Daikin SkyAir FHQ24PVJU - Freeze-Up Prevention

Outline of Control (Indoor Unit) SiUS281811EA
134 Part 4 Functions and Control
6.8 Freeze-Up Prevention
Freeze-Up Prevention by Off Cycle (Indoor Unit Individual Control)
When the temperature detected by the 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 electronic expansion valve is closed, the drain pump
turns on and 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 (30.2°F) (for total of 40 minutes)
or
Liquid pipe temperature ≤ – 5°C (23°F) (for total of 10 minutes)
Condition for cancelling:
Liquid pipe temperature ≥ +7°C (44.6°F) (for 10 minutes continuously)
Concept of freeze-up prevention control
System avoids freeze-up
 For comfort, system avoids unnecessary thermostat ON/OFF
 For ensuring compressor reliability, system avoids unnecessary compressor ON/OFF
When freeze-up prevention control starts, system makes sure the frost is completely removed.
 System avoids water leakage.
Normal operation
Start
Cancel
Liquid pipe
temperature
Start
Cancel
Normal operation
–5ºC
(23°F)
0ºC
(32°F)
+7ºC
(44.6°F)
–1ºC
(30.2°F)
t1 t2 t3 t4
0ºC
(32°F)
+7ºC
(44.6°F)
10 min.
OR
10 min.
10 min.
t > 40 minutes
Freeze-up prevention control
Forced OFF by thermostat
Freeze-up prevention control
Forced OFF by thermostat