Freeze-Up Prevention - Daikin RXYQ-TA Series Service Manual

Outline of Control (Indoor Unit)
8.7

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)
Liquid pipe
temperature
(44.6˚F)
(32˚F)
(23˚F)
OR
(44.6˚F)
(32˚F)
(30.2˚F)
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.
83
+7ºC
0ºC
–5ºC
10 min.
+7ºC
0ºC
–1ºC
t1 t2
Freeze-up prevention control
Forced OFF by thermostat
Start
Freeze-up prevention control
Forced OFF by thermostat
t3 t4 t > 40
Start
10 min.
Normal operation
Cancel
10 min.
Normal operation
minutes
Cancel
Functions and Control
SiUS341615E