Modular Standard HP Chiller for Carel driver
Carel code +030221236- Rel. 1.0 dated 7 July 2003
34
15.6.2 Proportional + integral control
The devices, whether they are valve or fans, will be activated in the second half of the control differential through the effect of the integrating
control. Their activation will be tied to the set integrating constant: the slower it is, the greater the value attributed to the specific parameter.
The amplitude of the valve control step will be 5.50% of the said control differential.
All proportional outputs relating to the different units of the system will be piloted in parallel
15.7 0-10 Volt Free Cooling ON/OFF valve
The Free Cooling valve is proportionally commanded in a different way depending on whether condensation control is in steps or by inverter.
The control diagrams of the two different situations are shown below.
15.8 0-10 Volt Free Cooling ON/OFF valve with stepped condensation
15.8.1 Proportional control
The proportional control ramp of the Free Cooling valve will be calculated inside the first activation step of the condensation fans. In this way,
when the first fan is enabled, the valve will be completely open, and, therefore, water flow in the Free Cooling exchanger will be at maximum
level.
The activation steps of the condensation fans will be positioned proportionally inside the Free Cooling control differential.
To calculate the amplitude of each step, use the following relation:
Step amplitude = Free Cooling Differential
(Number of Master fans X number of cards)
It is assumed that all the circuits controlled by the pCO cards making up the system are equivalent and that the number of controlled devices is
the same.
Evaporator Outlet
Temperature
Free Cooling Differential
5.0 %
0 Volt
10 Volt
Free Cooling
ON/OFF Valve
Free Cooling Set point
Inverter Ramp 0 to
10 V
Free Cooling Differential
2
Free Cooling Se
V1
V2
V3
0 Volt
10 Volt
Free Cooling 0 to 10 V
Valve
Free Cooling Differential
Evaporator Outlet Temperature
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