EVCO c-pro nano CHIL - Manual (Page 98)

C-PRO NANO CHIL AND C-PRO MICRO CHIL – APPLICATION MANUAL
Pag. 98
6.3 Configuration of Circuits
When dealing with units comprising two circuits (twin-circuit units, PG01=2), some basic features
need to be defined:
1) Single or separate condensing (parameter PG11)
This configuration has an effect:
- On condensing regulation, which, in the case of a single fan, is carried out on the highest
of the acquired values of condensing pressure/temperature;
- On heat pump units, during defrosting, since in the case of a single fan it is not possible
to carry out separate defrosting of each circuit (while the other one continues to operate,
thus partly compensating water cooling, as a consequence of inverted-cycle operation of
the circuit being defrosted);
- On free-cooling operation, where the same fan splits into condensing regulation and
free-cooling regulation (in case of a single air circuit, PG13=0).
2)
In the case of NEUTRAL ZONE regulation (PC11=1), compressor regulation is based on
the average value of the two outlet temperature probes. Via parameter PC02, it is possible to
select the distribution of the chilling steps required by thermoregulation on the two
compressor circuits; PC02=0 requirements are balanced between the two circuits, whereas
PC02=1 saturates the steps of one circuit, before requesting any of the other.
3)
Which circuit must start delivering chilling is decided on the basis of the two outlet
temperature values. In the case of mode=Cool (chiller), the circuit from which the chilling
request starts is the one with the higher outlet temperature, whereas in the case of
mode=hEAt (heat pump), the first circuit to turn on user loads is the one with the lower
temperature. The selection of the circuit on which regulation is to be started is only carried
out in the absence of chilling requests from both circuits, i.e. when the total number of
chilling steps is zero.
4)
Position of pressure sensors on heat pump units (PH48)
On air-to-water heat pump units, during winter operation, defrosting control can be carried
out by reading the pressure value of the same transducer used to control condensing pressure
during summer operation. In this case, the transducers is normally positioned close to the
finned heat exchanger, i.e. after the cycle-inverter valve. A more rigorous control can be
achieved by using two separate transducers (one on the defrosting compressor air-delivery
piping and one on the condensing delivery piping). Parameter PH48 specifies whether the
same transducer is to function in both summer and winter operating mode.