Outline of Control (Indoor Unit)
SiUS30-1301
82
Function and Control
9.14 Freeze-up Prevention
Freeze-up
Prevention by Off
Cycle (Indoor
Unit)
When the temperature detected by liquid pipe thermistor (R2T) of the indoor unit heat exchanger
drops too low, the unit enters freeze-up prevention operation in accordance with the following
conditions, and is also set in accordance with the conditions given below.
When freeze-up prevention is activated, the electronic expansion valve is closed, the drain pump
turns ON and the fan tap is fixed to L airflow. When the following conditions for stopping are
satisfied, it returns.
Conditions for starting freeze-up prevention: Temperature is 30.2°F or less for total of 40 minutes,
or temperature is 23°F or less for total of 10 minutes.
Conditions for stopping freeze-up prevention: Temperature is 44.6°F or more for 10 minutes.
continuously
[Conditions for starting when airflow direction is two-way or three-way]
Conditions for starting: Temperature is 33.8ºF or less for a total of 15 minutes or 32ºF or less for 1
minute continuously.
Note:
1: Fixing of the fan H tap
2: The operation should continue for a certain period of time after the heater turns OFF.
3: High pressure condition
4: Liquid pipe temperature condition
23ºF
32
ºF
44.6ºF
30.2ºF
t1
t2
t3
t4
32
ºF
44.6ºF
10 min.
OR
10 min.
10 min.
t
>
40
min.
Freeze-up prevention operation
Forced OFF by thermostat
Freeze-up prevention operation
Forced OFF by thermostat
32
ºF
44.6ºF
10 min.
1 min.
33.8ºF
t1
t2
t3
t4
44.6ºF
10 min.
OR
t
>
15
min.
Freeze-up prevention operation
Forced OFF by thermostat
Freeze-up prevention operation
Forced OFF by thermostat
&
Condition A
•
Thermostat step 2 = "ON"
•
Heating mode
•
Not during test operation
•
Not during control operation
•
High pressure condition = "ON"
∗
3
•
Liquid pipe temperature condition = "ON"
∗
4
•
Electrical heater setting = "3"
ON
OFF
40
45
Thermostat
(˚F)
ON
OFF
37
40
(˚F)
Thermostat