Airflow; Equipment Orientation - HP Rp3440-4 - 9000 - 0 MB RAM Manual

HP temperature and humidity recommendations follow newly established industry standards
in the following operating ranges:
• Temperature of 20–25 °C (68–77 °F)
• Humidity of 40%–55% relative humidity
• Filtration at 35%–55% spot efficiency per American Society of Heating, Refrigerating, and
Air-Conditioning Engineers (ASHRAE)
• Air-conditioning heat load limits at 80% of total heating, ventilation, and air-conditioning
(HVAC) capacity

Airflow

A public misperception exists that cool, ambient air is consistent throughout a datacenter. That
is, if the temperature of the room is measured at 20 °C (68 °F), then the equipment should be
stable. In reality, microclimates can exist in various parts of the room such that generated heat
in the equipment might not efficiently make its way out. Microclimates are difficult to detect
and prove; therefore, prevent microclimates by encouraging a high rate of airflow from source
to intake of HVAC and uniform distribution of the heated air. Underflow blockages, such as
cabling and piping, can disrupt the airflow predictability. Improperly positioned floor vent tiles
or equipment can create air dams and decrease airflow. Follow these precautions to ensure proper
airflow:
• Use a heat load to 80% of total HVAC capacity to maintain a thermal safety margin.
• Place vented floor tiles only in heat load areas.
• Do not place vented floor tiles within two floor tiles of HVAC (thermal short circuit).
• Do not place heat loads closer than two floor tiles of HVAC.
• Be sure the maximum distance from the HVAC to the heat load is less than 75 feet (23 m).
• Seal all cable openings as unsealed openings create a loss of static air pressure.
• Lay out equipment aisles parallel to airflow; not perpendicular to it.
• Concentrate high-density heat loads in a tightly controlled area. High-density loads are
equivalent to one cabinet of 3 kilowatts or more.
• Maintain airspeed through vent tiles at more than 500 feet per minute (152 meters per minute)
but at less than 700 feet per minute (213 meters per minute) for high-density cooling.

Equipment Orientation

Data center equipment orientation, or heat load, must encourage sufficient airflow. If exhausted
heat must move over or around a cabinet, air vortexes might be created, resulting in airflow
inefficiency throughout the data center and inside the equipment. Equipment might develop
internal hot spots, resulting in sluggish performance or even system failure.
Rather than designing a layout to maximize a planning grid worksheet whitespace, create "hot"
and "cold" aisles. In a hot aisle, equipment is oriented so that exhaust vents face other exhaust
vents. In a cold aisle, intake vents face other intake vents. Place vent tiles in the cold aisles, with
few to no vent tiles in the hot aisle. Position equipment in parallel to encourage the lowest air
resistance and turbulence. Consider the following when determining equipment orientation:
• Orient equipment in parallel to airflow.
• Place cabling in such a way as to aid airflow rather than impede it.
• Arrange equipment to form hot and cold aisles.
• Use vent tiles to control airflow in heat load areas.
• Place vent tiles in cold aisles.
• Place higher heat load devices at floor level.
16 General Site Preparation Guidelines