[K12OSN] electricity use

[Robert Arkiletian]

On 3/13/07, Brad Thomas <bthomas at bhbl.org> wrote:
> I am a social studies teacher and I've been building a lab in my classroom
> of old, discarded computers over the last two years (I was up to 20). I
> have been using small distros like DSL (DamnSmallLinux) to make them work,
> but was planning to switch to a k12ltsp setup before the end of the year.
> However, my principal just sent an e-mail last week instructing me to
> remove all but 6 of the computers from my room implying that they were
> using too much electricity. I just got back from a school planning council
> meeting where she and an assistant principal said that they called Dell
> (we buy all our new fat machines from Dell) and Dell said there should
> only be one computer per 20 amp circuit (which translates into one per
> room I think). As far as I can tell (using a Watts Up meter) one
> computer-and-monitor use a little more than 1 amp of power, so I don't get
> this. Can anyone out there give me some guidelines they go by? Or steer me

I am not an electrician but I do teach basic electric circuits in
physics. The basic equation for power is P=IV (Power=VoltagexCurrent)
So 120 Volts (which is a north american standard) x 20 A of current
equals 2400 Watts of power.  Now if you remember those old boxes
probably have 200W power supplies max + monitor ~75W. Add another 25
for safety. So I would say 300W/box is reasonable. Although less would
probably work because I doubt they would draw the max of the PS unit.
So with a 20A circuit (2400W) that equals 8 machines working at full
tilt.

Now compare that to an ebox 2300 + and a 19in lcd monitor consumes. 15W + 40W
Plus the server, don't forget.

> to a good site? How much planning goes into ensuring proper electrical
> flow into your k12ltsp labs?
>
> Brad
>
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-- 
Robert Arkiletian
Eric Hamber Secondary, Vancouver, Canada
Fl_TeacherTool http://www3.telus.net/public/robark/Fl_TeacherTool/
C++ GUI tutorial http://www3.telus.net/public/robark/