The Nibe F1245 is a ground source heat pump that communicates with TapHome via Modbus RTU over RS-485. Communication requires the NIBE MODBUS 40 accessory — an external RS-485 interface module that plugs into the heat pump’s internal bus. The template reads holding registers in the 40xxx range (sensors and status) and writes to the 47xxx range (settings and control), using 9600 baud, 8N1, with a default Slave ID of 1.
The F1145 and F1245 share the same register set and are interchangeable from a Modbus perspective.
Hardware connection
MODBUS 40 accessory
The Nibe F1245 does not have built-in Modbus support. An external MODBUS 40 accessory (sold separately) is required. This module connects to the heat pump’s internal communication bus and exposes an RS-485 interface for external Modbus RTU masters such as TapHome Core.
Connect the MODBUS 40 RS-485 terminals to TapHome Core:
- A+ on MODBUS 40 to A+ on TapHome RS-485
- B- on MODBUS 40 to B- on TapHome RS-485
- GND to GND on TapHome
The GND wire must be connected between the MODBUS 40 and TapHome Core. Without proper grounding, communication may be unreliable, especially over longer cable runs.
Communication parameters
| Parameter | Value |
|---|---|
| Protocol | Modbus RTU |
| Baud rate | 9600 |
| Data bits | 8 |
| Parity | None |
| Stop bits | 1 |
| Slave ID | 1 (configurable) |
Configuration
Enabling Modbus communication
- Install the MODBUS 40 accessory into the heat pump according to the NIBE installation guide
- The accessory should be automatically detected by the heat pump
- Verify the Slave ID setting — default is 1, configurable if multiple units share the bus
- In TapHome, add a new Modbus RTU device using the IP address of the RS-485 gateway (if using a TCP-to-serial converter) or configure the direct serial connection
The S-series heat pumps (S1155, S1255) have built-in Modbus TCP on port 502, activated via menu 7.5.9. The F1245 does not have this feature — the MODBUS 40 accessory is the only supported communication path.
If the Slave ID is changed from the default (1), update the corresponding parameter in the TapHome template import settings.
Device capabilities
Operating mode control
The template provides full control over the heat pump’s operating mode:
- Mode — selects between Auto, Manual, and Additive Heating Only. In Auto mode, the heat pump manages heating and cooling demand automatically. Manual mode allows direct control, and Additive Heating Only disables the compressor and relies solely on the auxiliary electric heater.
- Allow Heating — enables or disables additive and manual heating
- Allow Cooling — enables or disables cooling mode with manual and additive heating
Hot water management
Hot water control is the most detailed part of the template, offering three thermostat modes and a mode selector:
- Hot Water Mode — switches between Economy (0), Normal (1), and Luxury (2). Each mode has its own temperature setpoints. Service actions allow configuring start and stop temperatures for each mode directly from TapHome (range 5-70 °C).
- Hot Water Luxury — thermostat reading the BT6 current hot water temperature and controlling the luxury-mode start/stop setpoints. The Delta service attribute shows the difference between start and stop temperatures.
- Hot Water Normal — same as Luxury but for the normal-mode setpoints.
- Hot Water Economy — same as Luxury but for the economy-mode setpoints.
- Hot Water Production — master switch to enable or disable domestic hot water production entirely.
Temperature monitoring
The template includes five temperature sensors, all reading from holding registers with automatic divide-by-10 conversion to °C:
- Outdoor Temperature — BT1 outdoor sensor, with service attributes for the hourly average and long-term average
- Supply Temperature S1 — BT2 supply line temperature for climate system S1
- Return Temperature — BT3 return line temperature
- Room Temperature — BM1 BT50 wireless room temperature sensor
- Hot Water Economy/Normal/Luxury — each thermostat also reads the current BT6 hot water load temperature
Environmental sensors
- Humidity — BM1 humidity sensor reading in %RH (values above 100% are filtered as invalid). A service attribute shows the adjusted humidity from the +Adjust accessory.
- Pressure — BM1 pressure sensor converted from kPa to bar (values below -30 bar are filtered as invalid)
Compressor and system status
- Compressor Status — binary on/off indicator from the compressor contact. A service attribute provides detailed state information: Stopped (20), Starting (40), Running (60), or Stopping (100).
- Cooling Status — indicates whether the system is in cooling mode. A service attribute reports whether freeze protection is currently active.
- Current Fan Speed — reads the current fan speed as a percentage
- Pump HW Speed — hot water circulation pump speed control (read and write)
Additional capabilities
The Nibe F1245 exposes a wide range of additional registers not yet included in the template. Key capabilities include brine inlet/outlet temperatures (BT10, BT11) for ground loop monitoring, condenser and hot gas temperatures for compressor health tracking, refrigerant circuit sensors (liquid line, suction gas), wired room temperature (BT50), flow rate measurement (BF1), three-phase current monitoring (BE1-BE3), degree minutes for smart heating control, and energy metering for hot water and heating. These can be added in a future template update.
The Degree Minutes register (H:40940) is a commonly used control parameter for advanced heating automation. It can be added as a custom Modbus device in TapHome using register H40940, data type s32 (two consecutive registers), with a scale factor of 10.
Troubleshooting
No communication with the heat pump
- Verify that the MODBUS 40 accessory is correctly installed and detected by the heat pump
- Check RS-485 wiring: A+ to A+, B- to B-, GND connected
- Confirm communication parameters: 9600 baud, 8N1, Slave ID 1
- If using a TCP-to-serial converter, verify the converter is online and correctly configured
Temperature readings show incorrect values
All temperature registers use a scale factor of 10 (raw value divided by 10). If readings appear 10x too high, verify the conversion is correctly configured in TapHome. Some registers also include NaN guards — values outside expected ranges are treated as invalid.
Hot water setpoints not taking effect
The hot water thermostat writes to paired start/stop registers. Verify the correct Hot Water Mode is selected (Economy, Normal, or Luxury) before adjusting temperatures. The write sets the start temperature directly and calculates the stop temperature using the Delta parameter.
Register 43xxx values not updating
Some registers in the 43xxx range (compressor status, cooling status, fan speed) are not documented in the official NIBE register map — they are derived from community sources. If these registers return errors, the heat pump firmware version may not support them.
