Carlo Gavazzi
MID-certified Modbus energy meters — the standard sub-metering component in European KNX commercial panels.
Carlo Gavazzi Automation Components (Lainate, Milan, Italy — founded 1936) is a European manufacturer of energy metering, monitoring relays and industrial automation components. The Carlo Gavazzi EM series energy meters — EM340, EM24 and EM111 — are the most widely specified MID-certified Modbus energy meters in European commercial KNX panel projects. The EM340 3-phase direct-connection and CT-input models carry MID Class B certification (Measuring Instruments Directive 2014/32/EU), making them legally valid for tenant billing and energy performance contract monitoring across all EU member states. With Modbus RTU RS-485 on every model (and optional Modbus TCP via the EM300-LAN add-on module), EM series meters integrate directly with KNX-Modbus gateways — WAGO 750-893, Weinzierl KNX ENO 634 or Intesis IBOX-KNX-MBS — to deliver circuit-level energy data to KNX visualisation dashboards, BMS platforms and building energy management systems.
Role in our panels
How we use Carlo Gavazzi
The Carlo Gavazzi EM340 uses IEEE 754 32-bit floating-point values stored in pairs of 16-bit Modbus holding registers (big-endian word order). Key Modbus register addresses: 0x0034 (decimal 52) = total 3-phase active power in Watts (float32 BE, 2 registers), 0x0100 (decimal 256) = total kWh import (float32 BE), 0x0102 (decimal 258) = total kWh export (float32 BE, for bidirectional measurement on PV solar installations). The EM340 default Modbus RTU settings: 9600 baud, 8 data bits, no parity, 1 stop bit (8N1), slave address 1 (configurable via front panel buttons). DIN-rail footprint: 72mm (4 modules) for 3-phase models. The EM24 energy analyser adds THD voltage and current measurement up to the 25th harmonic — used upstream of capacitor banks and at mains incomers where power quality monitoring is required. The EM111 single-phase meter (1 DIN module, 18mm) is used for individual circuit monitoring in residential apartments and tenant sub-metering.
KNX panel wiring for Carlo Gavazzi energy meters: EM340 DIN-rail position in the panel — after the circuit MCB on the load side, before the load. RS-485 bus wiring: 2-core shielded twisted pair (e.g. Belden 9841 or equivalent, 120 Ohm termination impedance) daisy-chained between EM340 terminals A+ and B- (not star topology). RS-485 bus termination: 120 Ohm resistor at the physical end of the bus (last meter on the chain). Shield: connected to earth at one end only (panel PE busbar). EM340 Modbus slave address: set via front panel — address 1 for first meter, 2 for second, and so on. Connect RS-485 bus to WAGO 750-653 module (A+ to A+, B- to B-, GND to GND terminal). In WAGO CODESYS program: ModbusRTU master task polls each EM340 by slave address in sequence — read registers 0x0034 and 0x0100 per meter per cycle. Convert float32 big-endian result using WAGO ModbusFloatBE_TO_REAL() library function. Publish result to KNX group address as DPT 9.002 (active power) or DPT 14.019 (energy kWh).
Used in these project types
Carlo Gavazzi products
Key components we install
Carlo Gavazzi EM340 3-Phase Direct 65A
3-phase 4-wire direct connection energy meter, maximum current 65A per phase (direct without CT). MID Class B accuracy (±0.5% at reference conditions per 2014/32/EU). Modbus RTU RS-485 (default: 9600 baud, 8N1, slave address 1). Measures: import kWh, export kWh, active power W, reactive power VAr, apparent power VA, power factor, frequency, voltage and current per phase. Front LCD display shows all values. 72mm DIN-rail width (4 modules). For circuits up to 65A: direct connection to busbars via 16-25mm2 cable lugs on meter terminals. Typical use: 3-phase distribution circuit monitoring — server room PDU, HVAC compressor, EV charger, floor distribution board. Register 0x0034 = total active power (W), 0x0100 = total import kWh — both as float32 big-endian, 2 Modbus holding registers each.
Carlo Gavazzi EM340 3-Phase CT Input
CT-operated version of the EM340 — for loads exceeding 65A where direct connection is not practical. Accepts CT secondary current 5A (standard CT ratio, e.g. 100/5, 200/5, 400/5 configurable via front panel). Same MID Class B accuracy, same Modbus RTU register map as direct version (register addresses identical). Requires three split-core or wound CTs (e.g. Carlo Gavazzi TA series) rated for the circuit load and with 5A secondary. CT polarity important: arrow on CT body indicates current flow direction — incorrect polarity reverses import/export measurement. Typical use: main incomer metering above 65A, large HVAC plant, MV/LV transformer feeder metering. Same 72mm DIN-rail footprint. MID seal on CT-input meter applies to the meter itself — CT accuracy class must also be documented for the complete MID measurement system.
Carlo Gavazzi EM300-LAN Ethernet Module
Modbus TCP ethernet add-on module for EM340 and EM24 series meters. Clips onto the right side of the EM340 DIN-rail body. RJ45 connector, configurable IP address (static or DHCP), Modbus TCP port 502, slave ID configurable (default 1). Same Modbus register map as Modbus RTU version — register 0x0034 for active power, 0x0100 for kWh import, readable from any Modbus TCP master on the LAN. Used when the EM340 is physically remote from the RS-485 Modbus RTU bus, or when Modbus TCP polling is preferred over RS-485. For WAGO 750-8100 projects: EM300-LAN allows Modbus TCP polling directly from the PFC200 Ethernet port — no RS-485 wiring needed. For tenant billing systems: EM300-LAN enables direct LAN-connected meter readout by billing software without a gateway PC.
Carlo Gavazzi EM24 Energy Analyser
Advanced 3-phase energy analyser with harmonic analysis — measures THD-V (total harmonic distortion voltage) and THD-I (total harmonic distortion current) up to the 25th harmonic, plus individual harmonic amplitudes. MID certified. Modbus RTU RS-485, same register base address structure as EM340 for kWh and power — additional registers for THD-V, THD-I and harmonic components. Used at main building incomers where power quality monitoring is required: identifies harmonic problems from variable frequency drives (VFDs), LED drivers and UPS equipment. EM24 at the main incomer upstream of a capacitor bank: monitor cos-phi and THD before and after switching PFC capacitor stages. KNX integration: WAGO gateway reads THD-V register and writes to KNX group address — ETS6 threshold logic sends alarm telegram when THD-V exceeds EN 50160 5% limit. Front panel display shows power quality data without laptop connection.
Carlo Gavazzi EM111 Single-Phase
Ultra-compact single-phase energy meter — 1 DIN module (18mm width), direct connection up to 80A. MID Class B accuracy (±0.5% at reference conditions). Modbus RTU RS-485 (same protocol parameters as EM340: 9600 baud, 8N1). Measures: import kWh, active power W, power factor, voltage, current. Front LED display (no LCD — space-saving). For tenant apartment sub-metering where DIN-rail space in apartment distribution boards is critical — one EM111 per apartment, 18mm per meter. For individual circuit monitoring in residential KNX panels: monitor washing machine, EV charger or heat pump circuit individually. Legal tenant billing: MID certified — same legal validity as EM340 for single-phase circuits. Connect multiple EM111 on one RS-485 bus (different slave addresses) to a single WAGO gateway. Register 0x0034 = active power W (float32 BE), 0x0100 = import kWh (float32 BE).
Carlo Gavazzi FAQ
How do you read EM340 active power via Modbus in a WAGO CODESYS program?
The EM340 stores all measurement values as 32-bit IEEE 754 floating-point numbers in two consecutive 16-bit Modbus holding registers using big-endian word order. Total 3-phase active power register address: 0x0034 (decimal 52), length 2 registers. In CODESYS 3.5 with the WAGO Modbus RTU library: set fbEM340.iStartAddress := 16#0034 and fbEM340.iLength := 2, then trigger fbEM340.Execute. After the read completes, convert the two 16-bit words to a REAL value using the WAGO ModbusFloatBE_TO_REAL() library function — this handles the IEEE 754 big-endian conversion automatically and returns the result in Watts. Manual assembly (if not using the library function): combine words as DWORD_TO_REAL(SHL(DWORD(aData[0]), 16) OR DWORD(aData[1])). To publish to KNX: divide by 1000.0 to convert W to kW, assign to a REAL variable mapped to a KNX group address as DPT 9.002 (2-byte float, resolution 0.01kW). Important verification step: cross-check the CODESYS-calculated value against the EM340 front display reading to confirm correct byte order — some Modbus masters default to little-endian, which gives an incorrect result with the EM340 big-endian register organisation.
Is Carlo Gavazzi EM340 MID certified for legal tenant billing?
Yes — the EM340DINAV53XOSX (direct connection) and EM340DINAV53XOSX1X (CT input) both carry MID Class B certification under Measuring Instruments Directive 2014/32/EU, which is the EU legal framework for energy meters used for billing purposes. MID Class B accuracy specification: ±0.5% of reading at reference conditions (balanced load, rated voltage, rated frequency, temperature 23°C), ±1% at rated conditions (temperature range, voltage variations per the directive). The MID approval seal on the meter body must remain physically intact for the meter reading to have legal validity — do not open the meter, tamper with the terminal cover, or attempt to modify calibration settings. For new tenant billing installations: the EM340 arrives factory-calibrated and sealed from the manufacturer. For added tamper evidence in the installation: thread a tamper-evident seal wire through the terminal cover retention screw and apply a numbered seal. The Modbus register value at address 0x0100 (total import kWh) is legally the same energy total shown on the front display — Modbus readout is valid for billing calculations.
Can EM340 measure energy export for PV solar systems?
Yes — the EM340 measures bidirectional energy flow automatically when installed at a grid connection point with PV generation. Register 0x0102 (decimal 258) holds total kWh export — energy flowing from the site back to the grid (solar PV generation exported when it exceeds local consumption). Register 0x0100 holds total kWh import (energy consumed from the grid). For net metering calculation: net = import kWh minus export kWh. For KNX PV self-consumption monitoring: map KNX group address for import (e.g. GA 5/3/0, DPT 14.019 4-byte float kWh) and export (GA 5/3/1, DPT 14.019). In ETS6, an arithmetic function block calculates self_consumption_kWh = PV_generation_kWh (from inverter Modbus) minus export_kWh (from EM340 register 0x0102). The EM340 requires correct CT polarity or correct direct connection polarity for accurate bidirectional measurement — an arrow printed on the meter body indicates the positive current flow direction, which must point from grid toward load in a standard metering installation. If polarity is reversed, import and export values are swapped — verify by comparing EM340 front display against known grid import conditions during initial commissioning.
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