Surge Suppression - Intermatic?
Joe
the computer just don't work. One on the rug behind the cabinet actually
burned during a surge. But effective surge protection must be possible
since the telephone companies don't replace most of their switching
computers every year. A computer with overhead wires located everywhere
would be very prone to lightning strikes.
So how does one install cheap effective protection? How does the
telephone company do it? I have been told that many backup power
supplies don't include surge protection and are also damaged by
lightning strikes. Is UL1449 important? I am told that effective
protection must be located where wires enter the building.
What should I purchase or have installed? What surge sources should
I worry about? What happens when the line transformer shorts to the
high voltage primary? What keeps a power company short to the Cable TV
wire from destroying my TV and cable modem?
An Intermatic device has been recommended. Does it solve the above
questions?
Ed Schick
for the surge or poorly designed, a surge can still
get through and samage your equipment. And
deterioration over time can reduce the amount
of energy they can absorb.
The best approach, in my view, includes using at
least 1 good quality supressor with a guarantee to
replace/repair your equipment if it is properly
connected to the protector and damaged by a surge.
I use whole house (installed at the panel), one good
quality Isobar, a Triplite UPS that includes supression
and a LOT of MOV's. I add 6 MOV's each year.
They are cheap, impossible to test and degrade over
time, but their energy absorbing capability is additive.
I have plenty of room inside the case of the "power
distribution" unit that sits under my monitor and
includes switched receptacles for the PC, monitor,
printer and 2 auxilliaries. So, because it is easy and
cheap, and because I can't test MOV's, and because
their protection is additive. I add a pair each year
between line & neutral, between neutral and ground
and between line and ground. Ed
Ed Schick
tom
surge protectors. At best, they only provide secondary protection. Stories
are numerous defining computers AND their surge protectors destroyed by
lightning - unnecessarily.
Any computer or other household device damaged by lightning is directly
traceable to the owner's failure to protect his equipment. As you noted,
the telephone companies don't sacrifice their multi-million dollar computers
to lightning. They use technologies pioneered in the 1930s. You should be
doing same but with the latest technologies.
Two surge types are defined here - the differential type from overvoltage
and the common mode type from lightning type surges. Differential types are
easy to protect, rarely occur, and are terminated if common mode type surge
protection have been installed. This discussion will be limited to
lightning type surges.
Lightning is seeking - what? Earth ground. You don't stop lightning. You
provide a shorter path to earth. The best place is where each wire enters
the building. Surge protectors don't stop lightning. They only short all
the wires together. They only protect if one of those wires is connected to
earth ground - by a short, heavy wire. Typically, this is the recently
required, NEC ground wire to ground rod. But experience dictates that this
wire must be less than 10 feet long to a very good earth ground connection.
Forty feet of ground wire to the water pipe is too long.
Your Intermatic device would be an IG1250 for a 200 Amp residential service
connected in the fuse box after the 200 Amp main breaker. Any lightning
surge that enters on any of three power wires is shorted to earth ground by
this device via the neutral ground bar and <10 foot ground rod wire.
All wire contains inductance. Because of lightning's higher frequencies,
the heavier earth ground wire provides less inductive resistance.
Llightning will take that lower reactance path. Furthermore, long 15 Amp
and 20 Amp interior power wires have higher inductive reactance that add
additional protection - but only if the primary surge protection is back
where the wire entered the building and is very adjacent to the earth ground
connection..
Those phone company grey boxes labled NIC are also surge protectors. But to
work, the earth ground connection must also be short to an earth ground.
Many telephone company installers failed to run this earth ground wire
directly to a ground rod. Every surge protector must have its own wire
direct to the earth ground rod - only joining the wires from other
protectors at the earth ground connection. Protectors must not share a
common earth ground wire.
Experience has proven that direct lightning strikes (one so large that it
partially melted a bus bar in the meter) need not ever damage electrical
equipment. A common damage scenario: Lightning enters the AC power, travels
on black (hot) wires to the computer in search of earth ground.
Encountering the scam type surge protector, lightning is shorted to all
computer wires. It enters the computer, travels through the motherboard PC
traces and semiconductors, where it finds the modem. It then travels down
the telephone lines back to where the telephone company has installed the
NIC - and exits into earth ground. Other paths may be via the linoleum
floor tile or the countertop. Regardless, your computer and modem have been
damaged - unnecessarily. Notice how the plug in surge protector can
increase damage because they are only intended to be secondary protection at
best. Many are simply scams.
The only "adjacent to the computer" surge protector that offers any
protection must be constructed using torroids. After you pay for all those
torroids, then what will you do to protect your microwave oven computer or
your clock radio computer or your TV computer? However, for $50, you could
have protected everything in your house with the Intermatic IG1250 or
something equivalent. I mention Intermatic because many other surge
protections companies could not provide technical information. In fact some
"in the fuse box" protectors are only defined as secondary protection -
implying that they don't have sufficient power handling abilities. Siemans
makes in box protection that may be sufficient, but I have not obtained
technical information.
The bottom line is that all electronic equipment can and should be protected
from surges AND most "adjacent to the computer" surge protectors provide so
little protection that they should be called scams.
Joe wrote:
> Experience proves that most if not all of those surge suppressors for
> the computer just don't work. ... But effective surge protection must be
> possible
> since the telephone companies don't replace most of their switching
> computers every year. ...
>
> So how does one install cheap effective protection? How does the
> telephone company do it? I have been told that many backup power
> supplies don't include surge protection and are also damaged by
> lightning strikes. Is UL1449 important? I am told that effective
> protection must be located where wires enter the building.
>
Ed Schick
as I see it.
But you contradict yourself. You stated that
lightning surges are common mode, then stated later:
"Lightning enters the AC power, travels on black
(hot) wires to the computer in search of earth ground.
Encountering the scam type surge protector, lightning
is shorted to all computer wires." You are describing
a differential mode surge. If it is a common mode
surge, then the logic you use (to support the idea that
there are scam protectors that actually cause more
damage) is faulty.
But there is nothing amiss with the idea that you need
a GOOD ground, which seems to be the main point
that is often missed when folks run out and plunk down
their five bucks to buy a "scam protector". They are
a scam, too, when you look at the packaging. They
often come with a lightning bolt drawing on the package.
I haven't seen one of these where they explicity state you
will be protected from lightning created surges, but it
is clear that at least some of them imply that.
A point you might find worth looking into:
a common mode, lightning created surge
entering the service panel can become a
differential mode surge. Ed