EVCO c-pro nano CHIL - Manual (Page 105)

C-PRO NANO CHIL AND C-PRO MICRO CHIL – APPLICATION MANUAL
Pag. 105
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 favours 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 favours 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 regulation 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.
6.6.3 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
- HA07: Position of solenoid valve digital output, Circuit # 1
- HA08: Position of solenoid valve digital output, Circuit # 2
Note: In case of alarm, the system must ignore the compressor switch-OFF delay.
6.6.4 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