2-20
Defrosting operation
(1) Defrosting system
A hot-gas defrost system is adopted in the units; i.e. the high temperature and high pressure refrigerant
(hot gas) from the compressor is sent to the evaporator and drain pan for defrosting. Since the evaporator
is heated directly by the hot gas (refrigerant), defrosting can be performed efficiently.
(2) Defrosting initiation
＊
1. 6 hours when the control temperature is –20.0˚C or below
＊
2. Not executed when the control temperature is –20.0˚C below
＊
3. On-demand defrosting setting
If "99" is set, the on-demand defrosting is carried out.
The on-demand defrosting is executed during the frozen operation, and the defrosting interval is
internally set to 12 hours. However, the defrost cycle will not activate if the evaporator does not have a
heavy frost when 12 hours have been counted.
("If chilled operation is selected when "99" is set, the defrosting interval will be automatically set to "6"
hours.)
Step 1: After defrost termination, the operation time per hour of the compressor (T1) is recorded.
Step 2: Aterward, the measurement of the operation time per hour of the compressor is continued,
and the time (T2) is recorded.
Step 3: If T2 > T1
×
1.15, the defrosting operation is initiated.
If T2
≦
T1
×
1.15 when 12 hours have been counted, the freezing operation is continued.
(3) Defrosting initiation conditions
Timer count
Short timer
Defrosting interval (frozen)
Out-range timer
Manual defrosting
EOS
≦
20.0˚C
EIS<5.0˚C&EOS
≦
20.0˚C
Initiation conditions for defrosting
Defrosting interval (chilled in-range)
Note 1: If the initiation conditions for defrosting are not satisfied during timer counting or the manual
defrosting operation, the defrosting operation is not executed based on the judgment that no
frost is detected.
Note 2: In the case of the unit equipped with a reheat coil for dehumidification control (optional)
(REHEAT setting "ON"), when dHU setting is "OFF", defrosting operation is executed
regardless of the temperature for the initiation conditions.
Defrosting initiation
Functions and timer setting
Pull down
Short timer
4 hours
＊
1
Automatic frost detection
Executed when the suction air temperature does not drop
by 0.2˚C or more per hour during frozen operation
＊
2
In-range
Defrosting interval
3 hours, 6 hours, 9 hours, 12 hours, 24 hours
99 “On-demand defrosting”
＊
3
Out-range
Out-range timer
30 minutes
Executed 30 minutes after the control temperature
rises out of the in-range
Manual defrosting (manual)
Executed by MSD key
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