Metal roof and lightning

[musikwerke]

The purpose of lighting rods on a building is to slowly bleed off the earth's energy in that area so that the difference in potential between ground and the atmosphere is as close to zero as possible.  Zero potential equals zero volts.  Think of your structure as the negative post of a battery and the clouds as the positive post.  If the battery is dead (zero volts) no spark, arc or lighting bolt will occur.

[Faron]

We had a wild experience here Wednesday night.  I was sleeping in my chair about midnight and was awakened by a thunderstorm.  I hadn't completely got my bearings when lightning hit the house.  Chris was asleep upstairs, and for some reason I was sure it had hit there.  About the time I reached the foot of the stairs, the smoke alarm in the living room went off.  Went ahead upstairs, and met Chris at the top of the stairs.  I have never seen anyone with a more terrified look about them.  The power had never even flickered.  We started looking around for any smoke, and the power flickered off and on.   A few seconds later, another tremendous blast. Chris was looking toward the barn and said, " That one hit the barn!"  She later said it hit the north peak of the roof, and rolled down the metal roof in what looked like waves. 
The smoke alarm shut off on it's own, and we never saw any smoke.  The strike to the house tripped most of the ground fault receptacles in the house.  The breaker to the air conditioner fan tripped as well.  All the appliances including the freezer seem to be ok.  My new fence charger was toasted.  I can find no structural damage to either the house or barn.

The scary part is Chris went to bed feeling fine.  When she got up after the strike, she had a tremendous headache, and just did not feel well.  That persisted all day yesterday, and much of today.  She says she has the impression of light rolling across the bed as she awakened, although she can't be sure just what was happening.  I am pretty sure she got shocked to some degree.

My cattle came back to the barn to drink for the first time late this evening.  I suspect they were in the barn when it got hit.

[Tom]

A quadruple shot of adrenalin would probably go a long way towards givin someone a headache too, even without electric shock.   Zowie, Batman  What  a Frizzle......Pop! :D

[Don P]

I'd tell her to slide to the far edge of the car seat next time you're driving in a storm just to be on the safe side  ;D.

My Mom wrote this morning that Granny Barnes house got hit this past week. She was my great grandmother. It is one of the old homeplaces. Great big pecan trees, smokehouse out back. The old coke box in the packhouse down by the tobacco barns served up drinks that would turn to slush as you popped the top on a blistering hot afternoon. Years before I was born my uncle got struck and laid out flat there dashing back from the privy but was not hurt. Some years later my cousin and I were playing a game of hide and seek and were up in a tree, not ready to be discovered even though a storm was brewing. A bolt hit Miss Elsie's phone pole right beside us. We decided to call it a day.
The old house started as a 2 room farmhouse that my Great grandfather moved into with his new bride. It has been added on to multiple times. The kitchen throughout my life had always been on what used to be the back porch so the floor had quite a slope. One of my great aunt's had gone through the floor when the termites got into it, luckily no dogs were injured in the incident. It is one of those family shrines people keep pouring money into restoring or keeping up. They have just finished another renovation so my cousin and her husband could move into it and their daughter with new family can have their house. The big news was the kitchen floor was now level and it has a granite countertop, what would granny have said. The strike did $10,000 in damage  . I reckon this will be the quickest change of appliances that house has ever seen. It used to have lightning rods, I'm not sure if they were still on for this last blast or not.

I don't know for sure but I suspect some spots are just hotter than others as far as strikes are concerned. I wouldn't consider our house particularly out of the ordinary as far as that's concerned but we are tucked down between 2 peaks that are roughly 600 and 1000 feet above us. I've seen 4 bolts land in the trees and yard and the trees show signs of others. So even with some pretty fair protection they still find their way down here.

[pappy19]

In my younger days I worked for a cabin builder in Island Park, Idaho. All of his roofs were metal. He had a number of owners that wanted lightning rods. Almost all of those that we installed eventually had lightning strikes, while those that didn't, only one had a strike and it wasn't hurt. Why?? The fellow made sure that his water lines were grounded. Back then all of the water lines were steel pipe in case they ever froze, they could be thawed using a a welders rig. Anyway, point being that grounding is more important than a rod system. Large diameter copper wire or mesh also works great. We ran some of this out from the home buried at 2-3 feet for 100'.

[Ron Wenrich]

My house and garage both have a metal roof.   The barn has an asbestos roof.  The barn and house both have lightning rods.

I've had 4 strikes in the area in the past 30 years.  One of them hit might have hit a lightning rod.  None of them hit any trees that are higher than the house.  One hit the dusk to dawn light next to the barn, and sits lower than the lightning rods.  That one blew the fuses out of the fuse box in the house.

The last one hit in the middle of the yard and missed all the buildings and trees.  It was during a birthday party, and the guests were sitting under the porch except for me and another guy.  We were in the barn.  When that one hit, we saw a glow inside the barn. 

I've been close to a number of lightning strikes.  I've always noticed you could hear the crackle of the lightning before the thunder. 

[DanG]

A direct hit can be devastating, but most of the lightning damage you will see in houses comes in on the power line or the phone line.  Frequently, that lightning has struck somewhere other than on the premises, maybe even miles away.  Your only defense from this is proper grounding of your incoming power line, and of the protector outside your house where the phone line comes in.  As FDH suggested, double up on your ground rods.  Your soil type may have a large bearing as well.  Heavy soils hold more moisture, and hold it longer, so they make better grounds.  If you have sandy soil that drains well, look into putting in larger and deeper ground rods.

Submersible pumps are notorious victims of power line hits.  To protect your pump, bond the neutral side of your power line to your well casing with heavy wire, via a copper bolt.

The best way I know to locate a real expert on grounding is to ask a telephone man who does their bonding for them.  It is usually a local electrician, and he would be the go-to guy to make sure you're protected as well as possible. ;)

[Fla._Deadheader]

We used to use a "Megger"-"Meggar" to test the ground for driving 8' ground rods, next to poles. Sometimes we would stack them 3 deep using heavy brass couplings. I HATED to drive them. Took forever and you used a sledge or the dinky Ground rod driver. That's usually the "Grunts" job.  : ;D :D

  The Megger-Meggar is very important for grounding Transformers for Underground-direct burial cable. At least it was in the 60's early 70's, when I was a lineman.  : :  ;D ;D

[DanG]

The megger would be the instrument of choice to test your ground, for sure.   The power company guys know all this stuff, but too often they don't take the time to check things out properly.  F'rinstance, when I put in the temp pole at the house site, both the brass clamps on the ground rods were cracked.  The building inspector didn't catch it because he never looked at them.  I replaced them after he had signed off on it. : :D  Then when the Electric Co-op guy came to hook it up, I was standing right there the whole time, and he never looked at them either. :

What I'm saying here is, YOU need to check these things out for yourself, or hire an electrician and stand over him while he checks them.  Otherwise, you will never get that peaceful night's sleep that was mentioned. ;)

[Larry]

The best way I know to locate a real expert on grounding is to ask a telephone man who does their bonding for them.

Hey...I know a guy like that...well maybe not a real expert and most defiantly a has been.  

Done my share of Meggering...is that a word?  Just for those wondering the megger is a fancy ohm meter for measuring ultra high resistance...and probably an antique instrument in this day and age.  For most residential housing the phone protector is simply grounded to the power ground rod to insure no potential differences between the phone line and power line.  Repeaters, and small equipment stations are normally grounded with 3 ground rods just as FDH described.  Towers, central offices, and bigger equipment stations were grounded with rings, and even wells.  I've spent sometimes as much as a week designing a ground system.  Many times connections had to be made by cadwelding and inspected by a guy like me.

So...we just moved from a house that was the highest point round and had a metal roof.  No lightening rods or ground but it worked for 18 years.

I have a question for you electrician types.  I'm building a new house and doing my own electrical.  I've heard the NEC has changed somewhat for the power ground.  Something new called a UFER...I haven't had time to investigate but I think?? I'm supposed to bond to at least a 20' stick of re-bar.  The reasoning is concrete is more conductive than soil. The guy that was telling me about it said something to the effect it was a great way to ground.  Somebody in the real know care to enlighten me before I get in too deep?

[TexasTimbers]

Done my share of Meggering...is that a word? 

Megging. Done my share of it too in the USCG. Of course I wasn't megging ground rods. We had to meg any antennas or cable we ever replaced on or in an airframe to make sure they weren't grounded to the fuselage.

Faron your story backs up what I said about grounding a metal roof. It should be grounded IMO. Hope your wife doesn't have any long term problems - it sounds like it passed through her to some degree.