IT Cooling
LogiCool InRak™
21
Introduction
InRak™ Technical Manual 7462807 V1.11.0_04_2016
Controls
Dynamic Pressure Control (DX units)
With DX units the fans will operate with constant pressure control except the fan speed will modulate within predefined
upper and lower limits, to maintain the target differential whilst maintaining the evaporating temperature.
Similar to air volume control, the compressor will maintain the “air off” temperature while the fans control to the aisle
pressure as long as the evaporating temperature remains within the operating band. However, if the evaporating
temperature changes beyond the high or low differential limits, the fans will modulate to bring the evaporating
temperature back within the band, up to the minimum or maximum aisle pressure band limits. If the evaporating
temperature changes beyond that, the compressor will modulate to bring the evaporating temperature back within the
control band.
Fan Capacity Control (CW unit)
Capacity control will allow the unit to modulate air volume based on demand for unit cooling. The controller will modulate
the chilled water valve alone to try and increase unit cooling performance whilst maintaining the fans at their minimum
speed. However, if the cooling performance is not increased sufficiently then the fan speed will increase to further satisfy
demand.
By default, the valve/fan changeover point is set at 50% cooling demand. The fans will therefore stay at minimum speed
until the cooling demand reaches 50% and then start to ramp up to satisfy the cooling demand. As the unit cooling
demand increases the fan speed is modulated to match the required cooling performance. This feature enhances
system energy efficiencies, by having only the required fan input power for particular loadings.
Heating
The InRak has the option of thyristor heating to give continuous analogue control to the heating produced.
The heating loop will be activated when the return air temperature falls below the set point, as with fan control the
heating present within the unit will modulate to satisfy the unit heating demand.