SiE-05C
Outline of Control
Functions PLUS Series
227
4.4
Defrost (For Heat Pump System)
Melts frost which might collect on outdoor heat exchangers during heating in order to recover their heat
conveying performance.
4.4.1
Conditions for Executing Defrost
(k:kg/cm
²
)
&
At least 20 minutes have elapsed since completion of oil return or since compressor starts.
High pressure < 19.9k (Tc = 52.4˚C)
Compressor is running at least 30 minutes since completion of previous defrost.
Liquid pipe thermal detection temperature
≤
T˚C for 5 minutes during operation for all outdoor units, or 15
minutes for any one outdoor unit.
T=C x (Outdoor temp.) -
α
(C is constant value)
&
Forced defrost test pin (MDS) is shorted.
Liquid pipe thermal detection temperature < 12.5˚C for 5 minutes for all units
High pressure < 19.9k (Tc = 52.4˚C)
Step 1: 4-way valve switched (30 sec. after start)
Compressor
EEV
Outdoor unit fan
Outdoor unit heat exchanger
Solenoid valve for oil discharge
Injection
Hot gas
INV outdoor unit
STD outdoor unit 1
Condenser
Condenser
Outdoor unit suction pipe temp.
≤
Te + 10 at when either 6 min. or 4 min. elapses.
Step 2: Defrost operation is executed
Step 3: Refrigerant is discharged from accumulator. (3 minutes)
(38Hz + ON)
2000pls
2000pls
OFF
OFF
*
ON + OFF
ON + OFF
ON
(ON + OFF)
+
+
Compressor
EEV
Outdoor unit fan
Outdoor unit heat exchanger
Solenoid valve for oil discharge
Injection
Hot gas
INV outdoor unit
STD outdoor unit 1
Condenser
Condenser
(106Hz + OFF)
2000pls
2000pls
OFF
OFF
ON
ON + ON
ON + ON
ON
(ON + ON)
+
+
STD outdoor unit 2
Condenser
2000pls
OFF
ON + OFF
(ON + OFF)
STD outdoor unit 2
Condenser
2000pls
OFF
ON + ON
(ON + ON)
Compressor
EEV
Outdoor unit fan
Outdoor unit heat exchanger
Solenoid valve for oil discharge
Injection
Hot gas
INV outdoor unit
STD outdoor unit 1
Evaporator
Evaporator
(60Hz + OFF)
SH control
H + ON
H + ON
OFF
ON + OFF
ON + OFF
ON at Lp < 2.5 k
(ON + ON)
+
+
STD outdoor unit 2
Evaporator
H + ON
ON + OFF
(ON + ON)
Operation
contents
Preparation
for defrost
1 minute
elapses
Upper limit frequency
limited to 38 Hz + ON
Liquid refrigerant collected in
indoor unit returned to receiver
*
Only outdoor units
stopped before
defrost ON
Returns to normal operation
3 minutes elapses or HP > 21k
or
•Thermal detection temperature for all heat exchangers
in the system is less than 12.5 C during defrost.
•High pressure > 20.5k
•10 minutes elapse
(VF109)
SI-05C.BOOK Page 227 Monday, November 6, 2000 4:13 PM
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