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Re: [TowerTalk] US Tower damaged by lightning

To: "'K4SAV'" <>, "Towertalk" <>
Subject: Re: [TowerTalk] US Tower damaged by lightning
From: "Jim McDonald" <>
Date: Wed, 28 Apr 2010 17:36:25 -0500
List-post: <">>

My questions really were about repairing the tower, but I welcome any
suggestions on improving the grounding.

The winch was connected to a dedicated 120VAC circuit with a GFI outlet at
the base of the tower.  The lightning followed the conduit into a nearby
barn to its subpanel and then split two ways - into another barn, where it
took out an Invisible Fence (buried wire for dogs) and into the house via
the conduit feeding the barn subpanel.  Another subpanel in the basement,
located next to the service panel feeds the radio stuff.  The surge strips
downstream from that were damaged, but the two computer UPS' and an APC line
conditioner were OK.  The radio outlets and equipment are about 20' from the
service panel.

Two of the lightning radials are 64' long, with an 8' rod next to the base
and rods each 16' after that.  They are buried a few inches.  The wire going
to the third rod came out of the ICE connector block during the strike.  The
wire continues on in a trench to the house, which is about 50' away, with
two rods in that trench.  It continues two directions - into a basement
window well with the grounding panel mounted on another rod and also to the
electrical and telephone ground rods.  In total I have 17 or 18 ground rods
all connected together.

I wish I had service panel arrestors but didn't because we have underground
wiring for phone and electric.

The DirecTV antenna on the roof of the house, about 50' from the tower was
zapped.  No TVs were damaged.  My wife's computer, connected to the router
through probably 50' of Ethernet cable was damaged; the RJ45 plug was
charred.  The Ethernet port in my shack computer in the basement was
damaged, as was the 4-port serial card.

In previous installations of this tower, the electric circuit to the motor
was in PVC rather than conduit.  I just had the outlet replaced at the side
of the barn, maybe 6' from the tower, and I will remove the buried conduit
to the base so I won't have a path from the tower base into the electrical

The phone box on the outside of the house exploded.  I think the lightning
came up the ground wire to it.  The wireless Internet antenna on the side of
the tower was damaged; the CAT5 cable was attached to an arrestor on the
grounding panel and then to a Linksys router, which was destroyed.  The
replacement wireless Internet unit is now on a roof tripod.

I would have disconnected if we had any nearby lightning but there wasn't

There was no other damage to the house or the two barns.  A couple of other
GFIs popped, as did the main breaker feeding the service panel and several
circuit breakers.

Two next-door neighbors reported balls of light on the ground in back of
their houses at the same time as my strike, which I assume were ground
strikes.  They are each about 500' from me (I live on 5 acres).

That's about it.  It was exciting - very loud, bright, and the house shook.
We had smoke outside from around the base of the tower, and we had three
fire engines here.  

Jim N7US

-----Original Message-----
[] On Behalf Of K4SAV
Sent: April 28, 2010 16:43
To: Tower and HF antenna construction topics.
Subject: Re: [TowerTalk] US Tower damaged by lightning

You have a large amount of damage that should have not happened.  You 
should really try hard to figure out why.  After you get all this 
repaired, it would be nice to know why this happened and that you 
corrected that problem that allowed that to happen.  Your insurance 
company won't  be happy to see you returning for a second claim of this 
size either.  It's difficult to make good suggestions just looking at 
the pictures because it is difficult to see the "big wiring picture".   
Making wild guesses is unlikely to help.  From all the burn marks on AC 
outlets and the main AC panel, it is obvious that the AC wiring 
conducted a huge amount of current thru your house. Try to figure where 
the path is that allowed it to get there.  I can see one possibility of 
it entering the tower control box and then down the AC wiring, but I 
don't know where that wiring goes or how it is routed.

I see the entrance panel but it is unclear where that is located.  It 
appears to be inside the house somewhere.  I can't see how long the 
ground wire is from the entrance panel to the AC service ground rod.

I can see three ground wires leaving the tower but I don't know how many 
ground rods are used.   In one picture it appears that one of those 
ground wires (the stranded one) is blown in two.  Is that true (or just 
an illusion in the photo)?  If so, I would want to know why.

Look to see if there are any other burn marks on other objects outside 
the house, like outside AC outlet boxes, water spigots, chimney (which 
usually has a metal liner), roof vents, or even concrete walls (which 
has rebar in many places).  Maybe there was a secondary finger that 
attached itself to one of those items.   Also if for some reason the 
tower ground was poor, the tower could have possibly been elevated to 
such a high potential that a side flash occurred.

Jerry, K4SAV



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