The SBC ALE3D5F is a DIN-rail mounted 3-phase energy meter (3 x 230/400 VAC, 50 Hz) with direct measurement up to 65 A. The device communicates via Modbus RTU over a 2-wire RS-485 interface. Since the TapHome template uses a Modbus TCP connection unit, a Modbus RTU-to-TCP gateway is required for integration. The template polls 14 holding registers (H:35 to H:51) providing per-phase and total readings for voltage, current, active power, and reactive power.
Hardware connection
RS-485 wiring
The ALE3D5F has a 2-wire RS-485 serial interface with shield connection. Connect using a daisy-chain topology through a Modbus RTU-to-TCP gateway:
- RS-485 A/B terminals on the meter to the gateway RS-485 port
- Shield connection for cable screening
- Gateway Ethernet port to the local network accessible by TapHome Core
Cable specification:
| Parameter | Value |
|---|---|
| Type | Twisted pair, shielded, 2 x 0.5 mm² |
| Max cable length | 1200 m |
| Max devices on bus | 247 (use repeater above 128) |
The RS-485 interface does not include an internal termination resistor. An external 120 ohm termination resistor must be installed at each end of the bus.
Mains wiring
The meter connects in series with the 3-phase supply:
- L1, L2, L3 — phase connections (each phase has in/out terminal pairs for direct through-wiring)
- N (PEN) — neutral connection
- Main circuit conductors: 1.5 to 16 mm², torque 1.5 to 2 Nm
The Modbus interface only works if Phase 1 is connected. Without Phase 1, the communication interface is not powered and the meter will not respond to Modbus requests.
Configuration
Communication parameters
The meter auto-detects both baud rate and parity — no manual configuration is required on the meter side. Supported settings:
| Parameter | Value |
|---|---|
| Baud rate | Auto-detected: 4800, 9600, 19200, 38400, 57600, 115200 |
| Parity Even | 8 data bits, 1 stop bit |
| Parity Odd | 8 data bits, 1 stop bit |
| No parity | 8 data bits, 2 stop bits |
| Default Slave ID | 1 (range 1-247) |
Configure the Modbus RTU-to-TCP gateway to match one of the supported baud rate and parity combinations. The meter will auto-detect and synchronize.
Slave ID
The default Modbus address is 1. To change it on the meter:
- Press and hold the down button for 3 seconds
- Use the up button to increase the address by 10, the down button to increase by 1
- Wait for the root menu to return — the new address is saved automatically
After importing the TapHome template, set the Slave ID in the module connection settings to match the meter address.
Gateway configuration
Since the ALE3D5F communicates via Modbus RTU and the TapHome template expects Modbus TCP, a gateway device is required. Configure the gateway to bridge RS-485 RTU traffic to TCP. Assign a static IP address to the gateway (or use DHCP reservation) to ensure reliable communication with TapHome.
Device capabilities
The template creates 14 read-only sensor devices organized by measurement type across the three phases. All values are read from holding registers using function code FC03 with Int16 data type.
Voltage monitoring
Three devices report the RMS voltage for each phase:
- Voltage Phase 1 — line voltage L1 (H:35, V, direct reading)
- Voltage Phase 2 — line voltage L2 (H:40, V, direct reading)
- Voltage Phase 3 — line voltage L3 (H:45, V, direct reading)
Current monitoring
Three devices report the RMS current for each phase, with a scale factor of /10:
- Current Phase 1 — line current L1 (H:36, raw value /10 to A)
- Current Phase 2 — line current L2 (H:41, raw value /10 to A)
- Current Phase 3 — line current L3 (H:46, raw value /10 to A)
Active power
Four devices report active power — one per phase and a total across all phases, with a scale factor of /100:
- Active Power Phase 1 — active power L1 (H:37, raw value /100 to kW)
- Active Power Phase 2 — active power L2 (H:42, raw value /100 to kW)
- Active Power Phase 3 — active power L3 (H:47, raw value /100 to kW)
- Active Power Total — sum of all phases (H:50, raw value /100 to kW)
Reactive power
Four devices report reactive power — one per phase and a total, with a scale factor of /100:
- Reactive Power Phase 1 — reactive power L1 (H:38, raw value /100 to kvar)
- Reactive Power Phase 2 — reactive power L2 (H:43, raw value /100 to kvar)
- Reactive Power Phase 3 — reactive power L3 (H:48, raw value /100 to kvar)
- Reactive Power Total — sum of all phases (H:51, raw value /100 to kvar)
Additional capabilities
The ALE3D5F also exposes power factor (cos phi) registers for each phase (H:39, H:44, H:49), dual-tariff energy counters with total and resettable partial readings (H:27-34), firmware and hardware version, serial number, and an error register with per-phase fault indication. These can be added in a future template update.
The data refresh interval on the meter is 10 seconds. Setting the TapHome polling interval below 10 seconds will not produce new readings and only increases bus traffic. A polling interval of 10 to 15 seconds is recommended.
Troubleshooting
No communication
- Verify that Phase 1 is connected — the RS-485 interface is powered from Phase 1 and will not operate without it
- Wait at least 30 seconds after powering on the meter — communication is not available during the startup period
- Check that the Modbus RTU-to-TCP gateway is properly configured (baud rate, parity, slave ID)
- Verify the RS-485 wiring is daisy-chained — swap A and B if communication fails
- Confirm external bus termination resistors (120 ohm) are installed at both ends of the bus
- Check the Slave ID in TapHome matches the meter address (default 1)
Error register
The meter provides a diagnostic error register (H:24) that indicates phase connection problems:
| Value | Meaning |
|---|---|
| 0 | No error |
| 1 | Error L1 |
| 2 | Error L2 |
| 3 | Error L1+L2 |
| 4 | Error L3 |
| 5 | Error L1+L3 |
| 6 | Error L2+L3 |
| 7 | Error L1+L2+L3 |
If phase errors appear, verify that the corresponding phase conductors are correctly wired through the meter terminals and that the phases are live.
Maximum registers per request
The ALE3D5F supports a maximum of 20 registers per read request. Requesting more than 20 registers in a single frame returns an ILLEGAL DATA ADDRESS exception (code 02). The TapHome template reads within this limit.
