Well, Happy 4th of July to all.

Had a real electrical storm at the ranch while out of town. I noticed that an oak tree [2.5 ft diameter] had the bark/cambiun stripped off of it from the top main branches all the way down to the trunk to the ground. It wasn;t until later that I went inside the shed next to it and noticed a broken [blue] plastic electrical box, with the on/off switch still in the center...the plastic cover plate was gone...it was shattered and shot across [20ft] the inside of the shed...obviously, the lightening tranfered somehow to the swtich/wire and exploded it.

The romex to the switch goes about 35 ft to a metal junction box, then the wire from the junction box goes about 140ft undergrd/pvc to the 100amp service..the 20amp breaker was thrown. I shut it completely off and tested the wire for any juice and negatitve...i then replaced the plastic box and plate, but used the same switch. afterwards, flipped the breaker and the light switch turns the light on/off fine and so did the other switchs/lights in the next shed that also runs off the same junction box.

I usually leave the breakers off unless i am there, but this time forgot to turn it off...I guess with the hit and everything working, I grounded it well and nothing is wrong from visual inspection. Is there anything I should do or check just to make sure? I am d-gone lucky I was not in the shed when the lightening hit...that switch plate was broken into 20-30 pieces and the plastic box was also shattered, split and burnt. The oak tree truck is about 25-30 ft from the switch...be careful in storms

tstex

you don't need a direct hit to have failures from a near strike. I have had lots of burned up boards and dead 4-wire modems in an old time data switch from strokes conducted down a tall tree, and induction into telco cable running near the roots.

(1) there is no "lightning protector." there are surge suppressors. they will be blown through a block wall if they actually have to deal with a direct strike.

(2) nobody has lightning rods installed unless it's the barn or 3-story farmhouse on a flat plain in the middle of nowhere. that's the only sure defence, taking a hit for the team and running it into an engineered ground with wire hefty enough to take the thousands of instantaneous amps and millions of volts in an average strike.

(3) trees are iffy conductors. a tree strike is likely to flash sideways to any better ground. lightning is always seeking the best route to ground at any time, any place. metal siding close to ground? ungrounded satellite dish or TV antenna? metal entrance mast or powerlines? homeowner dude in the back yard with an umbrella and metal flashlight looking to see if there was any damage from the last hit?

if you're at the highest spot around, you need to have a solid conductive good path to ground pointing up in the air to sucker off the strikes and bleed 'em away from you. TV and radio stay on the air due to massively good grounding off the (often insulated from ground) tower's lightning leads.

there are bleeds with each strike into the transmitter. transmitter cabinets often have "strike balls" of brass or stainless that shunt most of that to the site ground web, and a safety circuit will take high voltage off that cabinet for a second or two to further protect the output stages.

these grounds are NOT one rod with #6 wire driven into the ground. they are hard lines able to carry several thousand amps in a radial or grid pattern with multiple rods sunk off the pattern into good conductivity earth. a house or ranch grounded to code on opposite corners is better than nothing.

inadequate grounds? oh, look, it's a fire truck.

but best off to provide an irrestible target that goes straight, harmlessly, to ground. several thousand bucks, easy.

oh... wired outbuildings should each be grounded and bonded to the service entrance ground with at least #6.

This message has been edited. Last edited by: swschrad,

The most likely place for any damage will be at any connections - switches, outlets, or fixtures. The good news is that these areas are accessible for inspection. Check a few of the above to look for burning across any connections. If you can't find any then it's a pretty safe bet that your straight wire runs (even underground) are likely OK.

Thanks Guys...And yes, that would be one HOA surge protector to hold the lightening back, and I will ck all of the connections...I just hope the tree makes out ok because it is on the west side of the shed and really shades it from the intense sun.

Hope you all had a great/safe 4th...tstex

I've seen it hit a tree and travel to a chainlink fence that was touching the side of a house in two places.
It blow a hole through the T-11 and looked like a cannon ball had gone through the wall, the sheetrock and insulation were across the roof from where the hole was. It blow apart the chimmney on the other side of the house where it touched.

On another house it hit one of those cheap pop up dining flys and traveled down the power line to the garage into the house and blew up all the phones, ansewering machines, we found a hole in the side of the house where a door bell had been and the button was out in the street.

Jaybee, a good inducted surge from lightning will poke holes in wire insulation, little pinholes all over the place. which is probably OK dry. should the cable get wet, that's a whole 'nother story.

that's the reason our telco's cable maintenance guys are out poking holes in aerial cable jackets and drying lines with welders strapped across the pairs all the time. it's OK dry, but crackly or down wet.

no clue whether anybody has done any studies on common THHN or THHW wiring used in homes and businesses. we used to have a renowned professor at U of MN who did that in the shade of a 330,000 volt transmission system and substation, but he's been gone 30 years, and his apparatus some 15 years.

Good post by others, and I am not surprised. That is the norm.
You may want to check your breaker with an induced short, ONLY IF YOU FEEL YOU ARE ABLE TO DO THAT SAFELY. Also put a meter on the circuit to test the voltage present might be a good idea as well.

This message has been edited. Last edited by: CommonwealthSparky,

wild-donkey question, sparky.

I made the acquaintance of a circuit breaker tester about 30 years ago working part time at a hospital. I presume that is a rare bird not carried by most practical electricians. but just how many techs do you think actually have one?

(( considering the consequences, I wouldn't live-test a breaker for fails without one, unless I had another pull-out panel I could install the suspect unit in, and then feed it from a presumed working circuit in the main entrance... ))

quote:

Originally posted by swschrad:
wild-donkey question, sparky.

I made the acquaintance of a circuit breaker tester about 30 years ago working part time at a hospital. I presume that is a rare bird not carried by most practical electricians. but just how many techs do you think actually have one?

(( considering the consequences, I wouldn't live-test a breaker for fails without one, unless I had another pull-out panel I could install the suspect unit in, and then feed it from a presumed working circuit in the main entrance... ))

Actually, I don't have one, as any piece of insulated copper could become one, rather quickly I might add. And has from time to time.
A good friend of mine has made up "AS HE CALL IT A TESTER" and I use that word with care. It is a small length of appliance cord dead shorted together in a covered handy box with a male three prong plug on the business end. Works every time. But I digress as he will use that to find the proper breaker to deaden. I run a Shop Vac or an XM radio 99% of the time to do that.

This message has been edited. Last edited by: CommonwealthSparky,

I went back to the 100 amp breaker [where the lightening went back to and where i ran off the main house 200amp breaker]. The electric hot water heater that I installed runs off this 100amp service, and all is fine,,,everything else seems to be checking out fine, and no signs of burnt/distored wiring or connections...hopefully the live oak will make a full recovery as well...as always, thanks a million for your help and feedback - regards, tstex

PS - I do have a huge racoon that keeps eating all of the bird seed out of my two b-feeders, so I am going to rig-up an electric grounding rod to both feeders so if he is eating at night and a storm comes by, I might get him...

sparky, in high school we called that a "test prep kit." the guys in the back row sometimes used it.

a dandy way to find out if you have serious faults with the wiring in the panel. if the house burns down, you had a bad panel. I say that, of course, after researching the good old arcwelder in our basement, a FPE.

fortunately, bus is good, and a master found five famous FPE no-trips for me. I found three more over the 6 years we've been in here during the process of remodelling rooms. man, those replacements are costly. but I can't get the wife onboard with an entrance replacement.