Hitachi RPC-2.0FSR - Page 77

CONTROL SYSTEM
TCI-20007-rev.1
1-67
<Condition for Starting Defrost>
(1) Standard Defrost
(a) Temperature Condition
Temperature
Condition
under
Defrosting
Operation
Outdoor
Temp. (
o
C)
Outdoor
Evaporating
Temp. (
o
C)
(Pipe)
Defrosting
Operation
Stop Area
Defrosting
Operation
Start Area
-5
-10
-15
6
-2
-6.7
-10
-15
5
0
5
10 15
-5
15
10
(b) Condition for Operating Time of Defrosting Operation Start
Thedefrostingoperationstartswhenthetemperatureconditionshownin“(a)Temperature
Condition”ismetaftertheheatingoperationisperformedfor40to120minutes.Theheating
operation time is determined by estimating the amount of frost on the heat exchanger.
(2) Forced Defrost
< Condition for Starting >
The forced defrosting operation starts when all the following conditions are met.
(a) Thereversingvalveis“ON”formorethan120minutes.
(b) The outdoor temperature is lower than 10
o
C.
(c) The accumulated heating operation time is more than 60 minutes.
(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 a half minutes.
(e) The outdoor evaporating temperature is lower than 5
o
C right before the operation starts.
(f) Thepressureswitchforcontrolis“OFF”.
<Condition for Completing Defrosting Operation>
The defrosting operation stops when any of the following conditions is met.
(1) The outdoor evaporating temperature reaches more than 25
o
C for 2 minutes after the defrosting
operation starts.
(2) The outdoor evaporating temperature reaches more than 15
o
C (the outdoor temperature < 10
o
C)
2 minutes after the defrosting operation starts.
(3) The outdoor evaporating temperature reaches more than 5
o
C (the outdoor temperature > 10
o
C)
2 minutes after the defrosting operation starts.
(4) Thepressureswitchforcontrolis“ON”.
(5) More than 9 minutes pass after the defrosting operation starts.
NOTE:
The defrosting operation does not start immediately even if the above conditions are met.
(The defrosting condition may be met temporarily depending on the refrigerant cycle variability.)
The defrosting operation starts when the conditions are met continuously for a period of time.