Carel plug-in User Manual page 27

AL: minimum temperature relative alarm
Selects the low temperature relative alarm. The value of AL does not indicate the alarm temperature but rather the maximum
difference allowed below the set point.
For all models:
Note that changing the set point automatically changes the low temperature alarm, in that maximum difference allowed remains the
same (=AL). The low temperature alarm has an automatic reset. This means that if the temperature returns above the threshold
value +A0, the alarm signal automatically stops. Finally, please remember that the low temperature alarm is also used in the
continuous cycle (see corresponding section on page 59). In fact, if the temperature falls to the alarm level the continuous cycle is
automatically deactivated, even if the selected period has not elapsed. The deactivation does not give rise to an alarm signal.
Def.: AL=0 (low temperature relative alarm inhibited). Available on all models.
AH: high temperature relative alarm
Selects the high temperature relative alarm. The value of AH not indicates the temperature of alarm but rather the maximum
difference allowed above the set point (working point).
Per all models:
Note that changing the set point automatically changes the high temperature alarm, in that maximum difference allowed remains
the same (AH). The high temperature alarm also has an automatic reset. When the temperature falls below the threshold value –A0
the alarm signal automatically stops.
Def.: AH=0 (high temperature relative alarm inhibited). Available on all models.
Ad: temperature alarm delay
Indicates after how many minutes the temperature alarm is signalled from when it is detected. If the temperature, after the delay
Ad, is back within the allowed limits, the alarm is not signalled.
Setting a delay to signal of the temperature alarms may help eliminate false alarms due to interference on the probe signal or
situations lasting a short time (for example, opening the cold room door briefly).
The temperature alarm delay has no effect on two special functions: defrost and continuous cycle. To delay any temperature alarms
after these functions, parameter d8 for defrost and c6 for continuous cycle must be modified. Remember that during defrost and
continuous cycle no temperature alarms are generated.
Def.: Ad=0 (instant temperature alarm). Available on all models.
A4: Multifunction digital input configuration
The MULTIFUNCTION digital input can assume different meanings according to the value attributed to this parameter, and
according to the model of control used. Following is a description of the possible functions:
A4 = 0: input not active
The Multifunction digital input is not used. This is the default value for all versions.
A4 = 1: external alarm
An external alarm requiring immediate intervention can be connected to the digital input (for example, high pressure or
compressor thermal overload alarm). In particular, the alarm is detected when the contact opens (normal operation with contact
closed). The management of the alarm can be instant, or with a delay according to the value of parameter A7 (0 = instant).
The activation of the alarm brings a bout a message on the display (see alarm IA), activates the buzzer, if featured, and causes the
following actions on the actuators:
compressor causes the compressor to shut-down from external alarm (immediate if A7=0 )
fans causes operation according to the fan parameters (F). If the external alarm is detected during a defrost or a
continuous cycle, the control exits the procedure
When the alarm stops, the machine returns to operation as follows:
defrosts can again be performed. The next starts after the set time dI (interval between defrosts)
DEFROST
compressor if at the instant the alarm ends the compressor is on, it stays on for the minimum set time (parameter c2). If it is
off, it stays off for a minimum time equal to the minimum off time (parameter c3)
The configuration with delay (A7 > 0) is especially useful for managing the low pressure alarm. It is frequent, in fact, for the unit
to detect a low pressure alarm when first turned on, due to the environmental conditions and not a unit malfunction. Setting an
alarm delay avoids false signals. In fact, by carefully calculating the delay, if low pressure is due to environment conditions (low
temperature) the alarm will automatically return before the set delay elapses. The effect on the compressor, fans, defrost and
continuous cycle are the same, after the set delay, as above.
Warning: as already indicated in the installation instructions, to ensure the safety of the unit in the event of serious alarms (for
example, the pressure alarms), the unit must be fitted with all the electromechanical devices required to guarantee correct operation
according to the standards in force. The electronic control on its own can not be used to guarantee safety in the event of serious
alarms.
Cod. +030221881 rel. 1.5 - 26/10/10
low temperature relative alarm = (set point) - (value of AL)
high temperature relative alarm = (set point) + (value of AH)
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plug-in