Re: Questions about APC UPS units

Thanks for your very useful response.

Additional comments inserted below....

On Sun, 4 Jan 2009 20:53:19 -0800 (PST), westom1@xxxxxxxxx wrote:

On Jan 4, 9:45 pm, Charlie Hoffpauir <inva...@xxxxxxxxxxx> wrote:
OK.... I tried that, and the bulb definitely dims a bit. Not a "lot"
but it definitely is "noticable". So does this mean that I shouldn't
try the UPS with a computer load? Or in other words, do I risk
damaging the computer when I unplug the line power from the UPS?

Low voltage never damages any properly designed electronics. An
industry standard even 35 years ago used this expression in voltage
regions of that chart: "No Damage Region". Other standards discuss
undervoltage only in terms of how long that voltage can be too low
before a computer halts. Damage is not even an option. If low
voltage caused damage, then power off also causes damage.

All 120 VAC computers are required to operate OK even when voltage
is only 90 volts. Most all my electronics designs routinely cut out
at 85 volts. Another even discovered:
... a TV which didn't die until I turned the variac down to
37 VAC! A brownout wouldn't have even affected the
picture on that set.

Yes, it is routine to lower voltage on electronics - to even learn
how low voltage can drop before electronics turns off. Power the
computer from that UPS. Damage is not possible if the computer's
supply meets so many standards including one from Intel.

That light bulb should have dimmed to half intensity if your numbers
are correct.


My guess is that is just about how much it dimmed. I'd compare the
intensity change to that of switching a dual filament bulb from 100 w
to 50 w. output.

Another test might string light bulbs on the UPS output to learn how
many watts are actually too many. For example, a 650 watt UPS unable
to power larger than 300 watts of lights implies half the UPS inverter
has failed - would also explain that low voltage.

I'll definitely try this, but my guess at this time is that you have
accurately diagnosed my problem.

Without a O'scope waveform, further definitive replies here are not
possible.

Some have suggested one reason why a UPS in battery backup mode may
fail. Because spikes output by UPSes are so large, then a power strip
protector connected to that output may damage either the power strip
or UPS inverter.


My "setup" is that I have the UPS powering a device that sits under
the monitor, containing multiple outputs and switches to power the
computer, monitor, and accessories like powered speakers. Obviously,
that is essentially a protected power strip.... so I have probably
damaged the UPS units.

Neither low voltage nor the very 'dirty' electricity output by a UPS
in battery backup mode can harm any minimally acceptable computer.
However we are only asking what has failed. Bottom line: that UPS
obviously is hardware defective.

Since you mentioned that someone reported still powering a TV at 37
VAC, I am going to try to use one of the UPS units to power my
satellite modem (I'm on Hughesnet) and my local network switch. If the
low voltage keeps them "on-line" they won't be a total loss for me. If
not, I'll salvage the still usable batteries and dispose ot the two
units.

Again, thanks for all the suggestions.

--
Charlie Hoffpauir
http://freepages.genealogy.rootsweb.com/~charlieh/
.

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