Lightning danger from ungrounded Sky installation?

sky
lightning

#1

I’m curious, I have an engineering background but not in EE and I have only minimal experience playing with electricity. If I install my SKY unit off the peak of my roof using a 3 foot steel pipe mounted off of an old satellite dish mount and don’t run a ground (because complicated geometry) what’s the danger? I imagine if the post or SKY unit itself were struck the unit would be annihilated but what else is likely to happen?

Where I live noticeable thunderstorms happen around every 5 years or so.


#2

You should likely consult a licensed electrician if you know anybody…


#3

True and I probably will if I need to go with that install location. I was just curious if anyone would throw out a “OMG you don’t want to do that, your house will explode” and explain why. :slight_smile:


#4

Let me give you the best reason. If your house is struck by lightning and burns to the ground, can you afford to pay for it should the insurance company declare that your ungrounded, non-NEC-compliant mast was negligence as they decide not to pay for the loss?

As for houses exploding, my late father built a house on top of a mountain. Before the walls were even framed in, it took a lightning strike that turned a telephone coiled cord into a charred knot of seaweed. He was a ham radio nut, and insane overkill with his lightning grounds. The week before the house was scheduled to be sold, it took another strike on the electrical service mast, which singed some outlet wires and started a smoldering fire in an outside wall, but was generally shunted to ground.

There’s a reason why I’m the forum lightning ground nag, and I pray that nobody else ever have to live through thunderstorm evacuations at all hours of the day/night because the house was hit so many times…


#5

I lost a rather expensive radio site in the South Pacific due to lightning an improper wiring to a copper plate. Who knew you should not attract an antenna array to one corner and the shack to the opposite corner of a 24 foot square plate.


#6

@vreihen is right that in many instances insurance companies have been known to decline to pay claims when it is discovered that there is any code violation in the affected structure. This can certainly include failure to comply with NFPA-780 (the National Fire Protection Association lightning protection standard).

Lightning protection serves two purposes. First, it is intended to bleed off the static charge that builds up during a thunderstorm in hopes of the lightning strike finding some other target where the static charge is greater. Second, it is intended to provide a more attractive path to the Earth than the rest of your bulding provides . . . hopefully allowing the lightning to go to ground without cooking your building in the process.

There are very specific standards for lightning protection, including such things as minimum bend radius of the ground wires as they are routed down from the top of the building (this is because lightning has a tendency to take the shortest route and will arc from one point on the ground wire to another if the bends in the ground wire are too sharp . . . and, of course, that arc is a good way to start a fire in the materials in its path).

If I were to put a metal mast up above the top of my building, I would certainly provide it with a good ground wire, routed as directly as possible to a good ground rod.

Dan.


#7

I grew up thinking that “QTH” was an acronym for lightning target… :slight_smile:


#8

You are too, too funny . . . :grin:


#9

@chris.king This is a good question. From what I understand, a lightning strike would have to come within “x” ft of your house in the first place in order to be drawn to a object at “x” height above your roof. Where x is 3ft in your case, your SKY might be the highest object attached to your house, but a bolt could just as easily connect with the other side of your roof instead.


#10

Lightning has hit the roof of my house in the past, I found a piece of partially melted roof tile on the lawn after a thunderstorm 15 or so years ago, near as I can remember that was about the extent of the damage nothing inside the house was affected, which may just have been dumb luck.
Based on the comments here I’m thinking I’d need to change my planned installation location because there’s no way I can reasonably run a ground wire without putting some significant bends in it.
Here’s a picture of where I’d been hoping to put the sky: