Airedale LogiCool FreeCool 40kW - Manual (Page 17)

Chillers LOGICOOL
™
Chillers
17
Technical Manual : 6521355 V1.8.0 07/2014
Controls
TEMPERATURE
CONTROL The unit has been designed to provide the cooling load required whilst optimising energy
efficiency at all times and as such will take advantage of free cooling whenever
available. If the free cooling available cannot satisfy the required full cooling load, DX
mechanical cooling is used to supplement the output.
Airedale recognises that all chiller applications are different but fall mainly into 2
application categories; Variable Supply Temperature and Constant Supply Temperature.
The onboard microprocessor has the capability of satisfying either control requirement
using the Airedale Variable Supply Temperature control scheme; energy savings are
available when compared with previous schemes and that of the Constant Supply
Temperature application.
Variable Supply Temperature control schemes offer energy savings where the supply
water temperature is not critical to its operation. By monitoring the temperatures of the
return and supply water the units cooling capacity is adjusted through use of the
microprocessor controls to maintain an average temperature set point between the supply
and return temperatures.
Selection of the best application control scheme can be made via a soft switch in the
microprocessor during initial commissioning.
CAUTION Factory set to Variable Supply Temperature Control unless otherwise stated
at order.
Only when the mode selection has been set can the unit be enabled.
Free-Cooling Operation In high ambients where free-cooling is not available the fan speed modulates in the
conventional manner to maintain a constant head pressure. Free-cooling is initiated
wherever the outdoor ambient is 1°C less than the return water temperature.
When free cooling and DX (mechanical) cooling are operating simultaneously the
condenser fan speed will operate at 100% maximising free cooling.
In ambients where the free cooling coil is capable of satisfying the full cooling demand, the
condenser fans are modulated to provide the desired duty. The condenser fans are
capable of being modulated between 25-100% of airflow to maintain the supply
water temperature.
During periods where the condenser fan speed has been reduced to a minimum, the
supply water temperature will then be controlled by the 3 way valve.