Controlling The Cooling Capacity; Operating Principle - Siemens PolyCool Superheat CPS40 Manual De Instalación Y Servicio

SMX
Example
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 su-
perheat within a certain range. The assignment is made proportion-
ally 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 (DT SP), and DC 10 V / 20 mA corresponds to the sum of
(DT 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 tem-
perature. 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 mini-
mum permissible suction pressure, refer to the compressor's specifi-
cation sheet.
If the cooling capacity is reduced too much, excessive icing can
occur on the evaporator (air coolers). The drop in evaporator tem-
perature should also be observed for chillers without frost protection.
Superheat - CPS40

Controlling the cooling capacity

by 3.1 %
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CE1U3372xx
2018-11-09