Page 1 of 2 12 LastLast
Results 1 to 15 of 22

Thread: Lightning Protection

  1. #1
    Join Date
    Apr 2017
    Location
    Michigan
    Posts
    1,772

    Lightning Protection

    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?

  2. #2
    Join Date
    Mar 2003
    Location
    SE PA - Central Bucks County
    Posts
    56,970
    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.
    --

    The most expensive tool is the one you buy "cheaply" and often...

  3. #3
    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
    Felder USA Territory Representative: Central & South Texas

  4. #4
    Join Date
    Mar 2003
    Location
    SE PA - Central Bucks County
    Posts
    56,970
    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".
    --

    The most expensive tool is the one you buy "cheaply" and often...

  5. #5
    Quote Originally Posted by Jim Becker View Post
    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
    Felder USA Territory Representative: Central & South Texas

  6. #6
    Join Date
    Jan 2010
    Location
    Tampa Bay, FL
    Posts
    2,608
    Quote Originally Posted by Erik Loza View Post
    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...
    - When God closes a door, he opens a window. Our heating bill is outrageous & six raccoons got in last night. Please God, this has to stop!
    - Outside of a dog, a book is man's best friend. Inside of a dog, it's too dark to read.

  7. #7
    Join Date
    Dec 2006
    Location
    Mesa, Arizona
    Posts
    1,656
    Changing the topic slightly: What are the group's thoughts on 'whole house surge protection' devices?
    David Walser
    Mesa, Arizona

  8. #8
    Join Date
    Apr 2018
    Location
    Cambridge Vermont
    Posts
    1,523
    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.

  9. #9
    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

  10. #10
    Quote Originally Posted by Alan Lightstone View Post
    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. What I was saying is that there is 0% chance most shops would actually unplug their machines. Just like safety guards, etc. LOL

    Erik
    Felder USA Territory Representative: Central & South Texas

  11. #11
    Join Date
    Feb 2009
    Location
    Cedar Park, TX - Boulder Creek, CA
    Posts
    541
    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.

  12. #12
    Join Date
    Jan 2008
    Location
    Western Nebraska
    Posts
    4,214
    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.
    Last edited by Steve Rozmiarek; 04-16-2021 at 1:49 PM.

  13. #13
    Quote Originally Posted by Steve Rozmiarek View Post
    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.

  14. #14
    Join Date
    Mar 2018
    Location
    Orwell, NY
    Posts
    573
    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.

  15. #15
    Join Date
    Jan 2008
    Location
    Western Nebraska
    Posts
    4,214
    Quote Originally Posted by Malcolm McLeod View Post
    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.

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •