Re: House Power Failures and Mac
- From: J.J. O'Shea <try.not.to@xxxxxxxxxxx>
- Date: Fri, 15 Feb 2008 06:08:20 -0500
On Fri, 15 Feb 2008 00:01:05 -0500, w_tom wrote
(in article
<a8263620-c039-4f4a-8c05-b99513c6085a@xxxxxxxxxxxxxxxxxxxxxxxxxxx>):
On Feb 14, 8:49 am, J.J. O'Shea <try.not...@xxxxxxxxxxx> wrote:
A UPS is a box with surge protection, an AC/DC converter, a battery, and a
DC/AC converter... but no switch. What happens is that power comes in, goes
to the AC/DC converter after being filtered by the surge protector, feeds
the
battery, which feeds the DC/AC converter, which feeds your system.
J J O'Shea describes a UPS that typically costs $500.
Err... no I didn't. I described a UPS which cost me, personally, $150.
The typical
$100 UPS (a computer grade UPS) connects directly to AC mains when not
in battery backup mode.
Err... no. That's an SPS, as noted in the part you snipped. Prices for UPSes
and SPSes used to be higher. You don't seem to have kept up with the
industry.
When in battery backup mode, UPS outputs a
modified sine wave. Two 200 volt square waves with a spike of up to
270 volts between those square waves. Modified sine wave? Yes.
Yes, it's a modified sine wave. No, it doesn't deliver anywhere near 270 volt
spikes.
Internal computer protection is so robust that even a 270 volt spike
is not harmful.
If a UPS output is so clean and conditioned, then why do UPS
manufacturer say to not put a protector on its output?
so that you don't overload the system. I, for example, _do_ have surge
protectors on the outlets. Two of them. However, I have made sure that the
total power consumption going into the unit is under 800 VA, which is the
rating for my main UPS. (I have two other, smaller, units... precisely
because I don't want to overload any one UPS, and I don't want to put too
much power on any single circuit.)
If there was anything close to a 270 volt spike, my surge protectors would
have long since popped.
That DC/AC
converter only operates when in battery backup mode.
That's a SPS. My units are UPSes. I paid extra because I wanted UPS systems,
not SPS systems. I know the difference. You do not appear to.
When in battery
backup mode, a UPS output is so dirty that either the power strip
protector or UPS would be damaged.
Incorrect. At least not in the case of my units. You might have a point wrt
to older SPS units. I don't know. I've never used SPS units, precisely
because I wanted the protection that true UPS delivers and SPS does not.
But since computer power supplies
are so robust, that dirty electricity is not harmful. Spikes that may
even harm a power strip protector are irrelevant to computer power
supplies. Computers are that robust as required by industry
standards.
Meanwhile, a UPS typically needs10 miliseconds to switch to battery
backup. No problem. All computer power supplies must maintain
uninterrupted power output when AC power is lost for more than 17
milliseconds. Another industry standard.
You are again describing a SPS. I don't have a SPS. I have UPSes.
A UPS that does provide surge protection is the building wide
system; that also has a necessary connection to earth ground. Many
confuse this UPS with $100 UPSes.
Again... my main UPS cost rather more than that. And it is properly grounded.
I know this because I checked the building circuitry myself.
More numbers that J J O'Shea did not provide. Many UPSes list 200
joules. Near zero protection.
Mine are rated at 320 joules each.
But large enough so that some will
believe a UPS provides surge protection. How many know what 200
joules is? Near zero surge protection. But enough to promote myths.
I'm beginning to think that you're clueless. 320 joules is sufficient in most
situations. It won't do anything to defend against a direct hit from a
lightening strike, but then nothing will. 320 joules _will_ stop a _near
miss_ by lightening, which is the best I can expect.
And even a direct hit by lightening will usually do no more than fry the UPS
itself. Yes, it'll blow right past the 320 joule protection... but not past
the AC/DC converter and the battery and the DC/AC converter, all of which
will burn. You'll have to replace the UPS, but not your equipment.
You're talking to someone who has seen this kind of thing in action. Who
should I believe, you or my lying eyes?
A typically $100 UPS does not work as described. If a UPS's AC/DC
converter and battery provided surge protection, then the computer's
power supply (required by industry standard to be a more robust AC/DC
converter) is better and total protection. Then the computer power
supply makes UPS surge protection irrelevant. No, then don't add up.
Err... one major reason to have a UPS (or even a SPS) is to have support in
the event of a power failure or a brownout. The computer's power system
cannot do anything about either of those. The batteries in the UPS can.
Yep, you're clueless.
The only protection that matter is the one with higher voltage.
Computer's power supply would make that UPS protection completely
irrelevant. So even the $500 UPS does nothing relevant in surge
protection.
So you deny my actual experience? Interesting. Again, who should I believe,
you or my eyes? Hint: it ain't you.
J J O'Shea - did you use your oscilloscope to confirm the UPS
outputs?
An oscilloscope program on a WinBox, yes.
I did. Just a little hint how many generations of design
experience is behind this post. Where on that schematic is the
protection circuit? Where are manufacturer spec numbers to confirm
what you posted here? Provided numbers define that protection as near
zero. Where are your manufacturer numbers? No numbers is how those
myth purveyors get us to believe them. Where is the required
connection to earth ground? No earth ground means no effective
protection.
The specs are in the bumf that came with the system. They said that I'd get
no more than 132 volts; my test showed 123 volts, max. (Less than half your
270 volt idiocy...) Given a choice between believing what the vendor said,
and my eyes confirm, and what you say, I go with the vendors. They're not
frothing and ranting and denying the evidence of many years (decades, in
fact...) experience. You, on the other hand, are doing exactly that.
My very first experience with a UPS was with my very first job. I was at a
SCADA system for an electrical utility. Strangely, they had a UPS installed
to keep the computers running until the backup generator could be started. It
appears that at least one power utility believes the 'myths' about UPSes...
Gee, who to believe, people who work with electric power for a living, or
you? Hmm. Tis a puzzlement.
Building wide UPSes that do provide surge protection (with specs
that define that protection) have a dedicated earthing wire and
contain more than a few hundred joules. Plug-in UPS does not. The
typical computer grade UPS connects AC mains directly to the computer
when not ijn battery backup mode.
Again, that's a SPS, a system I specifically warned against. You don't seem
to be paying attention.
Direct with only a relay in
between. Get out your oscilloscope. Read the manufacturer specs.
The UPS does not provide and does not claim to provide surge
protection from a surge that typically does damage.
Amazing. Simply amazing.
--
email to oshea dot j dot j at gmail dot com.
.
- References:
- House Power Failures and Mac
- From: Dudley Henriques
- Re: House Power Failures and Mac
- From: J . J . O'Shea
- Re: House Power Failures and Mac
- From: w_tom
- House Power Failures and Mac
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