User manual

48
ENG
MPXPRO - + 0300055EN rel. 1.3 07/03/13
Important: for multiplexed hot gas defrosts, the setting is only
valid on the Master and the defrost is synchronized across the
Master/Slave network.
Pressure probe alarm management during defrost
(parameter d12)
During defrost and dripping, so as to avoid false pressure probe error
signals, errors are ignored. The supervisor update can also be disabled.
Par. Description Def Min Max UoM
d12 Pressure probe alarm management during
defrost
probe error supervisor update
0 disabled enabled
1 enabled enabled
2 disabled disabled
3 enabled disabled
003-
Tab. 6.ah
Sequential stops (parameters dS1, dS2)
Par. Description Def Min Max UoM
dS1 Compressor off time in “Sequential stop”
defrost mode
0 0 45 min
dS2 Compressor operating time in “Sequential
stop” defrost mode
120 0 240 min
Tab. 6.ai
Sequential stop mode is especially useful for high-normal temperature
refrigeration controllers, and is based on the intelligent stopping of
control to allow the evaporator to defrost naturally by the fl ow of
ambient air only, without activating the defrost output and consequently
the defrost heaters. If the function is enabled (parameter dS1>0), two
counters are activated:
• OFFTIME: counts down during the stop time and on hold during
control;
• ONTIME: counts down during control and on hold during the stop
time.
Two events may occur, with reference to the following fi gure:
1. OFFTIME is reset (instant C): OFFTIME and ONTIME are reset with dS1 and
dS2 value and the defrost is considered completed. Control resumes;
2. ONTIME is reset (instant A): OFFTIME is reset with the default value
and the natural defrost starts, lasting the time dS1. At the end of the
defrost (instant B), OFFTIME and ONTIME are reloaded with dS1 and
dS2 value and control resumes;
C
OFFTIME=0
t
t
ON
1
CMP
regulation regulation
OFF
ONTIME=0
dS1
AB
t
regulationregulation defrost
ON
2
CMP
OFF
Fig. 6.m
Key
CMP Compressor t Time
The purpose is to stop control and allow natural defrosts only when
necessary.
Note: the setting of parameter F3 has no eff ect. Evaporator fan
management depends on parameter F0.
Skip defrost (parameters d7, dn)
The function applies to defrosts that end by temperature, otherwise it
has no eff ect. The Skip defrost function evaluates whether the defrost
duration is less than a certain threshold dn1 (dn2) and based on this
establishes whether or not the following defrosts will be skipped.
Par. Description Def Min Max UoM
d7 Skip defrost
0 = disabled; 1 = enabled;
001-
dn Nominal defrost duration for “Skip defrost” 75 0 100 %
dP1 Maximum defrost duration 45 1 240 min
dP2 Maximum secondary evaporator defrost
duration
45 1 240 min
Tab. 6.aj
Thresholds dn1 (evaporator 1) and dn2 (evaporator 2) are defi ned by:
dn1 = tE11, dn2 = tE12
dn
100
dn
100
The algorithm keeps a counter of the defrosts to be skipped:
• if the defrost ends in a time less than dn1, the counter of the defrosts
to be skipped is increased by 1;
• if the defrost ends normally, the next defrost is performed;
• when the counter reaches , 3, three defrosts are skipped and then the
counter is reset to 1;
• on power-up, the defrost is performed 7 times without increasing the
counter, from the eighth on the counter is updated.
Note: in power defrost mode (see the following paragraphs), the
maximum defrost duration dP1 and dP2 is increased by the value
of parameter ddP.
Power defrost (parameters ddt, ddP)
Power defrost is used to increase the end defrost threshold dt1 (dt2
for the second evaporator) and/or the maximum defrost duration dP1
(dP2 for the second evaporator). These increases allow longer and more
eff ective defrosts. Power defrost are performed on each defrost call
during night status or when suitably confi gured by the RTC parameters
(sub-parameter P of parameters td1 to td8), so as to allow the user to
choose the conditions that are most suitable for this special procedure.
Power Defrost is activated when at least one of the increases, ddt or ddP,
has any value other than zero.
Par. Description Def Min Max UoM
ddt Additional end defrost temperature delta
for Power defrost mode
0.0 -20.0 20.0 °C/°F
ddP Additional maximum defrost time delta for
Power defrost mode
0 0 60 min
P__ Defrost 1 to 8 – enable
Power defrost
0 = normal; 1= Power defrost
001-
Tab. 6.ak