Text 14136, 177 rader
Skriven 2006-11-19 13:48:40 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.

Hmm. I thought these SmartUPS were high-tech devices?


> >
> >>
> >>
> >> > 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...

I thought it was supposed to remain constant within a volt or two? So, there's
no load balancing?


> >
> >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.

Well, it's a residential building and god knows what they did with those cables
or if they even hooked them all up. They banged holes in the walls in the
hallway and ran the cable into something, but my electrical power was never
shut off. Nor was the building power, so I have no idea what they did. It's
possible they just dropped them in the wall planning to connect them later to
the individual breaker boxes in the apartments.

Could this damage the UPS? I may have an old anlaog voltage meter here
somewhere. Maybe I can test the voltage. This is odd. I read the voltage on
some of the wall outlets. If I'm reading this thing correctly, it's about 112
volts. The outlet giving the high-voltage indication also reads 112 volts (it's
a double outlet and I plugged into the unused outlet). That doesn't appear to
me to be an overvoltage at all.



> >> 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.
> >
> >Yeah, a friend recommended one of those. How much do those things cost?
>
> You don't buy one unless you are in the power industry, or you run a
> data center and are very concerned about power.  Renting for a month or
> so while you troubleshoot is better.
>
> But if you want to buy one, think thousands not hundreds.

I'll pass. <g>


> Tripp-Lite is good.  APC is a marketing-oriented company, better UPS's

They spend a lot of money on marketing, yes. I agree. You hardly here from the
other companies. They also have a very aggressive upgrade policy. They'll give
you credit for trading in any Tripp-Lite or other equipment you might have.
They discounted one of my units when I upgraded, for example.


> through better marketing.  Technology-wise, they are so-so.  One of my

But maybe good enough for home or SoHo use?

> favorites from APC was a line in their marketing brochure that went
> along the lines of, ~there is no such thing as an uninterruptible power
> supply because the AC line current goes to zero 60 times each second.~
> Never mind that 60Hz power goes to zero 120 times each second, but they
> missed the whole concept of uninterruptible power supplies.  The APC
> marketing people were trying to say that their 5 to 10mS break time in
> clean power was OK.  At the time APC didn't have a real non-break online
> UPS, so they tried to convince you that no one did.  I engaged their
> marketing department in a snail mail conversation once.  I should have
> kept the letters, the cluelessness was astounding....

The SmartUPS are supposed to deliver clean power (sine wave output). Now, I
don't want to start that argument again, and I'm not an EE anyway, so maybe
that's good, maybe it's not. A friend of mine, who is an EE, says it doesn't
matter much anyway given the tolerances of modern power supplies in computers.
However, I *have* suddenly had the power cut off to my apartment and I was glad
I had these units in place. Gave me time to shut down.


>
> My preference at this point is Powerware (formerly Best Power

I remember them. They're expensive as I recall.

> technology). http://www.powerware.com/  Currently I have a Powerware
> 5125-1500 with one Extended Battery Module on my home network.  I use
> NUT (http://www.networkupstools.org/) to control the UPS and shut down
> the servers should the power go down.  I get about 7 hours runtime on
> battery (NUT shuts down the media server after two minutes on battery to
> conserve the batteries for the firewall, switches, access point, webcam,
> etc.)

One thing I discovered was that Tripp-Lite and other companies simply used a
rebranded version of APC's PowerChute software on their hardware. I figured I
might as well go with the people that wrote or developed it. And if Powerware
doesn't have OS X software, it won't help me much.


>
>   :)
>
>  /m

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