Path: utzoo!utgpu!jarvis.csri.toronto.edu!rutgers!tut.cis.ohio-state.edu!ucbvax!decwrl!shelby!neon!kaufman
From: kaufman@Neon.Stanford.EDU (Marc T. Kaufman)
Newsgroups: comp.sys.mac.hardware
Subject: Re: Leave it on?  Or once a week?
Message-ID: <1990Feb21.064352.11895@Neon.Stanford.EDU>
Date: 21 Feb 90 06:43:52 GMT
References: <7715@tank.uchicago.edu> <1189@swbatl.UUCP>
Organization: Computer Science Department, Stanford University
Lines: 49

In article <1189@swbatl.UUCP> george@swbatl.UUCP (George Nincehelser 5-6544) writes:

>Is it really worthwhile to unplug everything when a thunderstorm
>approaches?  In my experience, when lightning strikes close by, my
>electronic stuff is the least of my worries.

The National Electric Code specifies that the neutral wire coming from the
utility is to be grounded at the service entrance.  In most houses, the ground
is not very heavy wire, and is often not really tied to a "ground" [in my
previous house, neutral was grounded to the water main ... which was a 3/4"
pipe coming out of the ground.  Unfortunately, just below the surface, the
pipe was connected to a long run of PVC pipe that went to the water meter].

I would guess that those with overhead service are more at risk than those
with underground service.  Lightning induced surges would tend to arc to the
grounded neutral.  All bets are off for a direct hit.
 
>My inlaws had their house hit recently.  Everything electronic was brain
>dead in this case, but my inlaws were more worried about the smoke 
>(luckily there was no flame) coming from the hit sight.

In my area a more common problem is the neutral wire becoming disconnected
at the supply transformer.  This puts 220 volts across all of the active
house circuits, in an unbalance manner.  One leg may have 50 volts, with the
other phase at 170 volts.  This also fries equipment (but shouldn't fry a
newer Mac, with the universal power supply).

>In both cases, fire seemed to be the biggest worry.  Insurance paid for
>all damages in both cases.  So for other than important data (which you
>should have backed up and stored off-sight ;-) is it really worth the
>effort to unplug everything?  It seems like a false sense of security
>to me.  (Yep, that litnin' sure burned my house.  Glad my 'puter was
>unpluged!)

There are lots of things that can put your computer out of action, electrically.
If you are really paranoid (or live in a high risk area: "it's not paranoia if
they're really out to get you") put a UPS between the line and the computer.
That way, the UPS will take the hit and not your expensive equipment.

BTW: If you are using spare telephone pairs for your Appletalk circuits, have
you considered what will happen when lightning strikes the phone wires outside?

Maybe we should go back to steam powered computers.

Marc Kaufman (kaufman@Neon.stanford.edu)

PS: My MacIIx, 8Megs, two hard disks, two video cards, one monitor,
    takes 183 watts (measured) from its UPS system. [the other monitor is not
    on the UPS] {from a previous thread}