Lightning Protection

[Tom Bender]

I believe my old VFD was toasted by lightning a few years ago and replaced it. It is 120 volts. The saw was wired with an "ON/OFF" switch thru the VFD and a "Power" switch on the power feed to the VFD. I replaced the power switch with a DPDT switch so lightning would not be able to fly in thru the white wire. I turn the power switch on when using the saw so it's off 99% of the time. Any value to this type of switch?

[Jim Becker]

The switch can be be helpful to isolate from more minor surgest, but a true lightning hit or major surge can easily bridge that short distance if it wants to. This is one reason why I totally unplug both my CNC machine and my Stubby lathe. Both have VFDs (and the CNC has additional expensive stuff...) and total isolation is my chosen method for protecting things. If a major event decides it wants to bridge across a couple of feet of air between the receptacle and the machine cord...they were meant to be fried no matter what I did to prevent that. :)

[Erik Loza]

I feel like I talked to a customer who had the boards fried in his combo machine by a lightning strike not too long ago. Shop was detached from the house, so he didn't realize what happened at first. Never thought of totally unplugging the machines. Good idea.

Erik

[Jim Becker]

Yea, it's not a horrible practice, Erik, when plugs are available. Otherwise, there "should" be a hard disconnect but a good jolt can certainly jump those "sometimes".

[Erik Loza]

Yea, it's not a horrible practice, Erik, when plugs are available. Otherwise, there "should" be a hard disconnect but a good jolt can certainly jump those "sometimes".

Jim, your logic is on point but I'll bet there is 0.00% chance this happens in any shop, LOL.

Erik

[Alan Lightstone]

Jim, your logic is on point but I'll bet there is 0.00% chance this happens in any shop, LOL.

Erik

Considering that I had $55K of electronics destroyed in my last house by a lightning strike (Here in the lightning capital of the World), I respectfully disagree that it might not happen. The lightning jumped everything, destroyed every light switch in the house, home theater, thermostats, HVAC system. I could go on and on...

[David Walser]

Changing the topic slightly: What are the group's thoughts on 'whole house surge protection' devices?

[Alex Zeller]

I'm not sure how much you can do. Putting up a metal rod on the gable end of a house connected to earth was the typical way of protecting a house but all that does is make a nice target for lightning. Unplugged is about the best you can do but not everything can easily be unplugged. I have lots of trees taller than my house close by and a hill right behind my house. My shop is even lower down the hill. Over the years I've had several strikes close to the house including two that blew apart ash trees (a couple years apart) into pieces. Both were less than 1000 yards from the house.

If you own enough land you could put up a tower to attract the lightning but that wouldn't be cheap and you would want it a long way from a building as lightning has arcs that come off the sides. When you are talking about something that's 100s of millions of volts and 100,000 amps plus it doesn't take but a small percentage of that to get diverted to your building. If you understand electrical theory then you understand that nothing has zero resistance. What that means is that a portion of the electricity will travel down each path no matter how low or high of a resistance each path has.

[Derek Meyer]

I have surge protectors on each of my 2 electrical panels in my house. I've had one fail in 18 years so far. Replacing it was easy but did cost about $140 for the new unit. I like to think of it as an additional layer of protection against surges, as I also use surge protectors and good quality UPS units on my expensive electronic equipment.

I am pretty sure that these protectors would do little to nothing in the event of a close lightning strike, though. In that case I'd have to rely on my homeowner's insurance and possibly any warranty provided by a UPS or surge protector, though those are not likely to apply in the case of a lightning strike.

Derek

[Erik Loza]

Considering that I had $55K of electronics destroyed in my last house by a lightning strike (Here in the lightning capital of the World), I respectfully disagree that it might not happen. The lightning jumped everything, destroyed every light switch in the house, home theater, thermostats, HVAC system. I could go on and on...

Alan, we're saying the same thing. :D What I was saying is that there is 0% chance most shops would actually unplug their machines. Just like safety guards, etc. LOL

Erik

[Wes Grass]

I had my CNC machines hard wired in my last shop. But lightning is a small risk where they currently are. The little splash we had here yesterday has me thinking of cords and plugs. I know an open breaker won't stop a hit like that.

[Steve Rozmiarek]

I've lived in three different houses that took direct hits from lightning. Tampa Bay may be the lightning capital of the world, but western NE in thunderstorm season is no slouch.

One hit was to an old fashioned lightning rod, it arced from the copper braid wire to a propane line a foot away. Things got a little dramatic with the fire, but it was long enough ago that we didn't really have sensitive electronics and I don't remember any damage to appliances.

Second hit a chimney, knocked some bricks off, must have followed the wire lath in some stucco because it blew some of that off. I was standing by the stove connected to the chimney when it happened, it charged the air or something, I'll never forget that sense or the ozone smell afterword. It killed a TV, a microwave and the corded phones. The shop that had some machines plugged in was on the same electrical service, and it did no damage there.

The third time hit our house when we were away, hit a tree in the yard, arced from a root to an underground sprinkler wire and then went into the garage where the control panel was. It was grounded, but the lightning still blew up the transformer in the panel and destroyed the outlet it was plugged into. Of course it got in the household wiring and cooked some tvs, a microwave and a computer. I had just bought a Felder sliding saw, and the sprinkler controller transformer blowing up actually blew shrapnel all over the saw, you can still see a burn mark. All the tools in the shop were plugged in, it did no electrical damage to the shop tools. It did start a fire in the shop which through some divine intervention put itself out before we got home.

My advise? Forget about trying to mitigate lightning, there are just too many unpredictable ways it can destroy things. Make sure you have insurance, and a few common sense things certainly won't hurt. Like Jim's suggestion of unplugging. Also, the fact that I'd swept my floor right before the third incident kept the whole place from burning down. I've seen it literally turn the windings in a 100hp motor to copper droplets. There is just so much power in a bolt of lightning that the surge protectors are absolutely useless if you take a direct hit. It also has no trouble going ariel again and arcing to some other path of least resistance, so a switch with a 1/4" gap won't even make it hesitate.

[Malcolm McLeod]

I've lived in three different houses that took direct hits from lightning. Tampa Bay may be the lightning capital of the world, but western NE in thunderstorm season is no slouch.

....

And thanks for the warning(s) too!!

From the TX panhandle we can see those storms coming while they're still in NE. Light shows are spectacular after sunset!

I opened a control panel once and wondered who would store a meteorite there. Then realized it was a PLC. Oops.

[Zachary Hoyt]

Since I got my drill press set up with a VFD last fall I only plug it in when I want to use it, maybe twice a week on average. Initially this was because I was too cheap to buy a DPDT switch, but now it sounds like I have a better excuse for my cheeseparing ways. The VFD hums when it is plugged in, and that seems sort of unnecessary for how infrequently I use it. I also put a nice thick plastic bag over the VFD when I am not using it. It takes me about 15 seconds or less to plug in the plug and remove the bag when I want to drill, and since it keeps the VFD clean and quiet the rest of the time I'm happy to do it.

[Steve Rozmiarek]

And thanks for the warning(s) too!!

From the TX panhandle we can see those storms coming while they're still in NE. Light shows are spectacular after sunset!

I opened a control panel once and wondered who would store a meteorite there. Then realized it was a PLC. Oops.

As I was writing that, I was thinking that's an almost unbelievable series of events. It is over 40 years though. I was trying to figure out how the lightning got into a center pivot panel one time that had those meteorite looking deposits left after a hit. Turns out the lightning must have blown through an insulated sheath of wire to get to the ground, which of course released the full power. Maybe there was a crack or something in the sheath, or maybe the lightning just really like that path better. Had to completely rewire that one. The storms are awesome to watch. Better if you don't have any vested interest in whatever is under them.

[William Hodge]

I believe my old VFD was toasted by lightning a few years ago and replaced it. It is 120 volts. The saw was wired with an "ON/OFF" switch thru the VFD and a "Power" switch on the power feed to the VFD. I replaced the power switch with a DPDT switch so lightning would not be able to fly in thru the white wire. I turn the power switch on when using the saw so it's off 99% of the time. Any value to this type of switch?

I have had a few hits. I could tell some stories about lightning hits, but most of them are made up. However, this is not the forum where one describes extramarital affairs uncovered by untimely lightning strikes.

I put plugs on everything after I lost some stuff. The ground was the problem. Lightning came in on the ground and cost me money.

Knowing when I'm going to get a storm is part of the problem. The shop is pretty sound proof. I use this web site and app. https://www.lightningmaps.org/?lang=en#m=oss;t=3;s=0;o=0;b=;ts=0;z=8;y=41.8245;x =-70.9387;d=2;dl=2;dc=0;

[Bruce King]

The two best things to do, install a surge device that plugs into both legs in the main panel.
Add another copper ground rod at least 8 feet from the other one. Clamping it to the first one is ok but make sure the clamps grind into the metal.

[Julie Moriarty]

Lightning can do some really weird things. A story I've told often happened while we were building a 10 story office building. One morning I get to work and my guys are telling me how some temp lights were bright, some were dim and some didn't work at all. The manlift wasn't working. The ironworker's foreman said the door knob to his trailer was hot, which made no sense because the trailer was grounded. As I was checking the voltage at the doorknob, the door to our trailer banged open and the guy inside threw out a smoking telephone. He said he was talking on the phone when it started smoking. And the ironworker's doorknob? I got 50 volts off it.

We always called in Harger to do our lightning protection installations. This is a page from their residential brochure

https://sawmillcreek.org/attachment.php?attachmentid=456189&d=1618746558

[Lee Schierer]

Years ago, lightning hit our steel flag pole, which is about 30 feet shorter than the surrounding trees. It melted the shackle the held the pulley to the top of the flag pole. The strike came down the flag pole, found the twisted pair wire of the dog fence 5 feet away from the base of the pole and vaporized over 200 feet of the dog fence loop. It also followed the twisted pair into the house where the supplier had a lightning protector that put the charge into the electrical ground for the house. We lost a couple of electronic devices and plug in power supplies. Not enough damage to file a claim with our insurance. The dog fence manufacturer replaced the lightning arrester free of charge.

The Bio Fuel plant I helped build in Erie,PA installed a lightning protection system that has recorded several thousand hits in the first few years of operation with no issues. It had an extensive ground plane of copper wires and special protection dome devices with strike counters mounted on high spots around the facility. As far as I know there was no other damage done by the strikes.

[Alan Lightstone]

All I have to say is that our NHL team is the Lightning. Can't be a coincidence.

[Malcolm McLeod]

I watched a friend trying to walk his dog on a leash - - the largest Great Dane I've ever seen.

I've seen some very elaborate lighting protection systems.

They have a common theme in that both the leash and the protection system are just suggestions.

[Bill Dufour]

In theory a lightening rod drains off electron charge before it gets high enough to arc.
Bill D