UPS/SPS testing re: AC protective ground

[Dave Levenson]

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