugged -- wireless network only) whenever there is a storm predicted.


👤 nonrandomstring
Electrostatic forces like lightning don't behave like regular AC/DC electricity. Around a massive discharge you get high field strengths that can induce potentials in objects not even connected. This is the EMP (electro-magnetic pulse). Sounds like the strike was close to you and you should be glad you only lost a PSU.

In modern electronics it's small capacitive gaps that get damaged. Electrolytic capacitors and CMOS gates get their insulation punched through, which destroys the component. As plastic housings have replaced metal ones there's little or no field shielding on gear these days.

As others have said, for prevention your supply circuits should be earthed. They should be anyway, for human health and safety reasons, including an earth rod (long copper pipe or pole driven down into soil at least 1 meter) so your earth return is not too far away. Usually you also want an earth leakage sensor set to cut the supply if any current is flowing through the earth circuit - very useful in a damp/rainy environment.

Problem is; most switched mode PSUs use only the active pair (live and neutral in single phase European terminology) so there's nowhere for errant currents to go. Often they have an arrestor, as old copper telephone systems did, and the idea is that it arcs across, closes the arrestor and shorts the path (often blowing a fuse). With nearby lightning you get >100kV very fast, and it all happens too quick.


👤 gubby
For some types of power supply, not having a proper ground can dangerous for reasons many people don’t realise. It’s not just about fault currents ‘flowing to ground’. Should just the supply neutral become disconnected, such as during high wind, then without a proper ground setup every metal item in your house that is grounded (such as microwave cases) can become live. It depends on how things are configured, but this type of lethal fault is a real possibility if neutral and ground are bonded at your house as they often are.

In the case where your power is derived from another property as you describe, in the UK we would normally call this a ‘TT’ power supply which you can google. It is absolutely essential (life and death) to have both a good grounding rod and an RCD at your end.

A others have said, get an electrician who understands the subtleties of outbuilding power supplies. If you cannot do that for whatever reason, I suggest first reading up extensively on the different kinds of earthing system, and finding out which one you effectively have.

Since you had no ground previously, it is likely that just live and neutral have been exported from your neighbours property (TT). You can probably check this by visual inspection, and it isn’t actually a problem provided you fix the grounding and protection at your end. To fix this grounding problem what happened? Did the electrician install a grounding rod? Did they happen to measure the impedance of it and write that somewhere? Do you have an RCD in your consumer unit (fuse box)?


👤 mschuster91
> Except for the palm trees, my house is the tallest structure in a 200 x 200 meters (300 feet)+ area

Do you have a lightning rod on the house? If not, you absolutely need one, and you have to make sure it has a proper grounding rod. If you don't know if the one that is there is reliable, put in a new one.

> It goes in to the owners house, where the meter is. From there they have pulled a 200 meter cable into ours.

... and let me guess there is no grounding connection at your house but only at the owner's house?

> Any suggestions on what to do next? A big metal stick somewhere in the garden?

For starters - I'll base it on German standards:

- generally, get a licensed electrician on site to review your whole electric installation. It may be severely damaged (e.g. by overvoltage breaking down the isolation of the wires)!

- both your house and the owner's house each need a proper, separate grounding rod for the electrical system. The closer to the house, the better. In Germany, it's standard practice to have one horizontal rod below the foundation and a separate vertical deep-going rod. You can have the electrician measure the quality of the grounding.

- both your house and the owner's house each need lightning rod(s) on the roof connected to the building's grounding rod

- your surge protector in the UPS isn't able to take a full lightning strike, which is why lightning protection usually needs three stages: the first one made out of spark gaps is directly at the point where the electric supply line enters the house, it will take out the brunt of the lightning strike but still leave a dangerously high overvoltage. The second stage is in the distribution cabinet, here varistors are used. The third stage is your UPS's SPD. And it will always need all three stages to work - leave one out and the system becomes useless!

- you also need lightning protection for the phone line and the TV antenna. In the latter case you need to protect the antenna itself by attaching the mast to the lightning rod and the antenna cable / distributor with an appropriate SPD system.


👤 kaetemi
I had ground added to my house in the Philippines. The electrician will not do it correctly until you specify exactly what you need. They will always bias towards the cheapest option, because that is what most people want here. You need to specify to install a grounding rod, as well as the length. Consult your local electric code.

I'm guessing your electrician connected your ground wire to the roof, or some other part of your house construction. That gives you a nice path for lightning to go between the utility neutral and your roof through your appliances.


👤 londons_explore
If you're the tallest thing for 200m and in an area with frequent lightning storms, you should get a lightning rod installed.

It's just a metal rod from the tallest bit of your building to the ground. It can be installed without much specialist skill, so should be cheap.

With that, the rest of your electrics will be fine in the future.

To repair your outlets, call a local electrician. It will probably just require a new breaker in the fusebox (breakers get damaged if lightning levels of current flow through them, then then they will refuse to turn on). The PSU is probably repairable if you find an electronics guy - it will need new diodes right at the input. Maybe a new fusable resistor too. But if youre paying USA labour rates, it's cheaper to just buy a new PSU.


👤 tuatoru
> Any suggestions on what to do next?

IMMEDIATELY turn off the power at the main circuit breaker.

NEXT, get a registered/bonded electrician to thoroughly inspect and test your building's power feed, its circuits, its grounding, and its surge protection equipment.

Until you do this, your building is a fire trap waiting to strike.

The building's surge/overvoltage protective devices should all be replaced, or some installed if there weren't any.

Some or all of the wiring may need to be replaced if its insulation was crisped.

Next, get all your electrical appliances checked for safety.


👤 pubby
The foolproof method is to unplug electronics when thunderstorms come.

👤 TowerTall
Updated the post. It sounded like it was an ad for an UPS and it is not, so I rewrote parts of it. Sorry about that

👤 adinisom
Grounding is important for shunting the surge to ground.

Keep in mind: surge protectors and UPSes are not necessarily going to prevent damage directly caused by lightning. Lightning has a lot of energy and is high frequency and can make its own paths to ground through and around protective devices.

Lightning strikes cause power outages in a larger area. When power returns, you can get a high voltage surge. This is what surge protection suppresses and protects against.


👤 formerly_proven
> There was a bright white flash inside of my living room, just under an open window and directly above the my UPS surge protector and then all my devices turned off including the surge projector. The PSU in one of the computers is gone, but not the motherboard and rest.

Sounds like a perfectly cromulent outcome to me, if accurate, you're actually pretty lucky.


👤 ajb
It's quite likely that the stuff connected to your UPS is also burned out. I hope you are lucky and it is not.

If your hard disk is a magnetic one rather than an SSD, it's possible that the data will have survived, even if the electronics died. HD retrieval companies work by swapping the media with a working device of the exact same model.


👤 j4tech
Lightning struck very close to my apartment and fried all equipment that was connected using Ethernet cable (cable modem/ router/VOIP unit, Roku). My TV was spared.

The apartment has a circuit breaker (which tripped) and I have a surge protector as well.

Did some research and read that a Surge protector with "Catastrophic Event protection" feature would have helped. This feature fries the surge protector instead of the equipment connected to it. A note from the mfr of the product I am considering buying: "most surge suppressors continue to let power through even after circuits have been damaged, leaving your equipment exposed to other damaging surges." The surge protector I have does mention that power will pass thru it, if power surge is more than what the suppressor can handle. HTH.


👤 darksofa
osamagirl69 and tuatoro have given you some good advice. Sadly (yet predictably) the rest is misguided, wrong, or dangerous.

To emphasize tuatoro's points, it appears some of your branch circuits were damaged by the strike. Their wiring needs to be inspected to see if the insulation was compromised. If yes, the wiring needs to be replaced. The dead kitchen appliances need to be evaluated for safety -- they could now be an electrocution risk.

Many of the comments display a dangerous (and common) misunderstanding of the purpose of a grounding rod. The language used for this topic is confusing, which doesn't help.

The important thing to know is: A GROUNDING ROD IS NOT A SAFETY GROUND.

Article 250 of the US National Electric Code covers "grounding" and "bonding." Note the two different words. "Grounding" (connect to earth) is done to limit voltage induced by lightening, line surges, or unintentional contact with higher-voltage lines.

"Bonding" is the connecting metal parts of enclosures, cases, and equipment to the supply source via an effective ground-fault current path. Bonding is what provides safety. This is what most people think of as the green "grounding" wire (in the code, called the "equipment grounding conductor."

Note it says "to the supply source." In your case, the source is the house 200 m away feeding your panel. The cable from that house should be 4 or 5 conductors, one of which is the equipment grounding conductor ("ground wire"). If the cable does not include the equipment grounding conductor, the cable MUST be replaced. It is not safe to run a separate wire back for the grounding conductor.

See this document on article 250 requirements:

https://www.mikeholt.com/instructor2/img/product/pdf/20NCT2-...

Thailand has 230 V / 50 Hz service, but the grounding and bonding principles are the same.


👤 nano9
> my house is the tallest thing around and we frequently have huge thunderstorms

Dude. Install a lightning rod.


👤 imgabe
Some surge protectors have a warranty that will reimburse you up to some amount for any equipment that gets fried while plugged into it. I've never tried to make a claim on these, but it might be worth looking into if yours offers anything.

👤 someotherperson
Name and shame the surge protector brand/model you used. I've seen them make outrageous warranty/guarantee promises between $10,000 and $100,000 so it might be worth using that to replace some of your hardware.

For everything else - you need an electrician. It's not as easy as just a "big metal stick somewhere in the garden" -- get someone (else) out to actually inspect and deal with it. The reason being is that IMO: your surge protection devices shouldn't have fried if they were properly grounded. So the previous electricians might not have properly grounded your property.


👤 libertine
>The PSU in one of the computers is gone, but not the motherboard and rest.

I had this happen to me, but I think it hit a phone line (back in the ADSL days) - and it caught more components then I initial thought, the ones that went under the radar were the RAMs.

The symptom was decompressing RAR files, sometimes it would give errors. The HDD also started to act oddly, so you should probably run some tests to see if everything is ok.


👤 lightlyused
My favorite resource is this: https://www.w8ji.com/house_ground_layouts.htm He has many years of experience with lightening, big towers, and electronics. It sounds like you still have a poor ground.

👤 quickthrowman
If you want protection against lightning strikes, you’ll want to add a surge protective device to your electrical panel that has a fault current rating of at least 100kAIC. Surge protectors for panelboards are required for residential electrical services, the change was implemented in the 2020 NEC.

👤 pram
This happened to me, somehow lightning caused some kind of surge in my Ethernet network and killed ports on 3 of my computers. Turns out cheap switches aren’t grounded, you have to manually put a wire on a screw. Sucks!

👤 traceroute66
Three words:

Get. An. Electrician.


👤 xlaacid
what you need, in addition to surge protection at the electrical device, is a whole house surge protector. It will stop the lightning strike immediately. Mine was 120.00USD plus 75.00 to install. totally worth it. These are used in place of lighting rods.

https://www.thisoldhouse.com/electrical/21194149/how-effecti...


👤 Fire-Dragon-DoL
Was your ethernet cable surge protected?