APC ACRD200 Installation Manual download pdf (Page 23)

15InRow RD Fluid Cooled Operation and Maintenance

Control the Environment

The primary function of the cooling unit is to capture the heat generated by IT equipment and neutralize

it before it mixes with the room. The control strategies employed by the cooling unit depend upon the

deployment strategy of the cooling group.

In an in-row environment, the cooling unit supplies constant-temperature supply air to the common cold

aisle. The fan speed is modulated to ensure that the required volume of air reaches the IT equipment. The

fan speed is determined by the difference between the cooling setpoint and the maximum rack air inlet

temperature of the cooling group.

In a HACS or RACS environment, the cooling unit neutralizes the heat accumulated in the common hot

aisle and expels it into the surrounding environmental space while maintaining the necessary

temperature difference across the IT equipment.

In a Spot cooling environment, the equipment operates like traditional CRAC equipment, providing a

constant return air temperature. In Discrete mode, the fans operate at a user-selectable speed (Fan Speed

Preference) and the compressor operates at maximum capacity. In Prop (Proportional) mode, the fans

are modulated to maintain the required return air temperature and the compressor output is modulated to

maintain the necessary supply air temperature.

Setpoints

Path: Main > Set Group Setpoint

A setpoint is the target value that a cooling group will maintain. The default setpoints are appropriate for

most cooling applications.

The setpoints for each mode must be within the following ranges:

• Cool: 18.0 – 32.2°C (64.4 – 90°F))

• Deadband: 0 – 10.1°F

• Supply Air: 13.8 – 21.0°C (57 – 69.8°F) Spot (Proportional) only

15 – 21.0°C (59 – 69.8°F) HACS, RACS or InRow

Note: The Supply Air setting is defined by APC authorized personnel only when the

cooling group is commissioned.

Note: The Supply Air setpoint must never be set higher than the Cool setpoint.

• Fan Speed: When the unit is programmed for HACS or RACS mode, this property specifies the

necessary temperature difference (DT) across the IT equipment. When the cooling unit is

programmed for Spot (Proportional), InRow, HACS or RACS with the Fan Control property set

to Manual, this property defines the fan speed. When the cooling unit is programmed for Spot

(Discrete), the fan speeds are also selected from the following table but the Fan Control property

is irrelevant.

– Low: 16.7°C (30°F) DT (60% of maximum fan speed)

– Med-Low: 13.9°C (25°F) DT (70% of maximum fan speed)

– Med: 11.1°C (20°F) DT (80% of maximum fan speed)

– Med-High: 6.3°C (15°F) DT (90% of maximum fan speed)

– High: 5.6°C (10°F) DT (100% of maximum fan speed)

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APC ACRD200 Installation Manual Page 23