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5.7.13 Fixed opening degree in the pump down / injection phase
There are 3 events, after which the controller performs an initialisation cycle in which the opening degree is
preset. These are only relevant in the context of superheat control via R5.x / R6.x (e.g. no suction gas pressure
transmission t
0
from the pack controller).
After first start and restart / manual shutdown
After any defrost (not until after expiry of the drip time)
In the case of any stall detection (blockade of the regulation)
During this cycle, the evaporator is first evacuated (opening degree = 0%) for a configurable time and then
injected with refrigerant at a fixed opening degree of 100% for an also configurable time. This procedure
prevents the evaporator input signal from assuming invalid values, particularly in the case of superheat control
with two temperature sensors.
The injection phase is interrupted when at least one of the following conditions has been met:
Expiry of the injection duration (safety function)
Exceeding the superheat setpoint by the difference of R6.x - R5.x (in the case of control with two
temperature sensors, this corresponds to the superheat) and falling below the return air setpoint + 5 K of the
evaporator input sensor R5.x
Suction gas pressure transmission t
0
fromthepackcontroller
5.7.13.1 Fixed valve opening degree for servicing purposes
As an alternative to automatically defining valve opening degree by the control functions, a fixed valve
openingdegreecanbedefinedforservicingpurposes.
ATTENTION
Compressor damage! Danger from liquid refrigerant on the suction side of the compressor!If
the value for the injection time for the evaporator to be regulated is set too high this can result in the
escape of liquid refrigerant at the evaporator end. On principle, no monitoring of an undershooting of
the minimum superheat is carried out during the set injection time.
ATTENTION
Compressor damage! Danger due to liquid refrigerant on the suction side of the compressor!
With a fixed opening degree the superheat controller is not active! Consequently there is a danger of a
flooding of the evaporator!
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