Path: utzoo!attcan!uunet!zaphod.mps.ohio-state.edu!tut.cis.ohio-state.edu!att!att!westmark!dave
From: dave@westmark.WESTMARK.COM (Dave Levenson)
Newsgroups: comp.sys.att
Subject: Re: UPS/SPS testing re: AC protective ground
Message-ID: <1349@westmark.WESTMARK.COM>
Date: 28 Oct 90 23:34:08 GMT
References: <35147@cup.portal.com> <554@mtndew.Tustin.CA.US> <727@limbic.ssdl.com>
Organization: Westmark, Inc., Warren, NJ, USA
Lines: 37

In article <727@limbic.ssdl.com>, gil@limbic.ssdl.com (Gil Kloepfer Jr.) writes:
> In article <554@mtndew.Tustin.CA.US> friedl@mtndew.Tustin.CA.US (Stephen Friedl) writes:

[ regarding the Tripp-Lite UPS, with the power cord disconnected... ]

> 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.

Did you get this shock immediately as the plug came out of the wall
socket, or some time later?

> 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 ;-)

I just unplugged my Tripp-Lite BC450 from the wall.  (I'm posting
this article on backup-power!)  I find that I can touch the plug and
feel nothing.  A volt-meter across the power pins on this plug reads
zero.  Could your Tripp-Lite be a different, or older, or defective
model?   I can imagine a failure-mode in which the relay fails to
disconnect the primary power from the load when it connects the
secondary power to the load, but I would expect this to cause the
whole thing to oscillate...as the secondary power would trick the
sensor into thinking the primary power had been restored.

Anybody at Tripp-Lite on the NET want to comment here?

-- 
Dave Levenson			Internet: dave@westmark.com
Westmark, Inc.			UUCP: {uunet | rutgers | att}!westmark!dave
Warren, NJ, USA			AT&T Mail: !westmark!dave
[The Man in the Mooney]		Voice: 908 647 0900  Fax: 908 647 6857