On Monday 18 March 2013 01:58 Metspitzer wrote in alt.home.repair:
Fairly sure - at least for the EU.
I had a small computer room at a previous job - 200-odd servers talking
around 70kW total. This particular room had an industrial meter wired into
the main incoming 3 phase circuit. Meter showed PF, amps and volts. PF was
The CE approval (for the EU) requires a PF >= 0.95 for >00W (lower soon,
if it hasn't already). Given that most far eastern PC PSUs these days are
wide input 100-240V so designed to ship anywhere, I'd be very surprised if
there was much available in the US that did not conform - unless there are
domestic PSU manufacturers and local regulation is not as strong?
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Nothing wrong with an oversized power supply. Will likely last
longer than a "right sized" or borderline supply. I almost always use
600 watt replacements - they generally cost me about $5 more than a
On Sunday, March 17, 2013 2:36:00 PM UTC-7, Hench wrote:
The original Kill-A-Watt is rated 0.2% basic accuracy,
and one person who tested it against an old Simpson analog
wattmeter said the two units gave identical readings. I
believe the Simpson is rated 2% accuracy, but I don't know
if that's 2% of the reading or 2% of full scale. Another
person who built an adapter for reading watts from the wall outlet (Electronics
Design magazine, maybe a Bob Pease
column) said the same. Also I tried plugging a P-4400
Kill-A-Watt into another P-4400 Kill-A-Watt (different
internal designs, despite same model number) and got
readings that matched within 1-2 counts. However a
person who writes reviews of PC power supplies said he
doesn't give efficiency numbers because he doesn't
think the Kill-A-Watt is quite accurate enough, but
that may simply mean its accuracy is in the range of
1% to 2% while the rest of his other instruments are
Apparently Kill-A-Watt type devices are really good at
measuring nonlinear type waveforms because I got about
the same watt numbers from a cheap backup power supply,
whether it was plugged into the AC outlet and putting
out real sine waves or running off battery and putting
out stepped square waves.
The 90W - 130W readings you get are probably accurate,
while power supply estimation worksheets can be way
off. XbitLabs.com and SilentPCreview.com measured
power consumption and found that few systems with
only one video card ever consumed over 500W:
Even old 7200 RPM hard disks didn't consume more than 9W
while spinning, maybe 15-20W while seeking. Here's what
some contemporary drives consume:
On Mar 18, 9:15 am, firstname.lastname@example.org wrote:
ronics Design magazine, maybe a Bob Pease
That helps confirm what I thought. The process of computing
the power isn't complicated, it's simple. You just have to
multiply voltage times current and do it fast enough that you
are accurately sampling the waveform. It doesn't take a
very complicated chip to do that. And we've had cheap
consumer electronics for decades that does a lot more,
The terms may not be correct, but normal power follows a sine wave curve
going from 0 volts to a plus voltage and back to 0. It then follows the
same sine wave curve to a maximum negative voltage and back to 0. For what
is often called 120 volts at 60 hz really has a peak voltage of around 170
Most old analog meters were designed to 'average' this value to what is
called a RMS value. Sometimes this has been the same voltage an equal
voltage of DC would heat a resistive load.
Newer devices often take the power in pulses so it does not use the whole
part of the sine wave curve, but just spikes of voltage or portions of the
sine wave. It is often difficult to measuer this voltage/power with simple
On Mon, 18 Mar 2013 06:15:34 -0700 (PDT), email@example.com
Good links. They push high watt PS's because they're more profitable.
Kind of like a 500hp car that can go 180mph. But never does.
Just a while ago I became aware of how much overpowered PS's are in an
internet forum discussion. The guy who knew all about it caught hell.
Somebody was doing a build and he recommended 400w. I thought that
was low, and said so. He responded with facts and cites, so I
reversed my position. He still caught hell from a bunch of others
with overkill PS's. Some of it was his attitude. Wasn't shy being
about being knowledgeable.
Bottom line as add up peak component watt usage, and possible future
additional watts, and buy quality at those watts.
Most people have more wattage than they need, just like many have more
hp than they need in their cars.
There's an efficiency penalty, but with a PS it doesn't add up to
much. I've got a 600w Corsair and a similar setup as the OP.
I added a second GPU this year to get good PhysX in a game, and noted
that by having the 600w PS I didn't give it a second thought.
That was only reason for disagreeing with his lowball watt suggestion.
He said 400w would have worked for me as well, so I really looked at
all the numbers. He was right.
But I don't regret having the 600w. It's overkill. Not a big deal.
The 750w Corsair is overkill, but not a big deal unless you want to
make it so.
On Sunday, March 17, 2013 5:36:00 PM UTC-4, Hench wrote:
build, and I'm using a kill-a-watt type meter to do so. Anyone know just h
ow accurate these meters are when it comes to power supplies? Most power su
pply sizing webpages imply that I'd be using 500-600 watts for my pc. I ass
ume this is under 75 or 90% load or somesuch. Yet when I measure with a kil
l-a-watt knockoff meter it's around 90-130 watts. Power supply in question
is a corsair TX750. PC in question is an I7 3770K with 1 ssd, 9 sata harddr
ives (all low RPM), 5 120mm fans, nVidia 650ti 1 gb vid card, 4 sticks of r
am, 2 pci cards, a few usb 2 devices.
It's going to draw a lot more if you ut all those drives to work.
You don't mention the drive sizes but 9 is a lot. Why low speed? I'd go 7
200 or 10k myself for a media server. But the network is probably your bot
Great power supply. I have several of those running our machines. The
actual wattage that the machine uses should always be less than the
capacity of the supply. It's certainly not hurting anything or costing
anything to have an oversized supply
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