Freeze-Up Prevention Control - Daikin VRV EMERION RXYQ-AATJA Service Manual

Outline of Control (Indoor Unit)
9.7

Freeze-Up Prevention Control

Freeze-Up Prevention by Off Cycle (Indoor Unit)
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)
Liquid pipe
temperature
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.
135
+7ºC
(44.6˚F)
0ºC
(32˚F)
–5ºC
(23˚F)
10 min.
OR
+7ºC
(44.6˚F)
0ºC
(32˚F)
–1ºC
(30.2˚F)
t1 t2

Freeze-up prevention control

Forced OFF by thermostat
Start
Freeze-up prevention control
Forced OFF by thermostat
t3 t4 t > 40
Start
SiUS342303E
10 min.
Normal operation
Cancel
10 min.
Normal operation
minutes
Cancel
Part 4 Functions and Control