Despite my way-too-long post, I forgot to address the question of whether all
grounds should be disconnected during a lightning storm.
As I mentioned, I don't have to unplug each and every devices in my shack, of
which there are many, because I have two AC disconnect boxes that allow my to
quickly cut off AC to the two circuits in the shack. The boxes are designed to
interrupt only the hot and neutral leads (even then they're just a few inches
apart.) But the incoming or outgoing house ground lead is supposed to remain
connected. I believe the disconnect boxes are designed for performing
maintenance on HVAC systems, and I would guess the idea is for the house ground
to remain connected so the large motor start capacitor can discharge, or to
prevent shock if it accidentally discharges to the chassis.
It's possible to disconnect the ground leads, too, but that requires opening
the box (where there's exposed hot AC) and unscrewing the incoming or outgoing
ground lead. And they'd still be just a few inches apart when disconnected, not
to mention repeated wear and tear on one of the ground wires that's being
repeatedly disconnected, bent away, bent back and reconnected.
My feeling is that if the ground system is well-designed and well-engineered
it's not necessary (or possibly inadvisable) to disconnect it from the
equipment. Or at least, it should be. But I don't know enough about how surges
work to be sure. Can someone elaborate? I've heard stories about equipment that
was completely disconnected from everything, including ground, getting damaged
by a lightning surge. Seems to me that if lightning can induce a surge in an
isolated radio sitting on the shack floor, then I'd rather have the chassis
connected to an effective ground system.
73, Dick WC1M
-----Original Message-----
From: Chuck Dietz <w5prchuck@gmail.com>
Sent: Wednesday, September 4, 2019 12:14 PM
To: john@kk9a.com
Cc: Towertalk Reflector <towertalk@contesting.com>
Subject: Re: [TowerTalk] Grounding
Disconnecting the coax, control lines AND ground connection can help protect
your equipment from voltages induced from nearby strikes.
Chuck W5PR
On Wed, Sep 4, 2019 at 10:45 AM <john@kk9a.com> wrote:
> GL rebuilding Keith.
>
> A tower lightning strike will cause an induced voltage spike in a
> home's electrical system, even if nothing is connected to the tower.
> I have had this occur while building a new tower and the control
> cables and coax were not yet connected or even touching the tower.
> Simply disconnecting the coax which many hams do is ineffective
> lightning protection. There is a lot of valuable protection
> information on this list. Assuming that you have a bunch of ground
> rods and a SPG, I would suggest a good whole house surge protector.
>
> John KK9A
>
> from [Keith Dutson] NM5G
>
> My experience is that lightning can be managed, to a point. A direct
> strike to your tower can be catastrophic. I suffered one on May 9.
> My daughter lives about 600 feet away and witnessed the strike. She
> said sparks flew in all directions. My losses are huge. I am working
> with the insurance company, and expect the total damage to be well in
> excess of $50K. There is evidence that high voltage appeared on the
> tower, power lines, phone lines
> (fiber) and even on my wi-fi connection from the house to the shack.
> Every gigabit switch was toasted, and every PC connected was blown.
> Another big loss was two large screen TVs, both connected to internet
> via gigabit switches. Repairs were successful by replacing the power
> supplies.
>
> All this, plus my main two stations, both with Yaesu FTDX9000D and
> Alpha 87A, are gone. Coax was not even connected because I had just
> reconfigured the station and had not completed the coax switching
> section. However, units were plugged into power, and the Yaesu
> transceivers were connected to the PCs.
>
> 73, Keith NM5G
>
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