Service Manual

SiUS04-921 Main Functions
Function and Control 33
2.21 Thermostat Control
Outline
When COOLING or
HEATING mode is
selected with the
remote controller,
the microcomputer
prevents the unit
from turning OFF
until the requested
room temperature is
achieved.
Details
In the table below you can find the thermostat ON and OFF conditions for a set point of 70°F(21°C).
Cooling operation:
The unit will turn OFF by thermostat when the room temperature reaches 19.5°C(67.1°F). When
the room temperature rises above 21°C(70°F), the thermostat turns back ON and the unit resumes
its operation. When the room temperature is between 20~20.5°C(68.0~68.9°F), it is in the
monitoring zone. If for cooling, the room temperature stays in the monitoring zone for more then 10
minutes, the thermostat will also turn back ON and the unit will resumes its operation.
Between the indoor unit and the position of the end user, there is taken into calculation a
temperature shift of 0.5°C(0.9°F in the control logic). This means that at thermostat OFF, the
temperature at the end user is e.g. 20°C(68.0°F).
Heating operation:
The unit will turn ON by thermostat when the room temperature reaches its set value + a shift of
2.0°C (3.6°F ) (e.g. room temperature : 21°C (70°F) => thermostat ON temperature : 23°C (73.4°F).
When the room temperature rises above 24.5°C (76.1°F), the thermostat turns back OFF. When
the room temperature is between 24~23.5°C (75.2~74.3°F), it is in the monitoring zone. If for
heating, the room temperature stays in the monitoring zone for more then 10 minutes, the
thermostat will also turn back ON and the unit will resume operation.
OFF ON Monitoring
Cooling
Set point 70°F(21°C)
--> shift 0.5°C
(0.9°F)
67.1°F(19.5°C) 69.8°F(21°C)
68.0~68.9°F
(20~20.5°C)
10min
Heating
Set point 70°F(21°C) --> shift 2.0°C
(3.6°F)
76.1°F(24.5°C) 73.4°F(23°C)
74.3~75.2°F
(23.5~24°C)
10sec
21˚C(69.8˚F) cooling
23˚C(73.4˚F) heating
Thermostat ON
21˚C(70˚F)
21˚C(69.8˚F)
20.5˚C(68.9˚F)
20˚C(68.0˚F)
19.5˚C(67.1˚F)
ON
OFF
Monitoring
(R10085)