Controlling The Cooling Capacity; General; Operating Principle - Siemens PolyCool CPS 40 Manual De Instalación

SMX
Exemple
Siemens
Building Technologies
6 Controlling the cooling
capacity

6.1 General

The cooling capacity of the refrigeration unit drops as the
superheat of the suction gas increases. This effect can be utilized
by PolyCool Superheat for controlling the cooling capacity.

6.2 Operating principle

The capacity controller continuously varies with the setpoint of
superheat within a certain range. The assignment is made
proportionally to a DC 0...10 V signal, or to the manipulated
variable of the capacity controller. DC 0 V / 4 mA corresponds to
the setpoint of superheat ( T SP), and DC 10 V / 20 mA
corresponds to the sum of ( T SP+SMX) based on the
configuration of. Both parameters can be entered in the parameter
mode. The greater SMX, the more the cooling capacity can be
reduced. But as the capacity drops, the evaporation pressure will
also drop, and thus the evaporation temperature. The average
drop for each additional K superheat is as follows:
The evaporation temperature by 1 C
The cooling capacity Q
Required is a reduction in cooling capacity of 50 %,
i.e. 50 % / 3.1 16 K for SMX
To ensure lubrication and cooling of the compressor at all times,
superheat cannot be increased beyond certain limits. For the
minimum permissible suction pressure, refer to the compressor's
specification sheet.
If the cooling capacity is reduced too much, excessive icing can
occur on the evaporator (air coolers). The drop in evaporator
temperature should also be observed for chillers without frost
protection.
CPS40
by 3.1 %
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2013-10-01