Stulz CeilAir CW - AWS Operation

19OCH0006F08/13/2024
CEILAIR
®
CW & DX IOM
1.8 AWS OPERATION
The compressor activates if the DX cooling stage enable-temperature setpoint has been reached or if the
control valve position reaches 100% open for 240 seconds (default compressor-on time delay). The free-
cooling circuit and the compressor operate in parallel on dual-circuit units to provide maximum cooling.
The 3-way control valve continually modulates the flow of coolant in response to temperature with the
compressor running.
The compressor cycles off based on the normal compressor temperature cut-out settings once the setpoint
is maintained.
As the outside air temperature increases above the ambient air switch-over setting, the fluid cooler controls
cycle back to typical DX heat rejection allowing the leaving fluid control setpoint to increase above the
prevailing ambient conditions. The indoor unit’s inlet fluid temperature sensor monitors the fluid temperature
and deactivates the free-cooling mode once the fluid temperature increases above the user adjustable
enable setpoint. The compressor system becomes the primary cooling source and will activate if the return air
temperature increases above the setpoint.
1.8 AWS Operation
The Alternate Water Source (AWS) configuration illustrated in Figure 5 utilizes an independent chilled water
source (chiller) to pipe coolant to an AWS cooling coil in the A/C unit. If AWS cooling is unable to handle the
load, the separate DX refrigeration circuit can be utilized to assist. Similar to free-cooling operation (see
section 1.7), AWS cooling activates when return air temperature rises to the AWS cut-in temperature setpoint
while the chilled water inlet temperature is 55 °F or less (adjustable). When AWS cooling activates the AWS
control valve opens and remains on while the activation conditions persist.