Service Manual

SiUS121502E Function of FFQ Series
Function and Control 57
Heating When heating, the hot air rises to the top of the room, resulting in the temperature being lower near
the floor where the occupants are. When controlling by body thermostat sensor only, the indoor unit
may therefore be turned off by the thermostat before the lower part of the room reaches the set
temperature. The temperature can be controlled so the lower part of the room where the occupants
are does not become cold by widening the range in which thermostat sensor in remote controller
can be used so that suction temperature is higher than the set temperature.

Assuming the set temperature in the figure above is 24°C (75.2°F), and the suction
temperature has changed from 18°C (64.4°F) to 28°C (82.4°F) (A → D):
(This example also assumes there are several other air conditioners, and the suction temperature
changes even when the thermostat sensor is off.)
18 → 25°C (64.4 → 77°F) (A → C): Body thermostat sensor is used.
25 → 28°C (77 → 82.4°F) (C → D): Remote controller thermostat sensor is used.

Assuming suction temperature has changed from 28°C (82.4°F) to 18°C (64.4°F) (D → A):
28 → 23°C (82.4 → 73.4°F) (D → B): Remote controller thermostat sensor is used.
23 → 18°C (73.4 → 64.4°F) (B → A): Body thermostat sensor is used.
Range in which thermostat sensor
in remote controller can be used
Range in which body
thermostat sensor can
be used
Differential
Suction temperature (TH1)
(R18812)
Set temperature (Ts)
12 14 16 18 20 22 24 26 28 30 32 34
53.6 57.2 60.8 64.4 68.0 71.6 75.2 78.8 82.4 86.0 89.6 93.2
°C
°F
°C
32
30
28
26
24
22
20
18
16
°F
89.6
86.0
82.4
78.8
75.2
71.6
68.0
64.4
60.8
TH1 = Ts + 12 ≤ 33°C
TH1 = Ts + 21.6 ≤ 91.4°F
TH1 = Ts + 10 ≤ 31°C
TH1 = Ts + 18 ≤ 87.8°F
TH1 = Ts + 1 ≤ 31°C
TH1 = Ts + 1.8 ≤ 87.8°F
TH1 = Ts – 1°C
TH1 = Ts – 1.8°F