As Fred mentioned, MOVs gradually fail. And the failure mechanism is a
gradual reduction of the "trigger voltage". As the trigger voltage
slowly drops, the MOVs start disappating power at the very peak of the
AC line voltage. If you are lucky, you find a warm device. But most
often they fail sight-unseen. Once in a while if installed in a plastic
"outlet extender", they start a fire. Beware.
John AF6QO
On 1/6/2016 3:28 PM, Fred Townsend wrote:
I would disagree with the use of MOVs at the service entrance unless there are
inductors preceding.
The key words in this discussion are protection systems. There is no one
component or silver bullet that will protect all. The chances are if you take a
direct strike there will be damage so unplugging is still a good idea. You
would like any damage to be to cheap things like surge protectors that are
easily replaced. Having said that MOVs are cheap but they are not lighting
protectors so it is foolhardy to build your principle lightning defense around
them. For those wondering a surge is like when the secondary power line falls
down on the low voltage line or a lightning strike AFTER the leading edge of
the wave front is diminished. In short MOVs work in milliseconds. The leading
edge of a lightning burst is in the microsecond range. Transorbs, gas
protectors, capacitors, and carbon protectors are shunting devices in networks
that work in the microsecond range and can be used at the service entrance.
Series Inductance is a great way to knock off the leading edge but absolutely
defeats your protection system when used in the grounding system or green wire.
Remember ALL conductors have inductance so shorter is better. Never coil or
square a ground wire.
Maintenance of protection systems is essential too. Transorbs and carbons fail
shorted. For this reason VDE sometimes requires these type components to be
protected by fuses as well. Gas protectors and MOVs fail open. MOVs fail
gradually too. Capacitors and inductors take physical damage too and can fail
either open or shorted. After your big lightning storm these components should
be inspected and replaced if you see black smudges on or around them. MOVs will
physically deteriorate and are easy to spot defective ones.
73,
Fred, AE6QL
-----Original Message-----
From: Elecraft [mailto:[email protected]] On Behalf Of Jim Brown
Sent: Wednesday, January 6, 2016 1:35 PM
To: [email protected]
Subject: Re: [Elecraft] Lightning Protection (was-Re: suggested PC???)
YES!
Another VERY important thing is to NEVER use "MOV surge protectors" on branch
circuits. They're great at the service entrance, as Bob recommends, but they CAUSE
equipment damage when used on branch circuit, because the MOVs dump the lightning spike
onto the Green wire, which creates a high voltage spike on the Green wire. That voltage
is different at every outlet and at every piece of gear, and the difference shows up as a
common mode voltage between interconnected equipment.
THAT'S what blows up stuff connected by wired Ethernet. We discovered this the
hard way about 25 years ago in the pro audio industry.
The ONLY safe surge protectors on branch circuits (that is, next to
equipment) are SERIES MODE protectors. They work by storing the surge in a big
inductor, then slowly discharging it. They're more expensive, but they won't
blow up your gear. The only mfrs I know of are Brick Wall, Zero Surge, and
SurgeX.
Also critical -- bond ALL grounds together, including the shack ground, CATV
ground, TELCO ground, etc., and back to the power ground.
73, Jim K9YC
On Wed,1/6/2016 11:35 AM, Bob McGraw K4TAX wrote:
Two things I've found to be a big deterrent regarding lightning damage:
(a) all driven grounds must be bonded back to the AC mains ground and
this must be done outside of the house. I use some 1/2" flexible
copper water line as my bonding conductor. It is trenched around the
outside of the foundation about 6" deep from the tower ground and coax
lightening protection system back to the AC Mains ground some 50 ft away.
(b) Install a whole house surge protector at the main breaker panel.
These are sometimes referred to as Secondary Surge Protectors.
Usually should be installed by a qualified licensed electrician.
73
Bob, K4TAX
On 1/6/2016 11:52 AM, Barry Baines wrote:
Neil:
On Jan 6, 2016, at 8:25 AM, Neil Zampella <[email protected]> wrote:
FWIW ... I've got everything setup wired in the shack, but
everything (cable coax, ethernet, power) runs through an
uninterruptible power supply (ups). Many of the higher end models
provide not only power surge protection and battery, but
lightning/surge protection for coax and ethernet.
By ‘coax’ do you mean cable TV coax or are you suggesting RF coax for
amateur radio transceivers? Clearly, UPS surge protection is not
designed for anything on the order that an amateur transmitter (even
QRP) can produce. Further, UPS devices presume 75 ohm coax systems,
not 50 Ohm as used in amateur radio antennas and transmitters. They
are designed to protect a TV antenna or a cable setup box/cable modem.
My shack in Georgia was impacted by an indirect hit in 2014 which
damaged computers, amplifiers, ethernet switches, and a myriad of
gear that was ’networked’ in the shack as well as the house, even
though I have Polyphasers on all of my RF cables going into the shack
from the tower with an extensive ground system for lightning surges.
What I didn’t have was adequate protection on my ethernet, coax from
DirecTV, and telco lines in the shack where presumably the surge
entered. I didn’t want to go wireless on the LAN because I operate
my station remote and wireless connections introduce a potential
failure point that can’t be fixed unless I’m there to reset
something. Wireless is also slower than wired ethernet.
My solution was to purchase Ethernet-to-Fiber converters to isolate
my LAN network in the shack from the rest of the LAN in the house as
well as provide isolation from individual components from one
another. Thus, I ran dual 110 ft. fiber from the house to the
hamshack (through existing buried conduit that also carries telco and
DirecTV) that will keep surges from coming into the house through the
ethernet connections from the shack. I installed switches in the
shack that have both LAN and Fiber so that I could isolate nearby
components from the network in the shack. I use ethernet-to-fiber
converters with short fiber jumpers to individually isolate my high
end equipment from the network (such as a Flex-6700 and the
computers in the shack). These converters have no impact on the
ability of the network to communicate (still 10/100/1000 MB depending
upon the component that it protects). I consider this an insurance
policy—the cost of the fiber being significantly less than the cost
of replacement of damaged equipment. Each converter has a 5V ‘wall
wart’ which is plugged into a UPS primarily for surge protection but
also keeps the network up in the event of power failure or momentary
power fluctuation.
I’m still in the process of installing protection for the DirecTV
line coming to the shack as well as the telco lines in the shack. I
have a central ground panel where I will install the protective
devices for telco and DirecTV by the existing RF surge protectors.
One challenge is finding a lightning protection device for DirecTV as
they feed power through the cable to power the LNB at the dish. When
I spoke with a DirecTV technician, he had no suggestions on what to
use. There are devices out there, just need to find them. I also
have a Speco Technology PTZ analog camera on the tower with 75 ohm
video, 12 VDC power, and RS-485 control lines will also be protected
at the same ground panel. I’ve found suitable devices for the
camera’s connections.
AC power is also a concern. A UPS is adequate for 120 VAC equipment
such as computers and monitors but won’t protect 220 VAC devices such
as high power amplifiers. I’m still hoping to find a suitable surge
protector designed for 220 VAC systems to plug between my amplifiers
and the 220 VAC wall connection.
From an Elecraft perspective, I use fiber-to-ethernet interfaces
between the Remote Rig devices and my network. Thus, if a surge were
to go from the K3’s RS-232 port to the RemoteRig RCC-1258MKII, the
surge won’t be extended through the Remote Rig to the LAN. My
KPA-500 is attached to a RC-1216H (which provides a web interface for
controlling the amplifier) which in turn has a ethernet-to-fiber
interface which protects the network from a surge coming through the
RC-1216H. My KAT-500’s serial line is attached to a Lantronix
Serial-to-Ethernet interface device which in turn is attached to an
ethernet-to-fiber interface. As my rotor controller RS-232 line is
attached to the same Lantronix box, any surge coming from the rotor
interface will also not go through the LAN network. Thus, there are
no RS-232 line connections directly from my ham equipment to a
computer, providing additional isolation for the computers. I can’t
say the same thing about USB connections, as some devices such as a
Fun Cube Dongle won’t work if attached to a USB-to-Ethernet
interface. However, I do use a USB-to-Ethernet device for my
Wavenode WN-2.
73,
Barry Baines, WD4ASW
Westborough, MA
Folkston, GA
Neil Zampella
KN3ILZ
On 1/5/2016 8:14 PM, Gary K9GS wrote:
Hi Jerry,
Don't use a wired network. I had my shack computer on a wired
network when I took a lightning hit a couple of years ago.
Everything connected on the wired network was zapped (2 PCs,
router, modem, K3 RS-232 port, WinKey (connected to one of the
PCs), and the Cable TV amplifier located over 150 ft away out by
the road. When I rebuilt everything i went wireless with all of my
PCs and have never regretted it.
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