EVCO EPU2LXP1CH Installer manual - Manual (Page 59)

EVCO S.p.A. c-pro 3 micro CHIL | Application manual ver. 1.0 | Codice 144CP3CHE104
page 59 of 120
last compressor to be switched OFF is stored in memory, then the next compressor in the sequence is switched ON, so as to avoid
always using the same compressor, thus exploiting in a better manner all configured elements.
2. LIFO
This method follows the “Last In First Out” logic, i.e. the last compressor to be switched ON will be the first to be switched OFF.
3. FIFO + number of operating hours
This type of rotation favors a comparison of the number of operating hours of the various compressors. At switching ON, the
compressor with the least number of operating hours will be privileged, whereas at switching OFF priority will be given to the
compressor with the greatest number of hours.
In case of having to choose between compressors with the same number of operating hours, a FIFO rotation is triggered, so as to
guarantee a rotation anyway, even in the presence of the same number of hours (see the previous FIFO case).
4. LIFO + number of operating hours
This type of rotation favors a comparison of the number of operating hours of the various compressors. At switching ON, the
compressor with the least number of operating hours will be privileged, whereas at switching OFF priority will be given to the
compressor with the greatest number of hours.
In case there needs to be a choice between compressors having the same number of operating hours, a classic LIFO rotation is
triggered.
On twin-circuit machines, it is possible to decide – based on parameter PC02 – how the steps requested by thermal control are to be
shared between the two circuits:
PC02 = 0. Circuit balancing: the system requests alternatively a step per circuit, so as to balance loads between the two circuits,
provided no alarms have been activated.
PC02 = 1. Circuit saturation: the system requests all available steps from the first circuit, and then all those available from the
second circuit, so as to always have one circuit under full load, provided no alarms have been activated.
8.7.3 Pump-down switch-OFF procedure
On machines with power above a certain limit and where there is a substantial amount of refrigerant, the pump-down procedure is
necessary to partially empty the evaporator of excess refrigerant. Therefore, the solenoid valve situated upstream from the related
evaporator is controlled in such a way that the compressor remains ON for the time interval Compressor switch-OFF delay in pump-
down (parameter PC42). At compressor start-up, the solenoid valve is opened at the precise same instant. In order to enable this
function, the following parameters must be set:
PC41 = 1: Function enable
PC42: Pump-down time
Note: In case of alarm, the system must ignore the compressor switch-OFF delay.
8.7.4 Relative-threshold pump-down
If low-pressure transducers are available, it is possible to carry out the pump-down procedure leaving the compressor ON only for the
time necessary to empty a correct part of refrigerant. At the end of the request by the last compressor to be ON from the affected
evaporator, the evaporation pressure value is stored, the fluid solenoid valve is disabled, and, once the evaporation pressure value has
fallen by the Pump-down pressure differential PC43, the compressor is switched OFF.