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From: gil@limbic.ssdl.com (Gil Kloepfer Jr.)
Newsgroups: comp.sys.att
Subject: Re: UPS/SPS testing re: AC protective ground
Message-ID: <727@limbic.ssdl.com>
Date: 28 Oct 90 18:34:56 GMT
References: <35147@cup.portal.com> <554@mtndew.Tustin.CA.US>
Organization: Southwest Systems Development Labs, Houston, TX
Lines: 24

In article <554@mtndew.Tustin.CA.US> friedl@mtndew.Tustin.CA.US (Stephen Friedl) writes:
>If the power goes out for real, however, the entire
>building is connected to the power cord of the supply,
>effectively providing a dead short.  For some makes of UPS (Safe,
>Datashield, Tripplite, and Topaz, for instance), the backup
>supply is connected to this dead short for a brief moment before
>the disconnect switch kicks in to break the connection with the
>outside world.

Actually, this is seems to be correct.  When I pulled the plug on my
Tripp-Lite 'UPS' a few weeks to 'test' it, I accidentally touched the
prongs on the AC plug, and got a small shock from it.  It didn't seem
like enough to do any bodily harm (but who am I to tell?).  It would
seem to me that there is a small amount of leakage back through the
AC plug when the supply is on battery power.

I know that this isn't good -- in fact, I think it is illegal.  Does
anyone have any specific measurements of just how much juice the
Tripp-Lite supply sends over the AC line when it is on battery power?
I'm not about to attempt testing it with my fingers again ;-)

-- 
Gil Kloepfer, Jr.              gil@limbic.ssdl.com   ...!ames!limbic!gil 
Southwest Systems Development Labs (Div of ICUS)   Houston, Texas