Freeze-Up Prevention Control - Daikin RXQ12AHR Service Manual

Outline of Control (Indoor Unit)
8.8

Freeze-Up Prevention Control

Freeze-Up Prevention by Off Cycle (Indoor Unit Individual Control)
When the temperature detected by liquid pipe temperature thermistor of the indoor heat
exchanger drops too low, the unit enters freeze-up prevention control in accordance with the
following conditions, and is also set in accordance with the conditions given below. (Thermostat
OFF)
When freeze-up prevention is activated, the airflow rate is fixed to L tap. When the following
conditions for cancelling are satisfied, it will reset.
Conditions for starting:
Liquid pipe temperature ≤ – 1°C (for total of 40 minutes)
or
Liquid pipe temperature ≤ – 5°C (for total of 10 minutes)
Condition for cancelling:
Liquid pipe temperature ≥ +7°C (for 10 minutes continuously)
Liquid pipe
temperature
The idea of freeze-up prevention control
Difficult to carry out freeze-up prevention operation
· For comfort, suppression of frequent thermostat ON/OFF is necessary.
· Suppressing the switching frequency of the compressor is required to ensure reliability.
After freeze-up prevention operation is carried out, the compressor can be defrosted properly.
· Water leakage prevention must be effective.
Note(s)
 When the indoor unit is a round flow type, if the air outlet is set as dual-directional or
100
+7ºC
0ºC
–5ºC
10 min.
tridirectional, the starting conditions will be changed as follows.
Liquid pipe temperature ≤ 1°C (for total of 15 minutes)
or
Liquid pipe temperature ≤ 0°C (for 1 minute continuously)
During freeze-up prevention operation, the airflow rate is fixed to LL.
(The cancelling conditions are same as the standard.)
Freeze-up prevention control
Forced OFF by thermostat
Start
SiAF341904E
10 min.
Normal operation
Cancel
Part 4 Functions and Control