What a heat meter delivers via M-Bus
A heat meter measures more than a meter reading. Via M-Bus it typically delivers energy, volume, flow and return temperature, flow rate and power. Which values the telegram contains exactly is defined by the manufacturer. The M-Center reads the telegram and assigns the values to the registers.
For passing them on there are fixed OBIS codes. This way the reading of a heat meter is always in the same place, even if meters from different manufacturers are installed in the building:
| Meter type | OBIS code | Reading |
|---|---|---|
| Cold water | 8-0:1.0.0 | Volume, meter reading |
| Hot water | 9-0:1.0.0 | Volume, meter reading |
| Heat | 4-0:1.0.0 | Meter reading |
| Heat | 4-0:3.1.0 / 4-0:3.2.0 | Flow and return temperature |
| Cooling | 5-0:1.0.0 | Energy, meter reading |
| Combined heat/cooling | 6-0:1.0.0 and 5-0:1.0.0 | Energy in the heating and in the cooling range |
| Gas | 7-0:3.0.0 | Volume, meter reading |
How the meters get into the M-Center
- Connect the meters to the M-Center with a two-wire M-Bus cable. J-Y(ST)Y 2×2×0.8 mm is recommended, shielded where possible. Star, tree and line are permitted; polarity does not matter.
- Start the search in the web interface. 2400 baud is recommended. The search by secondary address runs over all possible addresses and finds every meter by its unique identifier.
- Check the meters found. For meters from other manufacturers, the M-Center uses device drivers. If one is missing, it can be created or imported in the web interface.
- Enter OBIS codes for the registers that are to be passed on.
- Set the readout interval and configure the target systems.
For the readout interval, follow the recommendation of the meter manufacturer. The lower limit is set by the installation itself: if a run over all meters takes longer than 15 minutes, choose a longer interval or set individual intervals for single meters.
Keep an eye on the bus load
Every meter loads the bus with about 1.5 mA (one unit load). The M-Center supplies 450 mA continuous load at 230 V AC and up to 1.6 A at 24 V DC. For 250 unit loads, therefore plan with 24 V DC. The maximum cable length is 5000 m at 100 nF/km and no more than 90 Ω. How the calculation works is explained in our article on M-Bus bus load (in German).
Where the values go
| Target | Route | Licence |
|---|---|---|
| Billing service provider | CSV, JSON or Excel via (s)FTP or e-mail | Advanced Exporter for processed exports |
| Building management | BACnet IP or OPC UA | BACnet IP or OPC UA licence |
| PLC and control system | Modbus TCP | Modbus TCP server licence |
| Dashboard, cloud, home automation | MQTT | MQTT licence |
| Energy management | Joulio-Web | – |
The routes do not exclude each other. The M-Center reads each meter once and serves all targets in parallel.
Order numbers
| Item | Article number | Shop |
|---|---|---|
| M-Center for 20 M-Bus devices | 210.000.00 | Shop: EMU M-Center 210.000.00 → |
| M-Bus licence 20 → 60 devices | 210.020.01 | Shop: M-Center M-Bus-Lizenz 20 → 60 Geräte 210.020.01 → |
| M-Bus licence 20 → 120 devices | 210.020.02 | Shop: M-Center M-Bus-Lizenz 20 → 120 Geräte 210.020.02 → |
| M-Bus licence 20 → 250 devices | 210.020.03 | Shop: M-Center M-Bus-Lizenz 20 → 250 Geräte 210.020.03 → |
| Advanced Exporter licence | 210.300.06 |
Order online in the EMU Metering shop.