Rev.01 03-27-17
Page 18 of 67
Compu-Aire
conditions. The optional Pressure Differential (No Water Flow) switch shall be provided for field
installation.
GLYCOL PUMP
: A matching centrifugal circulating pump is provided for field mounting and piping.
Pump Operation
When compressor is on the pump and fluid cooler will be enabled. Note that this is in DX cooling.
In free cooling the logic is the same, as pumps is enabled with economizer cooling.
3.9
Special Pump and Dry Fluid Cooler control logic
Pump speed adjusted based on differential pressure across pumps as 2-way control valves modulate.
Dry cooler and Pump controller Sequence of operation
Free cooling mode
Either outdoor air temperature is monitored or a signal from each crac unit (free cooling and DX
condenser) is sent to the pump controller to determine which function is provided.
Fan speed may be increased sufficiently to allow pump minimum operating speed to be maintained
should zone loads decrease, thus decreasing flow below safe pump operation.
Outside air temperature reaches 48F
Pump controls switch to free cooling mode
–
Fans run 100% until condenser outlet temperature reaches
38F, at which time fans speed will reduce to maintain 38F or minimum pumps speed is reached, then
fans will reduce speed to maintain minimum pump speed, which is accomplished by 2-way valves
modulating open is response to increased condenser water supply temperature.
Controls shall monitor both fan KW and Pump KW energy consumption and determine best speed
combination to maintain lowest condenser supply water temperature during free cooling more.
DX Cooling mode
Outside air temperature 50F
Pump control increases fan speed as condenser water temperature increases. Maintain 65F condenser
outlet water by modulating fan speed. At 75F exiting condenser water temperature fan speed is 100%.
Controls shall monitor both fan KW and Pump KW energy consumption and determine best speed
combination to maintain lowest condenser supply water temperature during DX cooling more.
