Shops and storms

[Ned Otter]

Hey folks --

Thinking about how to safeguard against lightning --

I have a sub panel in my shop, connected to the main panel in my basement, about 150 feet away. I can flip the breakers on both panels, but I'm not sure if that's the best approach. If lightning strikes, can it "jump" across the breaker, for lack of a better phrase? The house and the shop have an iron bar in the earth next to each structure.

I know that Jim Baker unplugs some of his equipment when a bad storm comes through, wondering how others prepare for this potential shop/equipment disaster.

Thx,

Ned

[Leigh Betsch]

Insurance.

[Jim Becker]

Yes, lightning can jump across breakers, etc., if it really wants to after a "direct hit". A whole house surge arrestor can help, but I agree with Leigh that ultimately, insurance is kinda the end-game for a real hit.

Unplugging things can provide greater protection. I unplug my CNC machine, for example, when it's not actively in use because it contains electronics and is more sensitive than most of my other woodworking tools. My lathe is unplugged for the same reason...to protect the VFD.

[John Lanciani]

Ligntning travels 1,000's of feet from clouds to ground, there is absolutely nothing that you can do to mitigate a direct or near strike. Turning off breakers, adding surge protection, etc. are just feel good measures. Unplugging is your best bet if you can get in the habit.

[Mike Wilkins]

Unplugging is your best insurance. When I was working as a claims adjuster I once had a home get hit twice about 1-2 years apart, hitting each chimney. Like John stated, surge protectors are just feel
good measures. Lightning can and will jump where it wants to.

[Eric Arnsdorff]

Lightning can provide well over a hundred million volts and plenty of current to back that up traveling through a gigantic air gap. While it could be managed the structure is impractical.

However, direct lightning hits aren't your highest risk. It is true there isn't really a practical way to protect against direct lightning strikes. A true direct strike isn't a high probability. It does happen and it is quite devastating for everything in your shop and house if attached.

The higher risk that can be mitigated is the transfer of energy into your power lines and other conductive paths. This is really what happens when most house lightning strikes are reported.

There are things you can do to lower the chances of this causing problems. You can install overvoltage protection. These are common in industrial and commercial electrical systems and available for residential housing/shops (they aren't that expensive either). These are basically a larger version of the power strips you buy reporting overvoltage and "lightning protection" (they'll use that term but the fine print reveals they don't claim full power lightning strikes).

But even before the overvoltage protection - having proper grounding and a solid grounding electrode system will provide quite a significant risk reduction. It is a common misconception that the copper rod driven in the ground is your ground. Your ground does not need the connection to earth to provide shock mitigation from your power lines. The GE is to drain "static" voltage such that the "zero" reference of your electrical system is approximately the same as the earth. In case of lightning it would be considered a "static" voltage (although a very brief version of static).

There are more "lightning protection" systems and such that do work. The science of directing high currents from high potential areas is well known. So they do work. What starts making them less and less attractive is the small percent risk reduction they provide.

I have to add - I am quite certain of this and I design systems with over-voltage devices. I know how they work and understand they do truly provide a substantial risk reduction from damage to electrical devices in my home and shop. However, I haven't put one in my house (my shop is in my basement). I do have a very good GE setup and grounding system for my house. So I take my chances with it.

I'm not disagreeing with what others have said - that if you feel you need 100% protection then insurance seems to be your only method of minimizing any possibility of worst case cost. Note insurance isn't free and ultimately you likely pay way more than the risk is to you but the insurance system thrives on this statistic and fear. You will likely find that adding the additional insurance for 100% coverage may not be a huge cost. This is because the risk isn't huge either. So this is how insurance makes big money but also benefits you with piece of mind and some small percentage end up benefitting from the coverage.

[Scott Winners]

Not an engineer. If I really want a thing to not get zapped, I unplug it between uses. Lathe, jointer, and planer are usually not plugged in. When the weather is threatening, I unplug my phones, laptop, iPad and home theater system. I also have my one at a time bench top tools (9"bandsaw, bench grinder, 2" drill press and belt sander) plugged into the same power strip. When I unplug the home theatre I typically unplug the power strip for those as well.

Agree with previous poster that hits on nearby power lines are far more common that direct lightning hits.

[Alan Lightstone]

Having lived through a direct lightning strike in the lightning capital of the US (no coincidence this is the name of our NHL team), I learned a few lessons. And Duke Energy told me that my neighborhood historically got the most lightning strikes in the county. Oh joy.

I sustained $55K of damage. And most of my home theater was destroyed, even though it was unplugged from the AC outlets. As it turned out, when the lightning entered the house, it travelled over the CAT-5 cables and destroyed the home theater, all the light switches, network devices, TVs, etc..

So by unplugged, we really mean unplugged from all wires.

After that I bought a gazillion UPS systems, surge suppressor strips, and whole house surge protection. And it got very costly to replace the batteries in all those UPS systems.

In my new house, I just have whole house surge suppression. When a big storm is coming, I just flip the breakers to the workshop. The rest of the house - I just hope we don't get hit. Basically, if mother nature wants to get you, it will.

[Ned Otter]

Thanks very much to all who responded, very informative - really appreciate it

[Carl Beckett]

Another risk that is worth mentioning: Fire caused by poorly designed (often cheap) passive electronics. My neighbor for some time was a power electronics expert and reviewed designs that had caused fires as an expert court witness.

He strongly recommended unplugging toasters that have any type of electronics 'buttons' on them (the old mechanical switches he was ok with). And other electronics when not in use, as much as possible, should be unplugged. He felt many times the power supply side to these were not well designed and failed and caused fires.

I dont unplug everything. But it has given me pause and I do now unplug items that I only use occasionally.

Not lightening. But perhaps a bigger risk than lightening, given the number of these type of appliances in my house...

[Osvaldo Cristo]

When I let the workshop by the end of the day one of my rites is to check if all plugs are physically disconnected. I do not let even a single humble battery charger connected.