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Odds of getting struck by lightning?


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#1 of 13 OFFLINE   DeathStar1

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Posted July 30 2006 - 05:21 AM

I'm curious... We've been leaving our computers on at the office, a one story building, during thunderstorms for the past ten years, not one has got stuck by lightning. Yet we turn the ones off at h ome each time a storm comes. What are the chances one will get struck? Also, would lightning really shoot everywhere in the house if it does get struck while on, or would it just make a noise, smoke, and die?

#2 of 13 OFFLINE   Kimmo Jaskari

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Posted July 30 2006 - 06:07 AM

The issue might be that if lightning strikes the electricity grid, it may well do bad things to anything connected to that grid.

Odds of being struck by lightning isn't affected by whether or not you use the equipment, but it's probably a bad idea to be gabbing away on the phone if there is a strike in the phone lines of your building. Similarly, using any other hands-on electric appliance is probably a needless risk. In other words, there are better times to be blowdrying your hair than during an active lightning storm.

Unplugging devices will probably save them in case of a lightning strike in the electricity network, which is the one good reason to unplug your TV, computer etc. No physical connection to the electricity grid, no chance of them being zapped. However, if they do get zapped I'd say the odds are they just burn out and stop working.
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#3 of 13 OFFLINE   mattCR

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Posted July 30 2006 - 07:27 AM

Even bigger issue for people with modems, actually. The thing is, all it takes is a spike in the phone lines and your modem becomes an instant ground point. I've seen that happen -way- too often. People forget about that kind of thing Posted Image Your phone line carries current too.. and it doesn't take much of a spike to really cause some damage Posted Image
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#4 of 13 OFFLINE   Jason Harbaugh

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Posted July 30 2006 - 08:58 AM

I've been struck three times, ie been in one house and one apartment and one lookout tower that was struck by lightning.

Wildfire Lookout Tower: Basically a giant lightning rod. No electronics so nothing fried. Curled over in 'face meets ass' position. Ears ringing, slept in tent. Posted Image

House: Completely out of the blue. Same loud crack. No electronics in house hurt. Guessing it hit the lightning rod and traveled through it to the ground.

Apartment: This is the one that freaks me out. Loud crack, phone physically flipped up and out of its holder. Turns out, every single person's phone in the building was fried. Just glad I wasn't on it. Nothing else was hurt in any of the apartments.

#5 of 13 OFFLINE   nolesrule

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Posted July 30 2006 - 12:48 PM

Just turning something off will not spare it damage from a lightning strike. It would need to be completely unplugged. The power and voltage of a lightning bolt is enough to jump even the gap of an open power switch in an electronic device.

#6 of 13 OFFLINE   Andrew Pratt

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Posted July 30 2006 - 02:02 PM

Quote:
Even bigger issue for people with modems, actually. The thing is, all it takes is a spike in the phone lines and your modem becomes an instant ground point. I've seen that happen -way- too often. People forget about that kind of thing Your phone line carries current too.. and it doesn't take much of a spike to really cause some damage

My mothers PC and sat dish just took a hit via the phone line's yet the other A/C gear in the house was all fine. I don't bother unplugging everything but the major things are all on surge bars.

#7 of 13 OFFLINE   Mike Fassler

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Posted July 30 2006 - 02:09 PM

no surge bar will protect you from a lightning strike, but a ups will.

#8 of 13 OFFLINE   Kyle McKnight

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Posted July 30 2006 - 04:05 PM

I was just wondering this two nights ago...but more about swimming (in a home pool) while it's storming. I've never (that I know of) had lightning strike a pool, nor has anyone that I know. I wonder how much more likely it is to happen if a person is swimming in the pool...
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#9 of 13 OFFLINE   nolesrule

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Posted July 30 2006 - 05:23 PM

Quote:
Originally Posted by Mike Fassler
no surge bar will protect you from a lightning strike, but a ups will.

A ups is an uninteruptable power supply. It is a surge suppressor with a battery backup so you don't lose power to your computers during brownouts and have time for a normal shutdown during blackouts. Whether a surge bar will protect from the surge from a lightning strike depends on its protection ratings.

Quote:
Originally Posted by Kyle McKnight
I was just wondering this two nights ago...but more about swimming (in a home pool) while it's storming. I've never (that I know of) had lightning strike a pool, nor has anyone that I know. I wonder how much more likely it is to happen if a person is swimming in the pool...

Lightning does not have to strike directly in a pool to cause a lethal amount of electricity to spread through it. Living in the lightning capital of North America, I've seen what lightning can do. If I can hear the thunder, you won't find me in any water, and that includes taking a shower. If there is lightning, you should be indoors or in a car...and even cars aren't all that safe, but it's better than standing on the ground.

#10 of 13 OFFLINE   westom

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Posted April 01 2009 - 03:07 AM

Quote:
Originally Posted by DeathStar1
I'm curious... We've been leaving our computers on at the office, a one story building, during thunderstorms for the past ten years, not one has got stuck by lightning. Yet we turn the ones off at h ome each time a storm comes. What are the chances one will get struck?
A typical nearby strike is once every seven years. A number that varies greatly even in town due to conditions such as geology. To understand why requires an answer to the simple question: what does lightning seek?

Well, a direct strike to earth can be via AC electric lines and to earth via computers. Will that silly little 2 cm part in a power strip protector stop what three miles of sky could not? Others here have made that claim. Will its few hundred joules absorb hundreds of thousands of joules in that surge? Again, that was claimed by others promoting a power strip or UPS protector. Will that UPS relay that connects a computer directly to AC mains open in microseconds? Of course not. Relays take tens of milliseconds. Just more numbers that others never consulted before *knowing*.

So where is that manufacturer spec that lists each surge and numbers for that protection? Does not exist on any power strip or computer grade UPS. So how do they know what even the manufacturer will not recommend?

Will a silly little gap in a switch stop what three miles of sky could not? Of course not. And yet many foolishly recommend turning off. Notice that your telcos always turns on phone service all over town to protect their switching computer. Connected to overhead wires all over town means it suffers maybe 100 surges during every storm. So how often is phone service down for four days while they replace that computer? They don't waste money on solutions recommended by others.

Instead, your telco does what was necessary to protector operators even 100 years ago. Operators did not remove headsets and leave the room. Instead, every wire in every cable was connected to earth ground via a 'whole house' type protector. Essential was the shortest distance to earth.

You install the same solution at the service entrance - on the breaker box or meter. A protector does not do what others have implied. It diverts the direct lightning strike to a pole into earth. And the effective protector is not even damaged by a direct lightning strike. Grossly undersized protectors that do not claim protection in specs - they may fail to get the naive to recommend them. But a properly earthed and properly sized protector even earths direct lightning strikes without anybody knowing a surge existed.

Why do the naive not recommend 'whole house' protectors? No damage protection means they did not even know a surge existed. Such protectors are sold by more responsible manufacturers such as Square D, General Electric, Intermatic, Leviton, Siemens, or Keison. A Cutler-Hammer unit sells in Lowes for less than $50. That is one protector for everything including the dishwasher, furnace, GFCIs, and smoke detectors. Some of the appliances that must work during inclement weather and surges.

Install one 'whole house' protector for the rare (once every seven years) event so that protection already inside every appliance is not overwhelmed. And upgrade the building earthing to meet and exceed post 1990 National Electrical Code requirements. Lightning that is dissipated harmlessly in earth need not find earth ground destructively via household appliances. Exactly why this is the solution even in munitions dumps where surges just are not acceptable.

So where are those numbers from the surge bar or UPS that claims protection? Those posters will never provide those numbers. Even the manufacturer does not claim to protect from the typically destructive surge. Urban myths are popular and widespread. A protector is only as effective as its earth ground.

#11 of 13 OFFLINE   westom

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Posted April 01 2009 - 03:15 AM

Quote:
Originally Posted by Kyle McKnight
I've never (that I know of) had lightning strike a pool, nor has anyone that I know. I wonder how much more likely it is to happen if a person is swimming in the pool...
Popular myths are that lightning strikes the highest point. Lightning is seeking the most conductive path to distant earthborne charges. More often the side of a mountain rather than its top is struck. Often a low valley point because the geology provided a better connection to those distant charges. Pools have some of the best earthing possible making them (maybe) a desirable target.

First, lightning strikes are rare events. Second, well over 95% of lightning strikes leave no appreciable indication. So how would anyone know if lightning strikes pools?

Second, I never saw research on the subject. But professionals did note this anecdotal story. Divers in water that were struck were unharmed if not touching the bottom. The divers that were touching the bottom suffered a shock. Makes sense if using basic electrical concepts. However that conclusion should only be treated as speculation based on trained observation.

#12 of 13 OFFLINE   mickel

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Posted April 20 2011 - 01:00 AM

if lightning strikes the electricity grid, it may well do bad things to anything connected to that grid.


#13 of 13 OFFLINE   Bryan X

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Posted April 20 2011 - 08:56 AM

It's Alive!!!!! :D Gotta love these old threads being brought back to life.


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