MID Energy Meter KNX Integration: ABB B24, Eastron SDM630 and Carlo Gavazzi EM270 Modbus TCP
MID-certified energy meters connected via Modbus TCP to KNX provide legally traceable energy data for BREEAM sub-metering, tenant billing, and ISO 50001 energy management. Selecting the right meter and mapping its registers correctly into KNX group addresses is the foundation of any building energy monitoring system.
MID certification requirements for legal metering
The MID (Measuring Instruments Directive, 2014/32/EU) establishes the legal framework for energy meters used in tenant billing and official energy reporting. Annex MI-003 covers active electricity meters (kWh) with two accuracy classes: Class A (residential) and Class B (commercial, required for BREEAM sub-metering).
MID compliance requirements — Class B active electricity meter
MID Annex MI-003 Class B requirements:
Accuracy: ±0.5% at full load (Imax)
±1.0% at 5% of Imax (low load accuracy)
Temperature range: -25°C to +55°C (Class B)
Harmonic tolerance: THD up to 40% without loss of accuracy
Tamper protection: Sealed cover and terminal shield required
Calibration: Factory calibrated, certificate issued
No field recalibration required within 10 years
MID marking on meter:
CE mark + M (metrology) + year + notified body number
e.g.: CE M 10 0123 (notified body 0123, certified in 2010)
For BREEAM Ene 02:
Class B MID certification is required for sub-metering
evidence (credits 3–5 require metered data with calibration
certificate provided to BREEAM assessor)ABB B24 3-phase meter: Modbus TCP register map
The ABB B24 is a 4-module DIN rail 3-phase energy meter with integrated Modbus RTU/TCP communication and MID Class B certification. It is the most commonly specified meter for commercial KNX sub-metering projects due to its comprehensive register set covering harmonics and power quality parameters.
| Register (hex) | Parameter | Type | Unit / scale |
|---|---|---|---|
| 0x0000 | Voltage L1 (V) | float32 | V, direct |
| 0x0002 | Voltage L2 (V) | float32 | V, direct |
| 0x0004 | Voltage L3 (V) | float32 | V, direct |
| 0x0006 | Current L1 (A) | float32 | A, direct |
| 0x0008 | Current L2 (A) | float32 | A, direct |
| 0x000A | Current L3 (A) | float32 | A, direct |
| 0x000C | Active power L1 (W) | float32 | W, direct |
| 0x000E | Active power L2 (W) | float32 | W, direct |
| 0x0010 | Active power L3 (W) | float32 | W, direct |
| 0x0012 | Total active power (W) | float32 | W, direct |
| 0x001E | Power factor L1 | float32 | 0.000–1.000 |
| 0x0020 | Power factor L2 | float32 | 0.000–1.000 |
| 0x0022 | Power factor L3 | float32 | 0.000–1.000 |
| 0x0024 | Total power factor | float32 | 0.000–1.000 |
| 0x0156 | Total import kWh | float32 | kWh, direct |
| 0x0158 | Total export kWh | float32 | kWh, direct |
Register byte order: ABB B24 uses big-endian byte order and big-endian word order for all float32 registers. Configure the Modbus gateway accordingly — incorrect byte order produces apparently plausible but wrong energy values (e.g. reading 12,345 kWh when actual is 54,321 kWh). Always verify against the meter front-panel display after initial commissioning.
Eastron SDM630: CT-connected metering for existing installations
The Eastron SDM630 MCT (Meter with Current Transformer inputs) allows metering of circuits where direct connection would require a service interruption. CT clamps are fitted around existing cables, enabling sub-metering to be added to operational buildings without distribution board shutdown.
Eastron SDM630 CT configuration
Eastron SDM630 MCT specifications: Input: CT secondary 1A or 5A (set via front-panel DIP) CT ratio: Configurable 1:1 to 9999:1 (set on meter) MID Class: Class B (import/export kWh) Modbus: RTU on RS-485, slave address 1–247 (configurable) TCP: Via external Modbus RTU–TCP converter CT selection guide: Up to 100A: 50/5A split-core CT (e.g. Hobut CM50/5) 100–400A: 200/5A split-core CT (e.g. Hobut CM200/5) 400–1000A: 1000/5A bar-type CT (requires bus-bar installation) 1000–5000A: 5000/5A Rogowski coil (flexible, no core saturation) DIP switch settings (SDM630 side panel): SW1: CT ratio hundreds digit SW2: CT ratio tens digit SW3: CT ratio units digit SW4: CT secondary (0=5A, 1=1A) SW5: Modbus address bit 0 ... (full table in SDM630 installation manual, p.12) Modbus key registers (same register layout as SDM630 direct): Register 0x0000: V L1 (float32, V) Register 0x000C: kW L1 (float32, kW) Register 0x0156: Total import kWh (float32, kWh) All registers: big-endian byte and word order
Carlo Gavazzi EM270: compact 1-module DIN rail metering
The Carlo Gavazzi EM270 occupies only 1 DIN rail module width (18mm), making it the most space-efficient option for sub-metering of individual distribution board outgoing circuits where DIN rail space is constrained.
Carlo Gavazzi EM270 specifications
- Single-phase, 1-module (18mm) DIN rail
- Direct connection up to 65A (no CT required)
- MID Class B (import kWh)
- Modbus RTU RS-485, 9600 baud default
- Display: kWh, W, V, A on 4-digit LCD
EM270 Modbus key registers
- Register 0x0000: Voltage (float32, V)
- Register 0x0002: Current (float32, A)
- Register 0x0004: Active power (float32, W)
- Register 0x0006: Power factor (float32)
- Register 0x000A: Import kWh (float32, kWh)
Intesis IN701KNX signal mapping for energy meters
The Intesis IN701KNX gateway reads Modbus TCP registers from energy meters and publishes the values as KNX group address telegrams. The MAPS configuration tool defines which registers are polled and how they are mapped to KNX DPTs and group addresses.
Intesis MAPS signal table — ABB B24 per sub-meter
Signal name Modbus reg KNX DPT KNX GA ───────────────────────────────────────────────────────────── HVAC total power kW 0x0012 DPT 13.010 6/0/0 HVAC import kWh 0x0156 DPT 12.001 6/0/1 HVAC power factor 0x0024 DPT 9.001 6/0/2 HVAC meter fault (poll fail) DPT 1.005 6/0/3 Lighting total power kW 0x0012 DPT 13.010 6/1/0 Lighting import kWh 0x0156 DPT 12.001 6/1/1 Lighting power factor 0x0024 DPT 9.001 6/1/2 Lighting meter fault (poll fail) DPT 1.005 6/1/3 Transport (lifts) power 0x0012 DPT 13.010 6/2/0 Transport import kWh 0x0156 DPT 12.001 6/2/1 MAPS general settings: Poll interval: 60 seconds (energy data, not real-time control) Timeout: 10 seconds per Modbus request Modbus device IP: <meter IP or Modbus TCP converter IP> Modbus unit ID: 1 (default for ABB B24)
10-meter sub-metering hierarchy for BREEAM
BREEAM Ene 02 requires a hierarchical sub-metering structure with the utility import meter at the top and individual system meters below. The 10-meter hierarchy covers all major energy end-uses required for the highest credit scores.
10-meter sub-metering hierarchy
Level 0 (utility):
M0 — Grid import meter (DNO meter, MID Class B)
KNX GA 6/9/0 (kWh, read only for cross-check)
Level 1 (major systems):
M1 — HVAC plant (chillers, AHUs, boilers combined)
KNX GA 6/0/x
M2 — Lighting (all distribution boards)
KNX GA 6/1/x
M3 — Transport (lifts and escalators)
KNX GA 6/2/x
M4 — Domestic hot water (DHW plant)
KNX GA 6/3/x
M5 — Small power (office equipment, IT)
KNX GA 6/4/x
Level 2 (sub-systems, BREEAM credits 4–5):
M6 — Chiller plant (subset of HVAC)
M7 — AHU fans (subset of HVAC)
M8 — Lighting zone A (floor 1)
M9 — Lighting zone B (floor 2)
M10— Server room (subset of small power)
Balance check: M0 = M1 + M2 + M3 + M4 + M5 ± 5%
Imbalance >5% indicates CT installation error or meter faultCommissioning and calibration verification
After Modbus mapping is complete, verify each meter reading against an independent reference — either the meter front-panel display or a calibrated clamp meter — to confirm CT ratio configuration and register byte order are correct.
Commissioning verification procedure
1. Power verification per meter: Read KNX GA power value in ETS6 Group Monitor (kW) Compare to meter front-panel active power display Tolerance: ±2% at loads >20% of rated current If >2% discrepancy: check CT ratio DIP settings, byte order 2. Energy accumulation check: Record kWh value at 09:00 from ETS6 Group Monitor Record same kWh value at 17:00 Calculate expected kWh from average power × 8 hours Compare: KNX accumulated kWh vs (average kW × 8h) Tolerance: ±1% over 8 hours 3. CT polarity check: Meter should show positive active power (import) for load If negative: CT secondary leads reversed → swap S1/S2 wires For SDM630 MCT: ensure CT arrow points toward supply 4. Balance check (if >3 sub-meters installed): Read M0 (utility import) and M1–M5 simultaneously from KNX GAs M0 should equal sum of M1–M5 ± 5% Note: M0 may be higher if some circuits are unmetered 5. Document: record meter serial numbers, CT ratios, and ETS6 Group Monitor screenshots for BREEAM assessor evidence
Need a BREEAM sub-metering panel with MID meters and KNX?
We supply and install ABB B24, Eastron SDM630 and Carlo Gavazzi EM270 meters with Modbus TCP gateway, Intesis KNX mapping, and full calibration certificates — delivered ready for BREEAM Ene 02 assessment.
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