Freeze-Up Prevention - Daikin VRV-WIII RWEYQ72PTJU Service Manual

Outline of Control (Indoor Unit)

9.14 Freeze-up Prevention

Freeze-up When the temperature detected by liquid pipe thermistor (R2T) of the indoor unit heat exchanger
Prevention by Off 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.
Cycle (Indoor
When freeze-up prevention is activated, the electronic expansion valve is closed, the drain pump
Unit)
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
44.6ºF
32ºF
23ºF
10 min.
[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.
44.6ºF
32ºF
1 min.
1: Fixing of the fan H tap
Note:
2: The operation should continue for a certain period of time after the heater turns OFF.
3: High pressure condition
82
10 min.
Freeze-up prevention operation
Forced OFF by thermostat
10 min.
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
Thermostat
OFF
40
44.6ºF
32ºF
30.2ºF
t1 t2
OR
44.6ºF
33.8ºF
t1 t2
OR
4: Liquid pipe temperature condition
Thermostat
(˚F)
45
SiUS30-1301
10 min.
Freeze-up prevention operation
Forced OFF by thermostat
t3 t4 t > 40 min.
10 min.
Freeze-up prevention operation
Forced OFF by thermostat
t3 t4 t > 15 min.
ON
OFF
37 40
Function and Control
(˚F)