[Tfug] UPS sizing

[John Gruenenfelder]

On Sun, Jan 04, 2009 at 07:27:00AM -0800, Bexley Hall wrote:
>> The oldest circuit was the original ancient low load stuff
>> which I only used for a lamp and a clock.  My neighbor, however,
>> kept stupidly plugging a hot plate into it which would instantly 
>> trip the upstairs breaker.  But... even with the modifications, 
>> it still all wound its way to an aging rats nest of
>> wires in the basement.  I'm surprised it didn't all
>> trip more often.
>
>One "giveaway" re: age is whether or not there are *individual*
>conductors (e.g., knob and tube), *pairs* of conductors (with a
>'drain" wire) in "armored" cable (e.g., BX) or two/three conductors
>in a vinyl sheath (e.g., ROMEX).

Well, certainly the oldest stuff was knob and tube.  Actually the first time I
had seen something like that in person as there aren't many places in Tucson
old enough.  :)  How exactly this was melded with the newer circuits I am
unsure, considering that the power requirements of 2009 are significantly
different from those of 1890.

>Possible.  I've seen APC units "click on" (i.e., go into
>backup mode) spontaneously.  I've always assumed it was the
>result of a brown-out -- though have never been able to
>correlate this with "dimmed lights", etc.  <shrug>  As long
>as it didn't happen too often, I just shrugged it off (I've
>got enough *other* stuff to do so why go looking for issues?)

Ahh... I'm glad you mentioned this.  Back in the old house my UPS would do
this click-click about once per day.  NUT would make a note of this in the
syslog each time.  Until now I hadn't realized that this hasn't occured once
since I moved back.  I had thought that perhaps it was some sort of self-test,
but since it has stopped that can't be it.

>> This was a major pain for a number of reasons.  It could
>> only be reset via manual intervention which made remote
>> action impossible.
>
>That sounds like an overload, then.  Note that most UPS's

I suppose, but then why hasn't it occured again since I moved back to Tucson?
My output wiring is almost identical.

Hmmm... based on what you wrote about the two types, I'm pretty sure my
relatively inexpensive $140 UPS is of the standby variety.  If that is the
case, then perhaps during some bizarre power event on the mains, my load will
see that event for at least 15ms.  Then, during that time span, this "event"
causes one of my devices to suddenly draw lots of power, thus kicking the UPS
into overdraw shutoff.

It's a possible explantion, anyway.  I guess the real solution is, if I ever
move back to a place with variable/lousy power and/or ancient wiring, I should
spend the extra money and purchase an online UPS.  Afterall, having a UPS
which only protects me from outages and brownouts when those constitute only
about 1/3 of my power problems isn't doing much.

>If you *really* are concerned about power, you can buy
>tools that will watch the AC line and log anomalies
>(brownouts, blackouts, dropped cycles, spikes, etc.).
>But, $$$$

I can get at least some of this information from my current UPS by using NUT.
There is an add-on graphing/stats package for it.  I attempted to set it up
when I first got the UPS, but never followed through.  The only event which
truly gets reported now is switching to and from battery.  But with decent
graphs I could at least deduce some trends.  However, power on the East side
of Tucson is so stable, there's not much point in doing that here.  :)

>Note that the output of many UPS's isn't very "clean".
>If you get neighbors complaining about RF interference,
>this is one quick fix to try (eliminating the long cord).

That wasn't a problem in the old house.  It had actual thick plaster walls.
Until I moved in I didn't know that plaster is remarkably good at absorbing RF
energy, wanted or unwanted.

>[1]  This ignores the effects of "surge supressors" in the UPS
>Personally, I think these "supressors" are a complete waste!
>They'll only handle trivial problems -- problems that the
>power supply in most electronic devices will already handle!

Are they really that bad?  Certainly this was one of the things I wanted when
I bought the UPS.  My PC is still plugged into a surge protector/power strip
as a matter of convenience, but I assumed the UPS would do at least as good a
job as that, if not better.


-- 
--John Gruenenfelder    Systems Manager, MKS Imaging Technology, LLC.
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