Automatic Cooling/Heating Changeover - Daikin 4MXL-T Series Service Manual

RA Indoor Unit Functions
2.4

Automatic Cooling/Heating Changeover

Outline 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.
Details
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).
2. The target temperature (Tt) is calculated as;
3. Thermostat ON/OFF point and operation mode switching point are as follows.
4. During initial operation
FTXR, CTXG Series
Ex: When the target temperature is 25°C (77°F)
Cooling → 23°C (73.4°F): Thermostat OFF → 22.5°C (72.5°F): Switch to heating
Heating → 26.5°C (79.7°F): Thermostat OFF → 28°C (82.4°F): Switch to cooling
CTXS, FTXS Series
Ex: When the target temperature is 25°C (77°F)
Cooling → 23°C (73.4°F): Thermostat OFF → 22°C (71.6°F): Switch to heating
Heating → 27°C (80.6°F): Thermostat OFF → 28°C (82.4°F): Switch to cooling
66
(Ts = 18 ~ 30°C (64.4 ~ 86°F))
Tt = Ts + C
where C is the correction value.
C = 0°C (0°F)
(1) Heating → Cooling switching point:
Tr ≥ Tt + 3.0°C (+ 5.4°F) (FTXR, CTXG, CTXS, FTXS series)
Tr ≥ Tt + 2.5°C (+ 4.5°F) (FDXS, CDXS, FVXS series)
(2) Cooling → Heating switching point:
Tr < Tt – 2.5°C (– 4.5°F) (FTXR, CTXG series)
Tr < Tt – 3.0°C (– 5.4°F) (CTXS, FTXS, FDXS, CDXS, FVXS series)
(3) Thermostat ON/OFF point is the same as the ON/OFF point of cooling or heating operation.
Tr ≥ Ts : Cooling operation
Tr < Ts : Heating operation
Target temperature – 2.0°C (–3.6°F)
= Thermostat OFF
Target temperature – 2.5°C (–4.5°F)
Target temperature – 2.0°C (–3.6°F)
= Thermostat OFF
Target temperature – 3.0°C (–5.4°F)
Cooling Operation
Target temperature + 3.0°C (+5.4°F)
Target temperature + 1.5°C (+2.7°F)
= Thermostat OFF
Heating Operation
Cooling Operation
Target temperature + 3.0°C (+5.4°F)
Target temperature + 2.0°C (+3.6°F)
= Thermostat OFF
Heating Operation
SiUS121827E
(R24030)
(R21862)
Part 4 Functions and Control