2-22
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 effectively.
(2) Defrosting initiation
Defrosting is initiated by the timer or the manual defrost key.
q
Initiation by timer (Timer is set at the electronic controller, refer to clause 3.3.2 for its operating method.)
Type of timer
Defrosting interval set
Function
Long timer
3, 6, 9, 12, 24 hours and 99
※
2
are
Defrosting is initiated according to the
selectable.
set interval.
※
1
Defrosting is initiated every 4 hours until
Short timer
4 hours
※
3
the control temperature comes within the
in-range after pull-down.
After the control temperature comes within
Out-range timer
30 minutes
in-range once, defrosting will be started 30 minutes later if
the control temperature rises out of the in-range.
※
1. However, defrosting is not initiated when frosting on the evaporator can not be detected.
¡
Evaporator inlet temperature : 5˚C or higher
¡
Evaporator outlet temperature : 20˚C or higher
※
2. On-demand defrost selection (12 hours for Frozen mode and 6 hours automatic for Chilled mode)
※
3. 6 hours when the control temperature is –20˚C or below.
w
Starting by MANUAL DEFROST key (on the operation panel sheet key)
Press the MANUAL DEFROST key, then press the ENTER/ESC key while indicate "ON" on the LED
display. The manual defrosting operation starts.
e
Initiation by frost detection
If the return air temperature does not drop at the speed of 0.2˚C/1hr during frozen pull-down
operation, defrosting will be initiated because it is judged that frost is formed on the evaporator.
However, if the suction temperature is –20˚C or lower, defrosting will not be initiated. (activated)
(3) On demand defrost
If "99" is set with the long timer, the on-demand defrosting is carried out.
The on-demand defrosting is done through the frozen operation, and the defrosting interval is internally
set to 12 hours. However, the freezing operation continues 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: 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.
02̲LXE10E100以降(16-28)̲E.qx 08.8.13 4:40 PM ページ 2-22
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