EVCO c-pro nano CHIL - Manual (Page 117)

C-PRO NANO CHIL AND C-PRO MICRO CHIL – APPLICATION MANUAL
Pag. 117
6.12.1 Defrosting management via external contact
This function is typically used to make it possible to start or end defrosting via an external
thermostat/pressure switch, which is connected to the digital input assigned to this function. In this
case, defrosting timings as an alternative to the external contact function are ignored. By setting
parameter Defrosting management via external contact Pd11 to a value different from zero, the
following operating modes are available:
- Pd11 = 0 – Normal operation
- Pd11 = 1 – Defrosting start by external contact: opening of the contact enables defrosting
start; with a closed contact, defrosting follows the normal procedure.
- Pd11 = 2 – Defrosting stop by external contact: opening of the contact enables defrosting
stop; with a closed contact, defrosting follows the normal procedure.
- Pd11 = 3 - Defrosting start/stop by external contact: if the value of parameter Defrosting
contact type Pd12 is “0” (Front) opening of the contact enables defrosting start/stop; with a
closed contact, defrosting follows the normal procedure; but if Pd12 = 1 (Level), opening of
the contact enables defrosting start, whereas closing enables defrosting stop.
A request for defrosting start is always accepted, unless the dripping process is taking place.
A request for defrosting stop is only accepted when a defrosting cycle is activated.
In order to enable this function, parameter Defrosting digital input position Hd09 must be set to a
value greater than zero, as it is otherwise impossible to utilise the associated digital input.
Note: On twin-circuit machines, defrosting start by external contact is managed by alternating the
two circuits. When the defrosting start event is detected by the associated digital input, the
defrosting circuit will be the one that has not defrosted at the previous request.
When a request if for defrosting stop by external contact, this ends the current cycle on the
associated circuit.
6.12.2 Defrosting cycle compensation
With the decreasing of the external temperature, the water vapour content in the air (which causes
the formation of frost on the evaporation battery, thus creating a need for defrosting) decreases, and
it may therefore be advantageous to increase the defrosting-activation delay in relation to the
decrease in the external temperature, to improve the overall efficiency of the system. If enabled by
parameter Pd20, this function is activated at an External temperature set point for defrosting
compensation start Pd21, below which set point compensation starts, with the increment of the
defrosting activation delay, up to a maximum value (Maximum defrosting delay Pd23) on reaching
the External temperature set point for defrosting compensation stop Pd22.
In order to enable this function, the external temperature probe (PH24) must also be enabled.
Pd23
Activation delay
Ext. T
Pd22 Pd21
Pd03