User manual

41
ENGLISH
ir33 +030220441 - rel. 2.5 - 16.06.10
dt2: end defrost temperature set point, auxiliary evaporator
dt2 acts in the same way as parameter dt1 described above, but referring to the auxiliary evaporator.
Note for dt1 and dt2: in the defrost by temperature, the parameter establishes the threshold for activating or deactivating the
corresponding defrost relay.
Default: dt2 =4°C.
‘dt3’: end defrost temperature SET POINT, probe 3 (hidden parameter)
This parameter is used to set the end defrost temperature measured by the third defrost probe. In any case, the maximum defrost
duration is equal to the value, in minutes, set for parameters ‘dP1’ and ‘dP2’.
• If there is just one only evaporator and 3 evaporator probes, the defrost starts if at least one probe measures a temperature
lower than the respective end defrost threshold; the defrost ends if all the probes have exceeded the corresponding end defrost
threshold;
• If there are two evaporators and 3 evaporator probes, the defrost is managed on the  rst evaporator with reference to evaporator
probe 1 and 3, on the second evaporator with reference to probe 2 and 3; the defrost starts on a evaporator if at least one as-
sociated probe measures a temperature lower than the respective end defrost threshold; the defrost ends if all the probes have
exceeded the corresponding end defrost threshold;
• If the third defrost probe has an error, the controller runs a timed defrost for a duration equal to the value set for parameters ‘dP1’
and ‘dP2’.
• If the end defrost set point is not reached within the time set for parameters ‘dP1’ and ‘dP2’, the defrost is stopped. If enabled
(parameter ‘A8’), errors ‘Ed1’ and ‘Ed2’ are displayed (with reference to the  rst evaporator or the auxiliary evaporator), which
persist until the start of the next defrost cycle.
In defrosts with temperature control, the value read by the third end defrost probe is not used.
Default: ‘dt3’=4°C.
dP1: Maximum evaporator defrost duration
Determines the maximum defrost duration on the evaporator in minutes (or seconds, see parameter dC) if defrost by temperature is
selected. If timed defrost has been selected, this is the actual duration of the defrost. Default: dP1=30 minutes.
dP2: Maximum defrost duration, auxiliary evaporator
As for parameter dP1 described above, but refers to the auxiliary evaporator.
Default: dP2=30 minutes.
d3: Defrost start delay
This parameter determines the time that must elapse, when the defrost is activated, between the
stopping of the compressor (electric heater defrost) or the starting of the compressor (hot gas defrost), and the activation of the
defrost relays on the main and auxiliary evaporators.
The delay d3 is useful, in the hot gas defrost, to ensure a su cient quantity of hot gas for the defrost before the activation of the cycle
reversing valve, in very special applications (see paragraph “Description of software functions”). Default: d3=0 minutes.
d4: Defrost when the instrument is switched on
Activates a defrost when the instrument is switched on.
Warning: this request has priority over the activation of the compressor and the continuous cycle.
The possible values are:
d4=0, no defrost is performed when the instrument is switched on;
d4=1, a defrost is performed when the instrument is switched on.
Starting a defrost when the instrument is switched on may be useful in special situations.
Example: frequent power drops occur in the system, which cause the internal clock to be reset. This clock calculates the interval
between two defrosting operations, restarting from zero. If the frequency of the power failure were, in an extreme case, greater
than the defrost frequency (e.g. a power failure every hour, against a defrost every 10 hours) the controller would never perform a
defrost. In a situation of this type, it is preferable to enable defrost on start-up, above all if the defrost is controlled by temperature
(probe on the evaporator), therefore avoiding unnecessary defrosts or at least reducing the running times. In the case of systems
with a large number of units, if selecting defrosts at start-up, after a power failure all the units will start defrosting, thus causing a
voltage overload. To overcome this, the parameter d5 can be used. It adds a delay before the defrost, and this delay must obviously
be di erent for each unit.
Default: d4=0 the instrument does not perform a defrost on start-up.
Available on all models except for IR33M.
d5: Defrost delay when the instrument is switched on or from multifunction input
The time that must elapse between start-up of the controller and the start of the defrost.
• if the digital input is used to enable the defrost (see parameter A4, A5, A9=3) or to start a defrost from external contact (see
parameter A4, A5, A9=4), the parameter d5 refers to the delay between enabling of the defrost or request to enable, and the
e ective start.
• the defrost digital input (see parameter A4, A5, A9) can be usefully employed to perform defrosts in real time, connecting a timer
to the input. The defrost will be activated when the timer contact closes.
• If several units are connected to the same timer, parameter d5 should be used to delay the various defrosts, thus avoiding power
overloads.
In addition, to avoid unwanted defrosts started by the clock inside the instrument, set parameter dI=0 (manual defrosts only,
started from the keypad, by the RTC, by the calculation of the compressor running time or by the multifunction contact).
Important warning: when connecting a series of units to the same timer, the best solution is to insulate all the contacts galvani-
cally,  tting intermediate relays for each contact.
Default: d5=0 => no delayed defrost when switching the instrument on or following the activation of the multifunction input.