I think you have a tad too much faith in the computer PSU.
The whole point of a good UPS is to remove doubt about the quality of power
available that would otherwise potentially damage the computer PSU.

Surges in the form of lightning are of such a huge potential magnitude that
some times the only solution is to unplug from the mains and move the
equipment away from conductors. I sometimes shutdown and pull the plug on my
own servers when a major electrical storm passes by.

It is the intermediate, unpredictable events that warrant UPS and surge
protection. The medium sized spikes that will fry the PSU and potentially
all the componentry in the computer. The power fails are the obvious
anomolies, as are the repeated failures. Continuity of service is only one
facit. ability to service is another.

I have come across some horrid scenarios: one a stock broker with 24 x 7
systems blown up because the earth wire was disconnected while attending to
an unrelated fault. There is no point in telling me what they did wrong - I
came in after the event.

Before all else, the purchaser really should try to understand what they are
buying, why, and why not buy it in a retail shop (how me a retailer that
sells good UPS). If the purchase is large then get and independant advisor
that knows his/her stuff.



"w_tom" wrote in message
...
A UPS from Mercury's first group is more than sufficient for
a computer. In fact, that "when a fail occurs, the relay
simply switches in a power converter to run off the batteries"
type UPS is also called a "computer grade" UPS. Those other
'group 3' UPSes cost on the order of $500+ to provide nothing
useful.

Learn what a power supply does. First 120 VAC passes
through line filters. Then 120 VAC is converted to 300 volts
DC. Virtually all noise, spikes, and surges are eliminated.
But your power supply provides more layers of protection. An
oscillator converts that hundreds of volts DC to an AC
voltage. Then voltage is filtered through a transformer -
galvanic isolation. The transformer output is again converted
to DC. Then that DC output is filtered but again. Then an
overvoltage protection circuit further eliminates excessive
spikes and noise. With so many layers of protection standard
in power supplies, then what does a UPS do? Typical UPS
provides less protection than what already exists inside a
standard power supply - even 30 years ago.

Those who recommend UPSes don't even discuss all this
existing protection and often don't even know what a power
supply does.

Those standard layers of protection in a power supply is
even why a square wave output (power that can harm some small
electric motors and power strip protectors) still does not
harm a computer. Computer power supplies are that resilient -
assuming a bean counter did not select the supply.

After so much hype about UPS protection, the bottom line
remains: a UPS only protects data from blackouts and
brownouts. Anything on power cord that protects hardware is
required and already inside that power supply. Look at those
so many layers of protection.

But power supply does even MORE. A power supply must
provide 100% power to every computer peripheral even when AC
mains voltage drops so low that incandescent lamps are at only
40% intensity. Brownout is also called a voltage sag. Just
another little fact that was standard even 30 years ago, and
yet routinely forgotten today to hype UPSes. That UPS is for
extreme brownouts (sags) and blackouts (no voltage).

Does that UPSes provide better surge protection? We always
demand numbers. The entire surge protection circuit is
measured in joules. How many joules in that UPS? Identical
circuit is also inside power strip protectors. Some
undersized power strip protectors have even more joules.
Why? Don't take my word for it. Look up the joules number
yourself.

Others will forget to cite numbers when making protection
claims. Bottom line: claims about hardware protection from a
plug-in UPS are mythical. All UPSes claim surge protection.
Then forget to mention how little that protection really is.
Both UPS and power strip have same undersized protection
circuit - as measured by the same parameter - joules. Worse
still: any protector damaged by a surge is ineffective - a
waste of good money. There is no protection from a "have a
life of ONE surge" protector. Yet even less joules of
protection is provided by the UPS.

If a power strip or UPS claims to protect from a surge that
typically does not do damage, then why would they bother to
properly size the protector? Notice that some "one time and
throw away" power strip protectors may have more joules.
Joules is a ballpark measurement of protector life
expectancy. Ineffective protectors minimize joules to claim
protection. They tell half truths so that others will
*assume*. 'Hype' is the protection provided by plug-in
UPSes.

Switchover time for a UPS: If a UPS switched over to
batteries too slowly, then the computer power supply is
defective. Again, specs even from Intel say the power supply
must provide interrupted power to computer; even when the UPS
takes a longest time to switchover. Again, review those
numbers yourself. Don't take my word for it.

Where is the real weakness in computer protection?
Repeatedly, everything necessary to protect at the power cord
must be inside a computer's power supply. This assumes a
computer assembler had sufficient knowledge to buy the
minimally acceptable power supply. Assumes he was not a bean
counter. Many computer assemblers could not even comprehend
what Mercury posted let alone list essential power supply
functions standard even 30 years ago. And Mercury did not
even post useful numbers that intimidate many computer
assemblers.

Asian manufacturers discovered a lucrative market of
technically naive computer assemblers. They dump inferior
power supplies into this market for greater profit. A
minimally acceptable supply must provide a long list of
numerical specs (such as how long power can be interrupted).
A minimally acceptable power supply must also cost at least
$60 full retail. So instead, many hype a UPS to *fix* missing
power supply functions?

Again, all minimally acceptable power supplies include
essential functions to protect a motherboard. Any function
effective on the power cord must be inside that supply. But
the rare and typically destructive transient can overwhelm
this internal protection. IOW an electrically 'literate'
computer expert appreciates why a less expensive and so
necessary 'whole house' protector, as part of a protection
'system', protects a computer. Again, that plug-in UPS
provides no such protection AND obviously cannot. The UPS has
no critically necessary 'less than 10 foot' connection to
earth ground. This alone indicates a glaring deficiency. So
instead, they even forget to mention the typically destructive
transient.

In summary: For effective protection of computer components
so that even a power supply failure does not damage
motherboard, disk drive, Ram, etc; the power supply must
contain functions that were even standard 30 years ago.
Functions so often missing in discounted power supplies.

For effective protection of data from blackouts and
brownouts, we install a plug-in UPS. Blackouts and brownouts
do not harm hardware - except where myths are widely promoted.

So that a typically destructive transient does not overwhelm
the computer's internal protection, we install and properly
earth a 'whole house' protector. It also protects other
appliances such as a clock radio, bathroom and kitchen GFCI,
smoke detector, dimmer switch, dishwasher and washing machine,
furnace controls, etc. Spend less money per appliance for
effective hardware protection. That means a minimally
sufficient power supply AND the 'whole house' protector.
$hundreds more for a UPS that provides no effective
motherboard protection? How does that make sense?

jimbo wrote:
What is a good uninterruptible power supply unit for the Asus
P4800E-Deluxe. I want to pick up a good one and avoid frying m
P4 3.2 and other components during the many summer brownouts
around here. I have 8 hard drives, 2 dvd drives and a 5550W PS.