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From: whit@milton.u.washington.edu (John Whitmore)
Newsgroups: sci.electronics
Subject: Re: Whole house surge suppresser ?
Message-ID: <17708@milton.u.washington.edu>
Date: 5 Mar 91 11:35:23 GMT
References: <1991Mar3.132431.22282@dg-rtp.dg.com>
Distribution: na
Organization: University of Washington, Seattle
Lines: 38

In article <1991Mar3.132431.22282@dg-rtp.dg.com> miller@dg-rtp.dg.com (Mark Miller) writes:

>	My house is starting to become littered with varistor equipped
>	power-strips, and now little individual outlet jobbie$, in an
>	attempt to keep some of my equipment from getting fried from
>	AC line spikes.
>
>	So I just had a thought: could you do something in the "fuse-box"
>	and take care of the whole house in one fell swoop? 

	The short answer is 'yes'.  There are some very large surge
absorbers available, which I've heard described as 'a grinding
wheel with metal plates bolted to the sides'.  It's not a joke,
either; the silicon carbide in a grinding wheel makes a fairly
well-behaved varistor.  Some gas-discharge absorbers can also
be found with HIGH current capabilities (kiloAmps); these are
basically neon lamps with heavy-duty electrodes and high-temperature
packaging.
	And there's at least one company that shows up at computer
fairs with their magic box; they had a claim for something large
(like 20 kJoules) that their box could absorb.  They were quick
to explain, however, that you would end up needing a new box
after that.  Lightning, of course, was the target.
	You will find, however, that none of these really wants
to be in a box with any delicate wiring.  If the thing really
DOES get a surge, it will likely melt (and take the main
fuse/drop wire with it).  Also, you will need a good ground
path to attach it to; in some locations that means burying a
few square meters of copper mesh and pouring CuSO4 solution
around it.  

	Is your area plagued by power surges?  I've never had
much trouble in Seattle.  Rural wires have longer runs between
transformers (the power transformer is a very good surge
barrier), so get more significant surges.  Microsecond excursions
to 700-2000V are not uncommon.

	John Whitmore