EVCO S.p.A.
c-pro 3 micro CHIL | Application manual ver. 1.0 | Codice 144CP3CHE104
page 74 of 120
• PA13 = Low-pressure alarm by-pass time
• PA14 = Maximum number of auto-reset low-pressure alarms
If, with the machine switched ON and in the presence of a request for chill from the controller, low pressure is detected, compressor
start-up is inhibited and a Start-up low-pressure alarm AL21 (and AL22 for Circuit # 2) is displayed. The purpose of this condition is
to inhibit compressor start-up in the absence of Freon® gas in the circuit (there could be a refrigerant leak from the piping system
8.17.4 Management of low-pressure transducer alarm (heat pump mode)
If intake pressure falls below a given threshold, a low-pressure alarm AL41 (and AL42 for Circuit # 2) is generated. The alarm causes
the immediate stopping of the refrigerating circuit, also shutting down any compressors which may be ON, and inhibiting the start-up of
others.
At start-up of the first compressor, the alarm is delayed for a given interval, to enable the compressors to take the refrigerating circuit
to full pressure.
The alarm is initially auto-resetting, unless it exceeds a given number of events within one hour (PA14), in which case it becomes a
manual-reset alarm, which can be reset if in the meantime pressure has risen above the minimum threshold by a certain differential
value.
PA11 = Low-pressure alarm set point
PA12 = Low-pressure alarm differential
PA13 = Low-pressure alarm by-pass time
PA14 = Maximum number of auto-reset low-pressure alarms
In the presence of low temperatures of external air, intake pressure could fall below the minimum- pressure threshold, thus inhibiting
compressor start-up. In such a situation, it is possible to activate a control, which shifts the alarm-control threshold to a higher value
for a given interval from start-up of the first compressor, leaving nevertheless in place all protection devices and pre-start checks.
PA16 = Low-pressure control enable at low outdoor air temperature
PA17 = Low-pressure alarm set point at low outdoor air temperature
PA18 = Low-pressure alarm differential at low outdoor air temperature
PA19 = Low-pressure alarm control duration at low outdoor air temperature
This control can only be enabled in heat-pump operating mode.
8.17.5 Low start-up pressure alarm
In a low-pressure condition (pressure switch or transducer-induced) and in the impossibility to activate any of the compressors at the
request of the same, there is a Low-pressure start-up alarm AL51 (and AL52 for Circuit # 2). This is an auto-reset alarm, and thus
should disappear, unless there is a leak of Freon® gas from the circuit.
At compressor shutdown following a low-pressure alarm, this alarm is delayed by a given interval PA20, to give the refrigerating circuit
the chance to enable compressor start-up.
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