Daikin VRV RXYQ72-384XAYCA, Service Manual

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Outline of Control (Indoor Unit) SiUS342004EB
119 Part 4 Functions and Control
9.7 Freeze-Up Prevention 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.
Freeze-Up Prevention by Off Cycle (Indoor Unit)
N ormal operation
Start Cancel
Liquid pipe
temperature
Start
Cancel
N ormal operation
– 5 ºC
(23˚F)
0 ºC
(32˚F)
+ 7 ºC
(44.6˚F)
– 1 ºC
(30.2˚F)
t1 t2 t3 t4
0 ºC
(32˚F)
+ 7 ºC
(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