Service manual

Main Functions SiUS12-928_B
41 Function and Control
1.6 Automatic Operation
Outline Automatic Cooling / Heating Function
When the automatic operation is selected with the remote controller, the microcomputer
automatically determines the operation mode as cooling or heating according to the room
temperature and the set temperature at start-up.
The unit automatically switches the operation mode to maintain the room temperature at the set
temperature.
Detail Ts: set temperature (set by remote controller)
Tt: target temperature (determined by microcomputer)
Tr: room thermistor temperature (detected by room temperature thermistor)
C: correction value
1. The set temperature (Ts) determines the target temperature (Tt).
(Ts = 64.4 ~ 86°F, 18 ~ 30°C).
2. The target temperature (Tt) is calculated as;
Tt = Ts + C
where C is the correction value
.
C = 0°F (0°C)
3. Thermostat ON/OFF point and operation mode switching point are as follows.
(1) Heating Cooling switching point:
Tr  Tt + +5.4°F (3.0°C) (CTXS/FTXS-L series)
Tr  Tt + +4.5°F (2.5°C) (other models)
(2) Cooling Heating switching point:
Tr < Tt – –4.5°F (2.5°C)
(3) Thermostat ON/OFF point is the same as the ON/OFF point of cooling or heating operation.
4. During initial operation
Tr  Ts : Cooling operation
Tr < Ts : Heating operation
CTXS/FTXS-L series
Ex: When the target temperature is 25°C (77°F)
Cooling  73.4°F (23°C): Thermostat OFF 71.6°F (22°C): Switch to heating
Heating 80.6°F (27°C): Thermostat OFF  82.4°F (28°C): Switch to cooling
Other models
Ex: When the target temperature is 77°F (25°C)
Cooling  73.4°F (23°C): Thermostat OFF 71.6°F (22°C): Switch to heating
Heating 79.7°F (26.5°C): Thermostat OFF  81.5°F (27.5°C): Switch to cooling
Target temperature +5.4°F (+ 3.0°C)
Heating Operation
Target temperature –4.5°F (–2.5°C)
Cooling Operation
(R16965)
Target temperature –3.6°F (– 2.0°C) =
Thermostat OFF
Target temperature +3.6°F (+ 2.0°C) =
Thermostat OFF
Target temperature +4.5°F (+ 2.5°C)
Heating Operation
Target temperature –4.5°F (– 2.5°C)
Cooling Operation
(R16966)
Target temperature –3.6°F (– 2.0°C) =
Thermostat OFF
Target temperature +2.7°F (+ 1.5°C)
= Thermostat OFF