Wired reading

Meter reading over M-Bus

M-Bus is the European standard built for reading heat and water meters over a two-wire line. Where cable can be pulled, it is the most stable path there is: no batteries to replace, no signal to lose, and the cost per meter falls as the count rises.

At a glance

Standard: EN 13757-2 (physical/link), EN 13757-3 (application)
Physical medium: Two-wire line, polarity independent
Topology: Master–slave; the master powers the line and starts reads
Addressing: Primary address and secondary (serial-based) address

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What is M-Bus?

M-Bus (Meter-Bus) is a communication protocol developed for remote meter reading and standardised in the EN 13757 series. Its physical layer is a two-wire line, and that line is polarity independent — reversing the two wires does not break anything. In practice this removes most of the installation errors that happen on site.

One master (a modem or M-Bus converter) sits on the line and the meters are its slaves. The master powers the line and starts every exchange; a meter answers only when it is asked. Because of this master-slave design, hundreds of meters can share one line and still be read one by one without collisions.

Reading depends on the telegram structure rather than the manufacturer's own software. Heat, hot water and cold water meters that produce standard telegrams are read regardless of brand — which is why M-Bus is the most practical way to move to remote reading without replacing the meters you already have.

How it works

Reading with M-Bus, step by step

The path from installation to an index landing in the panel.

The line is installed
A two-wire line runs from the meters to a modem or M-Bus converter. It can branch in tree, star or mixed topology, and polarity does not matter.
Meters join the line
Each meter is connected in parallel. Meters draw very little current from the line, so a single master can power a large number of them.
Addresses are assigned
Each meter is identified by a primary address (a short number) or a secondary address — a long identifier made of manufacturer code, serial number, version and medium. NovuSoft stores this identity in the meter inventory.
The master runs a reading round
The read command is issued from the panel. The master addresses meters in turn and requests data; the returned telegram is decoded into index, flow, power and temperature fields.
Data lands in the archive
Every value is archived with its source and timestamp. Meters that do not answer are flagged with a reason and pushed to the unread list.

Technical summary

Standard: EN 13757-2 (physical/link), EN 13757-3 (application)
Physical medium: Two-wire line, polarity independent
Topology: Master–slave; the master powers the line and starts reads
Addressing: Primary address and secondary (serial-based) address
Typical rate: 2400 baud (300 and 9600 also used)
Meter types: Heat, hot water, cold water; electricity on capable devices
In NovuSoft: Loop — modem and converter are defined on the loop

Choosing

When is M-Bus the right choice?

There is no single right path for every building. These two lists are the criteria we apply during a site survey.

Good fit

New buildings or those undergoing renovation, where cable can be run
Projects with a high unit count and dense meter placement
Operators who do not want to manage battery replacement cycles
Sites that need uninterrupted daily reading

Poor fit

Existing buildings where cabling is not possible
Campuses made of scattered, distant buildings
Isolated points with only a handful of meters

In NovuSoft

How M-Bus reading is managed in the panel

Supporting a protocol is not enough; what the data means and what happens when a meter cannot be read must be defined too.

Loop-based management

The line is defined as a loop in the panel. Modem and M-Bus converter definitions live on the loop, and its scope can be the whole project, a few blocks, selected units or individual meters.

Line health monitoring

Bus voltage, short-circuit state and last-seen time are tracked. When every meter on a loop goes silent at once, it is immediately clear that the fault is in the line rather than the meters.

Every telegram field

Alongside the current index, the due-date index, instantaneous flow and power, flow and return temperatures, temperature difference, operating hours and device error codes are read and stored.

A defined process for unread meters

Reading is retried, the line is checked, a field task and — if needed — a fault work order is opened; on the billing side, regulation-compliant estimation keeps the period on schedule.

Frequently asked questions

Questions about M-Bus

What happens if the M-Bus cable is connected the wrong way round?

Nothing. The M-Bus line is polarity independent, so communication works even if the two wires are swapped. It is a design choice that removes a whole class of installation errors.

How many meters can share one line?

It depends on the master's power budget, cable cross-section and line length. In practice a single converter often powers hundreds of meters; where the budget is exceeded, the line is split or a repeater is added. This calculation is done during the site survey.

Does the meter brand matter?

No. Reading is based on the standard telegram, so any meter producing EN 13757 compliant telegrams is read regardless of brand. You do not need to replace your installed meters.

How often can M-Bus meters be read?

Because the wired line is continuously powered, reading frequency is not limited by battery life. Daily reading is standard, and several rounds a day are possible if needed.