Carel µC2SE User Manual page 50

- High temperature alarm delay on power-up
P17: High temperature alarm delay when the control is switched on (power ON), from the remote ON/
OFF contact or from the keypad.
- High pressure alarm from transducer set point
P18: Sets the value beyond which the high pressure alarm is generated. Each circuit will be managed by
its own transducer.
P18= 0: the function is disabled.
For all other values greater than 3.0, due to the hysteresis (3 bars), the alarm is managed according to the
set value.
- Low system start-up temperature alarm set point
P19: Represents a threshold for the low temperature (measured by probe B1) alarm, without hysteresis; it
is reset automatically (the alarm relay is not activated and the display shows the message "ALt").
- System start-up protection for high/low temperature
P20: If set to 1, this parameter enables the system protection function when starting, both at power ON
and when switching ON from Standby.
In chiller mode (cooling), for values of B1 greater than the set point P19, an alarm is activated and the
unit is not started (display "AHt").
In heat pump mode (heating), for values lower than the set point P19, an alarm is activated and the unit
is not started (display "ALt").
The alarm is reset automatically.
P20=0: the function is not enabled.
- Low pressure alarm waiting time in heat pump
P22: Delay in generating the low pressure alarm in heat pump mode
If the pressure remains below 1 bar for the time p22 and the circuit has 2 compressor steps, the circuit
can operate at part load (see P04). This preventive capacity control function remains active until the
pressure rises above F08-F09.
- Low pressure alarm waiting time during defrost
P23: Delay in generating the low pressure alarm in heat pump mode during defrost
- Deactivate compressors in capacity control for HP and LP
P24: Decide which compressor must be stopped in each circuit during capacity control
P24= 0 stops compressors 1 and 3
P24= 1 stops compressors 2 and 4
- Low pressure alarm set point from transducer
P33: : Sets the value beyond which the low pressure alarm is generated when the unit is operating in
heat pump mode. Each circuit will be managed according to its own transducer.
P33= 0 the function is disabled.
- Mute alarm relay using "PRg/mute" button
P35=0 the PRG/mute button does not alter the status of the relay, if the alarm is active and in progress.
P35=1 the PRG/mute button alters the status of the relay even if the alarm is active and in progress, as if
it were a buzzer or a siren.
- High pressure alarm management
P36: the parameter is used to consider the high pressure alarm even when the compressor is off or
consider it only when the compressor is on, depending on whether the pressure switch is directly
connected to the digital input on the controller or via another circuit.
P36=0: high pressure alarm always considered (pressure switch connected directly to the digital input).
P36=1: high pressure alarm considered 2 seconds after starting the compressor.
• Control settings: parameters (r*)
- Cooling set point
r01: between r13 and r14
r02: cooling differential value of DTE when the unit is fi rst started (autotuning enabled)
- Heating set point (heat pump)
r03: between r15 and r16
r04: heating differential value of DTE when the unit is fi rst started (autotuning enabled)
- Compressor rotation
r05: The rotation of the compressors allows the operating hours to be balanced either statistically, using
FIFO logic, or absolutely, by counting the effective operating hours. Settings:
r05=0: rotation disabled; The customer can use compressors with different power ratings according
to the desired logic or manage the capacity-control functions. The compressors are started/stopped in
proportional mode.
r05=1: rotation with FIFO logic (fi rst ON, fi rst OFF, and vice-versa fi rst OFF, fi rst ON); in this mode the
operating hours are optimised together with the number of starts, even if the compressor safety times are
always respected.
r05=2: rotation with control of operating hours; in this way the compressors will have the same operating
hours, as the compressor with the least operating hours is always started fi rst, again observing the safety
times. This does not however consider FIFO logic and does not optimise the starts and stops. In the case of
capacity controlled compressors (1 per circuit), FIFO logic or timed operation will refer to the actual circuit
and not the compressor valves. If, for example, when capacity is required from circuit 1, compressor 1 starts
fi rst, capacity controlled (not at full capacity), and then the valve is managed as a second step, so that the
compressor will work at maximum effi ciency. If less capacity is required, the second step will be deactivated
fi rst, and then the compressor. There is no rotation between the compressor and the valve. If extra capacity is
required, the second circuit will start with compressor 2 and then, if required, the valve is operated.
50 µC 2 SE - +030220426 - rel. 2.0 - 03.08.2009