Control Specification SiUS041829E
48 Part 4 Functions and Control
3.3 Controls at Mode Changing/Start-up
3.3.1 Preheating Control
Outline The inverter operation in open phase starts with the conditions of the outdoor temperature, the
discharge pipe temperature, the radiation fin temperature and the preheating command from the
indoor unit.
Details Outdoor temperature ≥ –2.5°C (27.5°F) Control A (preheating for normal state)
Outdoor temperature < –2.5°C (27.5°F) Control B (preheating of increased capacity)
Control A
ON condition
Discharge pipe temperature < 0°C (32.0°F)
Radiation fin temperature < 85°C (185°F)
OFF condition
Discharge pipe temperature > 2°C (35.6°F)
Radiation fin temperature ≥ 90°C (194°F)
Control B
ON condition
Discharge pipe temperature < 10°C (50.0°F)
Radiation fin temperature < 85°C (185°F)
OFF condition
Discharge pipe temperature > 12°C (53.6°F)
Radiation fin temperature ≥ 90°C (194°F)
3.3.2 Four Way Valve Switching
Outline The four way valve coil is energized/not energized depending on the operation mode (Heating: ON,
Cooling/Dry/Defrost: OFF). In order to eliminate the switching sound as the four way valve coil
switches from ON to OFF when the heating is stopped, the OFF delay switch of the four way valve
is carried out.
Details OFF delay switch of four way valve
The four way valve coil is energized for 160 seconds after the operation is stopped.
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