Hitachi RAS-2-HVNP Service Manual page 150

5. Control System
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Defrosting Operation
The following defrosting operations, "Standard Defrost", "Forced Defrost" and "Manual Defrost" are available.
1 Standard Defrost
This operation is started according to the outdoor temperature, the outdoor evaporating temperature and operating
time.
2 Forced Defrost
This operation starts when the indoor unit is operated Thermo-ON/OFF repeatedly and the standard defrost is not used.
3 Manual Defrost
This operation starts when the push switch "PSW1" on the outdoor PCB is pressed and hold for more than 3 seconds
during the maintenance work. (It is not performed when the defrosting operation is started, the high pressure and the
outdoor evaporating temperature is high.)
N O T E
Do not repeat defrost operation frequently.
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Condition for Starting Defrost
1 Standard Defrost
a. Temperature Condition
Model
Temperature
condition under
defosting ope-
ration
b. Condition for Operating Time of Defrost Operation Start
The defrosting operation is started when the temperature condition is met "(a) Temperature Condition" after the
heating operation is performed for 40 to 120 minutes. The heating operation time is determined by estimating the
amount of frosting on the heat exchanger.
2 Forced Defrost
Condition for Starting
The forced defrosting operation is started when all the following conditions are met.
a. 120 minutes are passed after the reversing valve is "ON".
b. The outdoor temperature is lower than 10
c. The accumulated heating operation time is more than 60 minutes. (*1)
(The accumulated time is reset when the operation is stopped or the defrosting operation is performed.)
d. The compressor is operated continuously for more than 1 and half minutes. (*2)
e. The outdoor evaporating temperature is lower than 5
f. The pressure switch for control is "OFF".
136
SMGB0079 rev.0 - 01/2013
RAS-(2-2.5)HVNP
RAS-3HVNC
-4
C.
o
C (*3) right before starting the operation.
o
RAS-3HVNPE
RAS-(4-12)H(V)N(P/C)(E)