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# Re: [K12OSN] electricity use

• From: "Robert Arkiletian" <robark gmail com>
• To: "Support list for open source software in schools." <k12osn redhat com>
• Subject: Re: [K12OSN] electricity use
• Date: Tue, 13 Mar 2007 19:50:08 -0700

```On 3/13/07, Brad Thomas <bthomas 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?

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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/

```

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