Unit installation

CDU Installation Guide Page 38
Cooling Distribution Unit
OPERATION (continued)
6.7 Control Loop Set-up
The PI temperature control loop calculation is:
Output = Proportional component + Integral component
This is commonly referred to as a ‘non-interacting’ or ‘parallel’ algorithm, where:
The Proportional Component = (Actual temp – Setpoint) / Propotional Band x 100%
The Integral Component = Integral component + [(Actual temp – Setpoint) / (Integral Reset)]
The Integral Component is limited to +/-100
The CDU cabinet has pre-set Proportional and Integral control loop settings for the control valve
operation that will give good overall control. If it is found that these settings require adjustment (i.e. the
control valve is sluggish to respond to load or is over sensitive and oscillates (hunts), then follow the
tuning procedure below:
1. Set Integral Reset (IR) to 0.
2. Set Proportional Band (PB) to the minimum value of 1°C (2°F).
3. Increase PB in steps of 1°C until a sustained and stable oscillation is obtained on the output.
4. Set the IR to 999.
5. Decrease IR in steps of 50 until a steady state is observed on the output.