52
ENG
ir33plus +0300028EN rel. 1.1 - 05.05.2017
11. APPENDIX 2: ADVANCED FUNCTIONS
11.1 Skip defrost
This algorithm is used to determine whether the shorter duration of a
defrost allows subsequent defrosts to be skipped. To enable the function,
set d12 = 2 or 3.
Par. Description Def Min Max UOM
d12 Advanced defrosts
d12 Skip defrost Automatic variation of dI
0 Disabled Disabled
1 Disabled Enabled
2 Enabled Disabled
3 Enabled Enabled
00 3 -
dn Nominal defrost duration 65 1 100 %
dH Proportional factor for variation of dI 50 0 100 -
dP1 Maximum defrost duration 30 1 250 min/s
dP2 Maximum aux evaporator defrost duration 30 1 250 min/s
Tab. 11.a
The nominal defrost times on evaporator 1 and evaporator 2 (auxiliary
evaporator) are determined based on parameter dn and the parameters
that set the maximum defrost duration for evaporators 1 and 2, according
to the following formulae:
dn1 =
dn
100
dP1
dn2 =
dn
100
dP2
The algorithm keeps a counter of the defrosts to be skipped:
• if the defrost ends after a time less than dn1, the counter of defrosts to
be skipped is increased by 1;
• if the defrost ends normally, the next defrost is performed;
• when the counter reaches a total of 3, 3 defrosts are skipped and then
the counter returns to 1;
• when powering on the controller, 7 defrosts are completed without
increasing the value, after which the counter is enabled (starting from
the eighth defrost).
Note: if there are two evaporators, the defrost duration used to
determine the defrosts to be skipped is the longer nominal defrost
duration.
Possible operating sequence (for example, if d12 = 2):
Start count Skip count Current count Defrost Outcome
7 0 0 Performed Not tested
6 0 0 Performed Not tested
5 0 0 Performed Not tested
4 0 0 Performed Not tested
3 0 0 Performed Not tested
2 0 0 Performed Not tested
1 0 0 Performed Not tested
0 0 0 Performed > “dn”
0 0 0 Performed > “dn”
0 0 0 Performed > “dn”
0 0 0 Performed > “dn”
0 0 0 Performed < “dn”
0 1 1 Skipped
0 1 0 Defrost > “dn”
0 0 0 Performed > “dn”
0 0 0 Performed > “dn”
0 0 0 Performed < “dn”
0 1 1 Skipped
0 1 0 Defrost < “dn”
0 2 2 Skipped
0 2 1 Skipped
0 2 0 Defrost > “dn”
0 0 0 Performed > “dn”
0 0 0 Performed > “dn”
0 0 0 Performed > “dn”
0 0 0 Performed < “dn”
0 1 1 Skipped
0 1 0 Defrost < “dn”
0 2 2 Skipped
0 2 1 Skipped
0 2 0 Defrost < “dn”
…
Tab. 11.b
11.2 Variation of the defrost interval
This algorithm is used to adjust the defrost interval based on the duration
of the previous defrost. To enable this, set d12 = 1 or 3.
The nominal defrost times on evaporator 1 and evaporator 2 are
determined based on parameter dn and the parameters that set the
maximum defrost duration for evaporators 1 and 2, according to the
following formulae:
dn1 =
dn
100
dP1
dn2 =
dn
100
dP2
With running the defrost, depending on the duration “dE”, the defrost
interval “dI” is adjusted by the value “dI”, calculated using the algorithm.
If there are two evaporators, the defrost duration considered is the longer
nominal defrost duration.
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