Re^2: Warning on some Unison UPSes

[Mark McWiggins]

rcd at ico.isc.com (Dick Dunn) writes:

>mark at intek01.uucp (Mark McWiggins) writes:
>> We recently had some power supplies fried by a Unison Unipower 600.
>> We had too much of a load plugged into the circuit the UPS was plugged
>> into, and instead of doing anything protective or rational like shutting
>> itself down, it burned up the power supply on a PC and a modem ...

>Can you tell anything about the failure mode?  What did the UPS do that
>caused the power supplies to fail?  It seems unlikely that an overload on a
>UPS would cause an overvoltage on the output.  I've been trying to
>postulate some other sort of failure (in which the nature of the power
>supply on the attached device would play some part) - such as clipping in
>the UPS output turning into garbage in the power supply.

Gosh, I'm just a software guy ... 1/2 :)  I was out of town when this
happened, but one of our guys talked with Unison.  He's working out of
the office this week, so I don't know what details he got.

>Is this UPS a sine-wave output type?

Supposedly, yes.

>> ...Unison is aware of the problem, but I don't know about any
>> upgrade/swap policy.

>Do they say anything about what to do to avoid it (other than the obvious
>"don't overload the UPS":-), or what types of devices would be susceptible?
>Is there a danger of damaging components beyond the power supplies in the
>attached devices?

I didn't hear any recommendations; my recommendation would be "ditch your
Unison and get something else."  I only have one data point, but nothing
behind my power supplies (on Telebit modem and 386 clone) seems damaged.
My NEC monitor had funny colors for a couple of days, but it now seems
fine too.

An analogy?  The fire department coming around for an inspection,
discovers that you're operating your fireplace without a screen, and burns
your house down!

-- 
Mark McWiggins			Integration Technologies, Inc. (Intek)
+1 206 455 9935			DISCLAIMER:  I could be wrong ...
1400 112th Ave SE #202		Bellevue WA  98004
mark at intek.com    		Ask me about C++!