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EN/09.2019/G41 © STULZ GmbH – all rights reserved
cybercool 2 screw original insTrUcTions
5.3 External water circuit
pipe compensator
mesh strainer
Chiller
flow water
return water
The chilled water circuit of the chiller contains a tube evaporator, several drain valves, several deventilation
valves, a flow monitor, a frost protection thermostat and temperature sensors in the inlet and outlet. The frost
protection thermostat is adjusted on 4°C in the factory. Below this water inlet temperature it releases a frost
protection management by the controller, which may lead to an antifreeze alarm. The adjusted value can be
modified and must be adapted to the local conditions (glycol content).
In addition to this, the free cooling version disposes of two motor driven control valves and another tempera-
ture sensor in the chilled water circuit.
The following additional components are necessary:
• circulating pump with sufficient delivery height.
• storage tank as an accumulator for heat energy to reduce the on/off cycles of the compressor. A storage
tank is recommended if the water volume of the water circuit is less than 10 litres/kW cooling capacity. The
storage tank should be lined out with thermical insulation.
• expansion tank with safety valve to ensure a possibility of expansion for the liquid at temperature variations.
The expansion tank must be dimensioned in such a way that the water circuit volume can increase by 2%
without draining off liquid through the safety valve.
• stop off valves upstream the chiller to be able to take the chiller unit out of the chilled water circuit in case of
repair works without having to drain the entire circuit.
• mesh strainer with mesh size of 800-1200 µm in the chilled water inlet
recommended: pipe compensator in the chilled water inlet and outlet
Another criterion for the external water circuit is the water quality. The most sensible component in respect
of pollution and corrosion is the tube evaporator, whose heat transmission features deteriorate in this case.
The water should be free from solid particles. For this purpose we recommend the installation of a fine mesh
strainer upstream the evaporator.
If you connect two or more chillers in parallel, we recommend to install regulating valves to keep the pressure
drop of each unit equally high.
Chiller 1
Chiller 2
flow water
return water
