µRack
Cod. CAREL +03P220431 rel. 2.2 dated 10/02/12
23
6.6
Prevent high discharge pressure
This function is enabled by parameter /32.
In order to prevent the activation of the general high pressure switch (total shutdown of the compressors, with manual reset), a “prevention” function can be enabled by
setting a pre-alarm threshold; this function gradually decreases the capacity of the unit.
The high pressure prevention (Prevent HP) function is only enabled during the activation and deactivation of the compressors.
If the discharge pressure exceeds the threshold set (parameter /33), the activation of any compressors is disabled and a prevent alarm is generated. In addition, all the
compressor load steps are deactivated, observing the times set for parameter C06.
If the discharge pressure falls below the Prevent threshold, any other compressor start calls are ignored, for a set time called Prevent time 1 (parameter A13).
If between the start of two prevent cycles a time less than Prevent time 2 (parameter A14) elapses, the “Excessive prevent frequency” alarm is generated, A29.
The “Excessive prevent frequency” alarm (display only) is reset automatically, if, within Prevent time 3 (parameter A15), the prevent function is not activated again. This
alarm can be reset manually by the user, momentarily disabling the PREVENT function, using parameter /32.
Fig.
6.b
Key:
OutPress
Discharge pressure
T
Time
NCmp
Number of suction steps required
ALPrv
High pressure prevention alarm
STPpr
Prevent HP activation threshold
T1
Time between compressor stops with prevent HP active
Dprev1
Step activation delay after end prevent HP (prevent time 1)
Dprev2
Minimum time for activation of high prevent frequency alarm (prevent time 2)
NCmp
OutPress
STPpr
T[s]
T[s]
1
2
3
4
Dprev1
T1
Dprev2
ALPrv
T[s]
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