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Re: [TowerTalk] whole house surge protectors

To: "'John Elsik'" <>, <>
Subject: Re: [TowerTalk] whole house surge protectors
From: "Wes Attaway (N5WA)" <>
Date: Wed, 19 Sep 2007 16:58:38 -0500
List-post: <>
I set up the following Cutler-Hammer protectors when I built a new house
about 3-years ago. Everything enters the house at the same spot, so all the
little protectors are in close proximity to each other.  They seem to work
great.  We have had several close hits that knocked out stuff in other
houses around us, but our house was fine.  One hit fried part of a cable TV
connector on the outer wall of our house, but again, nothing happened on the
inside.  All my grounds go to one spot.  

The model numbers shown are Cutler-Hammer, and should be available through
most major dealers or electrical contractors.

CHSPMAX (AC power lines)
DHW4PT (4 Telco lines)
DCXCAB2 (2 cable/sat coax lines)

-----Original Message-----
[] On Behalf Of John Elsik
Sent: Wednesday, September 19, 2007 4:06 PM
Subject: Re: [TowerTalk] whole house surge protectors

It appears I need to do more shopping for the AC protection.
Don't happen to know the GE model number do you?
John wa5zup

> Date: Wed, 19 Sep 2007 16:52:43 -0400> From:> To:> Subject: Re: [TowerTalk] whole house surge
protectors> > I had the ICE suppressor on my mains. I had a lightning strike
earlier > this summer and the internal parts of the ICE box were fried. The
> electrician who inspected the house and did some repairs said it >
probably saved us from much more extensive damage (radios, computer, > VCRs,
TVs, etc. were dead.) He replaced it with a GE unit that has a > quicker
response time and greater Joule rating, and was more expensive> Barry W2UP.>
> John Elsik wrote:> > I have been reading this with great interest. I am
installing a ground system now. I was going to use an I.C.E 330 for the AC
mains (whole house). Would that be adequate? Something is better than
nothing. It looks like it is a shunt type also.> > > > John wa5zup> >> >> >>
> > >> Date: Wed, 19 Sep 2007 10:34:55 -0700> From:>
To:> Su
 bject: [TowerTalk] whole house surge protectors> > I've been doing a bit of
browsing> Most of the whole house protectors are shunt mode (which, by the
way, > can actually cause some problems, making things worse)> > Intermatic
IG1240RC> Leviton 51120-1> Panamax gpp8005> Siemens various models> > etc.>
> In any case, a shunt mode suppressor will also suppress transients >
originating within the house.> > There is a case where they will be of less
effectiveness.. if you have a > transient induced on the branch circuit
between the panel and your load, > then the transient propagates both
directions, and, depending on the > relative lengths of the wire, it will
get to the load before it gets to > the clamp. Once the clamp goes into
effect, an inverted transient gets > reflected back, so you can calculate
the maximum width of the > unsuppressed pulse. (you could use something
like> > >> > > 2 ns/ft as a > propagation speed... so for a 100 ft run, with
the transient induced > next
  to the load (or downstream from the load), you get half a > microsecond or
so before the voltage is clamped.> > > If the transient is induced on a
branch circuit other than the one your > load is on, the suppressor is
between the transient source and your > load, so it would clamp the
transient before it arrives at the load.> > If you put a point of use
transient suppressor *with a higher voltage* > than the whole house
protector, it will take care of the half > microsecond impulse before the
whole house protector kicks in, and won't > have to absorb as much energy.>
> FWIW, statistics show that most transient damage occurs from transients >
originating outside the house, typically from a lightning strike or MV >
line / LV line fault somewhere (MV = 10-30kV, LV = 120,240,480V). That >
makes the rise time of the transient much slower (it's low pass filtered >
by the power line), and a> ls> > o makes the whole house protector more >
effective.> > In the event of a MV/LV short
  (the only kind of line transient I've had > personal experience with in
Southern California.. we don't have much > lightning here), you've probably
got a significant overvoltage that > lasts 8-10 milliseconds or longer
(until the MV breaker trips or fuse > blows). You'd have to hope that the
surge suppressor can hold on that > long without blowing its internal fuses.
Or, ideally, it would short, > and trip your main breaker. Since most of
these whole house protectors > have energy absorptions in the few kilojoule
range, I'm not very > sanguine about their ability to protect against this
kind of fault. > Figure the case of a 14.4kV feeder shorting to the 240V
drop into your > house (this has actually happened to me). If the series
impedance of > the feeder, through the drop, into the grounding system, is
on the order > of an ohm or so, the fault current is around 10-20kA.> > If
the surge pr> ot> > ector is based on an MOV, the 400V MOV is going to >
dissipate about 4-8 MW, o
 r, 4-8 kJ/millisecond. If it takes a half > cycle for the breaker to
trip/fuse blow, that's 8 ms, and about 50kJ > (which is why things literally
explode when this happens).> > A surge protector based on a spark gap,
which, once it fires, has a much > lower clamping voltage, will dissipate
less energy in the protector, so > has better survivability.> >
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