General Assist Technical Reference
Outdoor Fan Control and Operation
Cooling, heating, low noise mode and snow falling protection
Fan control reference for AJ*A72LALH, AJ*A90LALH, AJ*A108LALH, AJ*A126LALH and AJ*A144LALH outdoor units
The outdoor fan is not controlled at one fixed speed. Fan step is selected according to operating mode, outdoor air temperature and refrigerant pressure conditions. At low fan steps, the outdoor fan may operate intermittently rather than continuously.
1. Cooling operation
Cooling fan speed by fan step
| Fan step | Fan speed (rpm) |
|---|
| AJ*A72LALH | AJ*A90LALH | AJ*A108LALH | AJ*A126LALH | AJ*A144LALH |
|---|
| 16 | 880 | 880 | 880 | 920 | 920 |
| 15 | 860 | 860 | 860 | 870 | 870 |
| 14 | 810 | 810 | 810 | 820 | 820 |
| 13 | 720 |
| 12 | 600 |
| 11 | 500 |
| 10 | 420 |
| 9 | 360 |
| 8 | 320 |
| 7 | 300 |
| 6 | Intermittent 6 |
| 5 | Intermittent 5 |
| 4 | Intermittent 4 |
| 3 | Intermittent 3 |
| 2 | Intermittent 2 |
| 1 | Intermittent 1 |
| 0 | 0 rpm |
Initial cooling fan step
The initial outdoor fan speed is selected from the outdoor air temperature sensor value (TAOUT).
| Outdoor air temperature (TAOUT) | Initial fan step |
|---|
| TAOUT > 30°C | 16 |
| 30°C ≥ TAOUT > 20°C | 10 |
| 20°C ≥ TAOUT > 10°C | 7 |
| 10°C ≥ TAOUT | 0 |
After initial selection, high-pressure is monitored at set intervals and the fan step is adjusted to keep high-pressure saturation temperature within the target range.
| Fan speed decreases when | Fan speed increases when |
|---|
| High-pressure saturation is below the lower limit of the target high-pressure saturation range and heat-sink temperature is ≤ 75°C. | High-pressure saturation is above the upper limit of the target high-pressure saturation range or heat-sink temperature is ≥ 80°C. |
2. Intermittent fan mode
Cooling fan steps 1 to 6 use intermittent operation. The fan runs at 300 rpm for 7 seconds, followed by an OFF period that varies with the selected step.
| Fan step | Fan mode | 0 rpm duration | 300 rpm duration |
|---|
| 6 | Intermittent 6 | 6 sec | 7 sec |
| 5 | Intermittent 5 | 12 sec |
| 4 | Intermittent 4 | 19 sec |
| 3 | Intermittent 3 | 26 sec |
| 2 | Intermittent 2 | 33 sec |
| 1 | Intermittent 1 | 40 sec |
Intermittent-step behaviour: When changing from a normal fan step to an intermittent fan step, operation always starts with 300 rpm for 7 seconds. If the intermittent step changes while steps 1 to 6 are active, the new step is applied when the current speed-duration timer expires.
3. Heating operation
Heating fan speed by fan step
| Fan step | Fan speed (rpm) |
|---|
| AJ*A72LALH | AJ*A90LALH | AJ*A108LALH | AJ*A126LALH | AJ*A144LALH |
|---|
| 16 | 880 | 880 | 880 | 920 | 920 |
| 15 | 860 | 860 | 860 | 870 | 870 |
| 14 | 830 | 830 | 830 | 820 | 820 |
| 13 | 700 |
| 12 | 600 |
| 11 | 500 |
| 10 | 420 |
| 9 | 360 |
| 8 | 320 |
| 7 | 300 |
Initial heating fan step
The initial speed of the first-boot outdoor unit is selected from outdoor air temperature (TAOUT). Other outdoor units are normally operated at fan step 16.
| Outdoor air temperature (TAOUT) | Initial fan step |
|---|
| TAOUT < 10°C | 16 |
| 10°C ≤ TAOUT < 15°C | 12 |
| 15°C ≤ TAOUT < 20°C | 7 |
| 20°C ≤ TAOUT | 7 |
| Fan speed decreases when | Fan speed increases when |
|---|
| High-pressure is ≥ 3.30 MPa and heat-sink temperature is ≤ 75°C. | High-pressure is ≤ 3.20 MPa or heat-sink temperature is ≥ 80°C. |
4. Low noise mode
Low noise mode can be enabled from the outdoor-unit PUSH SW setting or by external input.
Setting and operating mode
| Capacity priority | Low noise level | Operation |
|---|
| OFF | Level 1 | Low Noise Mode 1 |
| Level 2 | Low Noise Mode 2 |
| ON | Level 1 | Automatic Switching 1 |
| Level 2 | Automatic Switching 2 |
Low noise operating limits
| Mode / condition | 8 HP | 10 HP | 12 HP | 14 HP | 16 HP |
|---|
| Low Noise Mode 1 | COOL | Fan upper limit | 600 rpm |
| Compressor upper limit | INV 45 rps | INV 53 rps | INV 60 rps | INV 72 rps | INV 72 rps |
| HEAT | Fan upper limit | 600 rpm |
| Compressor upper limit | INV 46 rps | INV 47 rps | INV 61 rps | INV 100 rps | INV 100 rps |
| Low Noise Mode 2 | COOL | Fan upper limit | 500 rpm |
| Compressor upper limit | INV 45 rps | INV 50 rps | INV 60 rps | INV 62 rps | INV 62 rps |
| HEAT | Fan upper limit | 500 rpm |
| Compressor upper limit | INV 46 rps | INV 46 rps | INV 56 rps | INV 62 rps | INV 62 rps |
Important: The constant-speed compressor is stopped in Low Noise Mode 1 and Low Noise Mode 2. Noise reduction is achieved by limiting inverter-compressor and outdoor-fan rotational speed.
- Low Noise Mode 1: operating sound is reduced by approximately 3 to 5 dB compared with the rated value.
- Low Noise Mode 2: operating sound is reduced by a further approximately 3 to 5 dB compared with Low Noise Mode 1.
Automatic switching
When capacity priority is ON, the system can automatically move out of low noise operation when capacity or refrigerant-pressure protection requires it. A switched state is retained for 30 minutes before another automatic change is made.
| Automatic Switching 1 | Automatic Switching 2 |
|---|
| Changes between Low Noise Mode 1 and Normal Operation. | Can step between Low Noise Mode 2, Low Noise Mode 1 and Normal Operation. |
Automatic switching criteria shown in the source include low compressor capacity, high cooling-side pressure condition (high-pressure saturation ≥ 58°C) or low heating-side pressure condition (low-pressure saturation ≤ 0°C).
5. Snow falling protection fan mode
When Snow Falling Protection Fan Mode is enabled and the outdoor temperature falls to 5°C or below, the outdoor fan is forced to maximum speed for 1 minute at the interval selected by PUSH SW function F2-23.
| Interval setting | PUSH SW F2-23 | Interval |
|---|
| Setting 4 (standard) | 00 | 30 min |
| Setting 1 | 01 | 5 min |
| Setting 2 | 02 | 10 min |
| Setting 3 | 03 | 20 min |
Snow falling protection ends when outdoor temperature reaches 7°C or higher, or when normal system operation starts.
6. Other fan control
To improve outdoor-air-temperature detection, the outdoor fan may be operated while the outdoor unit itself is stopped.
Technical data reproduced from the supplied outdoor fan control and operation service-manual pages. Always confirm the exact model and applicable service documentation before diagnosis or adjustment.
