Modular Standard HP Chiller for Carel driver
Carel code +030221236- Rel. 1.0 dated 7 July 2003
32
15.4.2 Proportional + integral control
If temperature conditions favour Free Cooling control, the Free Cooling ON/OFF valve will be activated as soon as temperature exceeds the
activation threshold of the individual step, identified by a temperature value of:
Control Set-point + 5.0% Free Cooling Differential
The step amplitude is fixed at 5.0% of the Free Cooling control differential.
15.5 Free Cooling ON/OFF valve with stepped condensation
15.5.1 Proportional control
Here is an example of Free Cooling control with ON/OFF valve and three condensation steps.
The ON/OFF valve activation step will, in any case, be positioned in the first part of the control differential and will have an amplitude of 5.0%
of the said differential.
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.
Free Cooling Differential
5.0 %
V1
V2
V3
Free Cooling ON/OFF
valve
Evaporator Outlet
Temperature
Free Cooling Se
point
Evaporator Outlet
Temperature
Free Cooling Set point
Differenziale Free Cooling
Free Cooling
ON/OFF valve
5 %
Free Cooling Differential
2
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