Defrost (For Heat Pump System); Conditions For Executing Defrost - Daikin VRV Inverter K Series Manual

SI-05C.BOOK Page 227 Monday, November 6, 2000 4:13 PM
SiE-05C
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

&
&
Operation
contents
1 minute
elapses
Preparation
for defrost
Upper limit frequency
limited to 38 Hz + ON
Liquid refrigerant collected in
indoor unit returned to receiver
Functions PLUS Series
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.
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)
INV outdoor unit
Compressor
(38Hz + ON) +
EEV 2000pls
Outdoor unit fan OFF
Outdoor unit heat exchanger Condenser
Solenoid valve for oil discharge
Injection
ON + OFF
Hot gas
Outdoor unit suction pipe temp. ≤
Te + 10 at when either 6 min. or 4 min. elapses.
Step 2: Defrost operation is executed
INV outdoor unit
Compressor (106Hz + OFF)
+
EEV 2000pls
Outdoor unit fan OFF
Outdoor unit heat exchanger Condenser
Solenoid valve for oil discharge
Injection
ON + ON
Hot gas
•Thermal detection temperature for all heat exchangers
or
in the system is less than 12.5 C during defrost.
•High pressure > 20.5k
•10 minutes elapse
Step 3: Refrigerant is discharged from accumulator. (3 minutes)
INV outdoor unit
Compressor (60Hz + OFF) +
EEV
Outdoor unit fan
H + ON
Outdoor unit heat exchanger
Evaporator
Solenoid valve for oil discharge
Injection ON + OFF
Hot gas
3 minutes elapses or HP > 21k
Returns to normal operation
STD outdoor unit 1 STD outdoor unit 2
(ON + OFF) + (ON + OFF)
2000pls 2000pls
OFF OFF
Condenser Condenser
*
ON + OFF ON + OFF
ON
STD outdoor unit 1 STD outdoor unit 2
(ON + ON)
(ON + ON) +
2000pls 2000pls
OFF OFF
Condenser Condenser
ON
ON + ON ON + ON
ON
STD outdoor unit 1 STD outdoor unit 2
(ON + ON) + (ON + ON)
SH control
H + ON H + ON
Evaporator Evaporator
OFF
ON + OFF ON + OFF
ON at Lp < 2.5 k
: http://splitoff.ru/tehn-doc.html
Outline of Control
(k:kg/cm²)
T=C x (Outdoor temp.) - α
(C is constant value)
*Only outdoor units
stopped before
defrost ON
(VF109)
227