Text 14137, 110 rader
Skriven 2006-11-19 14:07:36 av RobertB. (1:379/45)
  Kommentar till text 14102 av mike (1:379/45)
Ärende: Re: UPS weirdness
=========================
From: "RobertB." <rb28@nyu.edu>

In article <li6vl2pscnabaqeokgpjsaijg6v7n26lm9@4ax.com>,
 mike <mike@barkto.com> wrote:

> On Sat, 18 Nov 2006 17:15:17 -0500, "RobertB." <rb28@nyu.edu> wrote:
>
> >In article <dhtul2l6e6vab4k0c5um3j4q4b9lvlgkoj@4ax.com>,
> > mike <mike@barkto.com> wrote:
> >
> >> 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.
> >
> >Oh, that's interesting. They are the same model, not sure if the specs
> >are identical.
>
> Normal component tolerances will account for that level of difference.
> That's not a critical set-point, so they're not going to use high-spec
> components.
> >
> >>
> >>
> >> > 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...).
> >
> >Isn't high voltage usually the result of something happening on the
> >mains. The local transformer down the street or something?
>
> The transformer sets the voltage level, say a nominal 120 volts.
> However, there is variation around that nominal level depending upon the
> load that is placed upon the distribution system.
>
> When I wrote my prior message,m I checked and the voltage in my house
> was 115 volts.  Now it is 116 volts.  When I fire up the clothes dryer
> in 20 minutes or so, it will drop, probably to 112 or so...
>
> >
> >>
> >> > 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...)
> >
> >Not sure I'd understand it if you did. <g> Been a while since I opened a
> >physics textbook. <g>
> >
> >>
> >> > 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?.
> >
> >Power cabling. New BX cable. Not sure why, exactly, but probably to meet
> >some code requirement. They don't do anything here unless they
> >absolutely have to. Actually, they ran it inside a trough in the
> >hallway.
>
> OK, they may have had a situation where the existing circuitry could not
> deliver enough power to the offices.  The new wiring provides more
> power, so the voltage won't sag as much.  In other words, the new wiring
> may be delivering a higher voltage to your office.

Odd. I shut everything down and plugged the UPS into the bottom outlet. The
Trim light went off. However, if I measure the flakey outlet with my meter, I
get the same voltage as on the other outlets. What gives here?

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