Carel E2V S0 Series - Protection function control parameters; Recommended parameters

Code +030220215- rel. 1.4 – 25.04.2007-
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8.2 Protection function control parameters
The software that manages the valve includes four protection functions:
• LowSH protection (low superheat)
• LOP protection (low evaporation temperature)
• MOP protection (high evaporation temperature)
• HITCond protection (high condensing temperature, optional)
The LowSH protection acts quickly to close the valve in the event where the superheat is too low, to prevent the
return of liquid to the compressor.
The LOP protection acts quickly to open the valve when the evaporation temperature is too low, to prevent the
compressor from stopping due to low pressure.
The MOP protection acts moderately to close the valve and limit the evaporation temperature if this reaches
excessive values, so as to prevent the compressor from stopping due to thermal overload.
The HITCond protection, can only be enabled if the controller measures the condensing pressure/temperature
, acts
moderately to close the valve if the condensing temperature reaches excessive values to prevent the compressor
from stopping due to high pressure.
Each of these protectors features a threshold and an integration time; the activation speed of the protectors is
higher the lower the corresponding integration time. The threshold, on the other hand, is defined depending on the
compressor and the application.
The use of the protectors is recommended, however this is at the user’s discretion.
8.3 Recommended parameters
Below are the most suitable values of the parameters for each application and specifically for CAREL valves. If
valves made by other manufacturers are used, the same recommended parameters can be used initially, modifying
the “Proportional gain” based on the maximum number of control steps for the valve installed.
Example of adapting the proportional gain for the different valves
Reference:
CAREL E2V (480 maximum control steps), proportional gain = 5
→ Sporlan SEI - 1, (1596 steps), proportional gain = 5 x 1596 / 480 = 16
→ Alco EX-5 (750 steps), proportional gain = 5 x 750 / 480 = 8
The following tables also show a specific category called perturbed system
.
Perturbed system
defines a refrigeration unit in which the condensing pressure and/or the refrigerant charge vary
continuously and rapidly. The superheat can also vary when the subcooling is low or null (critical refrigerant charge)
and the superheat set point is less than the value specified in the tables or low in general.
In a perturbed system, the control variables (superheat and evaporation temperature) vary significantly, however not
due to the electronic valve, which consequently must have more intense reactions to be able to keep the superheat
around the set point. Obviously, the more perturbed the system, the lower the probability of achieving a stable
superheat.
control