R32 H-Series Indoor Fan Behaviour During Thermo Off
1. What changed on the R32 H-series?
For R32 H-series models, indoor fan operation during thermo off has been partially changed from previous R410A models. The actual fan response is determined by the combination of indoor-unit function settings and, where fitted, wired remote-controller settings.
| Condition | What may happen |
|---|---|
| Cooling / Dry thermo off | Fan may follow the manual setting, operate intermittently, or switch OFF depending on FS49 and temperature-sensor settings. |
| Heating – single split | Fan is normally S-Lo under standard sensing, but can switch OFF when the wired remote-controller sensor is used. |
| Heating – multi split | Fan behaviour varies with compressor status and temperature-sensor selection. Intermittent operation, S-Lo or fan OFF may occur. |
2. Settings that control fan behaviour
| Setting | Description |
|---|---|
| FS49 | Indoor unit fan control for energy saving during cooling. Values include 00: Disable, 01: Enable and 02: Remote controller. 02 is the factory setting. |
| FS43 | Cold air prevention. On PAC models this setting is available only on duct units. Factory setting is 00: Enable. |
| FS42 | Room temperature sensor switching. Factory setting is 00: Indoor unit. |
| FS48 | Room temperature sensor switching (Aux.). Used when determining whether sensing is shared or taken from the wired remote controller. |
| RC sensor setting | Determines whether the wired remote-controller temperature sensor is used. |
| Energy saving – RC setting | Used when FS49 is set to 02: Remote controller. The factory setting is ON. |
3. Cooling and Dry operation
During cooling or dry operation, R32 models can behave differently from R410A models when thermo off occurs.
- Fan follows the remote-controller manual setting when energy-saving fan control is disabled or not active. With Auto airflow, or in Dry mode, intermittent operation may apply.
- Fan intermittent is used when energy-saving fan control is active and the indoor-unit temperature sensor remains part of the control strategy.
- Fan OFF can occur when the wired remote-controller sensor is being used as the controlling room-temperature sensor.
Cooling / Dry intermittent fan timing
| Indoor unit type | X – Fan OFF period | Y – Fan ON period |
|---|---|---|
| High static pressure duct ① / ② | 360 seconds | 120 seconds |
| All other applicable models | 180 seconds | 60 seconds |
Note: Airflow during the intermittent ON period varies by indoor-unit type. In Dry mode, fan speed is controlled by the unit's Dry-operation logic.
4. Heating operation
Single split – RAC
With the factory room-temperature sensing arrangement, the R32 indoor fan operates at S-Lo during thermo off. When the wired remote-controller sensor is selected as the controlling sensor, the fan can switch OFF.
Single split – PAC
With FS43 = 00: Enable (factory setting), the same general behaviour applies: S-Lo with standard sensing, with fan OFF possible when the wired remote-controller sensor is used.
Where a duct unit has FS43 = 01: Disable, the fan follows the wired remote-controller manual fan setting. When fan speed is set to Auto, the bulletin states that the speed is fixed at High.
Multi split – RAC and PAC
During heating thermo off, the indoor fan response also depends on whether the outdoor compressor is operating for another indoor unit. Depending on sensor selection, the R32 indoor fan can operate intermittently, run at S-Lo, or remain OFF.
Heating intermittent fan timing
| Indoor unit type | Intermittent operation |
|---|---|
| Wall-mounted / Floor / Compact cassette | 3 min ON / 6 min OFF |
| Slim duct | 2 min ON / 6 min OFF |
| Other applicable models | 1 min ON / 6 min OFF |
5. Australian models covered by RAC-0131
| Indoor unit type | Models |
|---|---|
| Compact cassette | AUTH24KVLA |
| Circular Flow cassette | AUTH24KRTA, AUTH30KRTA, AUTH36KRTA, AUTH45KRTA, AUTH54KRTA |
| Ceiling | ABTH18KRTA, ABTH24KRTA, ABTH30KRTA, ABTH36KRTA, ABTH45KRTA, ABTH54KRTA |
| High static pressure duct ① | ARTH24KHTA, ARTH30KHTA, ARTH36KHTA, ARTH45KHTA, ARTH54KHTA, ARTH60KHTA |
| High static pressure duct ② | ARTH60KHTB, ARTH65KHTA, ARTH72KHTA, ARTH90KHTA |
6. Technician diagnostic approach
- Confirm the indoor model is included in RAC-0131.
- Confirm the operating mode – Cooling, Dry, Heating single split or Heating multi split.
- Confirm the system is actually thermo off. Do not assess this bulletin while the unit is actively calling for cooling or heating.
- Record FS49, FS42 and FS48. For PAC duct units in heating, also record FS43.
- Check the wired remote-controller sensor setting and whether its energy-saving fan-control setting is ON or OFF.
- Compare the observed fan operation with the expected behaviour above. Allow enough time to observe the intermittent sequence before concluding that the fan is operating incorrectly.
- If the fan behaviour matches the bulletin, do not diagnose a fan motor, PCB or control fault solely because the indoor fan continues to run after set temperature is reached.
A customer may report that the outdoor unit has stopped but the indoor unit is still blowing air. On an affected R32 H-series unit this can be normal thermo-off fan control. Confirm the model and settings before treating the complaint as a product issue.