Carel MPXone - Page 58

58
ENG
mpxone +0300086EN rel. 2.2 - 13.11.2023
Functions
Defrost by temperature differential and time (par.dd1, dd2, dTd, tdd)
This function determines when the refrigeration unit needs defrosting. In particular, if the difference between two probe read-
ings (dd1, dd2) is higher than a predefined threshold (dTd) for a certain time (tdd), the evaporator may be frozen and a defrost
is activated.
300086_084_R01
tdd
dTd
ΔT>10C
t
t
ON
DEF
OFF
dd2
dd1
Ref. Description
Sd Defrost probe
DEF Defrost
t time
Fig. 5.v
Code Description Def Min Max UOM User User terminal
dd1 Assign probe 1 to determine start defrost
(dd1-dd2) - see FSa
0014- SNO
dd2 Assign probe 2 to determine start defrost
(dd1-dd2) - see FSa
0014- SNO
dTd Temperature differential threshold to start defrost 50 -99.9 99.9 °C S NO
tdd Threshold evaluation time to start defrost 60 15 240 min S NO
Pressure probe alarm management during defrost (par. d12)
During defrosts and dripping, so as to avoid false pressure probe error signals, errors are ignored. The supervisor update also
needs to be disabled.
Code Description Def Min Max UOM User User terminal
d12 Pressure probe alarm management during defrost
probe error supervisor update
0 disabled enabled
1 enabled enabled
2 disabled disabled
3 enabled disabled
003- MNO
Sequential stops (par.dS1, dS2)
Sequential stop mode is especially useful for medium temperature refrigeration units, is based on the intelligent stopping of
control to allow the evaporator to defrost naturally by the flow of ambient air only, without activating the defrost output. If the
function is enabled (parameter dS1>0), two countdowns are activated during normal control:
• 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
figure:
1. OFFTIME is reset (instant C): OFFTIME and ONTIME are reset with the values dS1 and dS2 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 entire time
dS1. At the end of the defrost (instant B), OFFTIME and ONTIME are reset with the values dS1 and dS2 and control resumes.
Code Description Def Min Max UOM User User terminal
dS1 Compressor off time in sequential stop
defrost mode 0 = function disabled
0 0 45 min M NO
dS2 Compressor operating time in sequential stop
defrost mode
120 0 240 min M NO
300086_068_R01
dS1
C
OFFTIME=0
t
t
ON
1
CMP
regulation regulation
OFF
ONTIME=0
AB
t
regulationregulation defrost
ON
2
CMP
OFF
Ref. Description
CMP Compressor
t time
Fig. 5.w