5 Control System
Standard operation sequence RAS-3HVRC2 and RAS-(4-6)H(V)(R/N)(C/P)2E
SMGB0136 rev.0 - 07/2021
102
Standard Defrost
1 Temperature Condition
28
(-2)
41
(5)
14
(-10)
-6
(-21)
5
(-15)
23
(-5)
42
(6)
50
(10)
59
(15)
Temperature
Conditions under
Defrost Operation
Outdoor Temperature [°F (°C)]
Outdoor Evaporating Temperature (Te) [°F (°C)]
Defrost Operation
Stop Area
Defrost
Operation
Start Area
2 Conditioning of Operating Time for Defrost Operation Start
The defrost operation starts when the temperature condition shown in “(a) Temperature Condition” is met after a
heating operation of 40 to 120 minutes. The heating operation time is determined by estimating the amount of frost on
the heat exchanger.
Forced Defrost
The “Forced Defrost” starts when all the following conditions are met:
1 The reversing valve is “ON” for more than 120 minutes.
2 The outdoor temperature is 50°F (10°C) or lower.
3 The accumulated heating operation time is more than 60 minutes.
4 The accumulated time is reset when the operation is stopped or the defrost operation is performed.
5 The compressor is operated continuously for more than 90 seconds.
6 The outdoor evaporating temperature is lower than 41°F (5°C) right before the operation starts.
7 The pressure switch for control is “OFF”.
Condition for Completing Defrost Operation
The defrost operation stops when any of the following conditions is met:
1 The outdoor evaporating temperature reaches 77°F (25°C) within 2 minutes after the defrost operation starts.
2 The outdoor evaporating temperature reaches 59°F (15°C) (the outdoor temperature < 50°F (10°C)) and high
pressure reaches 218psi (1.5MPa) after a lapse of 2 minutes or more from the defrost operation start.
3 The outdoor evaporating temperature reaches 41°F (5°C) (the outdoor temperature ≥ 50°F (10°C)) after a lapse of
2 minutes or more from the defrost operation start.
4 The temperature at the top of the compressor reaches 270°F (132°C).
5 The temperature switch for control is “ON”.
6 The high pressure reaches 479psi (3.3MPa) within 20 seconds after the defrost operation starts.
7 The high pressure reaches 450psi (3.1MPa) after a lapse of 2 minutes or more from the defrost operation start.
8 More than 9 minutes have passed from the defrost operation start.
? NOTE
• The defrost operation does not start immediately even it the above conditions are met, because these conditions may be met tempo‑
rarily depending on the refrigerant system variability.
• The defrost operations start when these conditions are met continuously for a certain period of time.
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