Specifications

Thermal Requirements
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Thermal Requirements
It is important that the SGI Origin 3900 servers be maintained within their rated thermal
range.
Refer to the section titled “Environmental Requirements” in Chapter 6 for the
temperature ranges for each rack, both operating and nonoperating as well as the
recommended operating ambient temperature. Typically, the upper limit of the
temperature range is more likely to become a problem than the lower limit.
Heat Output
All of the systems that this guide describes have a maximum rated operating temperature.
Exceeding this temperature greatly increases the rate of hardware failure and, in many
cases, causes the system to shut itself down.
All of the power consumed by a computer system must exist as some form of energy. For
air-cooled systems, this energy exists in the form of heat in the surrounding air. Every
watt drawn by a system is eventually dissipated as heat. This heat tends to raise the
temperature of the air in the room that houses the system. Therefore, some method is
needed to keep the temperature within the required range. The typical method is to install
additional process cooling capacity.
The maximum heat dissipation-to-air per rack is listed in Table 5-1.
Air-conditioning Terminology
Air-conditioning capacity is generally measured in Btu/hr, tons, or kilocalories (kcal).
A Btu, or British thermal unit, is the amount of energy needed to raise the temperature of
one pound of water by one degree Fahrenheit at a constant pressure of one atmosphere.
One ton of air conditioning removes 12,000 Btu of heat energy per hour.
The more systems that are installed in a given area, the larger the air-conditioning
capacity that is required. It is important to calculate the total thermal load of the systems
that you will be installing and determine whether the existing air-conditioning system can
handle the additional load. If not, you must provide additional cooling capacity.