Check an M-Bus primary address plan before commissioning: duplicates, meters left at address 0, and reserved addresses.
Address plan
Ready to commission
Check the values to see a result.
Valid assigned primary addresses = 1…250remaining capacity = 250 − unique assigned addresses
6 meters on their own addresses between 1 and 250 leave 244 addresses free on this bus.
Tip: Label each meter with its primary address as you set it. A duplicate found on site costs far more than one found here.
Every meter on a wired M-Bus segment needs its own primary address between 1 and 250. Address 0 is where most meters ship, and 251 to 255 have special roles, so a plan that uses them, or gives two meters the same address, fails at commissioning. The checker finds those problems before anyone is on site.
One meter per address; 250 addresses per bus
The master reads a meter by sending a request to its primary address. Two meters on the same address both reply at once, their frames collide and the master reads neither.
Unconfigured
Most meters leave the factory at 0. A bus with several meters still at 0 has the same problem as any duplicate. Set each meter’s address, with the manufacturer’s tool or through the M-Bus master, before connecting them together.
253: secondary addressing; 254 and 255: broadcast
These are not meter addresses. 253 tells the bus that a meter has been selected by its secondary address, the eight-digit identity every meter carries. 254 and 255 are broadcasts. 251 and 252 are reserved.
Secondary addressing avoids setting primary addresses at all: the master finds each meter by its unique identity number. It is slower to scan and not every master supports it, which is why most small sites still use primary addresses. More than 250 meters on one bus needs secondary addressing or a second segment.
Each of the six meters has its own address, none is left at 0 and none is special. The plan shows Ready to commission, with 244 addresses free for later meters.
Address plan Ready to commission Open in the calculator
Two meters are set to 3, so neither can be read reliably, and one is still at 0. The checker says Fix the plan first and names both. Readdress one of the pair to 4 and the unconfigured meter to 6.
Address plan Fix the plan first Open in the calculator
254 is a broadcast address that every meter on the bus answers, so it cannot pick out one meter, and with more than one meter the replies collide. The plan shows Fix the plan first: move the meter to an ordinary address such as 3.
Address plan Fix the plan first Open in the calculator
What each primary address means on a wired M-Bus network (EN 13757-2 and the OMS specification).
| Address | Use |
|---|---|
| 0 | Unconfigured: how most meters ship |
| 1 to 250 | One meter each |
| 251 | Reserved |
| 252 | Reserved |
| 253 | Selects a meter by its secondary address |
| 254 | Broadcast; every meter replies, so only for a bus with one meter |
| 255 | Broadcast with no reply |
Up to 250 by primary address. In practice the master’s supply sets the limit first: each meter draws one or more unit loads of 1.5 mA, and the cable’s resistance and capacitance limit the length. The wired M-Bus segment calculator checks those.
A primary address is a number from 1 to 250 you set on each meter. A secondary address is the meter’s own eight-digit identity, usually its serial number, set at the factory. Secondary addressing needs no setup but takes longer to scan.
Yes. Addresses only have to be unique on one bus, so a second M-Bus master or a second segment can start again at 1.
A ZHM connects one M-Bus meter and reports it wirelessly, so there is no shared bus to address; wired masters with many meters follow this plan.
