Overview
The Auto Changeover feature automatically switches between heating and cooling operation modes based on room temperature and the configured tolerance range around the set temperature (Ts).
This ensures optimal comfort and system efficiency without manual intervention.
Auto Changeover is available for both heat-recovery and heat-pump VRF systems.
1. System Type Requirements
a. Heat-Recovery Type Systems
The Auto Changeover function must be enabled individually for each indoor unit where it is required.
Only the indoor units with the setting activated will perform automatic mode switching.
Indoor units not configured for this feature will operate normally in the selected mode.
b. Heat-Pump Type Systems
Auto Changeover relies on a master indoor unit setting.
The master unit controls the operation mode for all indoor units on the same refrigerant system.
All linked units automatically follow the master’s set temperature and mode.
5.Auto change over operation 20…
2. Setting Procedure
To enable Auto Changeover, configure Indoor Unit Function Setting No. 65, titled:
“Mode Change Criteria Temperature Setting.”
This setting determines how far above or below the set temperature (Ts) the system will change between cooling and heating.
Factory Default:
2.0°C temperature difference
Adjustable Range:
| Set Value | Mode Change Criteria (α) | Description |
|---|---|---|
| 00 | 2.0°C | (Default) Standard comfort balance |
| 01 | 1.0°C | Faster changeover, tighter control |
| 02 | 1.5°C | Slightly tighter temperature range |
| 03 | 2.0°C | Standard range |
| 04 | 2.5°C | Wider range, reduced cycling |
| 05 | 3.0°C | Maximum difference before switching |
⚠️ Caution:
If this parameter is not correctly matched to installation and environmental conditions, frequent ON/OFF cycling (hunting) may occur, reducing efficiency and comfort.5.Auto change over operation 20…
3. Operating Principle
The Auto Changeover logic compares the room temperature with the set temperature (Ts) and changes operation mode within a tolerance band defined by the chosen value of α.
When the room temperature rises above Ts + α°C, the system switches to cooling.
When the room temperature drops below Ts – α°C, it switches to heating.
Between these thresholds, the system maintains standby or holds the current mode.
Temperature Control Logic
| Condition | System Mode |
|---|---|
| Room Temp ≥ Ts + α°C | Cooling ON |
| Room Temp ≤ Ts + 0.5°C | Cooling OFF |
| Room Temp = Ts | Neutral Point |
| Room Temp ≤ Ts – 0.5°C | Heating ON |
| Room Temp ≤ Ts – α°C | Heating OFF |
As illustrated in the temperature operation graph on page 4 of the source document, the hysteresis ensures stable operation and prevents unnecessary mode switching
5.Auto change over operation 20…
.
4. Example of Operation (from Diagram)
At a set temperature of 22 °C and α = 2.0 °C:
Cooling ON: when room temperature exceeds 24 °C
Cooling OFF: at approximately 22.5 °C
Heating ON: when room temperature drops below 20 °C
Heating OFF: at approximately 21.5 °C
This hysteresis zone ensures smooth transition and prevents “mode hunting.”
5. Best Practice Recommendations
Verify indoor unit addresses and master/slave assignments before activation.
Confirm function setting 65 values are consistent across connected indoor units.
In multi-zone systems, apply wider changeover margins (e.g., 2.5 °C – 3.0 °C) to minimize conflicts between zones.
After configuration, test under both heating and cooling conditions to confirm proper switching.
6. Summary
| System Type | Setting Requirement | Control Reference |
|---|---|---|
| Heat-Recovery | Enable per indoor unit | Each operates independently |
| Heat-Pump | Master indoor unit only | All follow master’s settings |
| Default ΔT (α) | 2.0 °C | Adjustable between 1.0 °C – 3.0 °C |
| Room Temp Accuracy | ±0.5 °C | System measures at 0.5 °C intervals |
Key Takeaways
Auto Changeover provides automatic seasonal mode switching between cooling and heating.
Configurable temperature criteria (α) determines when the switch occurs.
Proper configuration prevents mode conflicts and ensures occupant comfort.
Always validate configuration per system type (heat-pump vs heat-recovery).
Support
For configuration assistance or advanced VRF settings:
? Fujitsu Assist Technical Support: 1300 364 484 AU or +64 4 568 8761 NZ