The Inepro PRO380-S-CT is a MID-certified DIN-rail mounted 3-phase energy meter designed for current transformer (CT) installations. It communicates via Modbus RTU over RS-485 and measures active energy (kWh), reactive energy (kvarh), and instantaneous electrical parameters (voltage, current, power, power factor, frequency). The TapHome template provides 15 devices covering total, per-phase (L1/L2/L3), and bidirectional (import/export) metering with per-tariff (T1/T2) breakdown as service attributes.
The meter supports multiple wiring configurations: 3-phase 4-wire (3P4W), 3-phase 3-wire Open Delta (Aron), 3-phase 3-wire Delta, and single-phase 2-wire (1P2W). All measurement and energy registers use IEEE 754 Float32 in Big Endian byte order, read via Modbus function code FC03 (holding registers).
Hardware connection
CT wiring
The PRO380-S-CT requires external current transformers with a 5A secondary. The CT ratio must be configured before energy readings are valid (see Configuration section below).
3-phase 4-wire (3P4W)
| Terminal | Function |
|---|---|
| 1, 2 | CT L1 (S1 input, S2 output) |
| 3, 4 | CT L2 (S1 input, S2 output) |
| 5, 6 | CT L3 (S1 input, S2 output) |
| 7 | L1 voltage input |
| 8 | L2 voltage input |
| 9 | L3 voltage input |
| 10 | N (Neutral) |
3-phase 3-wire Open Delta — Aron (3P3W)
| Terminal | Function |
|---|---|
| 1, 2 | CT L1 (S1 input, S2 output) |
| 3, 4 | Not used |
| 5, 6 | CT L3 (S1 input, S2 output) |
| 7 | L1 voltage input |
| 8 | L2 voltage input |
| 9 | L3 voltage input |
| 10 | Not used |
3-phase 3-wire Delta (3P3W)
| Terminal | Function |
|---|---|
| 1, 2 | CT L1 (S1 input, S2 output) |
| 3, 4 | CT L2 (S1 input, S2 output) |
| 5, 6 | CT L3 (S1 input, S2 output) |
| 7 | L1 voltage input |
| 8 | L2 voltage input |
| 9 | L3 voltage input |
| 10 | Not used |
Single-phase 2-wire (1P2W)
| Terminal | Function |
|---|---|
| 1, 2 | CT L1 (S1 input, S2 output) |
| 3, 4 | Not used |
| 5, 6 | Not used |
| 7 | L1 voltage input |
| 8, 9 | Not used |
| 10 | N (Neutral) |
The CT secondary circuits must never be open while the primary is energized. Open CT secondaries develop dangerous high voltages. Always short-circuit the CT secondary terminals before disconnecting the meter.
RS-485 wiring
Connect the RS-485 bus to the meter terminals:
- Terminal 22 — RS-485 A (Data+)
- Terminal 23 — RS-485 B (Data-)
Use twisted pair cable (Cat5 or dedicated RS-485 cable). For cable runs exceeding 50 m, add a 120 ohm termination resistor (0.25 W minimum) at each end of the bus. Maximum cable length is approximately 1200 m at 9600 baud. Up to 32 devices can share one RS-485 bus.
Configuration
Communication parameters
The default Modbus settings match the TapHome template:
| Parameter | Default | Configurable |
|---|---|---|
| Baud rate | 9600 | Yes (300–9600) |
| Data bits | 8 | No (fixed) |
| Parity | Even | Yes (Even, Odd, None) |
| Stop bits | 1 | No (fixed) |
| Slave ID | 1 | Yes (1–247) |
Communication parameters can be changed via Modbus registers: Slave ID (register 0x4003), baud rate (register 0x4004), and parity (register 0x4011). The slave ID can also be changed via the meter pushbutton menu.
When connecting multiple PRO380 meters on the same RS-485 bus, each meter must have a unique Slave ID. After importing the TapHome template, adjust the Slave ID in the module connection settings to match the meter.
CT ratio configuration
On first power-up, the CT version displays a CT ratio warning. The CT ratio must be set before energy readings are valid. The default ratio is 5/5 (1:1).
Configuration via meter menu:
- Press and hold the pushbutton for 3 seconds to enter setup
- Navigate to the CT ratio screen
- Set the primary current value (e.g., 200 for a 200/5 CT)
- Confirm with the pushbutton
The CT ratio can also be written to Modbus register 0x400C (Float32). Common ratios: 100/5, 200/5, 400/5, 600/5, 800/5, 1000/5, 1500/5, 2000/5.
If the CT ratio is not configured correctly, all energy and power readings will be incorrect. The meter scales all current-derived measurements by the configured CT ratio.
Combination code (energy direction)
The combination code (register 0x400F) determines how forward and reverse energy is calculated:
| Code | Description |
|---|---|
| 1 | Arithmetic sum (L1+L2+L3) — standard 3P4W |
| 2 | Absolute sum (|L1|+|L2|+|L3|) |
| 3 | L1 only (single phase) |
| 4 | L1+L2 (Aron connection) |
| 5 | L1+L3 |
The default combination code should match the wiring configuration. For standard 3-phase 4-wire installations, use code 1.
Device capabilities
The template creates 15 devices organized into five groups: per-phase voltage and current sensors, per-phase and total active energy meters, per-phase and total active power sensors, apparent power and power factor monitoring, and reactive energy/power metering. All devices are read-only.
Voltage and current monitoring
Six sensor devices provide per-phase electrical measurements:
- L1 Voltage, L2 Voltage, L3 Voltage — phase-to-neutral voltages (V)
- L1 Current, L2 Current, L3 Current — phase currents (A)
An additional Grid Frequency sensor reports the line frequency (Hz).
Active energy metering
Three energy devices track active energy with per-tariff (T1/T2) and per-phase (L1/L2/L3) breakdown as service attributes:
- Total Active Energy — combined 3-phase energy (kWh) and instantaneous total active power (kW). Service attributes provide T1/T2 tariff totals and L1/L2/L3 per-phase totals.
- Forward Active Energy (Import) — energy imported from the grid (kWh) with T1/T2 and L1/L2/L3 breakdown.
- Reverse Active Energy (Export) — energy exported to the grid (kWh) with T1/T2 and L1/L2/L3 breakdown. Useful for solar PV installations with bidirectional metering.
Active power monitoring
The Total Active Power device provides instantaneous total active power (kW) with per-phase breakdown as service attributes (L1/L2/L3 Active Power in W, converted from kW by the template).
Apparent power and power factor
- Total Apparent Power — instantaneous apparent power (kVA) with per-phase service attributes (L1/L2/L3 in kVA).
- Total Power Factor — system-wide power factor (0.00–1.00) with per-phase power factor as service attributes (displayed as percentage).
Reactive energy and power
- Total Reactive Energy — total reactive energy (kvarh) and instantaneous reactive power (kvar), with T1/T2 tariff breakdown, L1/L2/L3 per-phase breakdown, and forward/reverse reactive energy counters as service attributes.
- Total Reactive Power — instantaneous total reactive power (kvar) with per-phase breakdown (L1/L2/L3 in kvar).
The import/export energy split (Forward/Reverse Active Energy) is particularly useful for monitoring solar PV self-consumption and grid interaction. The combination code setting determines how the meter calculates the energy direction.
Additional capabilities
The PRO380 also exposes registers for line-to-line voltage (L1-L2), total current (sum of all phases), per-phase and per-tariff forward/reverse reactive energy breakdown, CT ratio and communication parameter readback, error codes, power down counter, and power quadrant indicators. The L3 Apparent Power register (0x5028) is available in the meter but the template service attribute currently reads the wrong register (0x502A). These can be added or corrected in a future template update.
Troubleshooting
No communication
- Verify RS-485 wiring: terminal 22 to A/D+ and terminal 23 to B/D- on the TapHome converter
- Check for swapped A/B connections — swap terminals 22 and 23 if communication fails
- Confirm the baud rate and parity match between the meter and TapHome (default: 9600, 8E1)
- Verify the Slave ID in TapHome matches the meter setting (default: 1)
- For long cable runs, ensure 120 ohm termination resistors are installed at both bus ends
Incorrect readings
- CT ratio not set — the most common issue. Verify the CT ratio is configured correctly for the installed CTs (register 0x400C or via menu). If the ratio is wrong, all current, power, and energy readings will be scaled incorrectly.
- Wrong combination code — if forward/reverse energy values seem incorrect, check that the combination code (register 0x400F) matches the wiring configuration.
- CT polarity reversed — check the L1/L2/L3 Current Direction indicators (registers 0x4012–0x4014). A “-” sign indicates reversed CT orientation on that phase. Swap the S1/S2 connections on the affected CT.
Zero or missing readings
- Confirm the wiring configuration matches one of the supported types (3P4W, 3P3W, Delta, 1P2W)
- In 3P3W configurations, some phase voltage registers may return zero — this is expected
- Verify that voltage inputs (terminals 7-10) are connected, as the meter is powered through these terminals
