APC ACRD500 Installation Manual download pdf (Page 30)

InRow RD Operation and Maintenance22

Control the Environment

The primary function of the cooling unit is to cool air from the hot aisle and deliver it to the cold aisle at

the temperature setpoint. The control strategies employed by the cooling unit depend upon the

deployment strategy of the cooling group.

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

aisle. The fan speed is modulated to ensure that the desired 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.

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

aisle and expels it back into the surrounding environmental space while maintaining the desired

temperature in the cold aisle.

How the Cool mode works

Cool. The equipment uses a direct expansion coil, a variable speed compressor to modulate refrigerant

flow through the coil, and a set of fans to control airflow through the coil. The cooling output is

determined by the difference between the cooling setpoint and the supply air temperature of all the

cooling units in the cooling group (if more than one cooling unit is present).

The cooling unit is equipped with compressor cycling control that tries to minimize the number of times

the compressor cycles on and off. The compressor will cycle off when the rack inlet temperature drops

below 15° C (59° F) whether or not the minimum compressor on time of 3 minutes has elapsed. Once

off, the compressor will not normally cycle on until the supply temperature reaches its setpoint and the

minimum off time of 2 minutes has elapsed. However, if the rack inlet temperature reaches 25° C (78°

F), the compressor will cycle on regardless of whether the minimum off time has elapsed.

Compressor cycles are monitored over a 7-day period. If the number of cycles average more than 12 per

hour over that period, the Excessive Compressor Cycling alarm is set.

See Supply Air and Return Air on page 29 for more information.

Setpoints

Path: Main > Set Group Setpoints

A setpoint is the target value that a cooling group tries to maintain in the rack. The default setpoints are

appropriate for most cooling applications.

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

• Cool: 18.0–25.0°C (64.4–77.0°F)

• Supply Air: 17.0–23.0°C (62.6–73.4°F)

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

cooling group is commissioned.

Note: If the Supply Air setpoint is greater than the Cool setpoint, the cooling unit

triggers an alarm and resets the Supply Air setpoint to equal the Cool setpoint.

1 2 ... 25 26 27 28 29 30 31 32 33 34 35 ... 59 60

No comments

APC ACRD500 Installation Manual Page 30