Do you leave your welder, grinder, drill press, lathe, mill, etc.
plugged in all the time?
We had a lightning strike. Luckily, it hit the house instead of my new
shop! :) It blew everything EXCEPT light bulbs. Some things were
turned on but most were not. That indicates to me that there was a lot
of arcing across switch contacts.
So, how great is the danger of burning some shop equipment? Has it
happened to you? Or even one of Steve B's mythical friends?
I unplug the machines I can, but the larger machines are wired in
permanently. I switch those off at the isolator. I don't think there's a
huge risk of your shop equipment being damaged by a lightning strike.
It's much more likely with electronic equipment. Was most of the
equipment damaged in your house electronic equipment like TVs, VCRs, DVD
players, cordless phones etc?
Here in WA state north of Seattle all my machines are either left
plugged in or are permanently wired. My building is all metal and all
the machines are properly grounded but I know that's no real
protection if powerlines are struck. We just don't seem to get that
much lightning. I did visit a fellow in North Carolina who had his
phone blow off the wall when the lines outside were struck. The
scorched wall was pretty graphic.
A couple of extra grounding rods at the service enterance, and if you
have a well, make sure the casing is grounded directly to the service
enterance ground with at least a #4 wire, the larger the better with no
To promote inferior and profitable products, some
manufacturers will hype a protector as if it were protection.
John has defined the protection. A protector is nothing more
than a 'wire like' device that connects to protection. The
protector (or wire) is only as effective as the protection it
The protection is earth ground - which is why better
protection means enhancing the earthing - as John has
demonstrated. A protector is simply a temporary wire
connection to earth. But if that protector has no dedicated
earthing connection, then that protector provides no effective
protection. Plug-in protectors have all but no earth ground.
Serious protector manufacturers have names associated with
responsible manufacturers - Square D, GE, Leviton,
Cutler-Hammer, Polyphaser, Siemens, and Intermatic.
Ineffective protectors are plug in types characterized by: 1)
no dedicated earthing connection, and 2) manufacturer avoids
all discussion of earthing.
Multi-layered protection will help. However many confused
what is meant by multi-layered. Multi-layered is not about
the protector. Multi-layered is about protection. Your
building earth ground is secondary protection. Primary
protection that a building owner must inspect:
Defined are two layers of protection. Each layer is
connected either by a copper wire (ie CATV wire) OR is
connected by a 'whole house' protector (AC electric and
telephone). 'Whole house' protectors are so effective that
one is installed, for free, by your telco. However, you - not
they - are responsible for the earth ground. Not just any
earth ground. Single point earth ground. All incoming
utilities must connect, 'less than 10 feet', to single point
earthing. If that incoming phone line does not connect 'less
than 10 feet', through the protector, to single point earth
ground, then you have a compromised protection 'system'.
Yes - 'system'. The protection for that electronic
equipment is a building wide 'system'. The most essential
component of that system is earthing.
That means even if a communication wire connects from one
building to another, that communication wire must first
connect to each building's earthing before entering each
building. Earthing is what an effective surge protector
does. Ineffective protectors completely avoid the earthing
Point of use protectors hope you never learn this. They
also hope you never learn that electronic equipment already
has internal protection. Any protection that will work on the
power cord is already inside the equipment. Protection that
assumes YOU will earth the incoming transient before it can
enter the building. Without a building wide protection
'system', then protection already inside equipment can be
Concepts were well proven long before WWII. Your telephone
switching computer, connected to overhead wires everywhere in
town, need not disconnect during every thunderstorm.
Disconnecting is dependent on something very unreliable - the
human. Furthermore, do you really think a few millimeters
separation inside a power switch will stop what three miles of
sky could not?
Ham radio operators even demonstrated the concept. They
would disconnect equipment from the antenna, put the antenna
lead inside a mason jar, and still suffer damage. However
when they earthed that antenna wire, then damage stopped.
Earthing is the protection - not some protector and not a
power off switch.
For residential buildings, Home Depot (Intermatic) and Lowes
(GE & Cutler-Hammer) sell effective 'whole house' protectors.
Other brands are available through an electrical supply
house. But again, the protection is defined by the quality of
earthing. Some examples of how that earthing becomes single
http://www.leminstruments.com/pdf/LEGP.pdf (page 14)
Notice in those figures: even ungrounded utility wires will
carry destructive transients into a building. Every incoming
utility must connect, 'less than 10 feet', to the single
point earth ground. How that earthing is routed and connected
is also important.
But again, the protector is not protection. Layering is
about protection - not about protectors. Building owner is
responsible for installing effective secondary protection -
the single point earth ground. Building owner should verify
that primary protection is also in place and properly
connected. Protection is defined by and is only as effective
as its earth ground - as John has demonstrated.
No doubt, I use to live in South Carolina and they have some unreal
lighting storms that seem to come out of the clear blue sky.
All of my machines were always hot, now the horizontal band saw gets
unplugged cause I can feel from the hair on my arms that it leaks.
I warn my 7 year old girl that they are on. After watching I robot she
came into the shop a couple of days later looking over her shoulders
and asked me if my machines would turn on her. :o) I reassured her
that they are my best friends and they would never come after her
cause she's my daughter. BTW she knows the machines are there to make
robots, but obviously hasn't quite figured out that they themselves
I'm in central Florida and we get a little lightning. I unplug my HF mini
Lathe and my HF miniMill, because of the electronics, but I leave the
Nichols Mill plugged in, as it has a double pole switch and a good ground.
Then again I also leave my computer plugged in , because I'm to lazy to
Are "surge protectors" any real help in protecting electronics? Some years
ago I had the details for wiring and components to make a home brew surge
protector - lost with all the other "gonna do" projects.
a proper surge protector will protect your electronics, but if you have
serious lightning, it must be a multi-stage device - you put a heavy duty
protector at the power panel, and then you can use a spark gap followed by a
small inductor and then a MOV to protect the electronics.
wrote in message
On Sun, 16 Oct 2005 22:28:13 -0700, "william_b_noble"
Lightning arrestors at the main power service and scattered through
the house will help greatly in preventing damage to your 'stuff' from
lightning strikes in the surrounding neighborhood, or that hit the
power line a fair distance away.
But if you get a direct strike on your property, or on the power
line within about a quarter mile of your house, all bets are off.
A healthy direct lightning strike right on the pole serving your house
can easily overload or outlast the shunting capacity of any arrestor.
Unless you believe in spending large coin on some serious overkill -
like the huge power utility duty arrestors and a big welded 4/0 copper
cable grounding grid running around the perimeter of your property
(the kind you'd use as a ground counterpoise on an AM Radio broadcast
transmitter tower) to dissipate the charge.
Oh, and don't forget that the lightning strike can come in on the
telephone and CATV lines, too. And can strike a broadcast antenna or
satellite dish on the roof. You have to bond and protect these other
I have the whole-house breaker-style Murray arrestor on our main
panel to deal with smaller surges, and if we ever get a really big
direct strike "Sh*t Happens". Luckily, lightning storms are a fairly
rare occurrence in Los Angeles.
--<< Bruce >>--
Bruce L. Bergman, Woodland Hills (Los Angeles) CA - Desktop
Electrician for Westend Electric - CA726700
Lightning isn't the only threat. I used to
loose an antenna preamplifier about twice
a year until I figured out that static buildup
was taking it out, usually after a strong
dry wind. Grounding the antenna and mast
fixed the problem.
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