RE: [EnergyPlus_Support] Compuer Load

["Donald Fast" <donald@xxxxxxxxxxxxxxxxxxx>]

The most accurate is to use the power meter for each computer, under typical
load conditions.

If this is not practical:

Here is an excerpt from http://silentpcreview.com/article28-page2.html --
...
How Much Power is Enough?

Typical 300W models have replaced 230W and 250W models as baseline units
since the introduction of the AMD Athlon. They feature a fan (or two) rated
for 35~40 cubic feet per minute (CFM) airflow. Presumably, this level of
airflow is required for adequate cooling at full power output to pass safety
approvals under UL, CSA, CE and other regulations.

Our own experience shows idle AC power consumption of 60~90W, and about
110~130W at 100% CPU utilization in several fairly representative mid-line
test systems. Given the typical 65~70% effiiciency of a PSU, the DC power
delivered is 40~60W at idle and 80~90W maximum. In other words, the amount
of power actually required by typical desktop systems is about 30% of the
capacity of the typical 300W power supply. Although some headroom is always
good to have, most of us are paying for power capacity that is never used.
One of the nasty side effects is the fan noise of high airflow required to
keep the PSU adequately cooled when delivering maximum power.

Why this state of affairs exists is a matter of marketing and technical
obfuscation, probably more by accident than any massive conspiracy. With
relatively low current requirements prior to the Athlon, the aforementioned
230W and 250W were perfectly adequate for PC systems, even if the power
supplies didn't deliver full rated performance. That changed with the Athlon
and then the P4. PSU makers were quick to introduce higher rated models said
to be required for the new power hungry processors. It was a good marketing
opportunity. Rather than "Our 250W PSU is better than theirs," it is easier
to sell the message "Our 300W PSU is better than their 250W PSU." Bigger is
always better, isn't it? It also allowed higher prices to be charged.

A counterpoint is AMD's system builder's guide, which suggests higher
numbers: up to ~180W for a typical system and ~250W for a high performance
system, but these numbers are obtained by adding the maximum power rating
for each component, then taking 20% off to account for real-world
conditions. It is actually difficult to get 80% of maximum power draw; how
many applications can actually demand 80% power from every component in a PC
simultaneously? Intel's PSU recommendations are similar. Suffice it to say
that as manufacturers, both AMD and Intel are looking at worst-case
secenarios. As custom builders, enthusiasts and system integrators can make
choices based on real needs and applications.
...

Donald Fast
Building Insight Technologies Inc.
Suite 1, 3661 West 4th Ave.
Vancouver, BC  V6R 1P2
*new* Tel (604)629-8300 ext 315
*new* Direct (604)629-8315
Fax (604) 732-9238
donald@xxxxxxxxxxxxxxxxxxx

> -----Original Message-----
> From: mahmud_khizir [mailto:mahmud_khizir@xxxxxxxxx]
> Sent: September 25, 2004 7:14 PM
> To: EnergyPlus_Support@xxxxxxxxxxxxxxx
> Subject: [EnergyPlus_Support] Compuer Load
>
>
> Dear All
>
> Recenlty i am simulating a office room load in Energyplus. In my
> simulation model there is a computer. Now i am facing problem about
> the heat generated by a computer. Is there any standard value or is
> there any procedure to calculate the heat load?
>
> If i calculate the heat load of the computer from a watthour meter
> consumes by a computer will it be ok ?
>
> Thank you all
>
>
>
>
> The primary EnergyPlus web site is found at:
> http://www.energyplus.gov
>
> The group web site is:
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>
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>
> Yahoo! Groups Links
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>
>
>
>
>



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