Daikin REYQ-XA, Service Manual

Page: 161 / 441

SiUS371901E Outline of Control (Indoor Unit)
Functions and Control 148
9.7 Freeze-Up Prevention
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)
Concept of freeze-up prevention control
System avoids freeze-up prevention
· 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
– 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