Best way to protect from lightning strikes?

[Yooshaw]

My setup: AX6000 with latest Merlin, with 2 switches downstream to various locations around my 2 story house (basement and main level). All major electronics (including modem, router, switches, etc) are on surge suppressors or battery back-up.

Last evening during a thunderstorm in Colorado, we were startled by an extremely loud bang and flash of light. Sounded like it happened a block or two away behind us. No power interruption at all. Shortly after, we noticed the wifi was down. Went to investigate, and the AX-6000 only had a faint power light on. The wan, lan, wifi lights were off. Modem was on and fine. Odd I thought, I'll just unplug and reboot. No change. Tried a hard reset, no change. One of my switches had no power lights or activity (it's dead), while the other was still working.

After dusting off my AX-88U I had on the shelf, I got everything working again (minus the dead switch, but the 8 ports on the AX88U made up for it). Also discovered that one of my devices (NVIDIA Shield Pro) lost it's LAN port.

I've deduced that the nearby lightning strike induced voltage in my lan runs throughout the hosue, and is probably what caused the damage.

What can be done to prevent this kind of damage in the future?

 

[Tech9]

You can't prevent it. Usually around 100-300 million volts charge finds its way. I had dead equipment twice through all the groundings and surge protectors done by the book. The voltage is so high it goes through meters wide air gaps and nothing guarantees survival of whatever is in the way. Home insurance including lightning damages may eventually offset some damage costs.

 

[Analog-1]

Yep what Tech9 said.

 

[degrub]

My setup: AX6000 with latest Merlin, with 2 switches downstream to various locations around my 2 story house (basement and main level). All major electronics (including modem, router, switches, etc) are on surge suppressors or battery back-up.

Last evening during a thunderstorm in Colorado, we were startled by an extremely loud bang and flash of light. Sounded like it happened a block or two away behind us. No power interruption at all. Shortly after, we noticed the wifi was down. Went to investigate, and the AX-6000 only had a faint power light on. The wan, lan, wifi lights were off. Modem was on and fine. Odd I thought, I'll just unplug and reboot. No change. Tried a hard reset, no change. One of my switches had no power lights or activity (it's dead), while the other was still working.

After dusting off my AX-88U I had on the shelf, I got everything working again (minus the dead switch, but the 8 ports on the AX88U made up for it). Also discovered that one of my devices (NVIDIA Shield Pro) lost it's LAN port.

I've deduced that the nearby lightning strike induced voltage in my lan runs throughout the hosue, and is probably what caused the damage.

What can be done to prevent this kind of damage in the future?

Incorrectly earthed or a broken shield on cabling could do what you describe but usually only for outdoor cabling. More likely, since your damage was limited to only parts of the house cabling , is elevated earth potential from the bolt dissipating through the earth. Your building electrical distribution box (breaker box) is tied to a grounding (earthing) rod that would experience the elevated potential. It is possible that earthing point is not in good contact with the soil or has low moisture in the soil around it. There are ways to test the resistance to earth, but some folks just use three rods connected together to improve the earthing resistance. There can be enough voltage ( >25 - 50 v usually) on the Neutral side to break down the zener diodes used to prevent reverse current flow into the electrical device such as a router, switch, computer, etc. Most lightning is in the 30-70 KA negative V range with extremely high current. Anything providing resistance to the current flow will either spark or melt/vaporize. You can put a whole house lighting arrestor/diverter at the breaker box to reduce the amount of energy that gets onto your internal wiring. You should seriously consider replacing all of the surge arrestors in the house as the MOVs used to provide the protection get chewed up with each incident. A competent local electronics repair shop should be able to do it. Otherwise, replace the units. They should be replaced every 5-7 years anyway. i live in a high lighting frequency part of the US and have experienced 3 very close strikes (within 100 ft) over a few decades.

BTW, if you experienced the strike as a flash-bang with no gap between the two, it was likely a very close strike to earth, maybe not down the block. Are you within the front range or out on the prairie ?

edit: corrected units

 

[Yooshaw]

Incorrectly earthed or a broken shield on cabling could do what you describe but usually only for outdoor cabling. More likely, since your damage was limited to only parts of the house cabling , is elevated earth potential from the bolt dissipating through the earth. Your building electrical distribution box (breaker box) is tied to a grounding (earthing) rod that would experience the elevated potential. It is possible that earthing point is not in good contact with the soil or has low moisture in the soil around it. There are ways to test the resistance to earth, but some folks just use three rods connected together to improve the earthing resistance. There can be enough voltage ( >25 - 50 v usually) on the Neutral side to break down the zener diodes used to prevent reverse current flow into the electrical device such as a router, switch, computer, etc. Most lightning is in the 30-70 KA negative V range with extremely high current. Anything providing resistance to the current flow will either spark or melt/vaporize. You can put a whole house lighting arrestor/diverter at the breaker box to reduce the amount of energy that gets onto your internal wiring. You should seriously consider replacing all of the surge arrestors in the house as the MOVs used to provide the protection get chewed up with each incident. A competent local electronics repair shop should be able to do it. Otherwise, replace the units. They should be replaced every 5-7 years anyway. i live in a high lighting frequency part of the US and have experienced 3 very close strikes (within 100 ft) over a few decades.

BTW, if you experienced the strike as a flash-bang with no gap between the two, it was likely a very close strike to earth, maybe not down the block. Are you within the front range or out on the prairie ?

edit: corrected units

Thanks for the detailed response! I'm on the front range in Colorado Springs. I'm interested in learning more, as I had a similar experience happen to me in San Antonio - the lightning strike there was a few houses over, and only caused two device that were hooked up to hard wired door/window sensors to fry.

I don't fully understand everything you laid out, but want to learn more. A liitle more background on my current house - it's a newer build built in 2024. If what you said did occur, wouldnt other devices around the house have been affected? At the time of the strike, we had two TVs on, which were unaffected. I find it curious that only ethernet devices (router, switch, and lan port of NVIDIA Shield) were affected. If not induced by the lightning strike, how can the surge have gotten only to those devices?

Out of curiosity, I went out and looked at the main breaker coming into the house, as well as the coax feed for internet (X-Finity). Looking at the XFinity feed, it doesn't seem like they grounded it right, as the grounding cable from the Coax box doesn't seem to making metal contact.





But if this was the issue, I feel like the modem would have gotten fried? Could a lack of coax grounding cause an issue to the Ethernet output of the modem to my fried router and further downstream?

Here's some pics of the main breaker box - I assume the green boxes in the surge portion means they are still good?





Thanks again for your response!

 

[Yooshaw]

Also, just realized that the exterior Coax box has two un-terminated ethernet runs in them, that lead back to my interior networking box. On the interior, they are not connected to anything either, just sitting in the networking box. Could this have had a role?



Yellow and grey wires are the ethernet runs going back to the interior network box.

 

[ColinTaylor]

Being in the UK I'm not familiar with how you do things. But is this green wire electrically connected to this bolt? It looks like it might only be held in place by the insulation. Perhaps the internal part that screws down on the cable has a IDC that pierces the insulation that can't bee seen from this picture.


I'm assuming that the bottom of the bolt is making good electrical contact with the bare metal of this box thing (which in turn is grounded).

 

[degrub]

Your main disconnect box has built in whole house surge arrest. That will help with any power line spikes. They should be across each phase (L) to neutral (N), and across phase (L) to earth (G), and across neutral (N) to earth (G) , although the latter may be equivalent since the two buss bars inside the breaker panel (presumably inside somewhere) are tied together. Depends on what the local code requires and the authority having jurisdiction (local inspector) requires. You won't be able to see all those connections, but can look up the install sheet based on the model number. Siemens generally makes good equipment. Those can handle up to 22 k Amps before they use up the MOVs.

Is the electrical distribution in the neighborhood underground or on poles ?

Green is good on the two Siemens arrestors . Red means they are completely used up. The previous strike probably used up some of the MOV life.

The coax bonding is likely ok if allowed by local electrical code. Personally, i would not do it that way as there may not be bare metal contact under the meter box cover by that grounding clip. The grounding tap used is a vampire type that pierces the insulation to make the connection. It should be fine. It's really up to what the local authority allows the cable co to do.

Those unterminated ethernet ? CAT ? cables are just antennas. Plastic boxes would not shield from EMI if the strike was close enough. What are they connected to inside ? If they were connected to the router or a switch, yes , that could be part of the reason you had damage especially if they were all directly connected to the same switch or router lan ports.

And the yellow and gray cables are not coax ?

 

[degrub]

Being in the UK I'm not familiar with how you do things. But is this green wire electrically connected to this bolt? It looks like it might only be held in place by the insulation. Perhaps the internal part that screws down on the cable has a IDC that pierces the insulation that can't bee seen from this picture.
View attachment 67955

I'm assuming that the bottom of the bolt is making good electrical contact with the bare metal of this box thing (which in turn is grounded).

Yeah, it's legit. Vampire type tap. Would also be concerned about corrosion building up in the female threads connecting the bolt to the clip. Usually , stainless steel is not painted though.

Some jurisdictions allow this sort of bonding approach. You have to watch out for gaps opening up in the conduit coming up to the service disconnect box unless it is directly connected with an earthing wire to the earthing point/grid. Somewhere else there is an earthing mesh or set of rods that all of this ties to. Should be outside of the building structure, but i don't know what the local authority having jurisdiction allows. Usually, they follow the NEC explicitly, but they have room for local "adjustments". This is an area with highly variable moisture levels in the soil and lots of rock/gravels.

 

[Yooshaw]

Your main disconnect box has built in whole house surge arrest. That will help with any power line spikes. They should be across each phase (L) to neutral (N), and across phase (L) to earth (G), and across neutral (N) to earth (G) , although the latter may be equivalent since the two buss bars inside the breaker panel (presumably inside somewhere) are tied together. Depends on what the local code requires and the authority having jurisdiction (local inspector) requires. You won't be able to see all those connections, but can look up the install sheet based on the model number. Siemens generally makes good equipment. Those can handle up to 22 k Amps before they use up the MOVs.

Is the electrical distribution in the neighborhood underground or on poles ?

Green is good on the two Siemens arrestors . Red means they are completely used up. The previous strike probably used up some of the MOV life.

The coax bonding is likely ok if allowed by local electrical code. Personally, i would not do it that way as there may not be bare metal contact under the meter box cover by that grounding clip. The grounding tap used is a vampire type that pierces the insulation to make the connection. It should be fine. It's really up to what the local authority allows the cable co to do.

Those unterminated ethernet ? CAT ? cables are just antennas. Plastic boxes would not shield from EMI if the strike was close enough. What are they connected to inside ? If they were connected to the router or a switch, yes , that could be part of the reason you had damage especially if they were all directly connected to the same switch or router lan ports.

And the yellow and gray cables are not coax ?

Yellow and grey cables are not coax, they are ethernet. On the inside at the networking box, they are terminated but connected to nothing. They sit alongside the other coax and ethernet runs that lead to 4 different areas in the house. Only coax hookup is the incoming connection for internet.

Electrical distribution in the neighborhood is underground. There is a distribution box on our property at the road (about 30 feet) from the main breaker in the picture).

Thanks again for your insight, much appreciated!

 

[degrub]

If they are not connected on either end, then any buildup would have to arc over which is not very likely. i would still suspect an elevated ground potential, reverse current flow, issue unless the surge protection circuits do not cover L-N, L-G, N-G.

i would not be surprised if you had additional device failures over the next few months from this hit.