EVCO c-pro nano RACK - Manual (Page 58)

C-PRO NANO RACK E C-PRO MICRO RACK APPLICATION MANUAL
Page 58
Setpoint = 0.5 bar
Proportional band = 2.0 bar
Power Compressor 1 = 3 kW
Power Compressor 2 = 5 kW
Power Compressor 3 = 10 kW
Measured Pressure
(bar)
Power Required
(kW)
Compressor 1
(3 kW)
Compressor 2
(5 kW)
Compressor 3
(10 kW)
Power Delivered
(kW)
0.5 - 0
0.6 0.9 X 3
1.0 4.5 X 5
1.3 7.2 X X 8
1.6 9.9 X 10
1.7 10.8 X X 13
2.0 13.5 X X 15
2.3 16.2 X X X 18
2.5 18 (max) X X X 18 (max)
Applying the formula of calculation for the required power, these values are obtained.
Below the setpoint, the power delivered is null, above the setpoint, the power delivered is at the maximum.
6.4.7 Compensation for load losses on the suction line
In certain systems, it may be necessary to decrease the suction setpoint with the increase in the yield of coolant,
to compensate for the losses of pressure along the suction line. Users, which should operate at a constant
evaporation pressure, will in essence find themselves working at higher pressures when there is a higher need
for cold temperatures, and vice versa. This means that, in order to guarantee the production of coldness at the
desired temperature even with loads in the proximity of the nominal values, one must work with a setpoint that
is appreciably lower even at partial loads, when it wouldn’t be necessary. The compensation works by
introducing an offset that is able to be set, which lowers the setpoint gradually at each call of cold steps; it
appears evident that this function acts with the intention of increasing the efficiency of the system, making it
possible to choose a higher setpoint for lower loads.
Through the PH35 parameter this function is enabled, which leads to a lowering of the setpoint by a factor of
compensation for each step inserted and to an increase in the setpoint by the same value for each step released.
This function is able to be activated only with adjustment in the neutral zone.
6.4.8 Throttling of the refrigerating power at high pressures
To prevent the intervention of the high condensation pressure regulator and the resultant blockage in cold
production, it is possible to reduce the refrigerating power and subsequently the power of exchange at the
condenser, lowering in this way the condensation pressure. This reduction is possible only with circuits that are
subjected to throttling (with at least two compressors or with a compressor equipped with throttling devices).
The parameters related to the first circuit for this function are the following:
- PC70 = Enables throttling at high pressures
- PC71 = Setpoint limit for pressure regulator check of condensation
- PC74 = Differential for pressure regulator check
- PC75 = Minimum maintenance time for pressure regulator throttling
- PC76 = Percentage value of throttling