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Wattage for computers + monitors ?

S

Sonco

Jan 1, 1970
0
I need to figure out how many 20 amp circuits are needed to power up 24
computers. Is there a standard wattage used for computer + monitors, since
they don't exist yet ?
 
J

Jim Douglas

Jan 1, 1970
0
Sorta crazy, but look on the back of the equipment, get the total for one
and multiply by 24. Most electronics have some type of indication of power
consumed somewhere.
 
S

SQLit

Jan 1, 1970
0
Sonco said:
I need to figure out how many 20 amp circuits are needed to power up 24
computers. Is there a standard wattage used for computer + monitors, since
they don't exist yet ?

I would figure 500 watts for the power supply and 1.5 amps for the monitor
making 2 amps per computer. 16*3 is 48.
Unless of course your talking about something more than normal work
stations.

3 -20 amp circuits would do. Printers or scanners would need to be on
other circuits. I would for sure not install any more outlets than needed.
That way some maroon does not plug in the vacuum and shut it all down.
 
R

repatch

Jan 1, 1970
0
I need to figure out how many 20 amp circuits are needed to power up 24
computers. Is there a standard wattage used for computer + monitors, since
they don't exist yet ?

Unfortunately it depends completely on the computers. On a recent
"endeavor" I found I could put 8 AMD 2200+ systems (without monitor)
on a 15amp circuit without blowing the breaker (120V supply).

Newer computers generally need more juice.

A ROUGH guide that usually will keep you safe is to simply add up the
wattages as marked. Usually those numbers are much higher then actual
draw, so you SHOULD be OK.

With monitors I'd guess for a 20amp circuit, in a 120V country, you can
get away with 6-7 computers. In a 240V country obviously that number would
be nearly double.

That's just a guess, you should definitely do the math. TTYL
 
A

Andrew Gabriel

Jan 1, 1970
0
Unfortunately it depends completely on the computers. On a recent
"endeavor" I found I could put 8 AMD 2200+ systems (without monitor)
on a 15amp circuit without blowing the breaker (120V supply).

Newer computers generally need more juice.

A ROUGH guide that usually will keep you safe is to simply add up the
wattages as marked. Usually those numbers are much higher then actual
draw, so you SHOULD be OK.

With monitors I'd guess for a 20amp circuit, in a 120V country, you can
get away with 6-7 computers. In a 240V country obviously that number would
be nearly double.

In the UK, the limiting factors are often the switch-on surge
(if you expect the breaker to survive power recovery when all
units come on together), and the total circuit earth leakage
from so many Class I appliances. When you have allowed for
those, you will generally find the steady state current is a
long way below the breaker rating and not an issue.

If you are installing in an educational establishment or similar
which requires all circuits to be RCD protected at no more than
30mA, then the number is quite small. Each Class I IT appliance
can leak up to 0.75mA, so that's 1.5mA for a monitor and base
unit. The maximum circuit design leakage is 25% of the RCD rating
(actually, that's gone from latest Wiring Regs, but still a good
rule of thumb), which is 7.5mA for a 30mA RCD, which is only 5
PC systems per circuit at 1.5mA leakage each.
 
R

Roy Q.T.

Jan 1, 1970
0
I should know this};-)

There is a formula for everything electical., but you'll need the
Highest & Lowest values of given computer systems at least, to work from
[do more research]
Then you can figure out how to divide the 48 loads equally amonst the
needed branch circuits, for computers it's slightly different & you
should use computer grade receptacles,( some don't care to be specific )
be specific.

For a 20Amp Branch circuit the maximum load is / oh shucks goto go
i'll try & get back to this later. ®oy
 
B

Brian

Jan 1, 1970
0
The new building for a Junior college in Kansas has one circuit for each computer. One circuit for
each television. And one circuit for each projection screen. All circuits for electronics are
isolated ground.



I need to figure out how many 20 amp circuits are needed to power up 24
computers. Is there a standard wattage used for computer + monitors, since
they don't exist yet ?
 
A

Andrew Gabriel

Jan 1, 1970
0
Build a uniformly sealed, light tight, box. Punch a tiny hole for a
thermostat. Put the computer and monitor inside and turn them on and
close up the box. Measure how fast the inside increases temperature
through many degrees.

Now repeat the experiement with a 100 watt light bulb running inside.
If it goes up faster that the computer, try a smaller bulb. If slower
try a larger bulb. When you get the bulb that heats up the inside of
the box at the same rate, you have your approximate wattage.

This is fine for working out power consumption for sizing the
aircon (although a true power meter would be much easier, and
avoid a number of potential experimental errors;-), but it's
useless for estimating the current consumption for sizing
conductors, circuits, and fuses/breakers. It fails to take
into account power factor, inrush current, etc.
 
R

Roy Q.T.

Jan 1, 1970
0
Tue, Mar 8, 2005, 6:07am From: [email protected] (Sonco)
I need to figure out how many 20 amp circuits are needed to power up 24
computers. Is there a standard wattage used for computer + monitors,
since they don't exist yet ?

Okay, someone said 4/20A circuits should do.

The rule is to compute not less than 180VA for each single or each
multiple receptacle on one yoke., AND, a single piece of equipment to a
multiple receptacle comprised of 4 or more receptacles shall be
computed at not less than 90VA per receptacle.

It is hard to help you any further, I don't know if your useing
Wiremold®, EMT or just what is the area you intend to add these
receptacle to.

It would be easy if you had the computers set-up, you could open a
circuit and plug a station unit in, measure the amperage from a fully
duped computer that is printer + whatever a single station inludes and
go from there with the calcs for intended total Amperage ...

I hate seeing computers on EMT & 1900 bes without proper receptacles.
they look so cheesy hope your useing somekind of raceway with all the
trimmings };-) btw Wiremold and perhaps other Co. have a panel mount
Surge Surpressor for computer/sensitve electronics room applications and
if I'm not mistake UPS's also, that provide full circuit protection...
wheph! I'm done.

nice call......
 
A

Anthony

Jan 1, 1970
0
I need to figure out how many 20 amp circuits are needed to power up
24 computers. Is there a standard wattage used for computer +
monitors, since they don't exist yet ?


As opposed to one poster, you probably should figure on 700 watts for the
computer alone. Newer machines are coming in with as big as 680 watt
power supplies. Especially those equiped with Serial ATA or Scuzzy set-
ups.
From a few glances at some actual power supplie specs, the AC input
required for a 550 watt power supply at 115VAC is 10A (6A @ 230VAC). (See
Tiger Direct - Power supplies). This is considerably higher than what 550
watts DC calculates out, so there must be some serious losses and/or
safety margin built in.
Most of the time I find that the actual voltage you will get is 110-
115VAC, so I always figure on 110VAC when rating a circuit.
Most 19" monitors I've seen are about 2A @ 110VAC

So, from this information:

((10A*115=1150)/110)=10.45A, 10.45A+2A=12.45A
12.45A*24=298.8A
298.8Ax125% = 373.5A (sounds like a lot huh?, but check the numbers.....)
373.5A/20A = 19 branch circuits.

My suggestion is to set these up on 230VAC, which halves your Amperage
load, bringing the number of circuits to 10.

The problem with all of the above...is you have 48 devices, or 24 10.5A+
2A devices.
Splitting the load up evenly is going to be a problem based on the above
calculations.
I would suggest, if you are dead set on 110V power, is to run 24 - 15A
branch circuits. This puts each computer on a dedicated circuit, or,
conversely, if you want to run 230V power, 12 - 15A circuits and two
computers/monitors per circuit.

A branch circuit should be rated for 125% of max expected/calculated
load.


--
Anthony

You can't 'idiot proof' anything....every time you try, they just make
better idiots.

Remove sp to reply via email
 
R

Roy Q.T.

Jan 1, 1970
0
There are also NEC requirements for Information Technology Equipment.

Depending on the location [Building Type] it behooves you to follow them
& adhere your work as close as possible.
Its covered in Art.645.

If it were my job to I'd run 12/20amp circuits from a subpanel with a
disconnect, for 24 computer stations, 2 stations per circuit, in
wiremold metal raceway with comp. graded receptacles. and anything else
the budget allowed.

but that's just me, dreamin };)
®
 
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