For a piece of equipment to satisfy this cooling compatibility specification, it must meet all of the following criteria when initially installed, at ultimate capacity and under any configuration or combination of options.

1. If the equipment is intended to be rack mounted, cooling air must be drawn in the front and discharged out the back of the unit. Requirements for air intake or exhaust which are either lateral (side to side) or vertical (bottom to top or top to bottom) are not acceptable. Air intake requirements for rack mounted equipment are independent of whether a raised floor is used. Free-standing units that can be stacked vertically must comply with the same requirements as rack mounted equipment.
   1. The following observations will confirm compliance to this criteria:
      1. Observe that the incoming cooling air movement follows an acceptable pattern, i.e., drawn in the front and discharged out the back of the unit.
      2. Observe that lateral or vertical external air is not used to cool the equipment
      3. Observe that the volume of intake air varies with the temperature of the supply air and the temperature change from intake to exhaust is at least 12°F.
2. If the equipment is free standing (or floor mounted), cooling air must be drawn in the front or bottom and discharged out the back or top of the unit. Requirements for incoming cooling air either laterally (side to side) or in the back are not acceptable.
   1. The following observations will confirm compliance to this criteria:
      1. Observe that the incoming cooling air movement follows an acceptable pattern, i.e., drawn in the front and discharged out the back of the unit.
      2. Observe that lateral or vertical external air is not used to cool the equipment.
3. Manufacturers who make rack enclosures with doors must specify the maximum equipment heat loads or the maximum equipment height allowed within the enclosure. The door perforations must be sized to prevent excessive resistance to the internal equipment fans. The rack enclosures must provide a means of preventing "cold aisle" air from being internally bypassed within the rack to the "hot aisle." In some rack enclosures, there may be blanking panels to close off unused rack spaces within the enclosure or skirts that can be extended down below the rack enclosure to seal against the floor and prevent the unnecessary escape of cold air.
   1. The following observations will confirm compliance to this criteria:
      1. For enclosed racks, observe the front and rear door perforations are sufficient to allow movement of cooling air up to the heat load rating of the enclosure
      2. Observe that cold air short cycling is not allowed by the enclosure design. If internal blanking plates are properly installed in empty rack positions, this air short cycling will not occur.
      3. If the rack design has extendable skirts, observe that skirts are provided to seal the space between the bottom of the enclosure and the top of the floor.
4. The maximum depth of free standing equipment, racks, or rack type enclosures must be 42" or less. This dimension includes any permanently mounted "tip prevention feet" installed at the base of the equipment or rack. Any equipment intended for use in a rack must be 34" or less in depth to allow for front mounting and for cable management in the rear.
   1. Observe the maximum depth of freestanding equipment or enclosures is less than 42".
   2. Observe the maximum depth for equipment intended to be mounted in racks is 34" or less.
5. The hardware manufacturer shall design the equipment with internal heat loads of more than 50 watts per rack unit for a temperature change from intake to exhaust (delta T) of not less than 15°F nor more than 20°F. If internal fans are used, they must be variable speed fans that are controlled by internal temperature to limit the volume of air drawn through the equipment to the minimum necessary to achieve the required delta T. This means that equipment at the bottom of a rack will draw less cold air than similar equipment located higher in the rack where the supply temperature may be significantly higher. Thus more cold air will be available for the units placed higher in the rack.
   1. The following observations will confirm compliance to this criteria:
      1. Observe the change in temperature from intake to exhaust for equipment consuming more than 50 watts per RU is not less than 15°F nor more than 20°F over the operating range of supply air temperatures as published in the manufacturer's specifications.
      2. Observe the volume of cooling air drawn by the hardware varies with the intake air temperature.
6. Alarms must be generated by the hardware when the equipment's air intake temperature is outside the manufacturer's published tolerances, when there is an internal over-temperature warning, or when thermal shutdown occurs. An alarm must also occur when the abnormal condition is corrected. Alarms must be transmitted within 60 seconds to an interface accessible by the user's building automation system and to the equipment's operating system
   1. The following observations will confirm compliance to this criteria:
      1. Observe that "intake air out of tolerance," "internal over temperature warning," and "internal thermal shutdown" alarms are transmitted within 60 seconds when the cooling is unacceptable.
      2. Observe that an alarm transmits within 60 seconds when the abnormal cooling condition has been corrected.
      3. Observe that alarms can be accessed by common building management protocols including Modbus, SNMP, (add other specifics).
7. The manufacturer's site planning guide for each product must identify the range of cooling air volume (CFM) that is circulated through the equipment under normal operating conditions.

In addition to the cooling specification compliance requirements above, the following are suggestions of good practice.

1. The manufacturer should specify both the acceptable operating conditions as well as the recommended operating conditions of the equipments intake air. This applies to both dry bulb temperature and relative humidity. For example, it may be acceptable to operate between 32°F (0°C) and 104°F (40°C) and 20% to 80% relative humidity, but improved reliability and longer electronic component life will be achieved by operating the equipment between the conditions of 68°F (20°C) and 77°F (25°C) and between 40% and 50% Rh.
2. Equipment designers should be sensitive to the reality that most data centers use air conditioning equipment designed to provide approximately a 12°F (7°C) temperature difference between "cold" supply air and "hot" return air. If a manufacturer elects to use a greater temperature increase through the computer equipment which exceeds the 15° to 20°F delta T provided in this specification, and this equipment is a predominate load in a space, the manufacturer should provide the user's Facilities group with suggestions on how to accommodate the larger than expected heat rise using commonly installed computer room air conditioning equipment.
3. If cable openings in the raised floor are specified, the dimensions recommended should be the minimum required to pass cables through so as to not waste cooling air. If openings are specified for ducting air into the computer equipment, the opening area shall be specified for a specific under floor static pressure.
4. Provide specific physical planning of configurations showing cooling air movement for mass deployments of 10 or more high heat density boxes in a concentrated area. (High heat density boxes would include any product or collection of products in a single footprint that exceeds 10 kW in power consumption.)
5. For computer hardware having a high heat density, the manufacturer should provide an alternative to air-cooling, such as the direct rejection of a substantial portion (>80%) of the dissipated heat to water, glycol, or aother liquid.

DRAFT April 5, 2002.

Comments or suggestions for improvement should be directed to Lars Strong of The Uptime Institute (505.986.3900 or LDS@upsite.com).

© 2002 The Uptime Institute