FENECON Modbus-API (grid)
The FENECON Modbus-API is the built-in Modbus TCP interface of FENECON energy management systems (FEMS), based on the OpenEMS platform. It exposes aggregated system channels over Modbus TCP so that external devices, building management systems, and energy monitors can poll live data without proprietary software. This template reads two grid-side registers: active grid power (address 315) and cumulative grid energy (address 359). Positive power values indicate grid import; negative values indicate feed-in. Use this template in the ModbusCloud portal to track real-time grid exchange and long-term energy totals for any FENECON installation on your network.
- Protocol
- Modbus TCP
- Connection
- Ethernet, Modbus TCP
- Registers
- 2, read only
- Brand
- FENECON
- Compatible models
- Modbus-API
- Last updated
Registers (2)
2 read, 0 write
| Name | Unit | Access | Address (Hidden until you enter your email) | Function (hidden) | Type (hidden) |
|---|---|---|---|---|---|
| power | W | Read | |||
| energy | Wh | Read |
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If a device is not in the library yet, we build the template for free as soon as we have the register data.
Use cases
- Monitor real-time grid active power to detect unexpected import spikes during battery-assisted operation.
- Track cumulative grid energy over time to verify feed-in totals against utility billing data.
- Alert on sustained grid import above a threshold to identify self-consumption shortfalls during daylight hours.
- Compare historical grid power trends across multiple FENECON sites from a single ModbusCloud dashboard.
- Report daily and monthly grid exchange totals for energy performance certificates or tenant billing.
Installation
Confirm the FEMS App Modbus/TCP Read Access is active on the FENECON system: log into FEMS Online Monitoring, open Settings, navigate to the system profile, and verify ctrlApiModbusTcp is listed as an active component.
Connect the ModbusCloud Gateway to the same LAN segment as the FENECON FEMS controller, ensuring the Gateway can reach the FEMS IP address on TCP port 502.
In the ModbusCloud portal, add a new device, import the FENECON Modbus-API (grid) template, and set the Modbus unit ID to 1 and the target IP to the FEMS IP address.
Spot-check register 315 (grid active power) in the portal live view and confirm the value matches the FEMS Online Monitoring display; if addresses appear shifted by one, set the client base address to 0.
Things to watch for
Register 315 returns a value shifted by one register. Why?
The FENECON Modbus-API uses zero-based register addressing. Many Modbus clients default to a base address of 1, which shifts all addresses by one. Change the base address offset in your client or in the ModbusCloud Gateway configuration to 0 to align with the FEMS register table.
The Gateway connects but grid power reads as zero or NaN.
The FEMS may not have grid meter data available if the grid meter is offline or not yet commissioned. Verify the grid meter is active in FEMS Online Monitoring. Also confirm the data type is float32 for register 315 (FC 4) and float64 for register 359 (FC 3); a type mismatch returns invalid values.
Modbus TCP connection is refused on port 502. What should I check?
The FENECON FEMS must be reachable on the same physical network as the ModbusCloud Gateway. Check that no firewall blocks TCP port 502 between the Gateway and the FEMS IP address. Also verify the FEMS App Modbus/TCP Read Access is installed and active, as the interface is only available when the app is enabled.
Energy register 359 seems to accumulate incorrectly after a FEMS restart.
Register 359 holds a cumulative float64 value maintained by the FEMS software. After a FEMS restart or firmware update, the counter may reset or briefly report stale values. Record a baseline reading in the ModbusCloud portal immediately after any FEMS update so you can apply an offset correction in your dashboard calculations.
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