Text 14096, 74 rader
Skriven 2006-11-18 16:18:36 av mike (1:379/45)
  Kommentar till text 14092 av RobertB. (1:379/45)
Ärende: Re: UPS weirdness
=========================
From: mike <mike@barkto.com>

On Sat, 18 Nov 2006 14:43:15 -0500, "RobertB." <rb28@nyu.edu> wrote:

>Any EEs out there or people who know electricity? I have two APC UPS
>SmartUPs in my office, a smallish 750 VA unit attached to my G4 iMac and
>a large 1000VA unit attached to my ancient Micron and my new iMac
>core2duo (Yowza!).
>
>Here's the deal. Previously, I used to not turn the Micron on much so I
>would shut the large SmartUPS off at night (since the computer was only
>on a couple of days a week at most). However, the new iMac, like all
>Macs, has an Energy Saver feature, so I simply put it to sleep at night.
>Easy. When it's on, the usage light on the large SmartUPS doesn't even
>go on, the machine is energy efficient. (The Micron, which has a couple
>of externals attached causes it to move up one notch). So there's no
>real voltage draw. OK. I noticed, twice now, that in the morning when I
>come into the office, the Voltage Trim light is on, indicating high
>voltage on the line. However, it only appears on one of the SmartUPS.
>Both machines are in the same room and, as far as I know, connected to
>the same circuit. After a while, the Trim light goes out.
>
>FYI, about two weeks ago, the same thing happened one night to the 750VA
>UPS. The Voltage Trim light was on for several hours, then went out. I
>have no idea why it would affect one UPS and not the other,

One UPS might have a slightly different threshold to enable the trim
capability.  For example, the UPS may switch over to trim mode when the voltage
is over 132 volts (+/- 2%).  So one UPS may switch to trim mode at 133 volts,
the other at 129 volts.


> why it seems
>to happen on a regular basis, and why it would come and go.

The voltage may be higher in the morning when the load is low.  I know the
voltage in my house is high (122 volts) until around 6:45am or so when lots of
people start waking up.  Then the voltage starts the descent for the day, the
lowest being early evening, or when I run my electric clothes dryer...).

> The owner of
>the building (an old tenement) installed a new boiler about six weeks
>ago and I'm wondering if they did something weird.

A new boiler could be more efficient in its electrical usage, reducing the load
on the system, therefore increasing the voltage.  Or, they could have run a new
electrical line for the new boiler (this is done if the old stuff wasn't quite
up to spec).  The new boiler connection to the main electrical line could be on
the other phase from your office. Which will result in a very different voltage
pattern in your office, i.e., when the furnace goes on you office voltage will
increase. (long story, I can explain if you want...)

> At one point this
>summer they were running new cabling up the walls on all the floors, but
>I have no idea if they ever connected the stuff.

They don't run cabling for their health. :)   Chances are they connected
it to something. Was it power cabling, or data cabling?.

>I can't figure it out.
>The voltage trim light just went out about 10 minutes ago. Bizarre.

I only touched on a few of the possibilities.  When I had a similar problem in
my office, I had to rent a Dranetz power analyzer to help track the root cause
down. (http://www.dranetz-bmi.com/) Turns out there was an issue at the main
breaker box for the building.  Once that was fixed, everything was fine.

 /m

P.S.  I would never use an APC UPS on any piece of equipment I care about.  But
that's just my opinion....

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