On Wed, Dec 15, 1999 at 02:31:54PM +1100, Dave Fitch wrote:
> How much current/watts does a PC (P200) and a sparc5 draw?
> I know the PC has a 250W power supply, but it wouldn't be
> actually using all that would it?
Usually nowhere near it.
> Next question is regarding those Centralion "backup power
> supplies" Jaycar sell. They're cheaper at $399 for the 800VA
> model (what does VA mean anyway?)
Volt-Amps
I'm sure someone who actually knows what they're talking about
will correct me, but my rule of thumb is
Watts / Volts = Amps
So for a 250W power supply, its maximum draw is near as dammit to
1Amp.
The problem with all this is that the power comes in Volts, the
back of PCs shows Watts, and the UPSs are sold in Volt-Amps (VA Ratings)
So for mere mortals, working out which one to buy is always a
fun task ;)
Another factor is that you've got startup spikes in the power
consumption. So turning all of your gear on at the one time might
not work, whereas if you turn them on one at a time it operates
correctly.
Keep in mind its always better to under-utilise a UPS than
to load it up to the maximum.
> but the blurb mentions they're
> not true UPSs because whilst the power is on it's not running
> through the UPS' batteries.
There are devices called UPSs. Then there are the boxes that people
sell that are *called* UPSs. The two are most often miles apart.
UPS = Uninterruptable Power Supply. The marketing blurb usually
says "True OnLine". The power from the wall powers a battery. The
other side of the battery power is drawn off to power your gear.
So there is no possibility of power surges, brownouts, spikes etc.
The downside to these boxes is that they cost quite a lot more than
the next type.
SPS = Switching Power Supply. What people think of as UPS. The
power comes in from the wall. A circuit does some cleaning (clamping
spikes etc), then its on to your computer. If the power goes screwey a
circuit switches the output over to run off the battery. These units
are cheap, ubiquitous and good enough for the casual user.
> Does this mean it still does "line conditioning" - ie. filters
> out surges, spikes?
To a certain extent. Nowhere near as much as a true UPS.
> what about "brown outs"? it would have
> to be a "proper" UPS to be able to supply the full power during
> a brown out I would've thought?
There are SPSs that do Buck and Boost stuff. That is, if the power
goes above a certain point (Buck) it trims it back down. If it goes
down too far it Boosts the voltage back up. I think it does this
without resorting to the battery, but I'm not 100% sure.
> There's also the question of automatic shutdown, support in
> linux and solaris unknown (by me at least!). It just says
> it's supplied with software for DOS, and lose-3.1/95/98.
Sola are associated with Best Power (www.bestpower.com) who have
software for Unix on their site.
> And lastly, do these type of UPSs do phone line protection too?
> (to reduce the chance of my modem, cordless phone etc dying)
Some do. The better units won't. They leave that stuff to the
throw-away market.
To work out how much power to budget for, try going to the various
USP maker web pages. I know that APC has a power calculator up,
and I think most other UPS makers do as well.
Cheers
Paul Haddon
Technical Services Manager
Hartingdale Internet
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