Daikin RZQ Series FCQ20EVA Service Manual page 51

SiME281501E
4.2.17 Forced Thermostat OFF
Thermostat OFF due to Freeze-up Prevention (Only in Cooling)
Conducts thermostat OFF under the following temperature and period of time to prevent the indoor unit heat
exchanger from freezing up.
Indoor unit heat exchange temperature < –5˚C for 1 continuous minute
{
&
Indoor unit heat exchange temperature < –1˚C for 40 cumulative minutes
Thermostat OFF due to Outdoor Air Temperature (Only in Heating)
If outdoor air temperature is high, turns OFF thermostat at the following temperature to protect the system.
 RZQ-LV
Outdoor air temperature > 32°C
 RZQ-MY
Outdoor air temperature > 30°C
"Freeze-up Prevention Control". Refer to P.28.
4.2.18 Low Pressure Difference, Low Compression Protection Control
To ensure the compression ratio under low outdoor air temperature cooling condition and the pressure
difference between liquid pressure and low pressure, controls the outdoor unit fan and changes the target
value of compressor PI control.
Low Outdoor Air Temperature Control in Cooling
Controls outdoor unit fan under low outdoor air temperature condition to secure pressure difference between
high and low pressure.
Hp: High pressure
Lp: Low pressure
Ta: Outdoor air temperature
Tfin: Radiation fin temperature
 RZQ20/24/36/45LVA, RZQ45/48MYL
Hp - Lp < 0.93MPa
OR
Compression ratio < 2.1
&
Hp < 1.86MPa
Ta < 25˚C
Hp - Lp < 0.78MPa
OR
&
Compression ratio 1.8
Hp < 1.57MPa
Hp - Lp < 0.78MPa
OR
Compression ratio < 1.8
&
Hp < 1.57MPa
Tfin < 66˚C
Frequency Restriction
Function and Control
Normal operation
Compressor operation frequency
restriction (refer to the followings)
Outdoor unit fan
-1 step/90 sec.
Outdoor unit fan: Stop
Frequency
restriction
Outdoor unit fan
+1 step/90 sec.
OR
Outdoor unit fan
Step 1
Lower limit frequency
Ta ≤ 20˚C
Step 22
Upper limit frequency
Ta > 25˚C
Step 2
Function Details
Hp - Lp > 1.08MPa
OR
Hp < 2.94MPa
OR Compression ratio > 2.4
Ta > 27˚C
Hp - Lp > 0.98MPa
&
Compression ratio > 2.2
Hp > 2.25MPa
Hp - Lp > 0.88MPa
&
Compression ratio > 2.0
OR
Hp > 1.66MPa
Tfin 81˚C
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