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4.4
Secondary system
4.4.1
General information
Designing a secondary system is a complex task where many things must be considered, for
instance:
•
load variations
•
pressure loss
•
service
•
maintenance
•
corrosion and erosion
•
fouling.
Note: Rapid temperature variations in the secondary system can damage the chiller. It is recom-
mended to keep temperature changes below 1 K/min. Install a buffer tank or balancing tank to
avoid great variations in load and temperature. Avoid fluctuating pressure and temperature as
this can damage the heat exchangers.
4.4.2
Cleaning in place
It is recommended to install valves and connections for chemical cleaning of open secondary cir-
cuits. ComPAC evaporators and condensers are fully welded heat exchangers and cannot be
cleaned mechanically.
For more information about chemical cleaning, please contact a Johnson Controls representative.
4.4.3
Temperature and flow control
The Unisab III controller adjusts the compressor load by means of input from a PT100 tempera-
ture sensor. A sensor threaded branch and sensor pocket are delivered with the unit. The sensor
must be fitted into the evaporator outlet pipe minimum 1 metre away from the evaporator.
4.4.4
Water and brine treatment
Brine and water for industrial refrigeration plants often contain impurities that can create a coat-
ing (fouling) on the heat transferring surfaces. This reduces the heat transmission and in some
cases the coating causes corrosion of the heat transferring surfaces.
It is therefore important to keep brine and water under observation for both evaporator and con-
denser. Consult a water treatment expert concerning additives to the system. The liability of
Johnson Controls Denmark does not include any damage that may occur due to harmful impur-
ities in the system.
Be aware that all cooling towers and evaporative condensers experience a constant loss of water
due to evaporation. In order to keep the concentration of impurities low, a bleed system must be
installed.
Note: In order to obtain the correct mixture, it is recommended to premix secondary refrigerants
(glycol or brine) and to check it subsequently.
4.4.5
R717 detector
Installation of R717 detectors in the room and in the secondary circuit of an indirect system must
be in accordance with EN 378 and/or local codes and rules. Detectors in the secondary circuit in
indirect systems are recommended regardless of the R717 charge limit according to EN 378.
The use of detectors in secondary circuits should be based on a risk assessment covering assess-
ment of:
38/56
Installation information
Operating manual - ComPAC
011769 en 2020.03
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